Well, after alot of contimplation I decided to rebuild my 4l80E myself. I haven't seen many transmission rebuild threads (there is a 4l60E thread on tech) so I am documenting this as best I can. I am attempting this using as few special tools as possible. I have bought 2 special tools at this point which I would highly recommend.

1: a transmission holding fixture. The 4l80E is just too big to manhandle.

2: an ATSG 4l80E manual.

Here is the junkyard 4l80E on the holding fixture ready for surgery. I love how they destroyed a perfectly good dipstick tube.

Here is the view from the front

**NOTE I had to reinforce my cheap workbench to handle the weight of the 4l80E. This particular transmission holding fixture is designed for a 200-r4,350, and 400. There is adapter for the 4l80E but I was able to make it work w/ a little help from my trusty angle grinder.**

Like many 4l80E's the drain plug on the pan was stripped but drainig it was possible w/o making a mess of the garage.

Trans rotated 90* on fixture.

Here's a view of the underside of of the trans w/ the pan removed.

valve body ready for removal. At the bottom of this pic you can see where I had to grind the holding fixture.

Don't lose your check balls! total of 8.

This is the wear the check balls cause to the holes on the valve body seperator plate. The transgo seperator plate is a tougher piece.

The manual calls for a puller to remove the pump assembly but you can put a prybar through this rectangular hole and gently pry under the pump to remove it.

I got a little carried away during teardown and forgot to take pictures showing every snap ring and what not but the manual is pretty clear as far as that goes.

removal of turbine shaft and overrun clutch assembly

4th clutches and piston

removal of 4th clutches and piston assembly

Removal of forward clutch drum assembly.

Direct drum/ clutch assembly removal.

Next you remove the intermediate band and intermediate clutch snap ring.

now the intermediate clutches come right out.

Next you remove the center support and gear train. There is a bolt which holds the center support to the case. I removed it durring the valve body removal This bolt will be replaced and should come with the overhaul kit.

Also the manual is not very clear on this, but you do need to remove the cooler line fitting because it extends into the center support.

center support and gear train on work bench during reassembly. *NOTE the round hole in the side of the center support is where the cooler line fitting seats*

At this point you can remove the center support spacer and rear band, which is now just sitting in the case.

hear is a pic of the inside of the case w/ everything removed. There is a selective thrust washer tha sits in the bottom of the case at the tail shaft hole. Remove it if it didn't stick to the bottom of the geartrain.

Here are the drums and valve body sitting in a tote waiting to be rebuilt.

here's the pump

Hereis my box full of goodies. I'm using Alto RedEagle powerpacks. They are a little pricey and might be a little overkill for an already stout transmission. You can get borgwarner or raybestos high energy clutches much cheaper. The Alto power packs come w/ their red eagle clutches and kolene treated steels in selective thicknesses to add extra clutch packs to the forward, direct, and intermediate drums. I was told that Alto will be coming out w/ a similar power pack for the 4th and overrun clutches soon.

Well here's the case all cleaned up. Looks much better than in the original post.

I've been replacing bushings in the gear train durring the weeek when I can find time to work on it what a PITA. Got alot of work done today I'll post more on the progress tomorrow.

While doing some searching for tips and tricks last night I found this th400/4l80E write-up on another site. It has alot of good tips.


I'm working on finishing the install of the cluthes and drums so I should have some updates later tonight once I upload all the pics. It's almost as much work to update the thread as it is to rebuild the trans.

I did have to get the 4th clutch seal protector. it is the only other special tool I've needed so far. I tore one of the 4th clutch lip seals and had to buy a whole new overhaul kit. A lip seal installer is a good idea too. I am using a feeler gauge as a lip seal installer, but I will be buying a lip seal installer before the next one I build.

I am replacing all the bushings as a part of my rebuild. Most seem to be in pretty good shape but a new bushing kit is about $30.That has been one of the bigger pita, just a little time consuming. I'm using a bearing/ race installer. They are available from most chain auto stores as loaner tools. When removing bushings from blind holes if you can get a small chisel or screwdriver behind the outer radius you can split it at the seam ( if you can find the seam).

When I removed one bushing out of the rear sungear shaft I was able to slip this 11/16 impact socket inside and knock the other one out by shaking it up and down.

Here's the low roller clutch.

Replacing the lip seals on the intermediate clutch piston.

Once they are installed lube them up with trans assembly lube and care fully seat the piston back in the center support. This is when a lip seal installer or feeler gauge is needed. carefully push on the edges of the lipseals as you turn the piston to seat it.

These are the two different types of teflon seals for the center support that came with the overhaul kit. I chose to use the split rings for ease of installation. The solid seals need to be stretched and then resized once installed. Be sure to lube them before you install the center support.

Time to rebuild the direct drum!

here are the frictions and rear band soaking in ATF while I rebuild the direct drum.

Just remove the snap ring, then the bacing plate 5 frictions, 5 steel plates and one cushion plate

removing the return spring calls for a special spring compressor, but I was able to make due with my handy quick clamps.

Next you can remove the bonded direct clutch piston. Older models use a piston w/ replacable lip seals.

the intermediate srag is located on the underside of the direct drum. Here it is w/ the snap ring and retainer removed.

next install the lip seal in the center of the drum.

lube up the piston and inner lip seal. I lube the sealing surface as well. Twist the piston into place. You may need a little help from your lipseal installer.

The transgo HD2 shift kit also comes w/ heavier return springs for the direct clutch piston.new spring is on the right.

You simply pry off the bottom spring retainer. The pull off the springs one by one with pliers.

How much stiffer are the new springs? Well it took 2 clamps to compress the old ones and here I am installing the new ones.

Once the return spring assembly is installed you can install the clutch packs.The Alto Red Eagle power pack is a nice upgrade. It takes the Direct drum from 5 frictions and steels to 7.

Next you can put it on the center support and air check it.(lube the teflon seals)

Then you can check piston travel with a dial indicator (.121"-.236"). I just stuck it to the side with a magnetic base.

overhauling the forward drum is not much different.

This time I had to use a trusty 2x4 to assist the qucik clamps in compressing the return springs. :)

I used a 3 jaw puller to gemove the inner bonded seal from the drum. And I finally found a use for the bracket I removed from the back the engine when I dropped in the 408. I'm sure you radix guys have these laying around too. :jest:

I used a cup style oil filter and a hemmer to drive it back on. It's a perfect fit and it also fits the truck oil filter (ACDelco PF46).

Installing the bonded piston and clutchpacks is pretty much the same. However, the Alto power pack calls for you to discard the bottom cushion plate. This will give the transmission a much firmer "garage shift", shift from P/N to the forward gears. The forward clutch is applied in all of the forward gears. The Alto power pack also takes the forward clutches from 5 frictions and steels to 7. :thumb:

Clearance is checked w/ a feeler gauge between the top friction disc and pressure plate groove(.040"-.070").

At this point I was ready to start assembly the drums in the case, but I decided to switch gears (get it?) and install the vacuum modulator fitting in the case. It requires drilling a hole in the case, and I figured it would be easier to clean any debris out while it is empty, although it was pretty clean anyway.

Just mark the hole. Then drill and tap for the fitting.

Fitting installed in case

View of fitting from outside of case

Next it's time to start assembling parts in the case. First install the rear case bushing, selective thrust washer rear band and center support snap ring.

Next comes the center support and geartrain. The only place you can hold this chunk of steal is at the very top of the shaft. Thats not quite large enough to get a good grip to lower it down so I rotated the tranny horizontally and carefully slid it in part way and then reached in to support it from the rear. Be careful not to knock the rear band loose. Then install the beveled snap ring flat side down.

Now to check rear endplay.(.005"-.025") You insert a pry bar through the lower hole in the case and pry up on the geartrain.

I took a 4" wide piece of 1/4" steel and drilled two holes in it and bolted it to the transmission with the pan bolts to hold the magnetic base dial indicator.

Next install a new center support bolt and torque to 32 ft. lbs. with a 3/8" 12 pt. socket.

Next comes the intermediate clutch pack. This clutch pack is installed directly into the case. The Red Eagle HP powerpack takes the intermediate clutch pack from 4 to 5 frictions and steels, and a thicker heavy duty snap ring (.106", about the same size as the transgo shift kit). Install the wave plate then the first steel and alternate friction/steel. Install the backing plate and new snapring and check clearance between the backing plate and snap ring (.040"-.070")

Next install the intermediate band making sure it is seated on the anchor in the case. You can also look through the servo pin hole to ensure it is in the proper position.

Next insert the direct drum and rotate it into place to seat it in the intermediate clutch pack. double check the intermediate band to make sure it is still properly seated.

Now install the forward drum. Again, rotating it to fully seat it in the direct clutch pack.

I'm not sure if your book tells the proper location of this snap ring. Take it and put it at the 3 o'clock position. Basically a 180* from where you have it. The reason for this is with a wider snap ring it will rub the direct drum(high reverse drum). When the intermediate clutch is applied the pressure plate will flex that snap ring and it will rub with it in the position that you have it. Looks like you are having a lot fun. Enjoy!!! Vince


07-26-2007, 09:54 PM

WOW, thanks alot!

Actually the book says to put it in the 9 o'clock position, but that is with a stock snap ring. The Alto instructions call for 9 o'clock also. :confused:

Looking at how it sits in the case what you are saying about it flexing makes sense. Plus you undoubtedly know your :turd: . It took me a long time to decide between an FLT or build my own. Guess I'll be pulling it apart again. Luckily I haven't bolted in the pump or valve body yet, although I thought I was ready.

Thanks again!

Vince @ FLT

07-26-2007, 10:54 PM

No problem man. Good luck with the rest of the build. Vince


07-30-2007, 08:22 AM

Well' I tore back into the tranny this weekend to turn the intermediate snap ring. I air checked the intermediate clutch pack and you could really see the snap ring flexing. Turning it 180* made a HUGE difference. It seems like the same thing would happen with a stock snap ring too.

I finished the build and hope to update the thread soon.

Thanks again for the advice Vince, and don't hesitate to let me know if you see anything else that needs attention.


07-30-2007, 10:47 AM

great pictures! I really like reading up on stuff like this.


08-01-2007, 10:24 PM

Allright, back on track. :judge:

Now it's time to tackle the 4th drum.

seems harmless enough all torn apart.

I tried installing the 4th piston without the installer tool. After trying to get it in for 30 mins or so I tore a lip seal. So I decided to buy the 4th clutch lip seal installer (about $150).

Installation is much easier with the seal protector. you just stack them up like this and push down on the housing to install the piston.

Then remove the top piece and install the return spring assembly.

Next install the clutches and backing plate. Currently there are no Alto Red Eagle clutches for the 4th and overrun clutches. I used Borg Warner High energy. Clearence is .040"-100"

Install the 4th drum in the case in this position.

The Transgo shift kit has a 4th clutch bolt with a smaller orifice. Transgo bolt installed, stock bolt on left. Torque to 12 ft lbs.

You can air check the 4th clutch piston through the 4th clutch bolt.

BTW I cut the :turd: out of my thumb when my hand slipped installing the 4th clutch return spring.

Now for the overhaul assembly.

Remove the snap ring and seperate the turbine shaft, planetaries and overdrive drum.

OK starting March of '01 GM updated the overdrive assembly because the rollers in the roller clutch could skew. Mine was the earlier style ('01 & earlier) and some of the rollers were skewed and lodged in the roller clutch so I decided this update would be a good Idea. You have to replace the overrun clutch housing , return spring, snap ring, planetaries, and overrun roller clutch. Both are pictured below the newer style can be identified by the blue inserts in the roller clutch.


First design roller clutch. You can see where the roller had dug into the plastic ring.

Here's the new design roller clutch. notice the rollers are smaller and the inserts keep them straight.

Tearing down the overrun drum is not much different although I needed smaller clamps.

when replacing the bushings I was able to split it at the seam.

To check the pinion end play I stuck the carrier on my 4" wide piece of steel and attatched my dial indicator w/ magnetic base. (.009"-.024")

I replaced the bonded piston and the friction clutches (borg warner) and reused the steels.Clearance is .033"-.094".

To stretch the teflon seals for the turbine shaft I used the cone tip from a standard trans clutch alignment tool.

To resize them I used a piece of plastic cut from a spray can lid and some hose clamps. (That was a great tip from the other 4l80e thread I posted a link to earlier)

Assemble the parts and snap ring and lower the assembly holding it by the turbine shaft into the 4th clutches. Rotate it to make sure all the clutches are engaged and the drum is seated properly. The drum should sit slightly lower than the 4th clutch backing plate.

Well I've been on vacation for a couple of weeks and now it's time to finish this thread. Tranmission is built I just need the time to install it.

Next comes the pump.

Here are the 2 halves seperated.

I basically just disassembled, cleaned and inspected the pump. The transgo shift kit does have you make some modifications to the pump, but I forgot to take pictures and the transgo instructions are pretty clear on those.

The boost valve, bushing, and springs are changed with the transgo HD2 shift kit.

I used 2 big hose clamps to make a pump alignment tool. I'm sure you could get one clamp that was big enough, but these were readily available at Home Depot. I planned on buying the proper alignment tool, but a generic one was about $150.00 :eek2: . That seems to be the magic $$$ for transmission tools.

Pump installed and torqued to 18 ft. lbs.

Next I checked the end play. This was alittle tough because all the new bushings made everything fit pretty snug. I basically had to push down on the turbine shaft, then set the dial indicator. Then I pulled up on the turbine shaft as I rotated it.

Checking rear end play ( I used the same steel plate for all the end play measurements. )

Here's the valvebody ready for cleaning and modifications.

Here's a pic of the seperator plate with some of the modified holes marked. Some get drilled larger and some get plugged and peened shut.

1-2 servo installed. Cover going on reverse servo and 1-2 accumulator. I did not check the pin lengths because the old bands and drums seemed fine and I am using stock sized carbon lined bands.(that would also require a special tool)

The Transgo shift kit has you leave out one of the check balls. 7 of the original 8 installed.

Here's the valvebody, pressure manifold switch, and new internal harness installed.

Here are the guts of the transgo vacuum modulator kit.

And here 's the vacuum modulator installed. This takes the place of the variable force motor, which controls line pressure.

The trans is in and runnin. The 2800 vig triple disc is a nice addition as well. Right now at WOT the shifts are WAY too hard. It feels like somethig is slamming into the pack of the truck. The TCC is even harder. part throttle shifts are ok. I think I need to shorten the pin on the vacuum modulator. I'm running the longest length Transgo reccomends 1.345 (says for commercial/ working trucks). Transgo says to shorten if shifts are too hard.

My line pressure ranges from about 75 psi at 20 inhg to 200 at 0 inhg. At WOT the pressure gauge fluctuates around 200psi so I'm pretty sure that's the pressure regulator doing it's job. Transgo said pressure ranges should be between 80-200psi. The stock pressure chart for an EPC (force motor) shows 177psi at .02 amps as the max. I'm pretty sure shortening the pin will solve my problems. I plan on taking care of that today. :burn:

You know, you could probably do the rebuild without the holding fixture, if you have plenty of workbench space. The 4l80E is one heavy MF though, so I'm glad I bought the holding fixture.


11-30-2008, 07:09 AM

I'm not sure if your book tells the proper location of this snap ring. Take it and put it at the 3 o'clock position. Basically a 180* from where you have it. The reason for this is with a wider snap ring it will rub the direct drum(high reverse drum). When the intermediate clutch is applied the pressure plate will flex that snap ring and it will rub with it in the position that you have it. Looks like you are having a lot fun. Enjoy!!! Vince

Hi guys,

Excellent read !

Can someone please explain to me how the snap ring would work better spun 180*

If it's a round ring how can it make a difference .

Wouldn't it sit exactly the same , no matter what clock position the split was at?

Sorry if it's a dumb question, I'm new to this sort of thing.


Vince @ FLT

11-30-2008, 12:15 PM

The snap ring will rub on the direct drum! That is why I pointed it out. When I see this it is usually done because the guy building the trans did not have a lot of experience building. With the factory snap ring being narrow compared to the wide ring that most of us get in the transgo kit, it may or may not propose a problem.

Wilde Racing

11-30-2008, 12:32 PM

The manual actually shows it being installed in the position above, but as Vince pointed out, the g.m snap ring is thinner and may not cause an issue....


11-30-2008, 01:46 PM

nice write up! good job so how is it doing


11-30-2008, 07:37 PM

The snap ring will rub on the direct drum! That is why I pointed it out. When I see this it is usually done because the guy building the trans did not have a lot of experience building. With the factory snap ring being narrow compared to the wide ring that most of us get in the transgo kit, it may or may not propose a problem.

I'm probably looking at the wrong thing but,

if the ring is the same width all round , how would rotating it give more clearance?

Apologies once again,


Vince @ FLT

11-30-2008, 10:04 PM

The problem is that the opening of the snap ring in the wrong position will flex when the clutch pack is applied. When this happens it will hit the direct drum. Try it and see for yourself. It's true. Vince


12-01-2008, 02:17 AM

The problem is that the opening of the snap ring in the wrong position will flex when the clutch pack is applied. When this happens it will hit the direct drum. Try it and see for yourself. It's true. Vince

Ok , i get it now.

Thank you very much Vince for sharing that information.

You are a highly regarded member on these forums and was never questioning what you where saying.

I was just trying to work out how.

Keep up the good work ,

This is an awesome site with many helpful hands.