Front Differential Mounting Question

[ehinlein]

I'm currently working on an '86 HMMWV. Getting to the front brakes and I realize there's something wrong with front diff mounts/geometry. Body is off, it's all there to see and I'm not quite sure what's up.

With the side hangars bolted tight to the front to back braces it sits too high in frame. So high that driver's brake caliper bumps bottom of frame rail. Frame is intact and straight. Cross members, and it would be mostly the rear one of the two front cross members, appear correct.

From removing other items it appears all these holes are "centered" and aren't elongated for up/down adjustment of cross members. It's about a 1/2" discrepancy. Maybe more. Odd thing is the input shaft mount plate wants the diff down also to line up and it's part of the rear (of the front 2) cross members.

My first question is : are there any shims or anything associated with the front mount?

Next question: Any ideas? I can't see how these cross members could be that far off. They are intact and straight as is frame.


Thanks in advance


-Erich

Pic below top is the front. Note: washers stacked under the bottom (rear) brackets so I could get an idea of spacing.

 

[Retiredwarhorses]

I can't see in the pic if your caliper yokes are installed....also, the nuts you are using should be Grade C lock nuts and all grade 8 hardware....that's area gets alot of vibration what with the diff torque and braking.
also make darn sure you use red thread locker on your bolts for the caliper yokes and diff hangars, you won't be able to retighten any of it if any of it comes loose with removing disk,caliper, halfshaft, plus if any of the bolts back off it will grenade what ever it comes in contact with.

All hardware on chassis and drive train is all grade 8 and secured with Grade C lock nuts and alot of times thread locker.

 

[Retiredwarhorses]

Oh, also.....did you change out the yoke for new ones? The front left is the ONLY one that if different....the front right and both rear are the same part number....the front left is hard as heck to find and you cannot use anything but the correct front left...or it will sit higher like yours is.

by yoke I mean the caliper bracket the bolts to the diff.....here's another rid bit, the bolts that hold your diff support brackets use a 1.25 in grade 8 bolt...not generally available at your local store....is I clean and reuse, the bolts that hold the calipers are grade 8 1.5in
and do not use any washers....use red thread locker.

 

[ehinlein]

Thanks for the info.

Yes the 4 nuts on top are soft. Will replace. And yes-red thread locker. Left yoke about 1/4" lower. Is this right? Or is it the wrong one and just 1/4" off? I'm guessing rear side brackets were used on the front. It's just too high. Actually hits cross member in the rearat input end.. A few things messed up on it but mostly it's been ok.


Body going back on soon hopefully.

 

[Retiredwarhorses]

Like I said, 3are the same, front left is different, look at the part numbers embossed on the bracket.
i just installed diffs today in my build...I always end up using the old front left bracket as they are expensive and hard to find cheap NOS. that's al I can think of...

 

[Retiredwarhorses]

No shimming is required at all....and yes, on each diff the brackets make one of the calipers hang a tad bit lower then the other...normal. What I do is put the diff in but leave the top bolts loose, then torque the 2 5/8 bolts that attach the diff at the rear, this way I know the Diff is where it's supposed to be, then torque the 4 1in long 1/2in bolts for the hangars.

 

[ehinlein]

Been a long time since I asked this and solved it but I figured someone else might come across it. Turns out whoever "worked" on my HMWV previously used the rear type hangers on the front diff. Also, the brake yoke was the wrong one. As was pointed out, the left front yoke drops the caliper a little further down than the 3 others.

 

[Retiredwarhorses]

Yep...that would do it. The fronts are longer then the rears...by about 1in. I know this as I just went through this on my truck. Curiosity killed the cat, so I measured them.