4L80E Rebuild


Contributing Member
Jul 10, 2013
In the next few weeks I'm going to make an attempt at rebuilding a 4L80E to swap into my Jeep this winter. Going to try and keep this thread going as best as I can to keep the info on mods/upgrades all in one place. Tons of info on the net regarding this, but you have to look in multiple places. Hopefully this will keep it all together and help someone in the future. Ordered the first round of parts last night, I'll keep a list of P/N and where I bought them from on this post to help make things easier.

I'm starting with a 2006 model 4L80E 4x4 core that came out of a 2500 pickup, seller claims it was working but had a tick coming from the pump area due to incorrect converter installation when they did an engine swap. We'll see what jumps out upon teardown.

As for the mods, I plan to dual feed the direct clutches, delete the 3 and 4 accumulators, rollerize rear output, mod the seperator plate, boost the line pressure, and drill out / add a couple of lubrication points.

Parts List

2006 4L80E 4x4 Core off of Facebook Marketplace $300
4L80E Transfer case round pattern adapter General Motors P/N 15724745 off EBay $70.39
ACDelco 868-1168 AT Extension Seal Genuine GM Rubber Ring Seal 8681168 off EBay $9.03
4L80E Deluxe Master Rebuild kit P/N DLXSKT4L80E-3 from Transmissionbench.com $529.99 from Transmissionbench.com (This includes the seals/orings/gaskets, clutches and steels, pump and extension housing bushings, all the solenoids and switches, and the 3 piece piston set.)
2 new AC Delco Speed Sensors P/N D34466 from Transmissionbench.com $18.69/EA
Transgo Actuator Limit Valve Repair Kit P/N 48-ACT-TL off EBay $104.84
Borg Warner High Energy Friction Kit P/N 34035KIT off EBay $69.00
Borg Warner High Energy Fwd & Direct Clutches P/N 32961AM off EBay $45.00 (May not be needed afterall)
Rostra Internal Harness for 2004-up 4L80E P/N 350-0071 off Ebay $48.17
ICT Billet 4L80E Transmission adapter fittings -6AN P/N 316-3000833 off Ebay $16.24
4L80E Manual Shift Shaft kit (late case to early shift lever, only needed if you have a later model transmission with the long shift shaft. P/N 38511-03K off EBay $69.07
Rear reluctor ring (Holley terminator has no low signal provision, so both my VSS signals need to be pre transfer case) P/N 34477A off EBay $31.85
Master Shift Recalibration and Assembly Upgrade kit from CK Performance (this includes several internal parts that I may not use, but was the best deal to get the parts I know I plan to use $228.45
Pump Body P/N 34510EA from Transparts Warehouse $135.90
Reverse Band P/N 34024E from Transparts Warehouse $36.28
Front Band P/N P/N 34022HD from Transparts Warehouse $18.93
Overdrive Sprag P/N 34650A from Transparts Warehouse $31.53
Intermediate Sprag (34 Element) P/N 34652A from Transparts Warehouse $57.87
Low Clutch Roller (Rear) P/N 34654EA from Transparts Warehouse $23.56
3 .090 Fwd/Direct steels P/N 34126A from Transparts Warehouse $3.60/EA
3 .077 Fwd/Direct steels P/N 34128 from Transparts Warehouse $4.10/EA

Total as of 10/18/21 $1886.57

(Still need a converter and that should just about complete it)

Tools List

Steel to build a transmission holder that mounts to engine stand $35 (Holders are available for $140 on Ebay, or $80 for a 4L60E and other GM transmission version)
Transmission Clutch Drum Compressor off EBay $48.99 (Many videos show these being used)
2 Lip Seal Installation tools P/N SST-0015 off EBay $11.44/EA
Filtran Gold Transmission Assembly Lube 1lb tub off EBay P/N 803986 $21.13
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Still to order as of 10/4/21:
Shift correction kit (still debating which one to go with, however the consensus is to avoid the Transgo HD2 kit)
Actuator limit valve repair kit (common issue with 4L80E)
Parts for rollerizing the rear output (may be part of the Shift correction kit depending on my choice there
Pump hard parts (Will see what I find upon teardown
Tone ring for rear speed sensor (need both VSS signals before the Tcase because the Holley Terminator kit doesn't have Low gear input)
Internal wire harness
Ordered the Actuator limit valve kit today, and went ahead and ordered a different set of clutches. After talking with several people, the Borg Warners are apparently the way to go in that department. Trying to nail down what cam I'm going to go with so that I can finalize how in depth to go with some of the other internal mods.
Not yet, I need to determine what cam I'm going with first. Looking at a few Texas Speed options, need to give them a call next week and talk to them.
I also have determined my cam, ended up ordering a Brian Tooley Racing Truck Norris Cam (new release) Specs are 212/22X, .552/.552, 107 LSA.
Dyno showed 408.9HP / 400.8 TQ on an otherwise stock engine. Best part is that it is stock converter friendly. I will probably end up getting something 400 or so RPM above stock, need to make some phone calls there though. Thinking I may go through Jakes Transmission for this..

I like that transmission stand. Where'd ya pick that up?
Built it. It bolts to the engine stand and can rotate around for easy work access. Copied a design for sale on the web. Works great so far, if I did it again, Id make a few tweaks. Cost me $ $40 or so to build, they sell on EBay for $140.
Well its apart, really it came apart pretty easily, fairly straight forward. What the seller said was true to a point, there was no doubt a tick coming from the pump area, they did not line the converter up during installation apparently. I can see the gouges from forcing it in with the bellhousing bolts I would assume. Ended up splitting the pump drive gear in half. Everything else looks pretty good, no hard part damage other than the pump. Clutch frictions were stating to get some damage, however bet that was due to low line pressure once the pump was failing. Steels show a few signs of heat, but nothing terrible. Going to see if the local transmission warehouse has a pump, all 3 sprags, and both the bands in stock tomorrow, if not ill order them in. Need to do some cleaning and we will begin reassembly this week. I'll add some pictures tomorrow of the progress so far.
Here is the biggest issue. This was solely caused by improper converter installation, and more than likely from pulling the transmission up to the Engine using the mounting bolts, a big no-no.IMG_3180.jpgIMG_3179.jpg


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Ill get some more pics of the rest of the teardown later this week. Hoping the rest of the parts I ordered today arrive by Friday and we will build this thing up Saturday. It will be way overkill, but it should be safe to 800HP/800 ft. lbs. Beyond that I need at a minimum a billet forward hub and an input shaft. Seeing as I will be in the 400 hp range, I should be plenty safe lol. Maybe some forced induction could come later, but I don't think the NP241 will like that .


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So the internals are back together. It actually wasn’t too terrible. Did a few internal mods, added 1 extra direct clutch and used a stronger TH400 direct piston and spring setup. Dual fed the direct clutches, rollerized the output (ditched the thrust washer setup and installed a Torrington bearing), added a relief hole on the intermediate drum, larger relief hole on the pump case, and added a way to better feed the converter at all times. Also changed the pressure spring to put me in the 165psi line pressure range. Still need to button up the valve body, which involves a few additional mods, and I should be good to go. Everything has air checked out, and my clutch gaps are within spec, front and rear endplay a are dead center of the spec, so fingers crossed it works like it should.


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Do you have more pics of this trans holder that you made?
I’ll grab some today. It’s just a copy off of the ones they sell on EBay. Worked great, as with everything else there are a few tweaks I’d make If I built another one, but all in all it did the job.