4L80E Trans refresh?

[1994ch]

I have a 4L80E trans out of a 96 truck with 336,000 miles on it. It was reported to run fine several years ago till the engine died on the truck. (probably 3-4 years) If I start running it will it most likely give out right away from sitting? I am a mechanic by trade but have never been in an automatic transmission. Would it be advisable to open it up and replace seals and such? And would I be crazy to attempt it myself? Thanks for any input.

 

[Will L.]

We all know it is @THEFERMANATOR you want to hear from, but my .02...

Flip a coin weighted by how muh it bothers you to down the rig and R&R the trans. If it is easy to do and a spare rig, I say try it and see, except replace the output seal for $10. Guaranteed to leak and easy while out.

Otherwise with that many miles on it, I would rebuild it completely if you bother opening it up. You are pretty much nearingthe end if it's normal lifespan. Doing so now might save collateral damage. All that new fluid your about to add- the detergent is going to "clean off" the clutch material in a not good way. If the other owner always did his trans services, youll be ok. But if it didn't and this is the first new fluid it is seeing, don't expect 10,000 miles b fore rebuild is mandatory.

 

[THEFERMANATOR]

It's a toss of the coin, but with that many miles, it is a safe bet to say it has given good service, owes nobody nothing, and is ready to be built. You can always replace the seals you can get to from the outside, but just remember, if the external seals leak, internal ones most likely will as well. External leaks leave puddles, internal leaks bleed off pressure, and lead to clutch failure. As to building it, that is up to you. If you haven't done one, then it's a toss up as to wether you can do it or not.

 

[Will L.]

The rebuilding yourself is not really hard. Very clean workbench, the manual, and patience. The hard part is the special tool nonsense. It has been 20+ years sonce I did it, so cant remember what tools they were. Just remember a big wacky bracket to hold it, a seal tool and something for a clutch iirc.
I remember a test procedure using an air compressor to bench test. The few that I did worked ok. It was enough to teach me I can if I have no choice, but to pay a real pro whenever there is the option.

 

[1994ch]

Thanks so much for the input. Half of me wants to learn about transmissions... but I would also like to get this back on the road...and I know it would take a while if I did it myself. So I gather it would be a lot cheaper to rebuild it now than to run it till it fails?

 

[THEFERMANATOR]

That depends on how comfortable you are with pulling it and putting it back in. Myself I'm more of a fix it while it's out than roll the dice, but that's actually bit me a few times now. With that many miles theres a good chance it's not going to last long. That's alot of miles for ANY automatic transmission to run. That being said, my uncles 05 2500hd with a 4l80e is well over 400k, and still shifting like it has from day 1. It's a toss up. If I had a crystal ball I could be a gazillionare, but alas I don't, so your guess is as good as mine if it will last or not.

 

[WarWagon]

I get the transmissions rebuilt locally for around $1200 including remove and install. (At that price it's not worth my education time and wasted gaskets to have to re-do it if I screw something up.) To change internal gaskets you are looking at and handling clutches and bands anyway so may as well rebuild it while you are there. The weak point is the Torque Converter Clutch and if the oil wasn't changed every 25K or so the apply solenoid cylinder in the valve body wears out leaking so bad the TCC burns up. The second weak point is the 3rd gear direct overrun clutch - not much you can do aside of be careful with it and compression braking: that undersized nearly irrelevant clutch burning up doesn't limit transmission life. The OD gearset is subject to extreme wear as it's the most miles run gearset and may need to be replaced.

The Torque Converter can be upgraded to a triple disc clutch with an aftermarket unit. Even at the factory stall speed it's a worthwhile improvement as the factory clutch will not hold diesel torque real well. The TCC has been the failure point for most of my 4l80E rebuilds. Other than the one we owned for only 3 days that went "Boom" as the OD sprag and locked up bearing went through the OD planetary gears. Such a mess they couldn't tell what failed first. Change the stall speed to suit your engine build esp with bigger turbo's.

Point of fact I just changed the Torque converter (and front seal) that was slipping on my current transmission to get it back on the road without a rebuild. Other reasons to change the stall speed but that's another story on here.

Note the years have different transmission controls so you are putting this 1996 into what year?

 

[1994ch]

It will be going in a 96. Probably using a transmission controller for it as it will be behind a 6.2 engine.

 

[THEFERMANATOR]

Note the years have different transmission controls so you are putting this 1996 into what year?

I wished people would quit spreading this false info. The ONLY difference in the controls from the 4l80e's inception to the last ones used was the 91-93 used a pcs that required a cleaning cycle every 10 seconds, and 91-92(some early 93's) used a different plug that was prone to leaking, and many have been swapped out to the new style to help stop leaks. Aside from the pressure control solenoid(which is only an issue if you have one of the early pcs's still installed, or use a 91-93 factory controller. And the unique pcs can be swapped out for a 94+ style and be controlled by any 94+ style controller), they are all controlled identically. The only other 1 off thing was 91-93 4x4 4l80e's had an output speed sensor in them and 40 tooth reluctor installed because the early 1st gen ecm's weren't capable of doing the low gear conversion to keep the shoft points correct in low range.

It was the 4l60e that had all the control changes through the years.

 

[EWC]

When I rebuilt mine , there was a choice about the PSC . Black or silver and I think one was Bosch . Also read somewhere that the baud rate was different in the 91-93 than the 94 and up . I am only talking about TCMs but would think this would carry over to ECMs . Also found some info that the valve body has an exhaust hole right behind the PCS that applies to the black or silver models . I used the GM manual and one from Transtar .

Where are you getting your info from Ferm ?

 

[THEFERMANATOR]

When I rebuilt mine , there was a choice about the PSC . Black or silver and I think one was Bosch . Also read somewhere that the baud rate was different in the 91-93 than the 94 and up . I am only talking about TCMs but would think this would carry over to ECMs . Also found some info that the valve body has an exhaust hole right behind the PCS that applies to the black or silver models . I used the GM manual and one from Transtar .

Where are you getting your info from Ferm ?

That dealt with the 91-93 VS 94+ style(there was a change in the early 21st cewntury in suppliers, but they operate the same). The aftermarket is now selling the same PCS(it's a PCS= pressure control solenoid) for ALL 4l80e/4l85e transmissions. The early PCS required a cleaning cycle every 10 seconds due to the lower frequency it operated at, but EVERY other solenoid works the same in all of them. As to the exhaust hole, it was an added passage to an accumulator to dampen the line pressure. When the cleaning cycle initiates every 10 seconds, it goes from no power to full power, then back to normal amperage. The accumulator is there to dampen line pressure during this clenaing cycle to avoid pressure spikes. It slows line pressure response basically. Later model trans do not have this added accumulator since GM switched to the same style PCS they used in other transmissions that did not require the cleaning cycle because of the different frequency they operate at. My info comes from the ATSG manual that lists the running line changes from 91 to roughly 2000(when it was printed), talks I've had with other builders, and my own internet research. You can look at a parts manual and see it backs up the info I list

 

[WarWagon]

I wished people would quit spreading this false info. The ONLY difference in the controls from the 4l80e's inception to the last ones used was the 91-93 used a pcs that required a cleaning cycle every 10 seconds, and 91-92(some early 93's) used a different plug that was prone to leaking, and many have been swapped out to the new style to help stop leaks. Aside from the pressure control solenoid(which is only an issue if you have one of the early pcs's still installed, or use a 91-93 factory controller. And the unique pcs can be swapped out for a 94+ style and be controlled by any 94+ style controller), they are all controlled identically. The only other 1 off thing was 91-93 4x4 4l80e's had an output speed sensor in them and 40 tooth reluctor installed because the early 1st gen ecm's weren't capable of doing the low gear conversion to keep the shoft points correct in low range.

It was the 4l60e that had all the control changes through the years.

Clearly there IS a difference as you helpfully explained that I felt the OP may need to know depending on what rig he was thinking about this transmission for. This is useful information and let me explain my thought process here:

One possibility was the OP is building a diesel rig from a gas rig with "who knows what". So he does need to be aware of the "Gotcha" early year difference for choosing an ECM to control it. Especially since the TCM (ECM) for the 1993 and older 4L80E's just control the transmission, behind 6.2's and 6.5's, without the 1996 ECM DS4 is missing SES codes because the 6.2 has a DB2 IP. His plan has since been explained for aftermarket "one size fits all" controller since the non-specific question post. The OP is now aware (or reminded) there is a cheaper junkyard option of an older 1993- ECM requiring mods to his 1996 4L80E - and at the end of the day he could be money ahead to just do the planned aftermarket controller.

Another possibility for a 1996 era trans controller is @bobbiemartin Bobbie Martin's DB2 conversion guide here:
http://www.thetruckstop.us/forum/threads/the-db2-conversion-guide.30127/

As the OP may be considering a rebuild other info is useful like 4 planetary vs. HD 5 planetary gear sets, internal lube mods, and other improvements that can be added as GM constantly improved the 4L80E's. As I don't rebuild them I don't know what my builder is talking about for gear lube mods on a 1993 4L80E and what years GM improved it themselves.

I haven't thrown any special clutch material or otherwise built my 4L80E's even with the Yank as the weak areas have been explained. Cooling is worth a mention as hot oil to radiator first then air to oil cooler 2nd for the best results of lower trans temps and longer life. Verify oil is flowing the way you want with a bucket.

 

[EWC]

Good stuff Ferm but as WW posted there is a difference in the 91 - 93 vs 94 and up ( lower frequency as you posted ) . Good to know that the newer stuff will work on the older as I have 2 91 model 4L80es in my Sub and dually .

Exhaust hole was not for a passage but right at the end of the PCS . Something on the web and how you can tell the difference between the 2 . Maybe it was not for the PCS but for something else ?

 

[THEFERMANATOR]

I'm trying to point out the difference is ONLY there for a cleaning cycle. It is NOT like the 4l60E with all the running changes like reversed 3-2 operation, does it or does it not have PWM TCC, is it an EC3, is it set up for a carbon fiber converter clutch, and so on? In fact, if you buy aftermarket replacement solenoids now, most all are the same from 91 to 08 or 09(whenever they last used them). And many have even used later model trans without the compensator, and not noticed any ill effects of running them. I believe that several of the aftermarket controllers use the SAME controller with the SAME program for all of them regardless of PCS installed. But they are ALL operated the same electrically with the exception of the cleaning cycle pulse.

So to be 100% accurate, EVERY solenoid EXCEPT for the PCS is the same, and all are operated the same with the exception of a different frequency sent to the PCS, a pulse every 10 seconds, but they all even operate at the SAME amperage to the PCS for X amount of pressure. Unlike say a 4L60E where one DOES have to be carefull of the year as some were 1 year only control systems.

 

[EWC]

Makes me wonder if that is the only difference between the TCMs . I have a couple of each , wonder what a swap might do .

 

[THEFERMANATOR]

The cleaning cycle has been shut off in 91-93 TCM's for people to drop in 4l85E's, or so they can go to the newer PCS and eliminate the pressure change delay the accumulator provides.