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I am working on my 1st 4l80e rebuild and am having some troubles with the pump install. Everything so far has gone pretty smooth, taking my time and following the manual step by step. I am at the point of installing the pump to check the end play and hopefully button it up. The input shaft was very tight going into the pump and couldn’t be turned by hand, I discovered the bushing on the pump was slightly crooked. I had a driver machined to press it in and have a shoulder that would sit against the pumps shaft to verify it’s square. The input shaft goes into the pump and can be turned by hand, but is kind of snug still. It’s the original pump also.
Installing the pump, it’s tough to get on and I can’t get it seated all the way. I am away from it now but it’s roughly .25” from sitting into the case completely. It’s very tight fitting into the case, and I have a hard time getting it out. I used a large hose clamp to even up the pump and stator. I have checked multiple times and I am pretty sure the overrun drum is seated completly. When the pump is almost in, I can’t turn the input shaft by hand.
In some of the literature I have it states the bushing in the pump body must be fitted. I haven’t been able to find a clearance on that shaft.
I have searched this on here and google with some help, but no ones seem to have the problems I am. Any tips/advice/criticism would be greatly appreciated!
Last edited by tonyorlo; Mar 28, 2025 at 06:15 PM.
But based on the knowledge I have from building other transmissions, something isn't installed right.
First, I'd try to find out if that bushing is an issue: take the input shaft out of the case and see if you can install the pump onto it without binding. If it goes on, then there is something wrong in the case.
Well the overrun drum was not seated completely. I’ve had it in and out a dozen times. I found it easier to out the drum in, then the clutches and steels.
I split the pump and installed the stator, it seems seated to me? Putting the pump half on it looks high to me, but it does match the surface rust to where it’s seated. I can turn the input shaft by hand with the transmission sitting horizontally.
I have a few problems and I’d rather not create a new thread. I’m embarrassed to even ask these, but I’m stumped.
It appears I am missing a spring and valve for my 2-3,3-4 accumulator. I took pictures and have kept everything in the same place, but there’s no trace of them. All the diagrams and manuals show them, but is it possible my trans did not have them? I’ll includ pictures from the manual.
Second issue is I have an extra spring and bushing. It’s possible it’s from another trans that was disassembled. I do not see this in any diagram I have.
I was looking at it and thinking, what exactly would it be doing if the plate and gasket were both blocked off? I’m thinking it never had the small “engagement” accumulator.
GM got rid of that valve after 93. it had to do with the self cleaning PCS.
on another note throw that Transgo pressure relief mod in garbage, do not do it.
I just saw on the transgo instructions that it’s only on some models. Man I need to pay better attention! Every diagram I’ve seen shows it though.
Well I already drilled the hole for the relief. A local trans rebuilder highly suggested it, honestly I didn’t know any different so I followed his directions. I’m not doubting you one bit, have you tried that kit before? Does it cause problems?
Measuring the end play, I am getting .109”. I have a jack on the output shaft to take up any play. Measuring that much I must have left something out.
EDIT: I left the overrun to planet thrust bearing out. Measures within spec. Output is easy to turn, input is on the tight side by hand.
Be sure and do measurement WITH GASKET . Many including myself prefer to set up pretty close and the gasket DOES MATTER what seems tight without it will many times be PERFECT with it.
__________________ Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
I just saw on the transgo instructions that it’s only on some models. Man I need to pay better attention! Every diagram I’ve seen shows it though.
Well I already drilled the hole for the relief. A local trans rebuilder highly suggested it, honestly I didn’t know any different so I followed his directions. I’m not doubting you one bit, have you tried that kit before? Does it cause problems?
Thanks for the reply!
Note on Transgo Instructions. I have rarely used TG kits but I have noted when helping people who are. The instructions can be needlessly confusing. Example they may have fixed it but with TG HD 3 4L60E set up for full manual they have you add a spring to other end of 3-4 shift valve, But it does not say discard the stock spring at other end or didn't. It literally said "remove valve and spring , install their spring inboard and reinstall valve. But mentioned no further about the stock spring or discarding it. So some would put both in, Result NO 4TH lol.
This why to somes annoyance when I explain something many time I tend to over explain . Better to tell several things you already know than miss something you didnt.
__________________ Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
Note on Transgo Instructions. I have rarely used TG kits but I have noted when helping people who are. The instructions can be needlessly confusing. Example they may have fixed it but with TG HD 3 4L60E set up for full manual they have you add a spring to other end of 3-4 shift valve, But it does not say discard the stock spring at other end or didn't. It literally said "remove valve and spring , install their spring inboard and reinstall valve. But mentioned no further about the stock spring or discarding it. So some would put both in, Result NO 4TH lol.
This why to somes annoyance when I explain something many time I tend to over explain . Better to tell several things you already know than miss something you didnt.
With this stuff, more info is better. I have to read and re read about 10 times for it to kinda stick. The instructions that came with my kit were pretty good actually.
And I did have the pump gasket in when checking my endplay.
I just saw on the transgo instructions that it’s only on some models. Man I need to pay better attention! Every diagram I’ve seen shows it though.
Well I already drilled the hole for the relief. A local trans rebuilder highly suggested it, honestly I didn’t know any different so I followed his directions. I’m not doubting you one bit, have you tried that kit before? Does it cause problems?
Thanks for the reply!
yes the transgo valve can hang open from debris or if you dont drill it 100% straight and you'll burn up the trans. it is highly recommended on here and else where if you are going to use the HD2 kit to discard that modification/step. you can easily fix it, the hole that goes through the valve body tap to 5/16 and install a set screw with some red loctite. you dont have to worry about the hole you drilled between the valve body partitions, it just goes into a void so no harm to leave it.
yes the transgo valve can hang open from debris or if you dont drill it 100% straight and you'll burn up the trans. it is highly recommended on here and else where if you are going to use the HD2 kit to discard that modification/step. you can easily fix it, the hole that goes through the valve body tap to 5/16 and install a set screw with some red loctite. you dont have to worry about the hole you drilled between the valve body partitions, it just goes into a void so no harm to leave it.
I did just that, 1/4-20 tap drill size was 1/64 bigger than the hole trans go had me drill. I put a short Allen head bolt in the hole with some loctite. I was not too impressed with the spring and plunger included. It felt cheap.
This question is beating a dead horse im sure, but am I able to re pin the harness in the trans to go to a 4l60e engine/trans harness? I would much rather do that than to add an adapter harness. Also, my harness appears to be in good shape, no cracked jacketing or plugs. Is it frowned upon to re use a harness?
"Is it frowned upon to re use a harness?" I assume that you are refiring to the internal trans harness, if the wires are in good shape and the connectors aren't brittle, I don't see anything wrong with reusing it.
I'm on the pump install in my 4l80e rebuild too. If I can't figure it out tomorrow I will make my own post. My stack is a hair too tall; even the thinnest pump spacer makes the overdrive center drum pinch too tight against the pump whe I lightly bolt down 2 bolts to try and find a front end play check. Gasket for pump to case is installed; but twice i can't get my stack of drums to sit down into the case enough to be proper. It's supposed to be level with the case ledge and it seems it's a tenth or an eighth of an inch too high. Gonna pull it apart and try again tomorrow but if anybody has any ideas on what could.be holding me up.
I got the billet forward drum hub and bearing from a ford transaxle? Tried the install with the thinner stock brass bushing on the other side of the forward drum and with the thicker one from the sonnax sure cure kit. I guess I'm worried this bearing mod is causing the high spacing. I'm gonna take a buncha photos tomorrow and make my own post. Thanks in advance for falls time and best of luck with your rebuilds. I'm loving the 4l80 cant imagine how weak 4l60s and 48rfe must be in comparison lol. Bought a 2002 gmc 1500hd from a painter for $1000. Gonna be a big bang for the buck if it drives again lol.
I'm on the pump install in my 4l80e rebuild too. If I can't figure it out tomorrow I will make my own post. My stack is a hair too tall; even the thinnest pump spacer makes the overdrive center drum pinch too tight against the pump whe I lightly bolt down 2 bolts to try and find a front end play check. Gasket for pump to case is installed; but twice i can't get my stack of drums to sit down into the case enough to be proper. It's supposed to be level with the case ledge and it seems it's a tenth or an eighth of an inch too high. Gonna pull it apart and try again tomorrow but if anybody has any ideas on what could.be holding me up.
I got the billet forward drum hub and bearing from a ford transaxle? Tried the install with the thinner stock brass bushing on the other side of the forward drum and with the thicker one from the sonnax sure cure kit. I guess I'm worried this bearing mod is causing the high spacing. I'm gonna take a buncha photos tomorrow and make my own post. Thanks in advance for falls time and best of luck with your rebuilds. I'm loving the 4l80 cant imagine how weak 4l60s and 48rfe must be in comparison lol. Bought a 2002 gmc 1500hd from a painter for $1000. Gonna be a big bang for the buck if it drives again lol.
I'm on the pump install in my 4l80e rebuild too. If I can't figure it out tomorrow I will make my own post. My stack is a hair too tall; even the thinnest pump spacer makes the overdrive center drum pinch too tight against the pump whe I lightly bolt down 2 bolts to try and find a front end play check. Gasket for pump to case is installed; but twice i can't get my stack of drums to sit down into the case enough to be proper. It's supposed to be level with the case ledge and it seems it's a tenth or an eighth of an inch too high. Gonna pull it apart and try again tomorrow but if anybody has any ideas on what could.be holding me up.
I got the billet forward drum hub and bearing from a ford transaxle? Tried the install with the thinner stock brass bushing on the other side of the forward drum and with the thicker one from the sonnax sure cure kit. I guess I'm worried this bearing mod is causing the high spacing. I'm gonna take a buncha photos tomorrow and make my own post. Thanks in advance for falls time and best of luck with your rebuilds. I'm loving the 4l80 cant imagine how weak 4l60s and 48rfe must be in comparison lol. Bought a 2002 gmc 1500hd from a painter for $1000. Gonna be a big bang for the buck if it drives again lol.
I wish I could add something helpful. It sure sounds like the bearing mod could be your problem. I know this is obvious, but you are sure everything is seated? That got me a few times.
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4l80 rebuild problems 
