1997 Cobra, 60K miles, bone stock. Rear diff is an 8.8, same at GT for past many, many years.
I have been noticing quite a bit of noise coming from the rear diff on the car. At slow speeds (<15mph), the noise is either not there or is barely noticeable. At higher speeds, it becomes a kinda loud noise, which is constant in pitch and level a a specific speed. The noise does not change pitch, level, or go away when I step on the brakes. I do not have a point of reference for how loud a rear should be in a late model GT/Cobra, so it might be completely normal.
I've had rear diff gear sets installed incorrectly in the past which resulted in 'howl' coming from the rear end. The noise I am hearing is definitely not the same as the 'howl' I have had in the past, its more like a dull grinding noise. Like something is rubbing, or a bad bearing (eg: outer axle bearing).
I took the rear apart today to try and narrow down the problem. With the rear on jackstands, I spun the rear wheels. It seems like I can hear something coming from the rear end while I turn by hand. Its not obvious, and the rear turns smoothly, but does require a moderate amount of effort. Again, I do not have a point of reference for how loud a rear should be, so it might be completely normal.
Figuring that there might be something wrong, and feeling motivated (maybe stupidly), I removed the rear wheels, rear brake calipers, rear caliper mounts and the rear discs. I then turned the rear axles by hand and the noise was the same. I then pulled the driveshaft and turned the axles again and still the same noise. I then pulled the center-section cover, removed the wrist-pin and c-clips and pulled the axles. Neither wrist-pin or c-clips show any signs of abnormal wear (grooves, galling, etc). I then turned the gearset by hand, and while it turns smoothly, it seems to make a moderate amount of noise while turning.
So basically I *think* I've eliminated rear brake noise, U-joint and outer axle bearing as sources of the noise. Now I am down to:
1) Pinion bearing/race
2) Carrier bearing(s)
Can I use a torque wrench to see how much resistance the rear gear set is providing?
I'd like to hear some thoughts on this.
Do 8.8 traction-lok rear make a good deal of noise? I had the rear diff fluid changed at a 'Mr Lube' about a year ago (similar to Jiffy Lube). They use a vacuum to suck the old fluid out and then put new fluid in. Now I know that 8.8 trac-loks need the friction modifier gunk from ford. I know I asked the guy at the Mr Lube if they were going to put the friction modifier in with the new fluid, and I am pretty sure he told me that since they were putting in GL-5* 80-90w I didnt need the friction modifier.
TIA for your responses.
P.S. Also posted to RAMFM and SVT Tech section in stangnet forums.
I have been noticing quite a bit of noise coming from the rear diff on the car. At slow speeds (<15mph), the noise is either not there or is barely noticeable. At higher speeds, it becomes a kinda loud noise, which is constant in pitch and level a a specific speed. The noise does not change pitch, level, or go away when I step on the brakes. I do not have a point of reference for how loud a rear should be in a late model GT/Cobra, so it might be completely normal.
I've had rear diff gear sets installed incorrectly in the past which resulted in 'howl' coming from the rear end. The noise I am hearing is definitely not the same as the 'howl' I have had in the past, its more like a dull grinding noise. Like something is rubbing, or a bad bearing (eg: outer axle bearing).
I took the rear apart today to try and narrow down the problem. With the rear on jackstands, I spun the rear wheels. It seems like I can hear something coming from the rear end while I turn by hand. Its not obvious, and the rear turns smoothly, but does require a moderate amount of effort. Again, I do not have a point of reference for how loud a rear should be, so it might be completely normal.
Figuring that there might be something wrong, and feeling motivated (maybe stupidly), I removed the rear wheels, rear brake calipers, rear caliper mounts and the rear discs. I then turned the rear axles by hand and the noise was the same. I then pulled the driveshaft and turned the axles again and still the same noise. I then pulled the center-section cover, removed the wrist-pin and c-clips and pulled the axles. Neither wrist-pin or c-clips show any signs of abnormal wear (grooves, galling, etc). I then turned the gearset by hand, and while it turns smoothly, it seems to make a moderate amount of noise while turning.
So basically I *think* I've eliminated rear brake noise, U-joint and outer axle bearing as sources of the noise. Now I am down to:
1) Pinion bearing/race
2) Carrier bearing(s)
Can I use a torque wrench to see how much resistance the rear gear set is providing?
I'd like to hear some thoughts on this.
Do 8.8 traction-lok rear make a good deal of noise? I had the rear diff fluid changed at a 'Mr Lube' about a year ago (similar to Jiffy Lube). They use a vacuum to suck the old fluid out and then put new fluid in. Now I know that 8.8 trac-loks need the friction modifier gunk from ford. I know I asked the guy at the Mr Lube if they were going to put the friction modifier in with the new fluid, and I am pretty sure he told me that since they were putting in GL-5* 80-90w I didnt need the friction modifier.
TIA for your responses.
P.S. Also posted to RAMFM and SVT Tech section in stangnet forums.
