Re: LONG: Help diagnose rear diff noise - 1997 Cobra
Thanks for the replies. I think its pretty much impossible to figure
out whether its pinion or carrier, so I am going to replace the whole
schmeer to be sure.
1) Does a new pinion bearing require a new race? I have always assumed
they get installed in pairs.
2) If I get a new pinion bearing, do I need to reset/check pinion depth?
3) (as above) Do new carrier bearing require new races, and if so, do I
need to confirm/set backlash with the new bearings/races?
I am all set to replace the outer bearings. While I own a mag base
stand and a decent quality dial indicator, I think that the pinion and
carrier bearings are beyond my current abilities. Besides, this might be
a great time to go to a 4:11 gearset. :)
Ashton Crusher wrote:
> On Sun, 24 Jul 2005 01:20:25 GMT, "firstname.lastname@example.org" <email@example.com>
>> 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)
> My guess is carrier bearings.
>> Can I use a torque wrench to see how much resistance the rear gear set
>> 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
>> TIA for your responses.
>>P.S. I am also posting this in the SVT Tech Stangnet Forum.