Possible Trans fluid leak
Thread Starter
Intermediate
Joined: Jul 2024
Posts: 47
Likes: 11
Possible Trans fluid leak
My corvette seems to have just lost a lot of trans fluid even though I cant see any new leak spots on the ground where it sits.
The engine runs great, so i dont believe it could be leaking internally into places where it shouldnt be going.
This was a gradual thing that has happened over 3 months i think... is it normal to have to replenish fluid like that over time?
im pretty new to car mechanics and definitely new to c3 vettes.
kinda concerned about this, some help would be appreciated
The engine runs great, so i dont believe it could be leaking internally into places where it shouldnt be going.
This was a gradual thing that has happened over 3 months i think... is it normal to have to replenish fluid like that over time?
im pretty new to car mechanics and definitely new to c3 vettes.
kinda concerned about this, some help would be appreciated
Race Director
Joined: Nov 2006
Posts: 13,229
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
I'm going to go out on a limb here, Automatic transmission???
The kind with a dip stick near the back of the engine and no clutch??
If so, are you checking the level properly? Warmed up, run it through all the settings, put it in drive while running, foot on brake, and check level with dip stick kind of stuff???
Or real transmission, car up on stands putting a finger in a hole in the side of the box kinda thing???
So, back out on that limb. If Automatic, no, it's absolutely not normal to keep adding fluid.
you could have a leak in a cooling line. You could have a internal leak in the radiator, it could be pulling fluid threw a vacuum line.
If your anything like most of us. You know very little about Automatic transmissions. I won't buy one.I know nothing as well.
I think you need to visit a Automatic transmission shop.
The kind with a dip stick near the back of the engine and no clutch??
If so, are you checking the level properly? Warmed up, run it through all the settings, put it in drive while running, foot on brake, and check level with dip stick kind of stuff???
Or real transmission, car up on stands putting a finger in a hole in the side of the box kinda thing???
So, back out on that limb. If Automatic, no, it's absolutely not normal to keep adding fluid.
you could have a leak in a cooling line. You could have a internal leak in the radiator, it could be pulling fluid threw a vacuum line.
If your anything like most of us. You know very little about Automatic transmissions. I won't buy one.I know nothing as well.
I think you need to visit a Automatic transmission shop.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Pilot1225,
You are leaving a couple chapters out of your book.
1st. Automatic, we will assume, ***-out-u-and me?
2nd. Quote, No NEW leaking spots under the car, on the ground.
Does that mean it leaked previously or never before?
Here are a few common spots for leaks:
Obviously, the pan gasket.
Dipstick tube "O" ring where it enters the trans.
Shifter linkage / shaft seal.
Tail-shaft housing / yoke seal.
You are leaving a couple chapters out of your book.
1st. Automatic, we will assume, ***-out-u-and me?
2nd. Quote, No NEW leaking spots under the car, on the ground.
Does that mean it leaked previously or never before?
Here are a few common spots for leaks:
Obviously, the pan gasket.
Dipstick tube "O" ring where it enters the trans.
Shifter linkage / shaft seal.
Tail-shaft housing / yoke seal.
Thread Starter
Intermediate
Joined: Jul 2024
Posts: 47
Likes: 11
yeah its a 3 spd auto transmission
the only leaks it has ever had before was an old lower rad hose that spewed some coolant, but thats it. it hasnt leaked any oil or trans fluid onto the ground from what ive seen.
the only leaks it has ever had before was an old lower rad hose that spewed some coolant, but thats it. it hasnt leaked any oil or trans fluid onto the ground from what ive seen.
Burning Brakes
Joined: Jan 2001
Posts: 1,217
Likes: 443
From: Loir Valley Sarthe, France
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
What you haven't said is what you call "a lot" of trans fluid. Are we talking a pint, quart...... gallon?!
And as 4 Vettes said, have you followed the check routine, with the car running (in Park by the way, not Drive) and warmed through.
One place to look is the vacuum line connection on the manifold that goes to the Vacuum modulator on the trans (right hand side). If that has fluid present then the modulator is failing and allowing the engine to suck up the fluid.
And as 4 Vettes said, have you followed the check routine, with the car running (in Park by the way, not Drive) and warmed through.
One place to look is the vacuum line connection on the manifold that goes to the Vacuum modulator on the trans (right hand side). If that has fluid present then the modulator is failing and allowing the engine to suck up the fluid.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,137
Likes: 4,247
From: US-PNW
How does the car up-shift and down-shift? Ever see white smoke out the exhaust?
If you don't see any drips anywhere on the trans or behind it on the frame, exhaust, or suspension, I'd investigate the transmission vacuum modulator for a leaking diaphragm. If you pull the rubber vacuum hose off the modulator (passenger side of TH400, passenger rear of TH350), there should be no trans fluid on the vacuum side. You could test the modulator with a Mity-Vac hand pump; it should hold vacuum with no leak-down.
If you don't see any drips anywhere on the trans or behind it on the frame, exhaust, or suspension, I'd investigate the transmission vacuum modulator for a leaking diaphragm. If you pull the rubber vacuum hose off the modulator (passenger side of TH400, passenger rear of TH350), there should be no trans fluid on the vacuum side. You could test the modulator with a Mity-Vac hand pump; it should hold vacuum with no leak-down.
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