I took on the task of rebuilding my friends 1994 4l80. He had a trans line come loose and lost all his fluid. After towing it home, they found the blown line, fixed it, and refilled the trans. From then on it would work until it started getting warm in which it would lose all gears. He asked me if i would rebuild it, since i had recently took on the task of building a custom 4l80e (2.97 tci first gear) for my 85 gmc crew cab with '05 6.0 lq4 (currently has th400).
Long story short, i cracked it open, and found nothing wrong. Replaced all clutches, steels, soft parts, pump gears, and a few worn bushings. Put it back in, ran great for about a half an hour, worked through all gears all the way up to 80 mph. After a while, still in D321 position, it started trans braking very hard to the point it would about throw you through the window. If you quickly pulled it into 321 it would release, but still sometimes grab. Sometimes while it was trans braking it would clunk real hard and then release the trans braking. I eventually tore it back out and found the 4th and overrun clutches fried and siezed. Everything else in the trans was perfect, even the overrun sprag was fine. I'm assuming i have a leak in the 4th or overrun circuits, but i'm not 100% sure. I've gone through my books and the trans a thousand times and haven't found anything obvious. I've checked those two circuits per my book and haven't found anything there either. We've since bought a new refurbished valve body, And i'm thinking of convincing him of getting a new pump....assuming we had some cross leaking in there from the original event of him running out of fluid with the blown line. You can tell the pump has already been machined flat before, so i'm betting a newer one would be in order since they only have so much metal to remove before you have gear clearance issues.

Does anyone have the slightest idea of:
-Why he lost all gears after warm after the blown line event
-Why i fried the 4th and overrun after rebuild
-If there's anything else we should do or look at before i put it
together with a new Vbody, pump and of course new clutches and
steels for 4th and overrun

Sorry this is long winded, but any wisdom would be greatly appreciated.

 

dam thats gotta suck i have no idea what it could be and im about to tare into my 4l80e to rebuild it if you could pm any pdfs or info on mods and tricks i would apreciate it...hope someone with the right knowledge chimes in

 

Did you replace the Torque Converter?

Did it have a trans cooler?

 

What seperator plate was used?

 

Where did you get the refurbed valve body from?

 

-Best resource for 4l80 literature
ATSG, the Technician's guide for Hydra-Matic 4L80-E transmissions, published by GM Powertrain, and all these great forums are the best place to learn this stuff on your own, but you might not want to take my advice since i'm obviously having problems.

-Did you replace the Torque Converter? Have trans cooler?
Didn't replace the Torque converter, tried to flush it out with some tubing and a pump setup i built......didn't work like i wanted. However, i'll be dropping it off at a trans shop in the city to have it cut open, cleaned and inspected for any damage and possible clutch replacement here next week. I would replace it, but i don't know what stall it is. No numbers, no nothin!!! Couldn't even power brake it to get an idea of the stall. Not to mention its behind a '94 Blown (kenne Belle) 454. It does have a trans cooler, which i just pulled and flushed and found probably a 1/3 of it plugged with filter media, but it still did flow through, just not very efficiently and not very effective on the cooling either.

-What seperator plate was used?
He wanted to go with a Transgo hd2 kit, so i used that seperator kit and only drilled up to the moderate firmer shift on 2nd and 3rd, and left 4th shift stock. I did notice that the kit had 3 plates in the kit riveted together. I assumed from observation they were 3 different setups based on the hole size differences, so i drilled the brass rivet out and picked the plate with the hole sizes closest to what we wanted for shift feel and made sure it matched the old plate. Was i wrong to assume 3 plates riveted together with different hole sizes were meant to be 3 separate setups? Or are they suppose to stay riveted together, which didn't make sense to me since they didn't have gaskets between them (cross leak nightmare if you ask me). Thanks in advance for your guys' help!

Where did you get the refurbed valve body from?
Just got the valve body off ebay from shiftritetransmissions, rebuilt and upgraded. I've bought other parts from them and they're pretty good on warranty and selling good products. I've yet to have any complaints with them. I have yet to put it in, so my fingers are still crossed. In all reality, the old valve body might still be good, but i've spent an easy 3 weeks studying my books and that trans trying to see where it all went wrong and have finally decided to start with a clean slate. Especially now that its had heavy clutch media through the entire trans twice now.

 

Those three plates are ment to stay together, by separating them you created numerous issues. The three plates is how transgo dual feeds the direct drum without taking the trans apart. No where in the instructions does it say to seperate the plates so not sure why that was considered a option, as for cross leaks you are correct it increases that chance. By installing one plate you messed up the fluid circuits, to what degree I am not sure.

 

-"by separating them you created numerous issues"
I guess that's what I get for assuming. I feel like an idiot now. Definitely my bad, and i'm gonna install all three plates when I put it back together.

 

Yep the three plates MUST stay together. If you look closely there are more differences between them than hole sizes. The center plate has a passage cut between two circuits to allow the direct clutch to be dual fed. When you drill the holes for shift firmness you drill through all three plates.

I have a 3-layer plate from my HD2 kit that I ended up not using, might be easier than trying to reassemble the three plates. PM if you're interested.

 

I did some more reading across the web on the three plate ordeal, and it seems a lot of guys recommend using the oem plate instead and internally dual feeding the direct. That way your not chancing the cross leaking issues the laminated plate might allow. Thanks for the offer on your plate though, I appreciate it. I still feel like a tool assuming what I did on those plates. But I guess that's what these forums are all about, you've got to learn it the rough way in order to understand it the right way.