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Still trying to get this car together. I had removed the pinion nut (seven years ago--probably to replace the seal) and am now just discovering that I should probably remove the seal and go through the preload process. Nothing inside of the diff has been changed, but I have no idea what it was torqued to originally. I guess my question is whether I have any options except buy a new seal and do the procedure as outlined in the FSM? If I skip that and torque to the middle of the range, would I really be screwed? Any tips or suggestions for this process?
Start reading the shop manual on page M-38. It outlines on that page into M-39 about pinion preload. If you were to just torque it to the middle of the range you are shooting in the dark. You could be on either side of the correct preload. To tight it will fail in short order, to lose it will whine. Pinion depth also greatly affects wear pattern / backlash.
Preload is done without the seal. The book specifies, 12 to 15 in-lbf. With brand new bearings I think that is a great preload. But with used bearings I think it’s ok to be on the lower range of that. Say 10-12 in-lbf. I’ve even heard of people doing lower numbers with used bearings, but you run the risk of it whining.
If I were in your position, I would start by removing the seal, installing the companion flange and torquing it to the minimum. Turn the assembly over a few rotations. Check the preload ( you need the correct swing arm torque wrench that goes this low ). Keep taking up torque by increments of 10 to 15 ft-lbs till you reach the correct preload. Then remove the nut and companion flange replacing the seal and retorquing to the correct amount as the book states. If you find that you reach the maximum torque number for the pinion flange before you reach the correct preload, you will have to replace the crush collar. I doubt this will happen because you have not made any changes to the internals.
After you attain the correct preload, you need to check the backlash and make sure it’s within spec. If you did not make any adjustments to the shim stacks or bearings that should return to where it was previously set. Whether that’s correct or not I do not know.
That will work nicely. I made something similar and used my bench vice to hold it while torquing. If you remove the two studs on the bottom of the diff it sits flat making it a lot more stable. The annoyance is removing it so you can spin it over and check the preload which feels like you do it 50+ times. I did forget to mention that you should squirt some oil on the pinion bearing and the axles must be removed. Self-explanatory I know, but I thought I would mention it. In my experience the preload goes up around 6-7 in-lbf with the seal. Throw some sealant around the pinion threads also. Good luck.
Thank you. I routed out a block of wood that lets the diff sit flat without removing the studs. Seems to be working and makes it a little more stable on the transmission jack.
