ph31mwl

I am rebuilding my 65 roadster and am about ½ way through it. Body is off frame and has been painted. The engine is done and I am picking up at machine shop of Monday. Frame has been straightened and suspension has been rebuilt and everything installed. A couple of days ago I noticed a puddle of gear oil under the differential. I was surprised at this since last year I brought the differential to a Corvette shop to have it disassembled checked and new bearings and seals installed. Indications are it is the pinion oil seal. Pinion nut came off easily with the air impact gun, of course I forgot to make a mark the nut and differential case so I could put it back where it was before taking it off. It looked like the pinion nut has not been removed and the pinion seal looked very old. I have had the car since 1973 so I am assuming that the seal and bearing are original. The companion flange is scored where the seal goes around it so that could be helping it leak. I am purchasing a new flange, seal, bearing and race.

Long intro for a short question. How do I get the bearing race out?? With the rest of the differential together and the pinion sticking out the front there is no room to get a puller in there to remove the race. If I am unable to remove the old race I can put the old bearing back in, but that is not a good idea. The old race looks good and is smooth when I run my finger over it so I could put the new bearing in with the old race, but that is not a great idea. I would prefer to put the new bearing in with its new race. I would greatly appreciate advice on how to get the old race out.

Thank you for any assistance you can provide.

Mark

pop23235

Step one, mark before removal Oops.
Step two, what is wrong with the old bearing? Most bearings are replaced when still good.
Makes step 3 through the last much easier.

New bearing, disassemble.

Critter1

Pop23235 is correct. It's not possible to replace the front bearing race with the pinion installed. and I don't know if it's a good idea to install a new bearing using the original bearing race. I suppose it's possible that the race surface is in the exact same angle as the new bearing rollers but most likely being different manufactures, it's possible the angle is slightly different.
Keep in mind, the new bearing inner race may also be a different dimension so the crush sleeve may not contact the race properly. The load on the sleeve may be less or greater. Actually, the crush sleeve is a one time use only and should be replaced if the bearing is replaced.
Also, it's not possible to set the pinion bearing rotational preload with the differential case and ring gear in place. I don't remember the exact numbers but it's something like 10 INCH pounds to rotate the pinion when the flange nut is torqued properly.
If it were mine, I would either reinstall the original bearing and hope for the best, or completely disassemble the unit and replace the bearings, crush sleeve, seal and pinion nut.
By the way, the seal is NOT to be installed completely flush with the diff housing. There should be about 1/8" gap between the flange of the seal and the housing. Chevrolet/Kent Moore supplied a U shaped spacer to be used when installing the seal to provide the gap and place the seal properly. If your seal is the original, you may have noticed that it was not installed completely and had the 1/8" gap. The tool is shown in the Chevrolet service manual.

There's a lot more to it than most think.

ph31mwl

Pop23235/Critter1, thank you for your responses. The information you have provided is just what I needed to know. I am glad I did not figure out a way to get the old race out as that would have opened a can of worms that I am not prepared to deal with. I wish the Corvette shop had done what I requested, but I do remember that he did say that when he checked everything he only changed those things that needed to be changed. I have never heard any noise from the differential and when I moved the bearing while in the race it moved smoothly with no problems. While the differential is 52 years old it only has around 40,000 miles on it so it is probably still OK to use. That will make things easier. I have read several posts on the Forum, along with other instructions on the web on what to do when installing a new pinion seal when the nut and case is not marked. I will follow those instructions and “hope for the best”. If something happens after I start driving the car again I can always remove the differential and take it someplace for a complete overhaul.

I just thought of another question. Between what leaked on the floor and what drained out after removing the companion flange I lost a little over 1 quart of gear oil (this is all new with no miles on the additive and oil). My question concerns the replacement of the limited slip additive. How much of the additive do I need to put back in? I believe GM calls for one 4oz bottle of the additive. Is adding a 4 oz bottle too much or should I just put in 2oz of the additive.
Again, thank you for your responses. You saved me a lot of grief.
Mark

Critter1

Scan from GM overhaul manual below discusses proper pinion seal installation/position. At the lower left corner of the page, note the proper 1/8" gap between the seal flange and diff housing. I can't find the image of the tool used but it's a "U" shaped piece of sheet steel about 1/8" thick. The tool is removed when seal is installed. Text above drawing describes gap.
This information is for a GM seal. I suppose it's possible that it doesn't apply to aftermarket seals.

GTR1999

I can offer an opinion if you like, I have rebuilt 100's of these diff's over the years. You are in the middle of a huge project, investing a lot of money and time, you have already trusted a corvette shop and to be nice you didn't get what you expected. So my question is why would you consider "hope for the best"? I am not trying to be critical of your question or work but if you can pull a body, do a lot of the mechanical work that you have been doing I can teach you how to properly go through that diff and what to look for. Why put a used diff back in a restored car when you can take care of it now? Guys have done just that only to have to pull it out when a problem came up.

If the seal appears old and has green paint on it then it could very well be the original one which means the pinion wasn't removed or worse nothing more was done to it. If original it will have Hyatt bearings in it, anything else are replacements. NDH bearings were not used until later years and those were New Departure - Hyatt bearings. Look to see if the bearing you have out has the info stamped in it or etched on. If the bearings were replaced the pinion preload would or should have been set to between 15-20 in/lbs & total would be 8-10 more all of which will drop to 5-7 once a load is placed on the diff.

If this was my diff and have it out I would mount it on an engine stand and pull the cover to look and just what was done. You can replace just the seal if you like and a much better way to do then lining up witness mark is to use a 0-30 in/lb dial torque wrench to setup the preload- again based on if the diff was worked on correctly. The outer pinion race is pressed into the housing. The cone is a slip fit on the pinion. The counter bore typically is machined to the point where a seal leaves about an 1/8" gap between the housing and seal flange but not always. I once wrote a paper on this years ago and did reference that but I no longer do at me seminars or when coaching someone. You need to measure the bore depth, seal thickness and then measure the pinion yoke shield to be sure there is clearance between the seal flange and pinion yoke- I have seen the machine shallow and hit the yoke causing a false reading. The pinion splines and yoke splines need a quality sealant applied to them or oil will weep out, the amount you lost indicates a bad seal. The wear groove on the yoke can be repaired with a speedy sleeve for about $30. The diff will hold 50 oz but you will never get that in with it level so the diff is good when the gear oil weeps out the fill hole.

Also some 65's, the early ones, had a transition pinion design in them. The earlier 63-4 R&P were Dana's and not good at all, they had a small "wedding band" crush sleeve that bottomed on the square shoulder of the 17 spline pinion. This is where they snapped in half under abusive use. The early 65's had the same sq shoulder but had 30 splines. 65 was also the first year for the Eaton posi's and while much better then the Dana's they were prone to crack and once they crack it's a time bomb before it reaches the cross shaft bore and implodes. That is why I suggest you at least check to see what you have and if you need to address things now.

With that said, I'm going to bed. Good luck.

ph31mwl

Critter1 – Thank you for the scan, that information clears up some questions I had. If I go forward on my own I can make a spacer to get the 1/8 inch gap between the seal flange and the carrier.

GTR1999 – Thank you for your detailed description of what should be done to do this correctly. Unfortunately, disassembling the differential and going through all the steps is waaaaay beyond my capability (as the line in a movie says “you have to know your limitations”). As a hobby for the past 50 years I can do body work and paint, and a lot of mechanical work. Much of the work is straight forward, but other things are not. For me, the differential is not, and it is too important to practice on then put back in the car. The seal that I removed has orange paint on it and the outer lip of the seal flange is rusty. The bearing is a Hyatt so I assume this stuff is original. I think what I may have to do is find a shop that I can trust to take it all apart and rebuild it. Or, maybe it would be better to purchase a new one.

Thank you both again for your responses. I have to now decide which way I am going to go so that I trust what goes back in the car.

Mark

1snake

You've already found someone you can trust, Gary (GTR1999). Send it to him and you'll never have to worry about it again.