Charles Corliss wrote:
>> Also sometimes a clunk is heard from the rear end when
>> going around a sharp turn. New U joints have been
>> installed. Does anyone have
>> any ideas, on this problem?
Scott Paisley wrote:
> the mention of the "clunk" makes me feel like you might have
> the dreaded broken diff mount. The diff mount can break over
> years of stress and they aren't too beefy in the first place.
Scotty is right, the "clunk" could very well be a broken
diff mount. If this is the case, you will probably
hear the noise when you suddenly apply power to the
drivetrain (like if you accidentally "drop" the clutch).
This is a definite "clunk" noise, although it can cause
squeaks, too, as Scott mentions. Fixing it properly
is not easy. I just went through this on my '74 TR6.
The mount that breaks first is the front right (passenger)
mount. Due to the diff geometry, this one mount, made
of only relatively thin metal, takes the brunt of the
torque applied to the diff by the driveshaft.
> Anyway, it would be worth checking. You should be able
> to see the mount by looking up there with a flashlight.
> It will be difficult to check without dropping the diff
> though. (ugg)
To check this, get the car well up on jackstands, and make
sure it is rock solid there. Have the car turned off,
in 1st gear, with the parking brake off. Get under the
car, and shine a light up at the diff mounts. Examine
the mount brackets on the frame carefully for visible
cracks. Feel the top side of the mount brackets carefully.
If there is a crack there, you may be able to feel it, even
if you can't see it -- your fingertips are quite sensitive,
even with the years of grunge that will be up there. (I hope
you don't mind getting your hands dirty! :-))
If all seems ok, have an assistant abruptly turn one of
the rear wheels while you are laying on your back, under
the car, looking up at the diff. Keep your hands clear
from the axles and driveshaft while this is done. The
intent of the helper is to suddenly start (jolt) the wheel
to turn, and then stop it equally abruptly. The helper
shouldn't let go of the wheel, but should grab it firmly
with both hands, suddenly turn it about a quarter turn
as abruptly as they can, and stop it equally abruptly.
The intent here is to apply a jolt to the drivetrain.
(Don't worry about hurting it -- a person "jolting" the
wheel as hard as they possibly can won't apply a jolt even
half as severe as even a smooth start in first gear.)
When this is done, the other rear wheel will spin in the
opposite direction (since the tranny is in gear). There
will also be a sudden rotational jolt to the diff when the
wheel is started and stopped. There should be only very
little movement of the diff on its mounts. If there is
significant movement, you definitely should replace the
diff mounts ASAP, and may find a cracked mount bracket
(probably the front right mount). A cracked mount can
be fixed by a competent welder by welding a re-inforcing
plate at the top section of the mount bracket, another
at the bottom section of the mount bracket, and by boxing
the mount bracket in on both sides. I recently had this
done on my '74 TR6, and am happy with the results.
--ken
'70 & 74 TR6 Daily Drivers
--
Kenneth B. Streeter | EMAIL: streeter@sanders.com
Sanders, PTP2-A001 |
PO Box 868 | Voice: (603) 885-9604
Nashua, NH 03061 | Fax: (603) 885-0631
|