1969 Differential Help

[Steve M.]

Doing a frame off on a 69 350/350 convertible. Refinished the Differential and while reinstalling the Positraction Carrier Unit, I cracked one of the cast iron shims for the side yoke. Does anyone know where I can purchase the shims and have it machined to match the cracked shim?
Appreciate any suggestions
Thanks, Steve Morrow

[Michael B.]

Re: 1969 Differential Help

Here's a diagram from Keen Parts. I think the piece you are looking for is unmarked though.

http://keenparts.com/pages/Catalog3.php?cat=440&diagram=44026&year=1969

You might try Toms Differentials

http://www.tomsdifferentials.com/

[Michael B.]

Re: 1969 Differential Help

I was just reading from the 1969 Chevrolet Chassis Overhaul Manual and it says "NOTE: Production preloading of the differential bearings is accomplished by the use of cast iron shims. These shims can not be used when rebuilding the carrier as they may break when tapped into place."

They go on to say "Service spacers are available in one thickness only .161" +- .001. Steel service shims are used with the service spacer. See the following Shim Chart for shim availability and identification." and they go on to show a shim chart .064 to .100. So what happen to you is what Chevrolet expected. See if you have a local gear shop that can supply you with the steel spacers and shims.

[Gary R.]

Re: 1969 Differential Help

Steve
You can machine new shims if you have access to a lathe and grinder but you can use steel side shims. They come in the master kits to replace the cast shims used in the 67-79's. Those were installed with a spreader but you do without. You want the final shim sizes thick enough to give you 5-8 lash and 8-10 more preload then the pinion bearings were setup to. For example, if you installed new bearings and set them to 18 in/lbs then install the case and side shims the total should be 26 -28 in/lbs. Again this is for new bearings, used would be about 5-7 in/lb.

If you can't find the shims shoot me a PM I have them in steel as well as the original cast.

FYI- the 63-66 used thin steel shims, same as a 12 bolt would.

[Steve M.]

Re: 1969 Differential Help

Thanks for the responses. I found a supplier with a kit that will allow me to make up the same dimensions as the cast iron ones. In some of the online rebuild papers, it indicated that the cast iron originals are likely to break. Only caveat was 'to be careful'? Guess I was not.
Thanks Again,
Steve

[Gary R.]

Re: 1969 Differential Help

Thanks for the responses. I found a supplier with a kit that will allow me to make up the same dimensions as the cast iron ones. In some of the online rebuild papers, it indicated that the cast iron originals are likely to break. Only caveat was 'to be careful'? Guess I was not.
Thanks Again,
Steve

Steve
I'm sure you were careful but those cast shims will snap. Sometimes they are loose others are tight. The steel stackable side shims should dial you in. You can file a small lead in on the shim to be tapped in place. I always install the LH shim and tap in the RH, just the way I like to do them. Remember to set the final pinion preload and then go to 8-10 in/lbs more for the total.