Jeep: Grand Cherokee 2 Lift, differential problems, pinion bearings

Question
Chris, I recently did a 2" lift on my 2003 Grand Cherokee Limited. It was done in Australia and was an ARB kit. 4 shockers and four coil springs. Since then I am exsperiencing noise from the front especially when I am free running. Is that exspected or what can be done to reduce the noise. Will it have an negative affect on my transmission or front diff. Thanks

Answer
Hi Dieter,

I'm a dealership guy, so most lifted Jeeps stayed far away! That said... what do you mean by free running? I assume it to be coasting or off-the-brake deceleration, which commonly causes noise issues in front differential/propeller shafts. The ARB is a good setup, but depending on the kit, do not account for  some lifted issues.

Diagnosing noises over the net is next to impossible, but I have a few thoughts. Is there *any* vibration associated with this noise? Does the noise oscillate (like a cheeping bird), or is it more of a roaring sound? If it oscillates, is it roughly 3x the speed of a tire rotation? Does it increase in amplitude (get louder) as the suspension goes down or up? These are just a few questions that come to mind. Often, it's best to invite a buddy for a ride, or stand outside while he drives -- two ears are better than one (actually, four better than two!).

Most front end oscillating-type noises are normally due to propshaft angles -- when under acceleration, the line-of-power straightens the torque transfer through to the differential. When you let off the gas, the pinion sags, and this is where most u-joints will complain. Similarly, if it's a roar -- this is where the actual pinion bearings will be the loudest. Even though the propshaft can extend, nothing makes the angles any easier -- unless the front differential is setup for it. In body lifts, this generally isn't an issue, but some suspension lifts greatly aggravate differential problems. Normally, a fresh set of bearings will cool the roar -- but unless altering the diff angle is done, the noise might eventually return.

I could ramble for pages on what it *might* be, but it helps being able to drive it. Then, things like type and speed of noise, when it does it, when it doesn't do it, the speed it does it at, the amount of 'jounce' needed for it to amplify, etc. are almost automatically answered. Perhaps you have a 4-wheel shop around (who installed it, unless it was you!)? Sometimes, those guys can clue you in better -- they'll be able to see it, and know what the common issues are. Other than that, I'd maybe let a pro drive it, like a Jeep tech, who is intimate with those particular vehicles. Nice ones might even let you drive them to lunch (show up at the shop about 11:45!), and give you a free diagnostic for it!

Good luck!