hey everyone,
i got a noise coming from the rear of my xj and i cant figure it out. it only makes the sound when you get on the gas above say 30-40mph. the harder you press the gas the louder it gets. take your foot off, and no more sound. it sounds like a high pitched humming of some kind. any input is welcomed! thanks!

 

It could be a number of things. Look at your exhuast first though. Make sure its not rubbing on anything!

 

I agree^^, then grab driveshaft see if moves up down side to side

 

U joints, exhaust, tailgate seal, and I dont want to suggest it, but maybe fuel pump. But don't jump right to the fuel pump, prolly isn't the case.

 

thanks guys! i really dont wanna admit it, but i do think it is the fuel pump.. pretty much can control the sound with your foot on the gas pedal.

 

the fuel pump has nothing to do with accelerator pedal, it runs at a constant speed/load, the exhaust,or ujoints will be affected by load i.e giving/reducing throttle input. also check for leaks and the level of the gear oil in the diff

 

ive embarassed myself for the day lol.. thanks everyone!

 

Sounds like you're heading for a differential overhaul to eliminate the noise. If you can put up with the noise, service the differential. Noisy differentials often remain serviceable for years.

If the noise bugs you, have a knowledgeable technician listen to your vehicle and give you options.

If you have a Dana 35 without ABS, it may be a good time to upgrade.