C3 Pinion Seal

**Duke W.** · July 25, 2003, 08:49 AM

Re: C3 Pinion Seal

The only sure fire way I know of to remove and install the pinion nut is an impact wrench. If you can borrow a compressor and impact, that's the way to go.

Be sure you clearly mark the relation of the nut to the pinion shaft so you can install it to the same point to establish the correct pinion bearing preload.

Duke

**Joe L.** · July 25, 2003, 02:26 PM

Re: C3 Pinion Seal

Don-----

As I've mentioned numerous times previously, removal of the pinion nut is the most difficult part of replacing the pinion seal. As you've found, doing it in the car adds considerable extra difficulty.

You will note in your factory service manual that there is a special tool for holding the pinion flange. This tool has a long arm. It's Kent-Moore J-8614. It's still available from Kent-Moore, but the price is WITHERING, especially because one wouldn't use it very much. Using this tool and a LONG breaker bar, you can remove the nut. Of course, an impact tool is going to be the best way, but you still need to FIRMLY retain the pinion flange while removing the nut.

**Richard E.** · July 25, 2003, 02:31 PM

Re: C3 Pinion Seal

Duke - When reinstalling the nut (mine's a 62), do you torque just to the pre-removal scribe mark? Or just a skosh past it as my ST-12 implies? Also, I guess it's OK to put some non-hardening sealant on the splines? Some say that seepage out the splines is possible.
Thanks much..Dick

**Terry M.** · July 25, 2003, 03:24 PM

**Mike McKown** · July 25, 2003, 03:47 PM

Re: C3 Pinion Seal

A big pipe wrench on the companion flange will work in place of the Kent-Moore tool. If you hold the flange solidly and put your back into it, I see no reason the nut won't come loose with a breaker bar.

**Craig S.** · July 25, 2003, 07:05 PM

Re: C3 Pinion Seal

An air impact is the way to go, I have generally found that holding the companion flange with my hand while wearing a welding glove works pretty well, but it would be convenient to have the Kent Moore tool or fabricate something similar. As Terry mentions, if you are going back on again without a rebuild and new crush sleeve, counting the revolutions is about impossible if you use the impact wrench method...Craig

**Chris H.** · July 25, 2003, 07:06 PM

Re: C3 Pinion Seal

Don,

I did this job last year, using jack stands and my neighbors impact gun. Fortunately he had enough hose to run the compressed air from his garage to mine. First you have to remove the drive shaft (easy, see archives or Chevy Chassis manual) and the front mount of the diffential that connects to the frame (easy).

Next, mark the nut and it's relation ship to the flange. I did not have a tool to hold the flange in place, so I applied the parking brake. The nut eventually came loose with the gun. You can then knock the old seal out with a brass punch. Lube up the new seal with wheel bearing grease and your good to go. Also put grease on the splines of the shaft so that the diff lube doesn't run out the splines. A pain in the butt, but way easier than pulling the diff.

**Peter Ansted** · July 25, 2003, 07:41 PM

Re: C3 Pinion Seal

Don - I just dropped the diff for the exact purpose of replacing the seal. I tried ti do it with the diff in place, but the new seal still leaked {I assumed I had a 63 diff, bought and installed seal only to find out I have a 70 diff and uses a different seal} The entire removal process took me about 5 hours. The most challenging part was lowering the diff/crossmember assembly to the floor. Check the archives for step by step instructions. With the diff out, I can have all bearings and seals replaced, have new spicer u joints put in the half shafts, clean and paint everything prior to installation. I've ben told that once all this is done, it will be like driving a new 40 year old car again.

**Duke W.** · July 25, 2003, 08:29 PM

Re: C3 Pinion Seal

I essentially agree with Terry, though I've used impacts to tighten the nut and have had no pinion bearing problems on the handful of these jobs I've done. You can clean up the area with mineral spirits and use paint to mark the position. Count the number of exposed threads on the pinion and record this for reference when you install the nut, so you get it on the correct number of turns. The pinion should have end play until the last fraction of a turn, so once the end play is taken up, you know you are preloading the bearings, so you can use this as a cross check on the exposed thread count.

Install the nut to at least the original position or just a skosh more, which will ensure that the crush sleeve has some compression Then push and pull on the pinion to be sure there is no end play. I believe I used a bit of Permatex Aviation Form-a-Gasket on the splines to preclude leakage, and be sure to clean off any old sealer first. A post down farther mentions grease, but grease might not seal in the long run.

Duke

**roy braatz** · July 25, 2003, 08:53 PM

Re: C3 Pinion Seal

OK guys , all good advice, I was a mechanic for years at a Chevy dealer working on PG,350 and 400 trans.Also rear ends Corvette only in the 60's. Rebuilt many pumpkins , the crush sleeve is to put tenion on both bearings, they are not ball bearings ( think of it like puting pressure on your wheel bearings).If your just replacing the seal , you don't have to worry about the END play, that has already been done when first made ( SHIMS) We used an air impact wrench to remove and install the pinion nut and when installing the nut we hit it with all the air impact could do ( short burst), then hit the pinion end with a heavy hammer to know that the crush sleeve was setting flat on the bearing race. If while turning the flange it felt loose we used the impact again till we had a little drag.We also used thread lock if the nut was not a new one to ensure it stayed tight.

C3 Pinion Seal

C3 Pinion Seal

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Debug Information