[prodrifterx]

ok im working on my car tonight....99 gt 5spd. have a possible bearing noise in the rear unless one may think its a pilot bearing.

noise doesnot dissipate with clutch in...
believe ti to be from the rear....
will chk it out tonite.....
wonder if its commmon for say pinion bearings or such to go out?
wonder if its caused by the need for fresh fluid and friction modifier.....i say this bc some vettes during a year range had such an issue and a revised fluid with better friction prtection eliminated the noise.

again rep for all insightful help that i can get.

[snoel123]

Hello. Here is the essentials to N-V-H (noise/vibration/harshness). The first thing you want to do is categorize. Is it a vibration, noise or harshness. Some are all three. It sounds like you have isolated it to a noise and possibly in the rear end. Drive the vehicle down the highway and listen for noise, pinion bearing noise is most likely to occur at 30-70 mph and will be loudest on light accel or decel. It is often described to me by customers as a howling or whirring sound. One way to be sure it is driveline is to push in the clutch at the speed it occurs. This takes the load off of your driveline and if anything from the pinion to your flywheel is making noise the pitch WILL change. So since pushing the clutch does not change the noise as you say, It would be safe to rule out trans , release bearing and pinion bearings. The next thing you can do is drive up to the speed where the noise is most evident and swerve side to side. If the pitch changes you are looking at wheel/axle bearings or differential side bearings as this changes the axial loads on these bearings. If it still does not change try driving on different road surfaces (ie dirt, gravel sand) and if the noise dissapears suspect cupping. If it is still evident and you might want to do this to start with put your car up on jackstands or a hoist and use the rear brakes to simulate load attempt to re-create noise. You should be able to isolate noise and then decide on further action. A 99 mustang came with 3 different rear axles depending on model. A 7.5 solid, 8.8 solid and a 8.8 with IFS. If you isolate the noise and need any information feel free to message or e-mail me. Hope this helps.

[prodrifterx]

i have a solid 8.8....stock rear end....stock driveline......nonetheless it hasnt done it much at all lately. any common issues anyone know of? i work on general motors&daimlyer-chrysler all day....i'm good with issues on those lol...it was louder to a degree on rpm id say...speed wasnt too much of an issue....yet when i let the load and all off of the rear it still existed..yet not so terribly..im used to depicting/diagnosing hub issues and noises and it doesnt sound much like the growl or low pitch noises im used too....its of a higher pitch.....

will get back into diag on it and let u know some more info once i get to work on it and drive it again...been in the body shop.


im pretty sure its gear noise and not so much a bearing....well like i said thanks and i will keep an update going.

[snoel123]

Just a thought but gear noise typically only is louder on one side of the gearset. By which I mean if you have a loud noise on the coast side (deceling) you typically don't have a loud noise on the drive side (accel). One way to be sure is to do a pattern. If you decide to do a pattern check clean the gears with brakeclean then apply yellow spray paint to the crown gear while rotating the differential all the way around. Wait a little bit for the paint to become tacky and then spin the diff both ways while applying a load to the crown gear (i use a brass punch and pry gently between the housing and diff case. Make sure to turn it all the way around both ways to get a good pattern on coast and drive side. Then inspect you're pattern, if it goes from good to bad to good suspect ring gear runout. If it is questionable in all places, you need to play with shims. Hope this helps. Thanks

[prodrifterx]

Originally Posted by snoel123 Just a thought but gear noise typically only is louder on one side of the gearset. By which I mean if you have a loud noise on the coast side (deceling) you typically don't have a loud noise on the drive side (accel). One way to be sure is to do a pattern. If you decide to do a pattern check clean the gears with brakeclean then apply yellow spray paint to the crown gear while rotating the differential all the way around. Wait a little bit for the paint to become tacky and then spin the diff both ways while applying a load to the crown gear (i use a brass punch and pry gently between the housing and diff case. Make sure to turn it all the way around both ways to get a good pattern on coast and drive side. Then inspect you're pattern, if it goes from good to bad to good suspect ring gear runout. If it is questionable in all places, you need to play with shims. Hope this helps. Thanks

good idea....i was taught to do that whendoing new gears and all but havent done an install in a while so i forgot about that.....thanks. gonna have to find some yellow paste (what ive always used).