M998 Differential work.

[Dave2018]

Howdy guys,
Working on my m998. I replaced all new drive shafts, ball joints, prop shafts, shocks, idler and pittman, stabilizer bushings, ect. Heard a loud ping twice coming from rear end?. On flat grass driving. Took home and put on blocks. Just guessing its the diff as it sounded closer to rear of truck. The problem is that all but 2 of the diff cover bolts come out all the way. 2 bolts back out but hit the caliper housing for the left rear brake. Its cast and not broken. Don't see any damage. Hate to have to pull extra stuff just to see inside the diff. Any help or suggestions are appreciated.

 

[Hell On Wheels]

I'm a bit confused on what bolts your talking about. Are you talking about the 5 half shaft bolts? or the diff cover plate? Try removing the drive input shaft and two out put shaft's to free turn the diff to hear any grinding.

 

[Action]

If the sound is consistent and predictable, you could raise one rear tire and chock a couple others. Put in H and D and let off the brake. Leave someone in the driver seat, just in case the jack fails. Only the tire in the air will turn (with proper working components). Stay out of path of tires and see if you can pinpoint where the sound comes from.
DON'T HIT THE BRAKE PEDAL WITH A SPINNING TIRE IN THE AIR. Just shift transmission into N and let it slow down on its own.
The tire won't spin real fast, but there will be no load on the drivetrain.

Why were so many driveline components replaced at the same time?

 

[AAVP7]

@Dave2018: Early Humvees had brake caliper brackets which indeed blocked some of the diff cover bolts. Later Humvee have modified brake caliper brackets with a cutout to allow all diff cover bolts to come out.

So for a look inside your diff you will have to take off the brake calipers and remove those brackets. Not as bad as it sounds. Since the brake lines are a bit flexible, you can strap the calipers to the frame with some strong cable ties. When you are at it, I´d recommend to install the newer brackets with the cutout. They are different front/rear and left/right, so make sure you get the correct ones.

 

[Dave2018]

@Dave2018: Early Humvees had brake caliper brackets which indeed blocked some of the diff cover bolts. Later Humvee have modified brake caliper brackets with a cutout to allow all diff cover bolts to come out.

So for a look inside your diff you will have to take off the brake calipers and remove those brackets. Not as bad as it sounds. Since the brake lines are a bit flexible, you can strap the calipers to the frame with some strong cable ties. When you are at it, I´d recommend to install the newer brackets with the cutout. They are different front/rear and left/right, so make sure you get the correct ones.

Thanks for the reply. Good information. Will grind a little iron away.
Dave

 

[Hell On Wheels]

if it turns out you need a diff I have a used take 2.56 really cheap and I'm in texas to hand it over.