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4L80E rebuild time.

3500GMC

3500GMC

What T F, over
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Location
Nashport, Ohio
Or so I think. This one is in the '93. (truck in sig) Got right at 250,000 miles but I think the thing has been 'rebuilt' at some point in time. Probably with just clutches and seals, just a guess. Doubt the roller sprags or bushings were done.. Like I said, just a guess.

So we have this problem, no reverse with a grinding sound and no movement. Got all forward gears in all ranges (1,2,D,OD) with no noises on acceleration..

Will not engine brake, only a clanky grinding sound. Even a coast with no torque load will display this not-so-nice noise in any range.

So what did I do? Band anchor? OD sprag roller?

I will probably have to tear it completely down anyway you look at it, so this thread can serve as a documentary for my compulsory exercise in futility, lol. :blackeye:

First I need to yank it out... T-case off first, right? Then trans.? Or can I drop the whole chunk out?
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Sounds like you either broke the low reverse band anchor(semi common due to pressure spikes), or the reverse piston cracked which is fairly common. Unfortunately this is a semi common issue with the 4L80E trans due to uncontrolled pressure spikes, and these spikes seem to be worse in early 91-93 trannies that utilized the cleaning cycle every 10 seconds which goes full line for a split second. If there is ANY problem i nthe PCS dampening circuit, it will also cause this problem. The reason it takes reverse out is line pressure is about 50% higher in reverse than forward, so it just makes the spikes even higher and can crack apply pistons, or brake off anchor points.
 
This may turn into a can of worms- as a matter of fact, I know it will. Need to replace a leaky hydroboost that's been oiling down the frame for way too long. Need a fuel level sender. Probably will need a t-case chain but donno this fo sure. Needs shocks and I'd like to weld in some new cab corners and rocker panels..

Maybe I can start by cleaning out a hole in the shop first....:meh:

And w, ww www.. winter is coming straight towards us and the Ol F-er won't wait for Nobody.
 
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