1969 Differential Restoration

[Steve M.]

I am doing a frame off restoration on a 1969 convertible. At this time I have everything disassembled and have been restoring the suspension. I am now working on the differential. I do not plan to do anything to the differential except take it apart and bead blast the case and yokes. I will be installing new seals. In the online videos and several Forums, it seems to indicate that the posi-traction unit should slide out easily. That did not happen. Before I start being too forceful. I thought I would ask if I am missing something and/or there any helpful hints. I will be careful to keep the shims and other pieces separated to put all parts back together on their respect side. Thanks for any help, Steve

[Edward J.]

Re: 1969 Differential Restoration

Steve, the carrier will come out if you take a pry bar and block of wood on housing surface and use one of the carrier ring bolts to pry up on, there are installed with a spreader when the factory does it, so it won't fall out. once you have removed the carrier inspect all the bearings on carrier and pinion, make sure that once ready to reassemble that the case is spot less. last thing you want is any grit or sand in the housing. I Wash the housing with brake cleaner to remove the oil. and then once the housing is blasted, be sure to wash with soap and water and if you have a air compressor blow out the case. put a coating of 80w90 on the bearings and polish the surface of the shim and coat them also to help with the carrier install. drop the carrier in with races and then slide the shims in after , the last shim will require lifting the carrier up with races and the one shim installed already slightly to aid the install of the last side shim.

[Gary R.]

Re: 1969 Differential Restoration

Steve
Ed covered a good deal. I will ad some more general info that may help. 69's were the first year to use what I call the 2nd design Eaton posi. The way to ID them is to look at the windows, the 65-68 used a case with a small 1.5" square window, the 2nd design has a larger, tear drop window. The spiders in the 69 should be the 10-18's which are ok but not as strong as the later 10-17's. The clutches should be solids. NDH bearings were the original brand used. The case shims should be about .250 thick and are cast. As Ed mentioned, spreaders were used to stretch the iron to drop in the preload shims. I never use a spreader and can get them preloaded correctly. Be very careful tapping in cast shims as they will break. I use steels for stock 10 bolts and grind shims to size on the 12 bolt conversions.


To disassemble the diff - mount it on an engine stand and mark the bearing caps so they go back in the same locations. You should check them on the races to see how much "rock" is in them. The case should be tight in the housing. Many times when I get in a diff that was rebuilt, fresh or old, the preload on the case is wrong and they slide out. A pry bar in the small window will pop it out or the old trick of putting a box wrench on a RG bolt and turning the pinion will pop it out. Before you take it apart I suggest you check the present lash, do a pattern check, and measure the drag on the pinion. The drag with used bearings should be about 5 in/lbs. That way you will know you have it back where it was before you started. I glass bead the housing but it is bare, no axle bearings, pinion races, nothing. After blasting I clean inside with a few different types of wire brushes. Bottom tap the pad holes to get better thread engagement and clean them up for true torque reading. If it were me would go through it and replace the bearings too but that's your call. A simple mod is to install socket head cap screws in place of the 5 line hex bolts. Check the pinion yoke seal OD, they sometime groove there are speedy sleeves made for this if you find it grooved. The pinion splines have to be sealed or it will leak. Use Loctite #271 on the pinion nut and stake it too. There are other checks to look at while you have it apart, axle end-play is important and should be between 005- 010". If your main concern is appearance I don't think I would take it apart. If you need any tips feel free to contact me.