1991 4L80E weaknesses?

[Schurkey]

I have my eye on a '91 K2500. The price is higher than I'd normally expect, but it does seem to have the "heavy duty" equipment I'm looking for--and there's not a lot of other trucks like it around here.

I know that '91 was the first year of the 4L80E. Does this trans have a specific set of problems I should be aware of? I remember the first five or so years of the 700-R4 were a total disaster.

 

[Schurkey]

Let's try other 4L80E questions:

HOW DEEP is a standard 4L80E pan?
HOW DEEP is a "Deep" 4L80E pan?

I've got a '97 4L80E, the pan seems about as deep as a standard TH400 pan, maybe just a bit deeper. The deep 400 pan would be much deeper than what I have--so I think I have a standard 4L80E pan.

My trans has reverse and four forward gears, but I can't feel the TCC engage or disengage. I'm planning to flush the fluid and change TCC solenoid while the pan is off. I'd like to order the filter and solenoid before I take the thing apart.

 

[454cid]

I know you shouldn't shift between drive and reverse without stopping... at a former job we had a G3500 that started hesitating to shift into gear. It was like it was in neutral and then after several seconds it would engage. I was told that often that was caused by someone shifting between forward and reverse gears without stopping. I mentioned that to the current driver and he said so&so who didn't work their anymore did that all the time. I don't believe the current guy was passing the buck, because he knew how old and fragile that van was getting and he was often the one to fix it. That time it took a transmission shop.

I think there is also something about not engine braking or downshifting to engine brake above a certain speed/gear but I don't recall the details. There is a hill in town that I'll often downshift to 2/3rd before I build up speed for it to shift above that...but I don't really know of I'm doing any good.

 

[smdk2500]

I wish I could help you schurkey. You seem to be a wealth of knowledge. The only GM transmissions Ive owned is a 700r4, 4l60e, T-5 and a nv3500. And both the autos Ive blown up.

 

[letitsnow]

My trans has reverse and four forward gears, but I can't feel the TCC engage or disengage.

With my 4l80e, you can tell when the torque converter locks. It feels like there are 5 gears. It locks consistently at 50 mph for me.

Not sure if that helps.

 

[Schurkey]

With my 4l80e, you can tell when the torque converter locks. It feels like there are 5 gears. It locks consistently at 50 mph for me.

Not sure if that helps.

It does. I drove it ~150 miles at highway speed to get it home after buying the truck, never felt it lock up, never felt it release when I tapped the brake. Not feeling it lock up I attributed to PWM engagement, but that's not an issue if you're feeling it engage.

At this point I'm fairly sure it's a regular/shallow pan, so I know what filter to order. I'll see what changing the solenoid for the TCC does when I flush the fluid. Won't be any time soon--weather turned crappy and I don't have an indoor area large enough for the truck with the snow plow attached.

 

[Schurkey]

Update: The engine had bad misfire on #8. Discovered a cracked spark plug. Misfire fixed.

Bought a service manual on DVD. Turns out, if the computer senses misfire, it locks-out the TCC.
https://www.summitracing.com/parts/BSK-12229

Fixing the misfire also fixed the TCC.

I bought a Transgo shift kit, and a shallow-pan filter kit. I'll probably install that stuff in April or May. At this point, the trans works great.

 

[df2x4]

Just FYI, there's a specific part of the TransGo HD2 kit for 4L80Es that apparently some people have had issues over. Top of the page in this link. The rest of the kit is fine, though.

https://sites.google.com/site/sloppywiki/everything-ls/4l80e-info

 

[Schurkey]

Bookmarked! Thanks.

 

[df2x4]

You're welcome! I thought about posting that link earlier than I did because of the outline of the 80E differences by year, but it's pretty basic stuff and I didn't see anything specific to '91.