Rear End Noise

[DMacRacer]

I bought my 95 GT about a month ago and now it has a whining noise in fourth and fifth gears at any speed above fifty and stops when I push in on the clutch or let off of the accelerator. The previous owner said there was a gear change but not sure how long ago it was. Anyone have any idea what the noise may be?

 

[Bosko5.0]

I am 98% sure its the gears, try changing the gear fluid + friction modifier

 

[BlownFiveLiter]

Whining from rear gears is usually indicitive of the backlash being set incorrectly. Having the gears changed in the past makes me point in that direction.

 

[94gts]

my car does that too sometimes. its been fine for 10k and i beat the crap out of it so i says its ok!!!!!

 

[True 5.0]

Sounds to me like either your backlash is set wrong or your pinion bearings may be shot. You can check the pinion bearings by raising the rear end off the ground and rotating the tires back-and-forth. If you see the pinion yoke moving in and out, your bearings are no good.

 

[DMacRacer]

Thanks I'll give that a shot and let you know how it works.

 

[91notchbk]

It sounds like the ring and pinion is not properly meshed. It may have not been se-up right when the ring and pinion were installed. Does the noise change pitch when you let off the gas or accelerate? If this is the case then this indicates the ring and pinion are improperly meshed. The shimming of the pinion gear (pinion depth) and the shimming of the carrier(backlash) will determine where the two gears mesh together. After installing a new ring and pinion this can be checked with gear marking compound. I would think that the bearings are ok because if it were the differential side bearings or the pinion bearings were bad then the noise would be evident all the time. You probably need a new gear-set to be properly installed.:SNSign:

 

[streetrcr50]

thats definitely a pinion bearing, if it were the carrier bearings the noise would be there only when you are coasting same as with the axle bearings, that pinion bearing will make noise when its under load

 

[91notchbk]

thats definitely a pinion bearing, if it were the carrier bearings the noise would be there only when you are coasting same as with the axle bearings, that pinion bearing will make noise when its under load

After setting up hundreds of ring and pinions and conducting testing on hundreds of prototype differentials I have diagnosed many many rear end noise issues and I have gained a pretty good understanding of what noises different components will make. Ring and pinion (gear noise) will usually change pitch from drive to coast. In some cases it will only make noise during acceleration. Some times only make noise when decelerating. Sometimes during acceleration and deceleration. It really depends on were the gears are meshing. This is usually due to an improperly set-up ring and pinion or worn ourt gears. Bearings that are worn make almost a growling sound. Carrier bearings and pinion bearings that are noisy sound almost the same.The noise is evident at all times during accelaeration and decelareation. I usually can tell the difference between a carrier bearing and a pinion bearing by the noise. Differential bearing are in sync with the wheels and tires so the noise has the speed similar to tire speed. Axle bearings are similar to differential bearing but the sound is not coming from the carrier, it comes from the wheel area. Pinion bearings (depending on gear ratio) are rotating at least three times faster than the carrier bearings and the speed is much faster. In order to diagnose these noises it takes time and a trained ear.:SNSign:

 

[blazrrr]

Here is a noise for you...when I am taking a sweeping right turn and I get off the gas and start coasting, there is a loud high pitched whine. Is that a carrier bearing? This sounds does not occur when taking a left.