I had always heard that the differential was the weak link in the GT-6 drive
line. The diff that came with the car when I purchased it 10 years ago lasted 8
years. I then purchased a used diff and all new bearings & seals and had an
experienced gear man reassemble (he does mainly trans and diff buildups for the
regional ASA and ARCA stock car boys and the same for the local drag racers) .
THis second diff lasted until this past Friday (only about 10,000 miles - no
warning, only a big bang followed by a rumble). Now I am trying to decide
whether to buy a replacement ring and pinion set and again have the diff rebuilt
or replace the diff with something stronger ( I am running: a 2.5L, Webbers,
mild street cam, 9.3:1 comp, headers, OD trans with 3.27:1 diff ratio. My seat
pants dyno estimates it near 100 hp net). Would a lower diff ratio be
advantageous for longer life? I like my current set up where I can run past 50
mph in 2nd gear and also be able to cruise with low engine revs. My
understanding is that the TR-7 diff 3rd member will swap into the Spit/GT-6 diff
housing - is it any stronger or only a gear ratio difference from the GT-6?
THis winter's project was to replace the rotoflex couplings with custom
driveaxles with CV joints. Obviously I need to resolve what diff I am mounting
the axles to prior to starting to fabricate them. Now to carry this thought
further - if I am already replacing the diff, what about the rest of the
driveline? With the interest in the NZ Toyota 5 spd trans conversion, why stop
there? WHy not replace the heavy, low powered engine also. I have been
following the RO-Spit project in GrassRoots Motorsports Mag the past 2 years and
though I am not that geeked about a rotary engine what about an all rice burner
driveline from say the old (Celica) Supera. I have not looked under the hood of
such a car to find out if the engine will even fit under the bonnet but I have
to assume that it must be a bit lighter than a tractor engine.
After owning (and selling) my first LBC, a '78 Spit, I intended to buy another
Spit with a bad engine and replace the entire drive line similar to what Barry
Schwartz has done. Instead I found a good deal on a GT-6, got a great deal on a
set of triple webbers and an OD trans and bought a Spit body. I like the
current vehicle package but I am tired of having to tell my wife what is broken
(now).
If I replace only the diff - what diff donor vehicles has anyone heard of being
used? And a follow up question - how much of the frame has to be modified for
clearance to fit a larger/stronger diff? Comments / suggestions please.
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