HEY GUYS - HELP ME OUT HERE!!! 8.25" VS 7.25" DIFFERENTIAL

From: Ginny P. Hartwig (dghartwig@juno.com)
Date: Thu May 03 2001 - 01:34:30 EDT


My 1991 Dakota V-6 with A500 transmission
has a rear axle assembly which is now whining
and howling loudly after 72,000 miles.

I don't know if it's related, but my RWAL brake
speed sensor exciter ring now has a tooth broken
off. An inspection failed to indicate ANY interference
with the ring to cause breakage.

HASN'T ANYONE HAD SIMILAR PROBLEMS?

Rather than repair my existing differential with 7.25 inch
ring gear (with hexagonal cover), I've been advised to
replace the rear axle with an 8.25 inch differential (with
round cover). I was told that the smaller differential
was prone to failure and the larger differential has
much greater reliability. One junk yard advisor said
the 7.25" differential was designed for mid-size
passenger cars. Both are 3.5:1.
 
Have any of you had failures with your 7.25" units?.
Dealers say "No difference" in failure rates for both
differentials, but wrecking yards say they can't stock them
as they are gone as soon as they arrive. Have not located
a used 7.25" unit.

If I do a swap, what problems will be encountered?

Springs are the same, but mounting location is
different on 1992 - 1996 rear ends. (Spring brackets
mount the springs further outboard.) Hollander lists only
the 1991 - 8.25" unit as a direct swap. The 1992 -1996
rearends are similar and require unknown modifications to
fit my 1991. Although I do not have access to any specs,
it appears that '92 through '96 rearends with the 8.25"
differential are about one inch wider. Driveshaft modifications
will be required.

Since the 8.25" unit's exciter ring has more teeth
(104 versus 102) will the RWAL computer require
modification?

Because there are few 1991 8.25" rearends available,
the '92 - '96 units are preferred. A fellow DML member has
offered a rebuilt 8.25" unit at an attractive price. But, how
difficult will the swap be? Or, is the 7.25" unit not as bad
as some have said?

Any advice?

Thanks.

Don Hartwig
Atlanta, GA



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