C-4 transmission gasket material

[40cpe]

I had a leak on my C-4 trans at the shift shaft. I took it to a transmission shop to get it stopped. After the "repair" I picked it up, took it home and parked it on a plastic sheet to check for leaks. The next morning it had a puddle under the drive shaft yoke and one under the rear of the pan. I took it back, told them to keep it until it wouldn't drip. Two days later they called and said it was ready. This time the yoke leak is gone, but the pan still drips enough to make a puddle on the plastic. I'd rather fix it myself than deal with them again. The gasket they put on it is a rubber looking compound. My question is: Does a cork gasket seal any better? I'm thinking a cork gasket with a thin film of RTV sealer might do it. I don't think the pan is warped (unless they warped it), it didn't leak with a cork gasket when I took it to them. Thanks for any suggestions.

[wayne petty]

a few things...

transmission parts suppliers sell better quality flat fiber gaskets..

i personally don't like the cork gaskets.. flat paper ones with some kind of semi gloss coating..


you might have a leak at one of the transmission pan bolts..  i have found many times that torque flight front pump bolt gaskets work great for these leaks..  it takes more than one tiny bag of them..  you could also toss some thin Orings on the bolts next to the head so it kinda seals the underside of the bolt head to the pan rail...    you could make your own out of a spare transmission pan gasket with a gasket punch set

http://www.harborfreight.com/9-piece-hollow-punch-set-3838.html

please check that the pan rail is truly flat.. and thats it;s not leaking from one of the transmission cooler fittings.. one of the band adjustment nuts.

out the vent on the top of the case... check the fluid level the next morning after a night being shut down.. how many inches above the full mark is it..





the shift shaft seal can be changed while you have the pan down...

wonder if they actually changed it???

Dura Built Transmission Parts
1041 Terry Rd, Jackson, MS ‎
(601) 352-9184 ‎ ·
you might give this place a call..

a C4 gasket set should be under 14 bucks..  just the pan gasket is 2 or 3 bucks...

[40cpe]

The first time I brought it home and it was leaking I put it on my rack to see where it was coming from. I wiped my finger along the gasket line in the rear and it was definitely wet enough that my finger was bright red. I'll have to get back under to look closer. I didn't see any drips from the shift shaft or from up higher. Maybe that part is fixed.

Thanks for some ideas of more places to look.

[40cpe]

The first time I brought it home and it was leaking I put it on my rack to see where it was coming from. I wiped my finger along the gasket line in the rear and it was definitely wet enough that my finger was bright red. I'll have to get back under to look closer. I didn't see any drips from the shift shaft or from up higher. Maybe that part is fixed.

Thanks for some ideas of more places to look.

Wayne, I checked more closely this afternoon. There was one pan bolt with a wet head and dripping under it. Also the band adjustment on the right side was red with fluid, but no drips from it yet. The fluid level was exactly 2" above the full mark on the stick with engine not running and after sitting 2 days. Does that throw a red flag? I haven't had a chance to run it to get it warm and check fluid level with engine running. I'll do that early next week.

Is there an o-ring in the band adjustment that can be changed externally without draining the fluid? I'll make a gasket for the leaky pan bolt.

Thanks for your suggestions.

[Okiedokie]

I wrestled with a leak on the C4 in my 46, replacing gaskets and even pans before I discovered it was the o ring on the dipstick tube causing the leak. It always appeared to be coming from gasket area. Worth a look.

[Crosley.In.AZ]

Is there an o-ring in the band adjustment that can be changed externally without draining the fluid? I'll make a gasket for the leaky pan bolt.

Thanks for your suggestions.

band adjustment nut has molded on rubber seal.  if you need one, let me know.

There are course threads and a fine thread nut at the front band.  I would need to know which one you have

[40cpe]

Thanks for the information and the offer, Tony. I'll look for one locally before putting you to any trouble.