Welcome to the Corvette Forums at the Corvette Action Center!

To all those transmission guros out there...

chevyaddict

Well-known member
Joined
Jun 12, 2002
Messages
894
Location
Tucson, AZ USA
Corvette
1990 Convertible
OK, so I now have two vehicles with this exact same behavior so its time to figure out what is going on. Tranny's are a weak point in my knowledge base so hopefully someone out there can help!

Both with a TH400 and a TH350 I'm having mass tranny fluid leakage. It ONLY happens after the car has sat about three days. I'm guessing what is happening is the tranny fluid is draining from the torque convertor, back into the transmission, making it overflow and its coming out the area around the dipstick tube. My question is WHY? Is there something failing in the torque convertors themselves or is there a mechanism in the tranny that keeps the fluid from backwashing into the trannies? THIS IS REALLY FRUSTRATING! No other noticable behavior as far as the trannys working - they appear to work fine as long as the fluid is in em!

Thanks!
 

c4c5specialist

Technical Advisor
Joined
May 29, 2001
Messages
3,682
Location
New Haven, Ct. USA
Corvette
Nope, but someday.
Hi there,.
ARE you sure that the leakage is NOT coming from the torque converter seal after it takes a set???
Check your bellhousing area underneath the shield.
Allthebest, c4c5
 
V

vette-dude

Guest
I've stumped ya'll out there!!!!!!!!!!

I have had this happen a couple of times. It could be the front seal but I would check the O-ring at the dipstick tube where it goes into the tranny case. If the dipstick tube has been out or the bolt holding it is gone it will ruin the o-ring and it will leak after the torque convertor drains fluid back into the pan/trans body. This creates the fluid level to be higher than the dipstick tube hole and it leaks by the broken o-ring. The hole the dipstick tube goes into is not always chamfered on some tranny's and it is very easy to cut the new o-ring when installing so get a couple of extra's if you find this is the case. Be sure that the dipstick tube is bolted down securely or you will get to do this again. If you have one of those fancy chrome aftertmarket dipstick tubes, you will have to remove enough of the tranny fluid so the level is below the case and then add a little orange/red silicone around the o-ring before installing. Careful here as you don't want a big glob to drop into the pan. I hope that this is all it is as it is really a cheap and easy fix.

Randy
 

NORTY

Well-known member
Joined
Sep 7, 2006
Messages
851
Location
Carlsbad,Ca.
Corvette
2006 C6Z DSOM
What brand of ATF are you using? I think I'd just ride the lil' ZX6R...
 

chevyaddict

Well-known member
Joined
Jun 12, 2002
Messages
894
Location
Tucson, AZ USA
Corvette
1990 Convertible
Hi there,.
ARE you sure that the leakage is NOT coming from the torque converter seal after it takes a set???
Check your bellhousing area underneath the shield.
Allthebest, c4c5

Not sure what you mean by "take a set"..... can you elaborate?
 

chevyaddict

Well-known member
Joined
Jun 12, 2002
Messages
894
Location
Tucson, AZ USA
Corvette
1990 Convertible
I have had this happen a couple of times. It could be the front seal but I would check the O-ring at the dipstick tube where it goes into the tranny case. If the dipstick tube has been out or the bolt holding it is gone it will ruin the o-ring and it will leak after the torque convertor drains fluid back into the pan/trans body. This creates the fluid level to be higher than the dipstick tube hole and it leaks by the broken o-ring. The hole the dipstick tube goes into is not always chamfered on some tranny's and it is very easy to cut the new o-ring when installing so get a couple of extra's if you find this is the case. Be sure that the dipstick tube is bolted down securely or you will get to do this again. If you have one of those fancy chrome aftertmarket dipstick tubes, you will have to remove enough of the tranny fluid so the level is below the case and then add a little orange/red silicone around the o-ring before installing. Careful here as you don't want a big glob to drop into the pan. I hope that this is all it is as it is really a cheap and easy fix.

Randy

Hi Randy;
This is interesting. The truck has a chrome dipstick tube that is not bolted down so it has movement..... The other is the 68 Camaro with an old original tranny in it so it could be that the o-rings are the problem. Interesting.... I didn't think that much fluid would back up into the tranny above where the dipstick tube goes in....... I didn't think it was supposed to do that but perhaps it does and this is it!!! I'll check it out for sure!
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,521
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
I have had this happen a couple of times. It could be the front seal but I would check the O-ring at the dipstick tube where it goes into the tranny case. If the dipstick tube has been out or the bolt holding it is gone it will ruin the o-ring and it will leak after the torque convertor drains fluid back into the pan/trans body. This creates the fluid level to be higher than the dipstick tube hole and it leaks by the broken o-ring. The hole the dipstick tube goes into is not always chamfered on some tranny's and it is very easy to cut the new o-ring when installing so get a couple of extra's if you find this is the case. Be sure that the dipstick tube is bolted down securely or you will get to do this again. If you have one of those fancy chrome aftertmarket dipstick tubes, you will have to remove enough of the tranny fluid so the level is below the case and then add a little orange/red silicone around the o-ring before installing. Careful here as you don't want a big glob to drop into the pan. I hope that this is all it is as it is really a cheap and easy fix.

Randy
Randy is Dead on!!!!!I've never seen a turbo 400 or a turbo 350 that didn't do this over time, if sets around alot!!!!! They will sometimes leak around the shifter shaft too!!! O-ring is about $.85 and the dipstick tube sometimes can be a B#$^%$&!!!:upthumbs
 
V

vette-dude

Guest
Hi Randy;
This is interesting. The truck has a chrome dipstick tube that is not bolted down so it has movement..... The other is the 68 Camaro with an old original tranny in it so it could be that the o-rings are the problem. Interesting.... I didn't think that much fluid would back up into the tranny above where the dipstick tube goes in....... I didn't think it was supposed to do that but perhaps it does and this is it!!! I'll check it out for sure!

First if it (dipstick) is moving the o-ring is gone. Second, about 1 qt of oil will drain back into the pan and raise the fluid level above the dipstick mounting hole after the car/truck sets for any length of time (taking a set). You will have to somehow suck enough oil out of the tranny to get the oil level below the diptick mounting hole. When you install new the dipstick tube, new o-ring, and lightly siliconed o-ring surface, be sure you push the tube into the mounting hole squarely or you will tear the o-ring. Finally, make sure the tube is secured/bolted to the bellhousing not the body of the car. Many times tranny shop diagnose this problem as a front seal failure and you pay an exhorbinant cost to have them remove the tranny and install a new seal. Try this first. GMjunkie is also correct about the shifter seal but I think you have a dipstick tube o-ring problem at this point. Good luck.

Now if I can just figure out this quadratic equation and apply it to my cold fusion flux generator I can get back to the future!!;)

Randy
 

SPANISHVETTS

Well-known member
Joined
Nov 5, 2002
Messages
1,143
Location
El puerto de Santa Maria Spain
Corvette
before 60,63&82 now 90 383 Stroker & 91 ZR1-Sold
junk and Randy have you on the right path.

That blasted O ring on the S-10 drove me nuts. It would leak when the truck was not driven during the winter months but was dry as a bone all summer – even if the truck was not started for several days. It never gets that cold here but the difference between 80º and 40º was enough for the O ring to shrink a tad and let the fluid by.
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Win Both Corvettes!

Win Both Corvettes and Get Extra Bonus Tickets Now!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Dead Center Foundation

Vetteskins

Advertise with the Corvette Action Center!

Partners

Top Bottom