Chevy Impala SS Forum banner

1 - 20 of 51 Posts

·
Registered
Joined
·
115 Posts
Discussion Starter #1
On a bone stock 96 BBB with 140k on the odo. Have recently noticed tranny fluid on the bottom of the pan, located on the driver side edge of the pan. What are the potential causes? This is the side where the shift linkage is located. I did notice that the rubber boot on the shift linkage was coated in tranny fluid.

Thanks in advance for any help
 

·
Super Moderator
Joined
·
8,625 Posts
After 25 years and 140k miles, it's amazing that old cars don't have MORE leaks than they do.

It's always best to blow down the area with brake cleaner and then wipe dry. Then watch for leaks.

It's most likely the shift shaft seal. When the trans is off, the fluid level is above this seal, so it will leak. It's easily fixed by a trans shop without removing anything beyond the shift linkage. Or, you can buy the seal remover from Napa as well as a new shift shaft seal from lots of places including the major chain stores. Do be careful if you DIY, because there are sharp edges that will easily tear the seal and you'll have another leak.
 

·
Registered
Joined
·
484 Posts
It could be the pan bolts coming loose and oil has blown upwards. Get a torque wrench and retorque as per Factory Service Manual with the vehicle cold. After having my transmission rebuilt, rear main seal changed, I parked my car for non op for a year. I looked under my car one day and all my tranny fluid poured on the ground over time. I went under my car and sure enough, the bolts were loose, some really loose. I retightened, refilled and not a drop.
 

·
Registered
Joined
·
115 Posts
Discussion Starter #4
After 25 years and 140k miles, it's amazing that old cars don't have MORE leaks than they do.

It's always best to blow down the area with brake cleaner and then wipe dry. Then watch for leaks.

It's most likely the shift shaft seal. When the trans is off, the fluid level is above this seal, so it will leak. It's easily fixed by a trans shop without removing anything beyond the shift linkage. Or, you can buy the seal remover from Napa as well as a new shift shaft seal from lots of places including the major chain stores. Do be careful if you DIY, because there are sharp edges that will easily tear the seal and you'll have another leak.
That seems like an awful lot of tranny fluid where it can be up at teh shift shaft, considering that the pan itself is about 1 1/2" deep
 

·
Registered
Joined
·
115 Posts
Discussion Starter #5
It could be the pan bolts coming loose and oil has blown upwards. Get a torque wrench and retorque as per Factory Service Manual with the vehicle cold. After having my transmission rebuilt, rear main seal changed, I parked my car for non op for a year. I looked under my car one day and all my tranny fluid poured on the ground over time. I went under my car and sure enough, the bolts were loose, some really loose. I retightened, refilled and not a drop.
What is the torque specification on those bolts?
 

·
Registered
Joined
·
3,895 Posts
That seems like an awful lot of tranny fluid where it can be up at teh shift shaft, considering that the pan itself is about 1 1/2" deep
Because it is a lot. Hence the reason you check a Transmission with the engine running.That pump isn't pumping, the transmission is like a dead body, all the fluid settles.

If it were me, I would get everything cleaned off, take the car for a drive. When you return, climb under it and see what is leaking. Just for shits and giggles let it sit overnight and get under it in the morning.

Also, if that gasket is an old cork one instead of rubber, torquing those bolt won't do anything but crush and crack it.
 

·
Registered
Joined
·
115 Posts
Discussion Starter #8
Do those bolts need to be replaced with new ones once you pull the pan or can they be re-used?
 

·
Super Moderator
Joined
·
8,625 Posts
Torque spec on pan bolts is 8 ftlbs. There's no pressure behind it, as the transmission is vented to atmosphere at all times. Don't overtorque.
 

·
Registered
Joined
·
115 Posts
Discussion Starter #11
In replacing the pan gasket, do I use an RTV or just assemble the pan gasket dry (no RTV)?
 

·
Registered
Joined
·
3,895 Posts
Just the gasket, they are made to do the job by themselves. There is a special place in hell for people that use RTV on gaskets. RTV is for things that DO NOT have gaskets. Well, sometimes, because different surfaces use different products.
 

·
Registered
Joined
·
484 Posts
Expanding on my above post. Here are the first and second page from the Factory Service Manual that states the sequences in changing the transmission fluid and oil filter. The transmission pan has to be removed and reinstalled for this job. The torque says 12 ft lbs. In the diagram the transmission oil pan bolt is indicated as (76). Also the text written indicates to tighten the same bolt (76) to 12 ft pounds. Above you asked if the bolts can be reused. The Service manual (diagram shown) says to inspect the conical washer that is on the bolt. If its smashed towards the head of the bolt (not reusable) .If its flared outwards away from the head (reusable). This is what the book says. I’d make sure the bolts all are the correct length. I’d make sure the male threads on the bolts and the female threads inside the transmission body are clean of any grit.
7FB66153-E28A-447E-BD32-44BD81C77073.jpeg
94BAE03A-B5C0-43CB-9D9C-26B33609FE65.jpeg
 

·
Registered
Joined
·
484 Posts
Type of fluid?
This is what the book from the same pages above States. Dextron 2E or Dextron 3E. When I went to the auto parts store they cross reference it as “Dexron/Mercon“ Automatic Transmission Fluid (ATF)
476C6451-D006-49C8-B7A0-3FC8A88DF03E.jpeg
.
 

·
Registered
Joined
·
48 Posts
To save yourself a redo, verify bolt (male) threads and trans case tapped (female) threads are very clean before installing and torquing pan bolts. An accurate torque makes a big difference in sealing and not over torque that will bow (bend) the pan mating surface. I like to verify thread condition by testing by hand (feeling the prevailing torque force) before installing pan. Old cars sometimes get dirt in the top of the thru holes and the bolt stops before correct pinch or force on the gasket. Just a heads up.
It takes more time but give yourself the best chance at success for no leak.
Good Luck, Dezrat
 

·
Registered
Joined
·
1,226 Posts
Years ago I saw a few drops of ATF and wet pan. Tightened up the pan bolts a bit and never saw a leak since. Try simple solutions first.
 

·
Registered
Joined
·
115 Posts
Discussion Starter #18
Tightened the pan bolts to 12 ft-lbs. Managed to get at least 1/8 turn at all 16 locations so hopefully this resolves the issue. If not, then its time for a tranny fluid and filter change anyway. It's been about 75k miles on this fluid.

I did read once before about the shape of the washers on the bolts and when to replace them.
 

·
Super Moderator
Joined
·
8,625 Posts
For what it's worth, the 1995 F-body factory service manual page 7A-28 recommends 9 ftlbs on pan bolts. An excerpt is attached. And yes, the pan bolts are the same B-body to F-body.
194947
 

·
Registered
Joined
·
115 Posts
Discussion Starter #20
Well I figure since I have a B body, I'm going with what the B Body service manual says. Strange the discrepancy between manuals :unsure:
 
1 - 20 of 51 Posts
Top