3 diffs - which brg kit

[vince1]

My 70 12 bolt 3.07 diff at the very least needs a bearing and seal kit. Rockauto lists quite a few. Why do they have so many? I was going to order USA std gear ZBKGM12T. Is this the right kit for me?

The only good diff I have is a 64 with 3.73 ratio. Eventually I was going to put those parts into the 66 housing that is original to the truck and change out the 4 spd manual for a 700R4. Do all three of these differentials take the same bearings and seals?

Thanks for your help.

[vince1]

I think I answered my own question and have ordered rebuild kit ZKGM12T.

[andyh1956]

It prolly has to do with the seal included in the kit...I only know of two 12 bolt axles, car & truck. The car 12 bolt has a much larger dia pinion than the truck, go figure.

[vince1]

I got the kit, put the truck on stands and had a look. The crown and pinion looked OK. I didn't feel confident enough to pull the pinion so settled on just a seal change. Gave it a spin in high gear and I could see one of the carrier shims turning. Took the carrier out and replaced the bearings. One was failing with some pitting or galling going on. Put it back in with an extra .005" shim to push the crown a little closer and still had some backlash so good to go. Today will put the wheels back on, fill with oil and try it out.

My next plan is to put the original 3.73 back together doing all the steps with crown and pinion setup.

My kit came with shims. I think the kit with the B in the P/N might come without shims. I think also that neither kit comes with axle bearings or seals.