Differential leak

[markplucenik]

I hope you can help with my problem. My car is a 1966 Corsa , 4 speed and I have just recently replaced the differential pinon seal 3 times now and it still leaks ‘allot”. This is the quarter size seal that goes inside the through-out bearing snout , C495. Pulling this drivetrain is allot of work. I do not see any cracks or problems with the differential snout and I polished the sealing area of the input shaft . I thought it all looked good.

Question, would it be possible to use 2 seals instead of just the 1?
And if I used 2 seals would you still use the special split washer in front of the seal/ seals?
Also this weekend I meet with a couple local club members about the problem , one is a true Corvair mechanic, very knowable. He recalls there is a certain way to fill the trans rear and differential to help avoid leaks. He could not recall which way but it’s important to fill either the rear first or the tranny first. I filled from the transmission only thinking the shared fluid would self-level. Can you shed any light?

Again, Thanks, Mark

[Dennis66]

Some are putting double seals. The problem is the first seal fits tightly in the hub (like it's supposed to). The hub is a slightly larger diameter for the second seal and silicone or something needs to be used to seal the outside of the seal There was silicone on the outer seal of mine when I replaced them (1962, but the seals are the same). I also installed the split washer. Can't say for sure about filling. Mine had fluid in the manual transmission, but the differential was dry. I hand pumped through the fill hole until I could get a dap on the end of my finger (back of car on ramps). Dennis

[davemotohead]

I put 2 seals in every one I rebuild with the split washer, they work with the Stock T-Bearing shaft even though clarks says they don't and tries to sell you their double seal shaft. Have you greased up the seal lips and slid them over the input shaft on the bench to see if its the correct seal and fits properly? You are putting them in with the garter spring towards the diff? I recall some seals were sold that do not fit correctly. I do coat the outside of the seals with a sealant to prevent seepage around the outside, I preferer Gasgacinch and do not recommend silicone, Also make sure you use a socket / or driver to drive them in that fits the outer edge of the seal so it does not get distorted and grease the seal lips. Another note, are you sure it's gear oil and not engine oil from the bell housing crank seal? When I do a Clutch job I replace that seal as well as the bell housing gasket, do it right and do it once as this is a job you don't want to do twice!

As far as filling them goes, there is no "Magic trick" to filling them, you fill the trans and diff separately level with the bottom of the fill plug, I do them outside the car when its level and keep both plugs off until fluid drips from both of them, You don't want to under fill them as the diff needs to be at the full mark as the front diff bearing uses a splash system to lubricate it and if the fluid is too low it wont get enough gear oil and the bearing will run dry and disintegrate, then you are rebuilding the entire diff, if it's over full oil will splash out of the top vent in the diff cover and make a mess until the fluid level goes down.

[markplucenik]

Thanks for the reply’s and suggestions. I got the drivetrain out again today and separated the transaxle from the motor. I inspected the through-out bearing snout inside and out for any cracks or problems, all looked good. I removed the input shaft, set it up in a lathe using the drilled centers on both ends of the shaft. With a dial indicator I checked the runout on the seal area and the piolet bearing end. Numbers were .007 and .004 respectively. A second shaft I got from a club member measured a little better, .005 and .002. I have an early model shaft which I also measured was around .004 and .002. I don’t know the specs for this but these numbers all looked usable to me. I am interested in your opinions.
On the double seal idea, I does look like it should work and still use the special washer. The only drawback is the OD on the second seal will be a loose fit. Still thinking about how I want to “tighten the gap” on the second seal.

Thanks, Mark

[markplucenik]

Here is an update on my differential leak. Finley got it fixed. I had a couple of shafts so I chose the straightest, checking them in my lathe and dial indicator. Both seemed to be acceptable, the worst being about .004 out. I also replaced the pilot bushing this time. Now the best part, I did use 2 seals, C495. The first seal fits tight just like you would expect. The 2ed seal is loose because of the “step “ in the differential. My solution was to use some brass shim stock to build up the OD of the second seal. I found that .002 shim stock worked perfect. I used a small amount of gel superglue to attach the shim stock to the seal, perfect fit. Also used the factory split washer. Everything goes together fine. Attached are some pictures of my seal correction, I used my old leaky seals for my test fitting.

[66vairguy]

Interesting! Thanks for the update.

[bbodie52]

It sounds like you have done just about all you can do to resolve your leakage problem, short of the major changes listed by Clark's below.

Modifying your differential to install a new dual seal throw-out bearing shaft requires complete disassembly of your differential. A brand-new input shaft would be a costly upgrade too. Hopefully the measures you just described will be enough!

We have made a limited run of these super tuff replacement input shafts. Made from top quality stronger material than the original input shafts. Each shaft is custom machined, hardened, checked for straightness and polished where necessary. Replace that bent, fatigued old shaft. For lengths of all shafts see TECH page 402.

Part number C5476: 66-69 3 & 4 SPD INPUT SHAFT-NEW

Weight: 5 lbs 0 oz
Catalog Page(s): 128
Price: $ 174.70



Part number C7463: THROW OUT BEARING SHAFT FOR 2 SEALS NEEDS(2)SEALS-60-63=C494,64-69=C495 & 1 C1179

Weight: 1 lbs 4 oz
Catalog Page(s): 124(14)
Price: $ 59.60