Lots of Questions about 4L80E Swaps

[HmmwvTim]

quick question on this trans. The speedsensor wire on my harness has been cut to the nub. All I see is two white wires. If I solder a new plug on, does it matter which direction I install it or is one a voltage source and the other data? How to tell which is which?

 

[FlameRed]

First post here, so please go easy on me guys!

I am expecting the truck to delivery my M998 any day now. I knew when I bought it that the M998 with the 3 speed would not be the greatest for my mostly street use purpose, and I know I will be needing to do a swap.

I am not the most skilled mechanic. I never swapped out a tranny mostly because I never had the need to do it myself before and I don't have a lift. I think I could tackle it though on a nice high humvee. My thoughts were to not remove the engine if I did it myself.

I had other cars with a 700R4 and burned them up and I want to stay away from them.

So let me ask if there is any vendor out there that sells a "kit" that includes everything I need to get a 4 speed install, with a "rebuilt" freshened up tranny, and anything else that might be needed to complete the job, including different transfer box, drive shafts, shifter, harness, controller, cross member, adapter plates, yada, yada, yada. I know in the hot rod world places like Gear Star and American Drive Train can help with swaps.

I would be tempted to look for maybe a local shop, but that defeats the purpose of having a "project" vehicle! Besides, the closest Humvee specialists are a couple hundred miles from me. But that would take all the "fun" out of it!

The other alternative from the hot rod world is Gear Vendors makes a seperate overdrive unit that bolts on to the back of GM 3 speed trannys. https://www.gearvendors.com/hrgm3s.html It can be used on 4WD apps, but will only work when in 2D mode. Of course it requires a different driveshaft and has it own controller. I am not sure if anyone ever used something like this on a Humvee.

Any advice for a newbie?

 

[MattNC]

I am one day from the start of my swap to a 700r4 that was built to level 3. My thoughts are I would get the truck and as-is kick the tires on it for at least a few months. Stuff is going to need to be replaced, there's going to be a few gremlins to iron out on any vehicle this age. I have had mine several years are feel good now about going to the swap stage. I hope everything is great one yours but if you find the engine is on its last legs you may want to go in another direction (i.e. a turbo-4L80 full driveline swap)

 

[MattNC]

I would also add the 3-speed is fine for street driving and bullet proof. The highway is where it will drive you crazy when you are at 55 and the engine is screaming.

 

[springer1981]

First post here, so please go easy on me guys!

I am expecting the truck to delivery my M998 any day now. I knew when I bought it that the M998 with the 3 speed would not be the greatest for my mostly street use purpose, and I know I will be needing to do a swap.

I am not the most skilled mechanic. I never swapped out a tranny mostly because I never had the need to do it myself before and I don't have a lift. I think I could tackle it though on a nice high humvee. My thoughts were to not remove the engine if I did it myself.

I had other cars with a 700R4 and burned them up and I want to stay away from them.

So let me ask if there is any vendor out there that sells a "kit" that includes everything I need to get a 4 speed install, with a "rebuilt" freshened up tranny, and anything else that might be needed to complete the job, including different transfer box, drive shafts, shifter, harness, controller, cross member, adapter plates, yada, yada, yada. I know in the hot rod world places like Gear Star and American Drive Train can help with swaps.

I would be tempted to look for maybe a local shop, but that defeats the purpose of having a "project" vehicle! Besides, the closest Humvee specialists are a couple hundred miles from me. But that would take all the "fun" out of it!

The other alternative from the hot rod world is Gear Vendors makes a seperate overdrive unit that bolts on to the back of GM 3 speed trannys. https://www.gearvendors.com/hrgm3s.html It can be used on 4WD apps, but will only work when in 2D mode. Of course it requires a different driveshaft and has it own controller. I am not sure if anyone ever used something like this on a Humvee.

Any advice for a newbie?

There is a lot to it and if you have no experience with even simple swaps then you need someone that does. It's not hard but takes lots of research to figure out all the parts you will need. The basic components are easy but all the little details and figuring out part numbers etc is time consuming. I collected parts for a couple of years before I did mine. I had a lift and a shop and full stocked tool boxes and lots of specialty tools and it took me a week to do it. I did other stuff while I was in there.

The Gearvendors is not a good choice and would probably cost as much or more by the time you are done.

I drove mine for 3 years with the 3 speed while I planned this out. You should start collecting parts and asking for advice as you go and read and learn before you start to disassemble anything. My build thread is linked in my signature and if you start around page 11 you can see the transmission swap stuff I did.

 

[lpcoating]

I'll add that if you've never driven a Humvee I'll recommend that you drive it for a while and make sure you actually like it for your intended use. This is after you throughly go over the truck doing basic pm work and looking things over.

 

[HUMMER H1]

I did my swap in 2015, I am using EZI TCU stand alone controller
It’s absolutely awesome.

 

[jake-cutter]

When doing the swap, how hard is it change to the correct body harness and fish the big cannon plug through?

 

[BLK HMMWV]

When doing the swap, how hard is it change to the correct body harness and fish the big cannon plug through?

Not sure where your trying to fish big cannon plug through. It only has to go through 1 hole and hole is big enough to accommodate plug then a grommet seals hole.
I've heard it's possible to change harness without removing body but it's a lot easier to remove body to swap harness.

 

[springer1981]

When doing the swap, how hard is it change to the correct body harness and fish the big cannon plug through?

That all depends on what you have in place now. What engine, transmission and transfer case do you have and what are you changing to? Serpentine or v-belts? I believe there are different engine harnesses depending on the engine and transmission combination. There are even some combinations, IIRC, that don't have a "correct" harness. My personal opinion is to use an aftermarket controller like the QuickShift 4 and not mess with all the wiring. It's a simple to install setup, works with any combination of engines and transfer cases, and much more advanced than the antiquated and expensive stock system.

 

[hahnmgh63]

I've got a M998 that I swapped to a 4L80E last year as well as a recently purchased M1097A2. Nice that the M1097A2 is over 15yrs newer and has other updates too. As mentioned, doing the M998 isn't difficult mechanically but pulling the old tranny and installing the new one, with or without the 242 installed is heavy and awkward by yourself. I have a lift, but did it by myself, tranny first, then added the transfer case on the back. Figuring out the drivelines (depends on what you are starting with), and the different Yokes, U-joints, U-joint U-clamps, and misc. all take some work. I went with the Quickshift 4 and glad I did. Only way I'd do the OEM factory install is if I had a cheap donor. I bought a tranny from Eastern surplus (came with the crossmember), drained the fluid, did filter, replaced the solenoids and harness, filled with fluid and good to go so far, shifts great.