insaneclown

I did a recent rebuild on my 1992 tranny this spring with all new clutches and steels. I also installed it with a Transgo kit and the "3-4 high rev spring kit".

It was working good until I took it to the strip and did about 5 full bore passes in OD. At the end of the strip I heard the trans let go all of the sudden. The rpms flashed from about 5700 up to 7000 and I immediately let off the gas. I also floored it again on the way home and managed to get it to let go again in top 3rd or early 4th (about 5800 rpms)

The TCC was locking on just before the trans let go because the temp switch was engaging it. I suppose this meant that it was in 4th when it slipped.
There was a strong smell of burnt clutches and the fluid looked darker than normal so I took it apart right away to rebuild thinking that the 3-4 clutch pack was toast.

As it turns out the 3-4 clutches and steels are ok (within spec) but the 2 overrun clutches are totally wiped and the steels are burned badly. All other clutch packs were still in great shape.

I should also add that the tranny has been operating considerably hotter than normal (probably because of the upper 90s weather).

In anycase, does anyone know what happened here? How could I fry the overrun clutches and not the 3-4 clutches? I thought the overrun clutches are never applied in OD, especially at WOT???

jxaxsxoxn

iTrader: (2)

Overrun clutches provide engine braking.
They are applied in MANUAL first, second, and third.
I believe if a forward sprag is not holding and it's manually in 1,2,3 the overrun clutches will try to hold it.

insaneclown

I noticed that the forward clutch pack is way under what is supposed to be... about 0.020 if even that. That is measuring between the top clutch and the pressure plate. Could this be applying the overrun plates when they are not supposed to be?

Automatics

The overrun clutch will go away when the overrun sprag starts to slip (not uncommon). The overrun sprag assembly needs to be replaced, and/or needs to be rebuilt (if savable) correctly. The inner race must be in near perfect shape, the overrun outer race surface area must be very rough. Always use a new overrun sprag assembly.

insaneclown

Ok I took the sprag apart and found out it was pretty badly worn. So I got a new sprag and good races from a local shop. Hopefully this was the reason for my toasted overruns.

The only thing that still worries me is my forward clutch and 3-4 clutch clearances. They are both under spec by quite a bit, even though the guys at the shop said this should be ok.

jxaxsxoxn

iTrader: (2)

It depends on if they meant stock spec or??
Forward isn't that critical, it's applied in all gears except reverse, p and N.
3-4 is critical since it can drag in all gears except third and fourth. 3-4 should be no less than .030 and no more IMO than .050.

Automatics

In 4L60E's the forward is not very critical .015" - .050". The 3-4 should be no less than .025" & no more than .035" when using the Trans-Go Performance Shift kit, & related HD replacement spring assembly for the forward drum.