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RE: Gear Box or Diff?

To: <RJSmalling@aol.com>, <6pack@autox.team.net>
Subject: RE: Gear Box or Diff?
From: "Navarrette, Vance" <vance.navarrette@intel.com>
Date: Tue, 5 Jul 2005 09:26:50 -0700
        Rich:

        As always, diagnosing issues via e-mail is problematic. I can
offer some suggestions, and things
to check...

        Since the problem occurs in any forward gear, it is unlikely to
be the gearbox particularly since it is shifting smoothly, not jumping
out of gear, etc. But let me ask this question: Does the pitch of the
grinding noise follow the car speed or the engine speed? That is, in
second gear at 20 MPH is the grinding the same pitch as it is at 20 MPH
in third gear? If the pitch is the same, the primary suspect is between
the drive shaft and rear wheels. While it is still possible that the
gearbox is the culprit, I would suggest moving it down the list of
possible culprits for now.
        If the pitch is different depending on which gear is engaged,
the suspect is the gearbox.

        Assuming that it is in the driveline or rear axle, a good first
guess is a u-joint. This will give the thumping you describe, and means
that it is on the verge of failure. I am mystified by the fact that it
only happens under deceleration, but anything is possible I suppose.
        Jack up one rear wheel, and put the tranny in neutral. Rotate
the wheel by hand in both directions. As much as possible, keep your
hands on the wheel while rotating the tire several turns in each
direction. Feel any grinding or "thumps"? Let down that wheel and repeat
on the other side. Feel any grinding or thumps?
        YES - I feel grinding on one wheel but not the other - suspect u
joints on the side the that grinds.
        YES - I feel grinding on both sides - suspect u joints on drive
line or perhaps the differential.
        No - I feel no grinding or thumps - Send Email to Vance thanking
him for his worthless advice.

        Some other random thoughts: Have you checked your diff fluid?
Does it have any swarf or metal lumps? Yes - Kiss your diff goodbye. Is
it at the correct level? No - top off and take car for test drive (not
likely to solve problem, but worth a shot).

        Cheers,

        Vance

-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of RJSmalling@aol.com
Sent: July 04, 2005 9:38 AM
To: 6pack@autox.team.net
Subject: Gear Box or Diff?

Dear 6-pack Listers,
 
I am getting a serious grinding noise and random thump from the
drivetrain  
when I come off the accelerator in any gear. Under cruise or
acceleration the 
car is smooth and you would not know anything is  wrong. Push in the
clutch 
and it goes away.  I thought is was coming  from the rear passenger hub
which 
had alot of play in it so I replaced that HUB  along with all 4 half
shaft u 
joints. Still grinding.  So now I need to  figure out if the problem is
in the 
Diff or the gear box or somewhere  else.  Diff was professionally
rebuilt about 
15,000 miles ago. Gear  box shifts smoothly in all 4 gears and reverse.
Any 
thoughts on where  the problem lies?
 
Thanks,
 
Rich Smalling
Sterling, Virginia
75 TR6 Carmine Red
CF35479U




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