Low Engine RPMs in Drive on '79 Dodge D100

From : jesse meyer

Q: i have a 1979 d100 truck that i consider my work truck. engine is the 318 transmission is the 3 speed auto. when the truck is in drive the engine rpms drop. when the truck is in park the engine rpms are high. it sounds about 2000/2500 rpms in park and about 900 rpms in drive. for the past five years that ive owned this truck its always been like this. in the past i drove the truck infrequently for this not to bother me but lately ive been driving the truck more often. im scheduling an appointment with a tranny shop to get their two cents but id really appreciate this groups ideas what might be the problem. two other bits of information that might be useful or might be unrelated 1 transmission has a strong tendency to burn any transmission fluid right after a fluid change. not to caramel brown consistancy but to a nice slightly brownish-pink. 2 somewhere in the drive train there is slack -- u-joint appears to be fine and so does the differential. thanks jesse meyer .

Replies:

From : budd cochran

dnwvc.1711$p8.1564@01.roc.ny... no tachometer get one guessing can be hazardous to your health. 2000-2500 rpm is way too high for an idle speed even on the fast idle cam cold engine. fast idle should be only about 1200-1500 rpm and warm idle about 700. good suggestion. i need to go tool shopping. i suggest getting a good one that can be set in the dash if you dont have guages to the right of the radio / heater controls or you can buy a simple dwell-tach unit. either will work. it sounds like your timing is set too slow not enough initial advance on the distributor. it should be at 10-12 degrees before top dead center. this may not match the manuals settings but it will work a lot better. slow timing will also require more throttle opening at idle to let the engine rev easier and not stall. get the timing right and the idle speeds can be set properly. will try this. when i bought my truck its idle was in the 1800 rpm range at curb idle. the timing was at 10 degrees after tdc so the previous owner a radiator repair man could run poor quality 85 octane without ping. it felt like it took a week to get to 30 and ran hot. im scheduling an appointment with a tranny shop to get their two cents but id really appreciate this groups ideas what might be the problem. which shop i recommend going to a reputable non-chain independent shop. there is a local shop that does free estimates will charge $80 for a fluid change and a band adjustment. i get a nice feeling from them. cool. youre welcome. how many miles on the truck when was the last fluid / filter change and/ or band adjustment band adjustment never in the 5 years i owned it. lol i know what you mean. the 727 i had is like an anvil. were going to adjust it next week and it will be the first time since i bought it in 96 about a 100k miles ago or so. fluid + filter about 25k ago. it needs replacing. sounds good. miles odometer says 33k. im guessing 133k based on the condition of the engine the age and the appearance that most of the engine and tranny seems to be stock. not surprising. theyre tough trucks and hold up well with normal care and dont fall apart if you miss an oil change or such. thanks again jesse meyer no problem. glad to help. let us know what you find out ok it helps keep the information fresh in the group. budd .

From : budd cochran

i have a 1979 d100 truck that i consider my work truck. they make good ones. my last vehicle was a 79 d-150 long bed 318 auto. engine is the 318 transmission is the 3 speed auto. good combination. when the truck is in drive the engine rpms drop. when the truck is in park the engine rpms are high. could be normal. a trans in gear puts some load on the engine. it sounds about 2000/2500 rpms in park and about 900 rpms in drive. no tachometer get one guessing can be hazardous to your health. 2000-2500 rpm is way too high for an idle speed even on the fast idle cam cold engine. fast idle should be only about 1200-1500 rpm and warm idle about 700. it sounds like your timing is set too slow not enough initial advance on the distributor. it should be at 10-12 degrees before top dead center. this may not match the manuals settings but it will work a lot better. slow timing will also require more throttle opening at idle to let the engine rev easier and not stall. get the timing right and the idle speeds can be set properly. for the past five years that ive owned this truck its always been like this. in the past i drove the truck infrequently for this not to bother me but lately ive been driving the truck more often. the high idle speed is a good reason for your noise and burnt fluid. im scheduling an appointment with a tranny shop to get their two cents but id really appreciate this groups ideas what might be the problem. which shop i recommend going to a reputable non-chain independent shop. two other bits of information that might be useful or might be unrelated 1 transmission has a strong tendency to burn any transmission fluid right after a fluid change. not to caramel brown consistancy but to a nice slightly brownish-pink. thats from the bands loosening due to the high idle speeds. 2 somewhere in the drive train there is slack -- u-joint appears to be fine and so does the differential. again it may be loose bands in the trans and the noise is them trying to slow that fast running engine down. thanks youre welcome. how many miles on the truck when was the last fluid / filter change and/ or band adjustment jesse meyer budd .

From : jesse meyer

dnwvc.1711$p8.1564@01.roc.ny... no tachometer get one guessing can be hazardous to your health. 2000-2500 rpm is way too high for an idle speed even on the fast idle cam cold engine. fast idle should be only about 1200-1500 rpm and warm idle about 700. good suggestion. i need to go tool shopping. it sounds like your timing is set too slow not enough initial advance on the distributor. it should be at 10-12 degrees before top dead center. this may not match the manuals settings but it will work a lot better. slow timing will also require more throttle opening at idle to let the engine rev easier and not stall. get the timing right and the idle speeds can be set properly. will try this. im scheduling an appointment with a tranny shop to get their two cents but id really appreciate this groups ideas what might be the problem. which shop i recommend going to a reputable non-chain independent shop. there is a local shop that does free estimates will charge $80 for a fluid change and a band adjustment. i get a nice feeling from them. youre welcome. how many miles on the truck when was the last fluid / filter change and/ or band adjustment band adjustment never in the 5 years i owned it. fluid + filter about 25k ago. it needs replacing. miles odometer says 33k. im guessing 133k based on the condition of the engine the age and the appearance that most of the engine and tranny seems to be stock. thanks again jesse meyer .