Rebuilding My 4L80E Transmission

[folkenheath]

I was looking at a Sonnax tutorial on front end play, and they are saying that input endplay can be measured with the pump bolts only finger tight. With my pump bolts only finger tight I have plenty of end play. It is when I tighten them down to torque spec (18 Ft Lbs.) all the end play goes away. I am going to call Sonnax tech line tomorrow to discuss this with them.

It should have end play when torqued down that you can measure with an indicator or caliper to spec. If all the endplay is gone when its torqued down you need a thinner shim. There is a minimum endplay, and it should be above the minimum still when torqued down.

I am thinking about not even pulling the 4th gear piston drum apart. I did a wet test on the drum and the seals seem to be in good condition, What are your thoughts on this?

Wouldn't it bother you that one set of seals in the whole trans is older than the rest? You want the whole trans to last another 15 years, not just 95% of it. I doubt you want to potentially pull a trans apart because of 1 failed seal that got old and brittle. You have a done a very excellent, thorough job thus far, don't take a shortcut at the end.

 

[1-ton]

It should have end play when torqued down that you can measure with an indicator or caliper to spec. If all the endplay is gone when its torqued down you need a thinner shim. There is a minimum endplay, and it should be above the minimum still when torqued down.

The instructions from Sonnax say to set the forward drum and hub onto the direct drum with no clutch pack in it. Then set the overrun drum with input shaft onto the forward drum. Then set the pump with selective washer and pump gasket onto that. Then tighten down two bolts finger tight, and then check end play. I did that and the end play is perfect at .015". The pump has the thinnest selective washer there is in the rebuild kit, but when I tighten down the two bolts to 18 Ft Lbs...there is no more end play.

Wouldn't it bother you that one set of seals in the whole trans is older than the rest? You want the whole trans to last another 15 years, not just 95% of it. I doubt you want to potentially pull a trans apart because of 1 failed seal that got old and brittle. You have a done a very excellent, thorough job thus far, don't take a shortcut at the end.

The 4th drum seal installation is considered difficult even by pro's. There are several videos on YouTube where even a pro screwed up putting those seals in, and had to pull the transmission back out to fix it.

 

[folkenheath]

The instructions from Sonnax say to set the forward drum and hub onto the direct drum with no clutch pack in it. Then set the overrun drum with input shaft onto the forward drum. Then set the pump with selective washer and pump gasket onto that. Then tighten down two bolts finger tight, and then check end play. I did that and the end play is perfect at .015". The pump has the thinnest selective washer there is in the rebuild kit, but when I tighten down the two bolts to 18 Ft Lbs...there is no more end play.



The 4th drum seal installation is considered difficult even by pro's. There are several videos on YouTube where even a pro screwed up putting those seals in, and had to pull the transmission back out to fix it.

Something doesn't sound right there. End play shouldn't disappear when you torque the bolts down. It should still have proper endplay after final assembly before you slide the converter on. I would recheck your assembly and orientation. Can you still spin the shaft after its torqued down? That will tell you how close it is whether its bound up or not.


You can air check the 4th drum before you reinstall it to be sure it's right correct? The seals alone are pretty cheap if you screw them up, I don't remember it being a problem when I did a couple, but it wasn't a lot of them. I did buy a used plastic sleeve tool set off eBay if its the overdrive drum I am thinking of, its been a while. It was a little finicky but you could feel if it wasn't right and reset it up, just don't force it if it doesn't want to go. I just didn't trust an old seal to last as long as the rest of the new ones. I remember thinking one of those round plastic tool things that come with the Sonnax or was it transtar parts might work better than the actual tool on some of the assemblies.

 

[1-ton]

omething doesn't sound right there. End play shouldn't disappear when you torque the bolts down. It should still have proper endplay after final assembly before you slide the converter on. I would recheck your assembly and orientation. Can you still spin the shaft after its torqued down? That will tell you how close it is whether its bound up or not.

yes I can spin the entire assembly after the pump is torqued down.

 

[CharlesC83]

The instructions from Sonnax say to set the forward drum and hub onto the direct drum with no clutch pack in it. Then set the overrun drum with input shaft onto the forward drum. Then set the pump with selective washer and pump gasket onto that. Then tighten down two bolts finger tight, and then check end play. I did that and the end play is perfect at .015". The pump has the thinnest selective washer there is in the rebuild kit, but when I tighten down the two bolts to 18 Ft Lbs...there is no more end play.



The 4th drum seal installation is considered difficult even by pro's. There are several videos on YouTube where even a pro screwed up putting those seals in, and had to pull the transmission back out to fix it.

It was common to tear or nick the lip seals during install. The shop had extra seals and the special tools for the OD drum. It wasn’t that bad and with patience you can do it without ripping the seals.

I used a blue point wire loop lip seal tool and had success

 

[1-ton]

It was common to tear or nick the lip seals during install. The shop had extra seals and the special tools for the OD drum. It wasn’t that bad and with patience you can do it without ripping the seals.

I used a blue point wire loop lip seal tool and had success

OK you guys talk me into it.

I believe I have found the problem for my input end play. I have a Sonnax billit forward clutch hub that comes with a roller bearing to be used instead of the bronze washer that the transmission used in stock form. That roller bearing is about .020" thicker that the stock bronze washer. I removed the roller bearing, and used the stock bronze washer instead. That seem to increase my end play even when the pump is tightened down. It sucks I cannot use the roller bearing, but "it is what it is".

 

[folkenheath]

I think when they use the roller bearing they include a hub that is thinner or machined down? Measure the billet one compared to the stock one.

I think I ran that when I built my 2nd 4L80E for about 1400 HP, it has a billet hub with roller bearing, 36 element super drum, 300M input shaft and either 4340 or 300M intermediate shaft, don't remember which one, but it still works whatever it is. It's on a transbrake and it's wicked fun to launch.

I think you are doing a thorough job and you'll be happy. Just remember, if you doubt anything, stop until you are confident you got it right, because its easier to fix it now than later. And a $3 seal and a small delay is a lot cheaper than tearing the whole thing down again.

Nice work and nice job documenting everything.

 

[1-ton]

I should have never taken that forth clutch assembly apart. I have tried 20 times now to get that thing back together, and I cannot get that thing back together for nothing. The old seals where in perfect condition. I may have to take the clutch housing to a transmission shop to have them put it back together.

 

[folkenheath]

They were in perfect condition for now, they were going to get old and brittle and fail eventually.

Sorry to hear you are having difficulty, but I still think you are better off in the end by replacing them, just make sure they air check good before you reinstall. Once you get it done and air check it, you'll be glad you did it, just a minor delay is all to do a complete job.

Do you have one of these type of tools?

T-2926 4th Clutch Piston & Lip Seal Installer Protector Tool GM 4L80E J-38731 | eBay

Feature Application Fourth Clutch Piston and Lip Seal Installer Protector works for GM 4L80E Transimmision Function Protects inner and outter seals when servicing on the 4th clutch piston. Replace for OEM J-38731, T-2926. Material Constructed fromhigh queality steel with black oxide cotaed...

www.ebay.com

 

[1-ton]

They were in perfect condition for now, they were going to get old and brittle and fail eventually.

Sorry to hear you are having difficulty, but I still think you are better off in the end by replacing them, just make sure they air check good before you reinstall. Once you get it done and air check it, you'll be glad you did it, just a minor delay is all to do a complete job.

Do you have one of these type of tools?

T-2926 4th Clutch Piston & Lip Seal Installer Protector Tool GM 4L80E J-38731 | eBay

Feature Application Fourth Clutch Piston and Lip Seal Installer Protector works for GM 4L80E Transimmision Function Protects inner and outter seals when servicing on the 4th clutch piston. Replace for OEM J-38731, T-2926. Material Constructed fromhigh queality steel with black oxide cotaed...

www.ebay.com

I do not have one of those. I have figured out how to get the inner and outer drums together. It is a bitch, but it can be done. They called those a lip seal protector, but that is wrong...they are a line up tool because that is the main objective of getting those drums together is to line them up. The problem is that there is a .005 to .007 thousand of an inch tolerance between the drums, and if those tools have a .020 manufacturing tolerance then they do not work. I have seen that in too many videos where those tools do not work, and they give up only to assemble the whole thing by hand.

 

[CharlesC83]

When I replace those OD seals. I use the tool shown below. Using one hand to run the tool and the other to hold the piston you walk this tool gently around the seal while pulling and pushing in the correct direction release pressure on the seal. I don't use those plastic lip seal guides on this piston. When it finally slips in then I rotate the piston down in. Another thing I did was use a mix of Motor Honey and thick gear oil for lip seals. And I use petroleum assembly lube for bearings and seals. Lip seals were brushed with the thick oil and installed then air tested.

 

[folkenheath]

I do not have one of those. I have figured out how to get the inner and outer drums together. It is a bitch, but it can be done. They called those a lip seal protector, but that is wrong...they are a line up tool because that is the main objective of getting those drums together is to line them up. The problem is that there is a .005 to .007 thousand of an inch tolerance between the drums, and if those tools have a .020 manufacturing tolerance then they do not work. I have seen that in too many videos where those tools do not work, and they give up only to assemble the whole thing by hand.

I didn't watch any videos that said it wouldn't work, I just put it together with the tool. It was a genuine Kentmoore or some other name brand I bought used online, and it worked successfully, it took a couple tries to get it to go on smoothly but it definitely worked like it was supposed to, it gave the seal a little ramp to go up on and then slide over the assembly without tearing the seal. They did not have all these Youtube videos and eBay tools available when I did mine, you kind of had to figure it out on your own, with just the ATSG book and an old TH400 book.


I did get one of these cheap plastic discs included with some of my trans parts, and it actually worked better than my little lip installer tool (I have the same one @CharlesC83 has shown above) on some assemblies. You start it on one side and then just roll it around, might be worth a shot because it's extremely simple and surprisingly effective.

 

[1-ton]

I successfully installed the inner piston to the outer piston a couple of times using the old seals for practice. I have a whole stack of lip wizards, and used one to get the piston together. One problem I ran across is my install kit instead of having one inner lip seal and one outer lip seal for my 4th clutch it had two outer seals in the package. Another hassle with trying build transmissions. I just took the 4th clutch, spring cage, and locking ring to a transmission shop here in town. They said they probably had spare seals laying around, and they would assemble it for me. I do not have a whole week to learn a new skill, which assembling those 4th clutches is a whole new skill in itself.

 

[1-ton]

Picked up that 4th clutch housing. It only took them about 2-hours before they called and said it was ready. Now that is out of my hair I can button up the whole thing. Double check my input shaft end play, and then go on to the valve body assembly.

 

[1-ton]

Got my 4th clutch, input shaft and pump in today, and checked my end play. My end play is .005 of an inch between the overrun clutch and input shaft snap ring. Then when I pull hard it goes to .020" of an inch which means my real end play is .015" of an inch. This should be perfect because my output shaft is a little tight at .010" inch of end play, and the input is .005" of an inch more than the output.

 

[vr1967]

Any updates? Looking to tackle my 4L80 rebuild soon and install in my 84. About finished with the swap harness and ecm

 

[Polymath]

This thread has simultaneously made me want to save up and go buy an overbuilt tranny with a warranty and also given me some modicum of confidence that it's not so much hard as it is complicated.

 

[1-ton]

Have not been able to get to my transmission in a while. I have the main internals all done. All I have left is the valve body that is disassembled, and cleaned I just have to put it back together. I found out I had installed something incorrectly years ago when I did a Trans Go shift kit. I installed an incorrect spring in the 4th accumalator. It took a while, but found a used correct spring so now the valve can go back together.

 

[1-ton]

I got the valve body, wiring harness, and all that stuff completed on my 4L80E. Now all I have left to do is install the torque converter, and then install it into my truck.

 

[Blue85]

Why not add a drain plug?