How to set 8.25 preload!

I've looked everywhere and I cannot get a straight answer on how to do this.

Here's my delima. Alldata says to torque the bearing caps down then set the preload. The problem is, once I torque down the bearing caps, there's no way in hell the threaded adjusters will move to set preload.

I dunno if something is wrong in my diff or if Alldata is wrong or if I'm just stupid and/or doing it wrong. :dunno:

So for now I've been adjusting backlash and preload with the bearing caps finger tight. But it's reeeeal hard to get backlash set when every time I get the backlash in spec, I torque the bearing caps down only to find that now my ring and pinion is completely locked up from lack of backlash :banghead:

On a related note, who sells gear set up paste? I can't find any around me.

The preload they are talking of is the pinion preload, which is set after the bearing caps are torqued down. Don't even attempt to twist the adjusters with them caps at 70 lb-ft--tis futile.

Ok that makes sense. So instead set them while bearing caps are about finger tight? And what do I do about the fact that torquing the bearing caps down messes with the backlash so much?

Setting up a diff is an art that takes practice. You'll learn that you'll have to do a 1/8th turn tight on the right adjuster, an 1/8th turn loose on the left adjuster, backlash will tighten up when you torque down the caps, etc.

No they are talking carrier bearring pre-load. Pull the caps down snug (side bearrings)set back lash tourque your caps. What are you using to turn the adjusters? A small spanner will not do the trick. Weld two bolts in the ends of a pipe to reach down the axle tube and turn the adjusters.

I've been told there is no way to put too much pre-load on the carrier bearings on the 8.25 but I use 125ftlbs.

Just make sure you recheck the BL after torquing, I guarantee it will move on you some

I as well have heard that you can't put too much preload on a diff that uses threaded adjusters.

I made a tool to tight the adjusters through the axle tubes so that's no problem, it's just that I've measured the backlash within spec (.006-.008) with everything torqued down and it's STILL whining on me! So I assumed it must be preload. Any other ideas?

Gear set up paste...white lithium grease with a small sprinkling of either red or yellow chalk dust (the stuff they use for chalk lines). Mix thoroughly.

I have found whining to be usually the contact pattern. Failing pinion bearings will let the pinion move and screw with the contact. How does your pattern look?

Whining accel or decel or cruise or all the time?

gradon said:

The preload they are talking of is the pinion preload, which is set after the bearing caps are torqued down. Don't even attempt to twist the adjusters with them caps at 70 lb-ft--tis futile.

Click to expand...

Pinion preload is set before you even install the carrier. Carrier bearing preload is set after you find the correct backlash. On a differential that uses carrier shims, you would set backlash then add another .005 shim to each side.
Setting 8.25 carrier bearing preload:
From my FSM: "using left side adjuster, set backlash to .003-.004 with each adjuster at 10ft/lbs. Torque bearing caps to 70 ft/lbs. Tighten right side adjuster to 75 ft/lbs. Seat bearings by rapidly turning pinion gear 1/2 turn back and forth 5-10 times. Reset right side adjuster to 75 ft/lbs again. Check backlash (should now be at .006-.008). Continue tightening right side until backlash is correct (.006-.008). Torque left side adjuster to 75 ft/lbs and seat bearings (see above.) Retorque left side adjuster to 75 ft/lbs. Install adjuster locks."

I have done this stuff before with perfect results in long term use as daily driver/ heavy wheeling. As said above, you need to set your pinion depth and bearing preload on that first which Im sure you did. The 8.25 is kind of a pain sometimes but once you get it you will find it easy. I basically set the whole thing up and tightened the caps slightly tight. Then I borrowed a sweet little tool to tighten the adjusters down to set preload on the bearings, again after the backlash, pinion depth, pinion preload, pattern etc was all spot on. The tool can easily be made by anyone. Take that nut/adjuster out and you will notice it has a bolt shape.....so you go to the local harware store or bolt supplier and buy a nut that fits in there snug. Buy 2 nuts and a stick of tubing and weld a nut to each end of the tube. You can stick this into the axle and slip it into the adjuster and then use a socket and torque wrench to set preload for the carrier bearings. The info above for FSM specks is right, though I use 75 ft lbs because thats what the dealer told me to set them at on both sides. If I were using old bearings I would set it up with 70 ft lbs, but new I run 75 thats just me. Hope this helps some. Also.......I cant stress this enough. Get a perfect pattern, even if that means it takes you 2 days or 10 days and have to pull things out over and over, and even pull bearings off. A perfect pattern will yield a stronger setup and better longevity. And rember after you have tightened it all up, check the pattern again to make sure.