Is smaller spare ok on AWD?

From : miles

Q: is using a smaller diameter tire ok or will it cause problems on my 2004 awd durango i want to replace the stock 245/70/17s with 265/65/17s but would rather not have to buy another spare as well since the spare has never been used and is only a year old. .

Replies:

From : tbone

it will not help the drivetrain to do this. the little bit of money you save here can cost you big $$$$$$ down the road in excessive wear in the transfer case components. -- if at first you dont succeed youre not cut out for skydiving is using a smaller diameter tire ok or will it cause problems on my 2004 awd durango i want to replace the stock 245/70/17s with 265/65/17s but would rather not have to buy another spare as well since the spare has never been used and is only a year old. .

From : tbone

it is not as simple as that. while the transfer case in a awd has a diff of sorts inside of it it is not an open diff more like a limited slip with locking capability. if you put a smaller tire on either axle it is going to cause that axle to turn at a different speed than the other one all of the time which will cause a continuous load and forced slippage on that internal diff causing possible overheating and excessive wear. -- if at first you dont succeed youre not cut out for skydiving rcsnyder wrote ditto. any odd sizing of tires on 4wd or awd will cause additional drivetrain stress and must be avoided. i was under the impression that stress would only occur if the differentials were locked. in the case of awd they are not unless i switched it to 4wd locked mode. that would be my thought as well. if all wheel drive is not engaged and even if it is is it truly all wheel drive i was under the impression although perhaps wrongly that all wheel drive used open differentials. roy .

From : roy

it is not as simple as that. while the transfer case in a awd has a diff of sorts inside of it it is not an open diff more like a limited slip with locking capability. if you put a smaller tire on either axle it is going to cause that axle to turn at a different speed than the other one all of the time which will cause a continuous load and forced slippage on that internal diff causing possible overheating and excessive wear. okay im learning. what if the transfer case is not in awd this is a spare tire that is just to get him out of the mess hes in not for everyday use. roy if at first you dont succeed youre not cut out for skydiving rcsnyder wrote ditto. any odd sizing of tires on 4wd or awd will cause additional drivetrain stress and must be avoided. i was under the impression that stress would only occur if the differentials were locked. in the case of awd they are not unless i switched it to 4wd locked mode. that would be my thought as well. if all wheel drive is not engaged and even if it is is it truly all wheel drive i was under the impression although perhaps wrongly that all wheel drive used open differentials. roy .

From : christopher thompson

not like you think. remember open rear only means that there is nothing forcing the wheels to turn at the same speed not that they can turn at different speeds with no effect to the axle speed. there is no magic here if the two wheels are turning at different speeds then the axle will turn at a speed between them as there is no way for the axle to take up the difference in an open rear other than changing speed. this will cause little wear on the spyder gears in an open rear as that is what they are intended to do anyway. agreed. the spyder gears are inteneded to take up differance in rotational speed between 2 wheels on the same axle during a turn. thus they do nothing while in straightline mode. running 2 diff tire sizes on the same axle essentially puts the axles differentail in a continuous turning mode as if it was in a constant corner if you had a limited slip otoh then it would cause added wear on the clutches by causing continuous slippage as it will to the clutch material in the transfer case if it is using a clutch type coupling. yes exactly my point in a limited slip or locker i can see where the strain of the tire size differance would send extra strain to the transfer case. the transfer case sees the same input on an awd as it does on a pt it only deals with it in a different way. in a pt system it really has no way to deal with axles turning at different speeds other than forcing the axles to turn at the same speed causing a wheel to slip which puts excessive strain on the drive train. in an awd system it deals with different it by allowing something internal to the transfer case to slip and that causes either wear or heat or both depending on the type of coupling the transfer case uses. ok. awd is i diff animal than anything ive worked on in the past. transmission/transfer case was not my specialty. but i understand about the transfer case not having the ability to diff between drive shafts thus the reason for the ole rule of use 4 wheel only on slippery/muddy surfaces. not hard paved surfaces. correct me if im wrong here. now all that being said im sure there are points im just not privi on along with system differances ect ect. -- if at first you dont succeed youre not cut out for skydiving at the same time if the axle diff is open would the size differance not be taken up in the diff gear set as its only one tire. granted wouldnt want to run missmatched forever on the axle as that would wear the diff gear set. but im with the other poster as long as the axle is open i personally dont see why the transfercase would see extra strain. -- -chris 05 ctd 99 durango it is not as simple as that. while the transfer case in a awd has a diff of sorts inside of it it is not an open diff more like a limited slip with locking capability. if you put a smaller tire on either axle it is going to cause that axle to turn at a different speed than the other one all of the time which will cause a continuous load and forced slippage on that internal diff causing possible overheating and excessive wear. -- if at first you dont succeed youre not cut out for skydiving rcsnyder wrote ditto. any odd sizing of tires on 4wd or awd will cause additional drivetrain stress and must be avoided. i was under the impression that stress would only occur if the differentials were locked. in the case of awd they are not unless i switched it to 4wd locked mode. that would be my thought as well. if all wheel drive is not engaged and even if it is is it truly all wheel drive i was under the impression although perhaps wrongly that all wheel drive used open differentials. roy .

From : christopher thompson

at the same time if the axle diff is open would the size differance not be taken up in the diff gear set as its only one tire. granted wouldnt want to run missmatched forever on the axle as that would wear the diff gear set. but im with the other poster as long as the axle is open i personally dont see why the transfercase would see extra strain. -- -chris 05 ctd 99 durango it is not as simple as that. while the transfer case in a awd has a diff of sorts inside of it it is not an open diff more like a limited slip with locking capability. if you put a smaller tire on either axle it is going to cause that axle to turn at a different speed than the other one all of the time which will cause a continuous load and forced slippage on that internal diff causing possible overheating and excessive wear. -- if at first you dont succeed youre not cut out for skydiving rcsnyder wrote ditto. any odd sizing of tires on 4wd or awd will cause additional drivetrain stress and must be avoided. i was under the impression that stress would only occur if the differentials were locked. in the case of awd they are not unless i switched it to 4wd locked mode. that would be my thought as well. if all wheel drive is not engaged and even if it is is it truly all wheel drive i was under the impression although perhaps wrongly that all wheel drive used open differentials. roy .

From : roy

is using a smaller diameter tire ok or will it cause problems on my 2004 awd durango i want to replace the stock 245/70/17s with 265/65/17s but would rather not have to buy another spare as well since the spare has never been used and is only a year old. it wont hurt a thing as long as the spare is never used. if you have to put the spare on the ground however it can cause damage to the drivetrain. mike mike it looks like a few of us need a bit of a education on this. jump in please. roy .

From : tbone

not like you think. remember open rear only means that there is nothing forcing the wheels to turn at the same speed not that they can turn at different speeds with no effect to the axle speed. there is no magic here if the two wheels are turning at different speeds then the axle will turn at a speed between them as there is no way for the axle to take up the difference in an open rear other than changing speed. this will cause little wear on the spyder gears in an open rear as that is what they are intended to do anyway. if you had a limited slip otoh then it would cause added wear on the clutches by causing continuous slippage as it will to the clutch material in the transfer case if it is using a clutch type coupling. the transfer case sees the same input on an awd as it does on a pt it only deals with it in a different way. in a pt system it really has no way to deal with axles turning at different speeds other than forcing the axles to turn at the same speed causing a wheel to slip which puts excessive strain on the drive train. in an awd system it deals with different it by allowing something internal to the transfer case to slip and that causes either wear or heat or both depending on the type of coupling the transfer case uses. -- if at first you dont succeed youre not cut out for skydiving at the same time if the axle diff is open would the size differance not be taken up in the diff gear set as its only one tire. granted wouldnt want to run missmatched forever on the axle as that would wear the diff gear set. but im with the other poster as long as the axle is open i personally dont see why the transfercase would see extra strain. -- -chris 05 ctd 99 durango it is not as simple as that. while the transfer case in a awd has a diff of sorts inside of it it is not an open diff more like a limited slip with locking capability. if you put a smaller tire on either axle it is going to cause that axle to turn at a different speed than the other one all of the time which will cause a continuous load and forced slippage on that internal diff causing possible overheating and excessive wear. -- if at first you dont succeed youre not cut out for skydiving rcsnyder wrote ditto. any odd sizing of tires on 4wd or awd will cause additional drivetrain stress and must be avoided. i was under the impression that stress would only occur if the differentials were locked. in the case of awd they are not unless i switched it to 4wd locked mode. that would be my thought as well. if all wheel drive is not engaged and even if it is is it truly all wheel drive i was under the impression although perhaps wrongly that all wheel drive used open differentials. roy .

From : tbone

it is not as simple as that. while the transfer case in a awd has a diff of sorts inside of it it is not an open diff more like a limited slip with locking capability. if you put a smaller tire on either axle it is going to cause that axle to turn at a different speed than the other one all of the time which will cause a continuous load and forced slippage on that internal diff causing possible overheating and excessive wear. okay im learning. what if the transfer case is not in awd this is a spare tire that is just to get him out of the mess hes in not for everyday use. it the transfer case has 2wd capability and truly decouples the axles then he would be fine. -- if at first you dont succeed youre not cut out for skydiving .

From : tbone

not like you think. remember open rear only means that there is nothing forcing the wheels to turn at the same speed not that they can turn at different speeds with no effect to the axle speed. there is no magic here if the two wheels are turning at different speeds then the axle will turn at a speed between them as there is no way for the axle to take up the difference in an open rear other than changing speed. this will cause little wear on the spyder gears in an open rear as that is what they are intended to do anyway. agreed. the spyder gears are inteneded to take up differance in rotational speed between 2 wheels on the same axle during a turn. thus they do nothing while in straightline mode. running 2 diff tire sizes on the same axle essentially puts the axles differentail in a continuous turning mode as if it was in a constant corner they dont take up the difference they allow the wheels to turn at different speeds by transferring the difference to the carrier otherwise you are completely correct. if you had a limited slip otoh then it would cause added wear on the clutches by causing continuous slippage as it will to the clutch material in the transfer case if it is using a clutch type coupling. yes exactly my point in a limited slip or locker i can see where the strain of the tire size differance would send extra strain to the transfer case. it would not. it would send the same thing to the transfer case it is the diff itself that would be under greater strain. the transfer case sees the same input on an awd as it does on a pt it only deals with it in a different way. in a pt system it really has no way to deal with axles turning at different speeds other than forcing the axles to turn at the same speed causing a wheel to slip which puts excessive strain on the drive train. in an awd system it deals with different it by allowing something internal to the transfer case to slip and that causes either wear or heat or both depending on the type of coupling the transfer case uses. ok. awd is i diff animal than anything ive worked on in the past. transmission/transfer case was not my specialty. but i understand about the transfer case not having the ability to diff between drive shafts thus the reason for the ole rule of use 4 wheel only on slippery/muddy surfaces. not hard paved surfaces. correct me if im wrong here. that is correct. in a turn the front and rear axles are turning at different speeds which winds up the drive train in a pt system. if a awd the transfer case has the ability to release that pressure with internal slippage but it will not be good for it to put it under that condition constantly. putting a smaller tire on will make the axle it is on turn at a different speed than the other and this will make the transfer case have to deal with that turn condition constantly. now if your vehicle also has a 2wd capability you can set it to that with your smaller spare and it will probably be fine until you get the tire repaired as long as you leave it in 2wd mode. the way i see it its your money your vehicle and your choice as to what to do good luck either way. -- if at first you dont succeed youre not cut out for skydiving .

From : christopher thompson

you are completely correct. if you had a limited slip otoh then it would cause added wear on the clutches by causing continuous slippage as it will to the clutch material in the transfer case if it is using a clutch type coupling. yes exactly my point in a limited slip or locker i can see where the strain of the tire size differance would send extra strain to the transfer case. it would not. it would send the same thing to the transfer case it is the diff itself that would be under greater strain. the transfer case sees the same input on an awd as it does on a pt it only deals with it in a different way. in a pt system it really has no way to deal with axles turning at different speeds other than forcing the axles to turn at the same speed causing a wheel to slip which puts excessive strain on the drive train. in an awd system it deals with different it by allowing something internal to the transfer case to slip and that causes either wear or heat or both depending on the type of coupling the transfer case uses. ok. awd is i diff animal than anything ive worked on in the past. transmission/transfer case was not my specialty. but i understand about the transfer case not having the ability to diff between drive shafts thus the reason for the ole rule of use 4 wheel only on slippery/muddy surfaces. not hard paved surfaces. correct me if im wrong here. that is correct. in a turn the front and rear axles are turning at different speeds which winds up the drive train in a pt system. if a awd the transfer case has the ability to release that pressure with internal slippage but it will not be good for it to put it under that condition constantly. putting a smaller tire on will make the axle it is on turn at a different speed than the other and this will make the transfer case have to deal with that turn condition constantly. now if your vehicle also has a 2wd capability you can set it to that with your smaller spare and it will probably be fine until you get the tire repaired as long as you leave it in 2wd mode. agreed. running the miss matched on any vehicle would need to be only temp. im not the op i was just trying to further understand the concern with the awd. and i now have a better handle on the concerns involved the way i see it its your money your vehicle and your choice as to what to do good luck either way. -- if at first you dont succeed youre not cut out for skydiving .

From : adolphe menjou adolphe

mike simmons wrote is using a smaller diameter tire ok or will it cause problems on my 2004 awd durango i want to replace the stock 245/70/17s with 265/65/17s but would rather not have to buy another spare as well since the spare has never been used and is only a year old. it wont hurt a thing as long as the spare is never used. if you have to put the spare on the ground however it can cause damage to the drivetrain. mike that is why they call it a spare. its not a drive on it all day tire. jam .

From : tbone

fair enough. i didnt feel it during normal driving but had one hell of a time getting it into and out of 4wd and could feel it pulling while in it. i thought that my transfer case was acting up until i remembered that my spare was still the old size and when i removed it the problem went away. i dont know where they are getting these numbers from but my 265s were at least an inch taller than my 245s not .06 taller like the chart says but if the tires that miles is switching to are also just about the same diameter as the old ones then he should be fine. -- if at first you dont succeed youre not cut out for skydiving tbone wrote im not sure if you have your math quite right but i did notice it with my pt 4wd with exactly the same tire combination. it may have been tire pressure or even a tread pattern difference you felt. even if you can notice the difference while driving its not enough of a diameter change to cause any damage. if its only going to be used as a spare it shouldnt matter much. i didnt do any math. i cheated. i used this http//www.miata.net/garage/tirecalc.html i checked the website math against my own and it came out pretty close. 245/70/17 tire 245/25.4*2*70/100+17=30.5039 diameter 30.5039*3.1415927=95.83 circumfrence. 63360/95.83=661.170 revs per mile 265/65/17 265/25.4*2*65/100+17=30.5629 diameter 30.5629*3.1415927=96.016 circumfrence 63360/96.016=659.890 revs per mile the difference is 1.28 tire revolutions per mile. imho not enough to cause any damage. -- ken .

From : nosey

tbone wrote fair enough. i didnt feel it during normal driving but had one hell of a time getting it into and out of 4wd and could feel it pulling while in it. i thought that my transfer case was acting up until i remembered that my spare was still the old size and when i removed it the problem went away. i dont know where they are getting these numbers from but my 265s were at least an inch taller than my 245s not .06 taller like the chart says but if the tires that miles is switching to are also just about the same diameter as the old ones then he should be fine. the 245 and 265 in the tire size is the section tread width in millimeters. it doesnt tell you the diameter. -- ken .

From : miles

rcsnyder wrote ditto. any odd sizing of tires on 4wd or awd will cause additional drivetrain stress and must be avoided. i was under the impression that stress would only occur if the differentials were locked. in the case of awd they are not unless i switched it to 4wd locked mode. .

From : roy

is using a smaller diameter tire ok or will it cause problems on my 2004 awd durango i want to replace the stock 245/70/17s with 265/65/17s but would rather not have to buy another spare as well since the spare has never been used and is only a year old. that was a problem with posi but id doubt that any harm would occur. not to say that running a mismatched tire is great for handling or prolonged use. roy .

From : miles

roy wrote okay im learning. what if the transfer case is not in awd this is a spare tire that is just to get him out of the mess hes in not for everyday use. on the durango i do not have 2wd mode. its awd 4w-lock and 4w-lo. .

From : coasty uscgret at comcast dot net

as if it was in a constant corner they dont take up the difference they allow the wheels to turn at different speeds by transferring the difference to the carrier otherwise you are completely correct. if you had a limited slip otoh then it would cause added wear on the clutches by causing continuous slippage as it will to the clutch material in the transfer case if it is using a clutch type coupling. yes exactly my point in a limited slip or locker i can see where the strain of the tire size differance would send extra strain to the transfer case. it would not. it would send the same thing to the transfer case it is the diff itself that would be under greater strain. the transfer case sees the same input on an awd as it does on a pt it only deals with it in a different way. in a pt system it really has no way to deal with axles turning at different speeds other than forcing the axles to turn at the same speed causing a wheel to slip which puts excessive strain on the drive train. in an awd system it deals with different it by allowing something internal to the transfer case to slip and that causes either wear or heat or both depending on the type of coupling the transfer case uses. ok. awd is i diff animal than anything ive worked on in the past. transmission/transfer case was not my specialty. but i understand about the transfer case not having the ability to diff between drive shafts thus the reason for the ole rule of use 4 wheel only on slippery/muddy surfaces. not hard paved surfaces. correct me if im wrong here. that is correct. in a turn the front and rear axles are turning at different speeds which winds up the drive train in a pt system. if a awd the transfer case has the ability to release that pressure with internal slippage but it will not be good for it to put it under that condition constantly. putting a smaller tire on will make the axle it is on turn at a different speed than the other and this will make the transfer case have to deal with that turn condition constantly. now if your vehicle also has a 2wd capability you can set it to that with your smaller spare and it will probably be fine until you get the tire repaired as long as you leave it in 2wd mode. agreed. running the miss matched on any vehicle would need to be only temp. im not the op i was just trying to further understand the concern with the awd. and i now have a better handle on the concerns involved the way i see it its your money your vehicle and your choice as to what to do good luck either way. -- if at first you dont succeed youre not cut out for skydiving mixing different size tires is never a good thing. other wise the nstb would not have issue with it nor would the manufacturers. virtually every manufacturer states in their owners manual states so. it is ok to have all tires the same size but not to have one tire a different size. you can do what you want but it is not prudent for your safety and others around you. doing so will totally change the handeling charastics of your vehicle especially an suv. why do you thing manufacturers have gone to full size spares on suvs by chance my 2 cents coasty .

From : nosey

miles wrote is using a smaller diameter tire ok or will it cause problems on my 2004 awd durango i want to replace the stock 245/70/17s with 265/65/17s but would rather not have to buy another spare as well since the spare has never been used and is only a year old. while i agree that running mixed tire sizes on a awd or 4 wheel drive is a bad thing these two particular tire sizes are so close in diameter that it will do no harm. the stock tire size will roll 661 times in a mile. the new tire size will roll 660 times. that is only one tire revolution difference in a full mile. this will cause your vehicle no harm. -- ken .

From : christopher thompson

not like you think. remember open rear only means that there is nothing forcing the wheels to turn at the same speed not that they can turn at different speeds with no effect to the axle speed. there is no magic here if the two wheels are turning at different speeds then the axle will turn at a speed between them as there is no way for the axle to take up the difference in an open rear other than changing speed. this will cause little wear on the spyder gears in an open rear as that is what they are intended to do anyway. agreed. the spyder gears are inteneded to take up differance in rotational speed between 2 wheels on the same axle during a turn. thus they do nothing while in straightline mode. running 2 diff tire sizes on the same axle essentially puts the axles differentail in a continuous turning mode as if it was in a constant corner they dont take up the difference they allow the wheels to turn at different speeds by transferring the difference to the carrier otherwise you are completely correct. if you had a limited slip otoh then it would cause added wear on the clutches by causing continuous slippage as it will to the clutch material in the transfer case if it is using a clutch type coupling. yes exactly my point in a limited slip or locker i can see where the strain of the tire size differance would send extra strain to the transfer case. it would not. it would send the same thing to the transfer case it is the diff itself that would be under greater strain. the transfer case sees the same input on an awd as it does on a pt it only deals with it in a different way. in a pt system it really has no way to deal with axles turning at different speeds other than forcing the axles to turn at the same speed causing a wheel to slip which puts excessive strain on the drive train. in an awd system it deals with different it by allowing something internal to the transfer case to slip and that causes either wear or heat or both depending on the type of coupling the transfer case uses. ok. awd is i diff animal than anything ive worked on in the past. transmission/transfer case was not my specialty. but i understand about the transfer case not having the ability to diff between drive shafts thus the reason for the ole rule of use 4 wheel only on slippery/muddy surfaces. not hard paved surfaces. correct me if im wrong here. that is correct. in a turn the front and rear axles are turning at different speeds which winds up the drive train in a pt system. if a awd the transfer case has the ability to release that pressure with internal slippage but it will not be good for it to put it under that condition constantly. putting a smaller tire on will make the axle it is on turn at a different speed than the other and this will make the transfer case have to deal with that turn condition constantly. now if your vehicle also has a 2wd capability you can set it to that with your smaller spare and it will probably be fine until you get the tire repaired as long as you leave it in 2wd mode. agreed. running the miss matched on any vehicle would need to be only temp. im not the op i was just trying to further understand the concern with the awd. and i now have a better handle on the concerns involved the way i see it its your money your vehicle and your choice as to what to do good luck either way. -- if at first you dont succeed youre not cut out for skydiving mixing different size tires is never a good thing. other wise the nstb would not have issue with it nor would the manufacturers. virtually every manufacturer states in their owners manual states so. it is ok to have all tires the same size but not to have one tire a different size. you can do what you want but it is not prudent for your safety and others around you. doing so will totally change the handeling charastics of your vehicle especially an suv. why do you thing manufacturers have gone to full size spares on suvs by chance my 2 cents coasty all of witch was why i wasnt saying for a full time use. but i wasnt fully understanding the concern for the transfercase in using a smaller spare in temporary situation. -- -chris 05 ctd 99 durango .

From : tbone

im not sure if you have your math quite right but i did notice it with my pt 4wd with exactly the same tire combination. -- if at first you dont succeed youre not cut out for skydiving miles wrote is using a smaller diameter tire ok or will it cause problems on my 2004 awd durango i want to replace the stock 245/70/17s with 265/65/17s but would rather not have to buy another spare as well since the spare has never been used and is only a year old. while i agree that running mixed tire sizes on a awd or 4 wheel drive is a bad thing these two particular tire sizes are so close in diameter that it will do no harm. the stock tire size will roll 661 times in a mile. the new tire size will roll 660 times. that is only one tire revolution difference in a full mile. this will cause your vehicle no harm. -- ken .

From : roy

roy wrote okay im learning. what if the transfer case is not in awd this is a spare tire that is just to get him out of the mess hes in not for everyday use. on the durango i do not have 2wd mode. its awd 4w-lock and 4w-lo. i was just out with the wifes envoy and decided to pay attention to things. the knob is labeled 2hi a4wd 4hi 4lo. so i guess i could do it in 2hi and be okay. id think that you would be able to in awd if it didnt sense a slip also as nosey pointed out the difference in size isnt that much. were it me id do it. roy .

From : nosey

tbone wrote im not sure if you have your math quite right but i did notice it with my pt 4wd with exactly the same tire combination. it may have been tire pressure or even a tread pattern difference you felt. even if you can notice the difference while driving its not enough of a diameter change to cause any damage. if its only going to be used as a spare it shouldnt matter much. i didnt do any math. i cheated. i used this http//www.miata.net/garage/tirecalc.html i checked the website math against my own and it came out pretty close. 245/70/17 tire 245/25.4*2*70/100+17=30.5039 diameter 30.5039*3.1415927=95.83 circumfrence. 63360/95.83=661.170 revs per mile 265/65/17 265/25.4*2*65/100+17=30.5629 diameter 30.5629*3.1415927=96.016 circumfrence 63360/96.016=659.890 revs per mile the difference is 1.28 tire revolutions per mile. imho not enough to cause any damage. -- ken .

From : mike simmons

is using a smaller diameter tire ok or will it cause problems on my 2004 awd durango i want to replace the stock 245/70/17s with 265/65/17s but would rather not have to buy another spare as well since the spare has never been used and is only a year old. it wont hurt a thing as long as the spare is never used. if you have to put the spare on the ground however it can cause damage to the drivetrain. mike .

From : rcsnyder

ditto. any odd sizing of tires on 4wd or awd will cause additional drivetrain stress and must be avoided. is using a smaller diameter tire ok or will it cause problems on my 2004 awd durango i want to replace the stock 245/70/17s with 265/65/17s but would rather not have to buy another spare as well since the spare has never been used and is only a year old. it wont hurt a thing as long as the spare is never used. if you have to put the spare on the ground however it can cause damage to the drivetrain. mike .

From : roy

rcsnyder wrote ditto. any odd sizing of tires on 4wd or awd will cause additional drivetrain stress and must be avoided. i was under the impression that stress would only occur if the differentials were locked. in the case of awd they are not unless i switched it to 4wd locked mode. that would be my thought as well. if all wheel drive is not engaged and even if it is is it truly all wheel drive i was under the impression although perhaps wrongly that all wheel drive used open differentials. roy .