I have a 99 Z71 with 5.3L and 4L60E. I need to change the fluids in the
front diff, rear diff, and transfer case. Do I really need three different
fluids? My rear diff is a limited slip (4.10) and calls for 75W-90
Synthetic. GM spec 12378261. Front diff calls for 80W-90 GM Spec 1052271
and the transfer case is one of those auto shift with the switch on the dash
that calls for GM 12378396. (Read: Dealer only!) My cheapo "capacities"
chart doesn't tell me how much to buy, either. Is there a common fluid for
all three of these? I gotta do the front pinion seal too and so far it
looks like I have to shell out to a dealer for the seal and a new nut! Dang
No, though you could go with synthetic in the front axle too, but you
need to update the plastic vent in the front diff so that the synthetic
fluid doesn't eat it. We have so many problems with these front
diffs that GM has basically told us to install synthetic and the updated
vent in all front diffs that we overhaul or repair.
You do not want to install anything other then the Autotrak fluid
in the transfer case. If this is the automatic t/case, it has a clutch
pack that transfers torque to the front wheels and it needs
Autotrak fluid to stay alive.
The front diff usually take about 1.5 liters, the rear
diff usually takes about 2.3 liters, and the t/case takes
2 liters. If you buy 4 liters of the synthetic diff fluid,
that should do both the front and rear diff. By the way,
if you are not in a particularly cold climate, the synthetic
fluid for the front is not that critical.
Thanks Ian, It hasn't been cold here since the ice age (Kansas) - I'll have
to go to the dealer for the transfer case fluid and the pinion seal with a
new nut. Its kinda surprising that nobody carries a pinion seal. It seems
like a common replacement thing to me. BTW, mine is a 5.3L and I haven't
heard what is referred to as piston slap. I'm almost at 100k miles and the
most I hear sounds like a dry lifter for a few seconds.
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