rear end noise

[charvel5150]

i have a 92 gt 5 speed somone has changed the rear gears but i dont know what kind or ratio. heres my problem when im driving and the rpms get between 1600 to 2000 i hear a noise from the rear end of the car if im on the gas it doesnt do it or if im off the gas but if im just cruzing it does it. here is the best way to describe it so bare with me it goes rrrrrrrrrrrrRRRRRRRRrrrrrrrrrrRRRRRRrrrrrrrRRRRRR the sound gets quieter and louder in and out and i can kinda feel it in the floor of the car.Other than that it is just fine i can lay into it and no problems it will burn out like crazy and go like a bat outta hell. Anyone know what i should check for? And how do i find out what gear ratio is in it? Thanks for any help guys

 

[Michael Yount]

To find out the gear ratio is easy. Jack up the back of the car (rear end on jack stands. With the tranny in neutral, you're gonna rotate the tire and count the number of times the driveshaft rotates for one rotation of the tire. Put a piece of tape on the shaft to get an accurate count. For one rotation of the tire -- 2 3/4 rotations of the shaft is a 2.73 rear; a little over 3 turns of the shaft is a 3.08; 3 1/4 turns is a 3.27; 3 1/2 turns is a 3.55; 3 3/4 turns is a 3.73; a little over 4 turns is a 4.10.

As for the noise when unloaded it could be lots of things. First thing I'd check is the condition of the u-joints. When they're shot they can make noise and vibrate in an unloaded state. If the joints are ok - then it's probably time to pull the rear cover and take a look inside. I'd measure the backlash (slack between ring and pinion). If it's out of spec, either the person who set the rear end up didn't know what they were doing, or things (Likely bearings) are beginning to wear back there. If you don't understand any of that -- best to take it to someone that does. Setting up a rear end properly is a bit of tricky business and requires some special tools.

 

[Michael Yount]

By the way - until you get it fixed, the 'bat outta hell burnouts' are probably not doing your rearend or ujoints any good.

 

[Notched90]

You got bigger tires on there??? My car started makin a grinding noise from the rear end when cruising and i assumed the worst....put it up on a lift at work....all it was was my r/r tire (295/50/15) rubbing the exhaust. Make sure nothing obvious is rubbing before you freak out like I did

 

[charvel5150]

well thanks for your help guys i changed u joints checked fluid looked for anything rubbing and all that is ok and i still get that grinding noise so looks like i will have to take it in because i have never set up a rear end. i hope nothing is bad in there hopefully its just a issue with the backlash. and i hope its not too expensive to fix.

 

[tarheel13]

Probably a bad axle bearing. If it is that and you continue to drive it, It will mess up the axle. Also, check the wheel bearings as well. That could also be it. I had to replace axles and bearings on both of my stangs. One this week. Good luck and have fun!!