Hey all! My name is Max, and I live in Thunder Bay, Ontario, Canada. I am new to the site (never posted anything before), but have been reading lots over the past year or so. I bought a 03 tracker ZR-2 (auto) last April after falling in love with my buddies (a.k.a. bush buster) 01 lifted Vit, and want to do something similar. However, a lift seems to be on the back burner now as I have run into some mechanical issues, and was hoping someone here could shed some light on the situation...   

So, here's what I know so far.  At low speeds (but only in gear) the truck emits this tin like rattling noise,   similar to a loose heat shield (but its not) during acceleration and deceleration, and also I experience a hum/ vibration between 94-98km/h. Thinking the hum was a warped rim or faulty tire (rear passenger side had a whole bunch of tire weights on it), I switched it out for the full size spare. Didn't help. So last week I took it into a shop for some professional diagnosis, and after about 6 hours of tinkering, they were able tell me that both noises were coming from the rear diff. Unfortunately though, they were unable to tell me what specifically is wrong with the diff. They said it could be just a barring, or third member, or the whole thing could be pooched. Without ripping the whole thing apart, they just couldn't pinpoint the issue. SO.... my question to you is.... has anyone else here had a similar problem? And if so... what was the issues? I'm just hoping to get some insight before I am forced to do something drastic lol. Thank you all for your time (and possible guidance), CHEERS!
- Max

Id be willing to bet its a rear axle bearing. Ive done a couple of them. Put it on jackstands and put it in gear. take a long screwdriver and put the handle end up to your ear and the other at the end of the axle tube. The vibration will be pronounced through the screwdriver and you will be able to tell which side it is.

Thanks Mikerpm4x4. Thats an awesome tip, I greatly appreciate your input!!!!

X2 on the axle bearing.  If the diff fluid has been changed a couple of times since it was new the chances of the diff being bad is remote.  The axle bearings sit just inside the rear hubs and they are an open bearing design, not sealed.  The axle seal sits immediately inside the axle bearing/s so any lube the axle bearing gets came from the factory.   

Hey MAX im from thunderbay ontario too. My name is Jesse give me a text or call at 807-251-6217. Maybe i can take a look at it. I have a 00 chevy tracker with a 3 inch body and 2.5inch suspension lift. ALso having diff problems but changing out my front and rear diffs this weekend and putting in the old sidekick diffs with lower gears.