I have been getting a humming noise while driving 40-70 mph and only while hitting gas. Being still under warranty I brought it to the dealer who tells me "found rear pinion noisy--vehicle is lifted & thrust angle in incorrect causing uneven were pattern to rear diff pinion". I am not a mechanic and need help understanding what is going on here. I have a 2 door with 4 inch teraflex lift and 5.13 Yukon's.

 

Do you have adj rear control arms to correct pinion angle in the rear?

 

No, I haven't gotten any new control arms yet. Does it sound like I am doing damage to my new gears possibly?

 

The gears were put in about 5 months ago.

 

Many people run 4" lifts and never NEED adj control arms in rear.

I have not upgraded my gears yet, so I do not know as much as some regarding them. Hopefully WOL or someone with more knowledge in gears will answer soon.

 

if you have replaced gears , sounds like they werent set up correctly pinion depth could be off or dealer could be right. if youve lifted it 4 inches its possible you do have pinion angle problems if you did not correct it . bottom line is dealer aint gonna cover it

 

Yeah I figured the dealer wouldn't cover it but I still had to try. Now I need to figure out who to take it to next. Maybe the place that did the gears? I had a lot of trouble with the place that did the lift, I was supposed to get a 3 inch lift and they put on a 4 inch. I expressed my concerns with lifting it that much but they assured me I would be fine.

 

Ok, I brought the jeep to a shop who specifically works on moded jeeps he tells me the sound is coming from the ring and pinion. He said might be not shimmed right or might have to replace the whole thing. So then I bring it to the guy who did the gears he said its no big deal they just make noise sometimes. Im pretty sure he just doesn't want to fix it. What do you guys think?

 

First thrust angle has no affect on ring and pinion wear. Thrust angle is the angle of the axle perpendicular to the body. So if you were to look at the Jeep from the top down to measure the angle at which the axle is to the body that is thrust angle. Obviously the axle sits perpendicular to the body, so 90 degrees is what you want. When one side of the axle is farther forward or back than the other side, that is when the thrust angle is off. As far as pinion angle goes, I wouldn't think that it would have an affect on ring and pinion wear. Pinion angle should have an affect on driveline vibrations and wear. The guy that installed your gears that said sometimes they just make noise, he is wrong. If your gears start making noise it is because they were not set up right, they are broken, or are worn out. The punch line is if your gears are making noise, it is because soemthing is wrong. If I had to guess I would say that the guy that set up your gears did something wrong. If gears just randomly made noise then your stock gears should have just randomly made noise.

 

The problem I have now is even if the people who did the gears originally offered to fix it for free I don't really want them doing it because they don't know what there doing. So I'm probably going to take it to the other shop I was at and pay them.