81 3 speed tranny issues:
Thread Starter
3rd Gear
Joined: Aug 2015
Posts: 3
Likes: 0
81 3 speed tranny issues:
Stock 81' C3 with a 3 speed auto. Tranny loses fluid. No visible leaks, no puddling or drips beneath car after driving, pan seal and filter have been replaced twice. Where is the fluid going?
Car will waste away a quart in approximately 200 miles.
Again, NO VISIBLE LEAKS anywhere under this car.
Car will waste away a quart in approximately 200 miles.
Again, NO VISIBLE LEAKS anywhere under this car.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Vacuum modulator on the trans. Vacuum line to the intake. Modulator gets a pinhole in the diaphragm and it sucks trans fluid in and burns it. I bet if you pull the line off the trans end it'll run like a river.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
It would have to be pretty bad to see it- and the factory steel line had an orifice built into it. Same with smell- the amount getting burned is so small compared to the amount of fuel it could be easily masked. You might see a small amount of white smoke during a high speed throttle off decal, but you'd have to watch very carefully for it.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
A puff of white on startup is indicative of valve seals. Really common Chevrolet problem. It can be fixed, but it's not really worth the $$ and effort until it's time to do the valves or replace the heads with better ones.
On the right rear of the intake, over the runners for cylinders 6-8, there's a vacuum fitting. One hose goes down to the trans. Pull it and I bet it's oily.
On the right rear of the intake, over the runners for cylinders 6-8, there's a vacuum fitting. One hose goes down to the trans. Pull it and I bet it's oily.
Thread Starter
3rd Gear
Joined: Aug 2015
Posts: 3
Likes: 0
Success...tentatively.
Replaced the vacuum modulator. Old one was rather full of tranny fluid. Shifts are smoother with less engagement "clunk" (it's a technical term) and car actually "feels" like it has more giddyup.
Still need to top off fluid for precise measurement on dipstick and then drive for a few days to verify fluid is not disappearing.
To those who assisted on the above thread, thank you VERY much.
Still need to top off fluid for precise measurement on dipstick and then drive for a few days to verify fluid is not disappearing.
To those who assisted on the above thread, thank you VERY much.
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