Bearing Preload Questions

[MGD72Monte]

I'm slowly accumulating all the tools to reassemble the differential, but there is a step that I'm not sure I will be able to do. Here are two questions:

 

1. What are the pinion bearing preload torque to rotate specs for a GM 8.2" open diff with new (Timken) bearings. The generic overhaul book I have states 20 - 25 in.lbs are typical values but a set up spec kit installation sheet someone gave me from Yukon Gear & Axle says 12 - 15 in.lbs for GM 8.2". Those seem to be big differences. Any other or master sources for these specs?

 

2. Book says too measure the torque I need a dial type torque wrench which reads really low values. I've priced them out at $250 . All I have is a click type that goes as low as 25in.lbs or an old beam type (that one starts at zero but the incredibly small amount of deflection to read such low values would be almost impossible to read.) Any tips on how to measure such low values?

 

Thanks for your time

[LIL' Mac]

It has been a long time, but I will offer what I remember. I would always lean to the higher torque spec, around 20 FT. pounds. Especially if your using your old pinion. Make sure you use a new crush sleeve, that is a must. Also a new lock nut, or at least ample blue threadlocker on the pinion nut. Your click torque wrench should be fine. That's what I used. Just my opinion, hope it helps. Scott.

[footballubet]

With new bearings you want the 20-25 in. lbs. torque. I would not trust a clicker torque wrench when setting up a diff. Try to find a beam or dial type instead. If you have an Advanced Auto or Auto Zone close by see it they rent them. This is where things need to be set up correct or bad things can happen.

[alex's72fgmc]

keep in mind the dial torque wrench will show the rotational torque needed to turn the assembly i have seen sheets with 2 foot pounds same as 24 inch pounds so go with what is in your kit. when reading the dial just read when turning slowly. also realize this is the rotational torque only not the torque needed to crush the crush sleeve and pinion nut to where you get the rotational torque spec.

[geartech]

Yes, the inch pounds setting is the rotational torque. With a crush sleeve it is set by how far you go tightening the nut. Have to be careful because the (new) crush sleeve with be difficult to crush at first then it will go quickly. I've only used my dial type torque wrench (inch-pounds), or by feel once you done it alot. You could probably find a deflection type inch pounds torque that will get you close enough.

Generally speaking, the spec is about 20-25 in/lbs for new bearings and 15 or so for used bearings. This is because the finish wears off a new bearing right away, and it will be a very little less preload after it has ran.

btw, I dont think a clicker type torque wrench would work at all for this.