The Eaton locker I recomend is for 82 to 92 cars. With a 93 up look for
a Positraction diff from a Camaro or Trans Am. Better yet get a
compleate rear end with 3.42 gears. Beleave me it will wake up your
Charles, I'm looking at a raft of posi units and gear sets on ebay motors.
It's a bit daunting because I've only looked at the rear end gears in my car
by removing the cover. Series 3 posi units seem to be for 3.23 and lower
(higher numerically) gear sets. I'm more than willing to change my gears to
3.42 or 3.73 but I don't know if just buying the gears and the posi unit is
enough. Do I need to purchase a different carrier too or am I still not
understanding how this all works?
I'm pretty certain I should buy a bearing rebuild package too. Driveline.com
has everything I need (new) including tech support but the cost is going to
be $800 or so if I go that way.... I'd like to go with good used parts for
around $200 if possible.
btw, my quite stock Z with 3.23 gears turned 13.98 @ 100 mph. My other Z is
the one with 2.73 gears and a worn out positraction unit. That is the one I
want to fix, gear down and maybe see a little better time and speed.
Thanks for replying: I've got a better understanding of the teminology now.
The gears bolt to the carrier (actually differential which is the posi /
locker / open case unit; that robust little drum with the side windows and
28 splines inside the pumpkin, where axles slide into and the spiders gears
reside). The late model Camaro GM 2 series carrier spacing was originally
designed for 2.73 - 3.08. However, there are lower gear sets out there that
will fit series 2 carriers. At least that's what the summit racing catalogue
is showing me. Two ** are series 3 and one * fits series 2. Both 3.42 and
3.73 gear sets show part numbers for series 2 (one asterisk) and another
part number for series 3 (two asterisks). I will call Summit to verify
My guess is the spacing between carrier and mounting surface of the ring
gear at some point must be increased for a series 3 gear set (3.23 - 3.78
and maybe 4.11 - 4.56) to fit a series 2 carrier. In other words, the series
3 carrier is wider than the series 2 carrier. The ring gear must be shifted
away (left) from the series 2 carrier or the ring will interfer with the
pinion rather than mating to it.
On the faq page of www.driveline.com the question is asked by a customer
that when he bought the 4.11 gears to go in his 2.73 Camaro rear end, they
would not fit. Driveline.com said they have a spacer to fix the problem.
This tells me that the 3.23 and lower ration gears have an interference
width to the pinion when mounted on a series 2 carrier. BTW, I've also
learned that the only difference between the 3.42, 3.73 and 4.11 gear sets
is the number of teeth on the pinion. which are 12, 11 and 10 respectively.
That makes the spacer / series requirement make even more sense seeing how
the ring gear will always be 41 teeth @ 7.5 or 7.625 inches in diameter.
Also, http://www.keliente.com/gears.htm illustrates the tear down and
rebuild of 93 firebird rear end. This helped me understand two things: How
the rear end construction works and that rebuilding a rear end can be done
by a novice but it will be a pia until s/he has all the necessary punches,
pullers and real life experience.
Thanks Charles and I would do this. I don't know if it's me or the area
where I live but I have called 11 salvage yards and the answer is always
that they don't have anything like that at this time. I'm assuming you mean
to change the entire axle housing. This of course presents another situation
for me as I would be out of my league trying to determine widths and
mounting points for suspension components, brakes and such.
See my post to Bruce regarding the gear set cross over. I'm in no way
pretending like I know anything but I sure have been asking questions. Two
of three mechanics have warned me about putting used gears in another
housing. One explanation was that used gears and bearings wear into their
role according to the housing they are within. Swapping them around is
certain to produce a lifetime gear and/or bearing whine and potential early
failure. The jury is still out as I'm listening for more advice.
I was suggesting replacing the entire housing with a direct bolt in
unit. Where you would un-bolt, un-clip, and remove a few lines and
reverse proceedure to install. Your rear end should be 1994 (due to abs)
to 1998 direct swap from a 6 Speed car (Camaro Z28-T/A) with
Posi/Locking Rear Diff. All 6 speed cars were 3.42 geared from the factory.
As for Used gear sets being swapped in to a different axle housing, I
have done it. It may not be the best thing, but I get away with it. I
perfer to just swap the diff, but in some cases it's not possible.
Depending on the vehical I really perfer to replace the hole axle
housing. Often less time, and less to go wrong.
I understand now and thanks. I just need a better resource for junked or
wrecked cars. I think my hurdle is that the performance stuff either never
makes it to salvage or it is scooped up in a hurry. Anything online like
that is always a thousand miles away. I think Summit Racing is going to get
about $350 of my money for bearings and gears. I have a used differential on
its way now. Wish there was a cheaper / easier way through this. What will
happen is after I spend the money for parts, a local salvaged car will
What's wrong with yours? Can it be rebuilt?
IMHO, even if it fits, a Blazer diff is a step down - it sure likely
wouldn't be stronger. A Blazer has a 4.3 with about 190hp... and your z
had 275 hp...
The guts (carrier?) may interchange, but the housing is definitely
different... unless you've got the world's only leaf sprung 95 Z28. ;)
Factory posi units are Auburn Cone. Although they are high quality and
efficient units, they aren't rebuildable.
My understanding is that all the 7.5 inch 28 spline positraction units are
the same whether they are in a blazer or a Z28. These are not known to be
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