64 differential gears to 66 housing

[vince1]

I have a 64 3.73 12 bolt diff in good shape and a 66 12 bolt housing where the gear set was trashed. If the spiders and axles are different in the 64 I can probably re-use them from the 66. Is it feasible to move the pinion and carrier assemblies from the 64 over to the 66?

I currently have a 3.08 from a 70 in my 66 truck with 4sp but thought the 3.73 would be better if switching over to a 700R4. Tires are 2.35 75 R 15.

Thanks for any advice offered.

[Clyde65]

I believe the only difference is the spline count. the 64 has 17 spline and the 66 should have 30 ( i think this is correct)

IMO, you would be just fine with the 3.73's and the 7004r. I have those gears in my 12 bolt and I run a 4l60e ( same as 7004r but electronic), plenty of economy and get up.

[Captainfab]

Yes you can install the '64 carrier and pinion in your '66 housing. You will want to check the backlash and tooth contact pattern in the '64 housing and then try your best to duplicate that in the '66 housing. You should be able to swap the spider gears also. I agree that 3.73's will be better with your 700R4.

[vince1]

Clyde65, did you have much trouble going the electronic route? Engine and EFI too? Speedo? Very worth it in the end I guess if one knows how to do it.