schirm

Last Tuesday I had USA standard gear 4.88s professionally installed. On the trip home from the shop I noticed, what I thought was driveline vibs. I figured the lower gears just exacerbated it. So I put some pinion shims under the leaf springs and no improvement at all. On the test drive after installing shims I was accelerating onto the highway and I started hearing a rhythmic, pulsing hum with bad vibrations coming from my rear! So I let off the gas to pull over and then it sounded like very loud growling hum upon deceleration. So my plan is to get a hold of the shop that did my gears on Monday but until then I gonna try to rule out my driveline/u-joints as the source of my problem by pulling the driveshaft and seeing if the diff still makes noise etc... Although I don't see how that could be the problem but you never know. The rhythmic pulsing vibes has me concerned about the pinion gear. Sound reasonable?

My question is, has anybody on here ever experienced these symptoms? What ended up being wrong?

I have a 2000 xj, 5.5" RE x duty long arm, 35/13.50 Toyos, SYE and double Cardin CV drive shaft, RC shackle relocation kit.

schirm

I can't edit the title, it should say; Anybody have their rear end go out on them 4 days after new gears installed?

hankthetank

uh oh. did you get it to the shop? all hypoid gears growl/hum/grind/whine when not set up properly. hope they get it fixed fast for ya.

schirm

Not yet but I will Monday. I'm pretty sure the pinion race wasn't seated properly and then 4 days of torque put it in place which created pinion slop. Gonna have it to back to the guy and fixed on his dime or I'm gonna be pissed!!!

schirm

Update: The diff specialist is claiming that I had pinion bearing failure because of pinion degree shims starving the pinion bearing of gear oil. He said chrysler 8.25s can't run degree shims. I call BS! Has anybody on here run into that problem?

Dan91

Tons of people run shims on these axles. Also, if you were having the problem before even adding the shims didn't you mention that?

schirm

Yup, and that's exactly what I told the guy. Thank you, I was just making sure I'm not crazy.

N20jeep

that is bull****. i have a number of 8.25's i have regeared out there with degree shims.

no failures.

OleBlue

Lol, that guy is full of ****. The screwed up your gears. It does sound like the pinion bearing.

Did he tell you about the break in period? If not, its something like 20 miles at low-moderate speed. Change gear oil. 100 miles normal driving, change gear oil. 500 miles normal driving change again.

jebmccall

that is bs about the shims, im running 6.5 lift and 4 degree shims on my 8.25 just geared to 4.56s 3 months ago no issues...... i need to reduce my shims though....

schirm

Yeah, I was abiding by the break in that USA standard gear recommends; 15-20 miles "driving without heavy acceleration", let cool, repeat until 100 miles is reached, no towing until 500 miles etc... I only got to 70 miles. I pick the jeep up tomorrow and he claims to have fixed it. I just think he's having a hard time admitting that he screwed up. Or it could have just been a faulty bearing to begin with? USA Standard dose not use Timken bearings in their master install kits. But either way ill find out tomorrow if its really fixed or not. I have heard of people claiming that shims can affect oil supply to pinions but not to such a degree that they cause near immediate failure. The shim, no shim debate is about long term bearing wear. Not, "Will screw your sh** up in 4 days of driving." Hell there's a lot of hills here in Idaho that are far greater then 6 degrees in grade, and go on for miles. So just by driving up hill I'd be starving my pinion of oil if that guy is right! Total BS. Thanx for the input guys

ohio95xj

i'm not saying that they didn't mess up your gears, but you said you were getting on the highway, which is definately not following the break in "rules"

schirm

Really? I have the break in instructions in my hand right now. They don't say you can't go on the highway. Just says, "avoid heavy acceleration for the first 100 miles". People can drive on the highway without heavy acceleration

schirm

Also, I didn't specify that I only made it 3/4 of 1 mile on flat ground after putting the shims in. I was speaking hypothetically when I mentioned long hills in Idaho

hankthetank

pinion bearings are tapered rollers. cup and cone. they are matched sets when you buy them. each cup is ground for its own cone, you can't swap cups and cones. they require a very specific torque to seat them together properly. too little torque can ruin them, as well as too much torque. i would say they were not torqued correctly or mismatched...which can only happen at install. free fix. good luck.