TH400 to 4L80E Swap for dummies, help needed (crossmembers)

[RickTheEngineer]

Hey all, I have a question about swapping an M1009's TH400 to a 4L80E transmission mated to an np205 tcase. There were some writeups on this site on how the swap went, but nothing went too deep into the crossmember and transfer case support. I plan on swapping to a np205 when performing the 4L80E swap too. Can the original cross member be used? If not, what cross member can I use? Explain this to me thoroughly, because this is one thing I want to figure out completely. Thanks so much!

EDIT - some ideas I had was maybe getting an M1008 cross member since it already has a bolt pattern suitable for an np205? Stronger maybe?

 

[corelokt]

Mine was moved back to put the front holes in line with what were the rear holes. A new driveshaft is also needed.

 

[corelokt]

It is a m1008.

 

[RickTheEngineer]

did you need to machine anything? Because if I am not mistaken, if you use an adapter to go from 4l80e to np208, the height of that adapter might be different... at least in the case of an m1009, so maybe a 1008 crossmember might be a good option?

 

[Barrman]

All the CUCV trucks have the same pedestal/transmission mount. You are asking 2 different questions.

1) How to put a 4L80E where a TH400 used to live?

2) How to mount a NP205 to a 4L80E?

To answer the 4L80E question first. It will bolt up to the stock CUCV flywheel and engine with no issues. As mentioned above, what was the rear hole in the frame rails for the cross member will now be the front hole. You will have to drill a new pair of rear holes. Just bolt the crossmember in and us it as a template for the new holes.

The oil fill/dipstick tube might need to be bent just a bit to clear the firewall and can only be installed from the bottom with the transmission out.

You shift linkage will not connect. I welded in another 3" to my shift rod so it would reach the 4L80E. The pivot point bolted to the frame will also have to be moved back 1-2". I used the rear hole as the front mount and have left it at that without any issues.

To get all 4 gears manually, you will need to swap in a 4 speed steering column. Get a delay wiper column and just add the delay module when plugging it back together to have intermittent wipers. Bonus!

That is the easy, for sure facts with any 4L80E. Then it gets to be an "If this, then..." thing.

If you have a '91-94 4L80E, then your TH400 shift linkage arm will swap over to the 4L80E for sure. If you have a '95 or newer 4L80E, then it might need to be notched a little or it might slide right on the shift shaft.

If you have a '91-'96 4L80E, then your cooling lines will need to be bent a little, but will screw right in 2" back. If you have the newer "rear oiller" 4L80E, then the return line will have to be spliced, added to or replaced to reach the middle of the 4L80E.

If you have a '91-'93 4L80E, then no aftermarket controller will bolt up to the internal wiring harness. Then, you have to replace the harness ($75 on Amazon) and all 5 internal solenoids which is very easy to do and about $200 total.

Aftermarket controller is up to you. Read my M1007 thread if you want to read pages and pages about this swap in more detail.

Transfer case to 4L80E. The TH400 had inch sizes and the 4L80E is metric. A TH400 pedestal will almost, but not exactly fit the back of a 4L80E. I gave one of my students a small hand file and told him to just go in circles on the cast iron TH400 pedestal until is fit the 4L80E. It took him about an hour. A person with a die grinder could do it in a few minutes. Even better is drop it off at a machine shop and come back the next day. Very easy. So is just buying the aluminum circle pattern 4L80E pedestal which has the same transfer case bolt pattern. So, if you have a TH400 to NP205 mount, just a bit of work will make it bolt up to a 4L80E and all is well.

This all make sense?

 

[RickTheEngineer]

Awesome write up!! But only one more thing... I asked this question a while back on other K5 forums as well as here if I recall if there is a such thing as a 4 speed column... I did get answers that said that the shift notches are caused by the trans, and not the actual column, thus there isn't exactly a 4 speed column, but rather you'd need a 4 speed gear indicator above the column for everything to line up... Is this true?

 

[Barrman]

I had a 1989 700R4 truck sitting next to a TH400 truck all stock. I unhooked both shift linkage rods because I had read the same thing about no difference. Then I tried to measure or figure out some difference. The 700R4 column shifter moved further down.

Once I had them both out of the trucks to swap, I figured out the housing metal on the engine compartment end had a little more metal notched off. Very easy to do. With no engine in the way but not so easy otherwise.

However, I am sure changing the geometry or length of the shifter linkage could give you enough travel to get to 1st with a TH400 column. I wanted delay wipers and the switch for that is very expensive if you can find one. A column swap was cheaper and easier to get all I wanted.

Yes, you will need a 4 speed indicator back ground as well.

 

[Back40ent]

So after reading several threads on this subject I still have a few questions. I have an 86 M1008 and a complete 95 4wd 1 ton donor with a 6.5 and 4l80e. I want to do the 4l80e swap with standalone and reuse the 208 and mechanical fuel pump from the M1008. Will the steering column from the 95 bolt up to the M1008? Will I need a different adapter for the 208 or will the adapter for the th400 work with the 4l80e?

 

[Barrman]

Is the 1995 a 4wd? If so, then the 208 will bolt up to the adaptor already on the transmission for the 241C. The mount from the adaptor to the cross member might need to be taken from the TH400 truck. I don't know that one.

Does the 1995 have airbags? If so, then the column is different. I am pretty sure it is a cable shift column which means it won't work in the CUCV as a bolt on replacement.

You will need to move the turbo oil drain from the 1995 either to the oil pan or use a Banks oil return plate to make the mechanical fuel pump work. I am pretty sure the camshaft on the 1995 has the lobe for the fuel pump. Again, not 100 percent sure. Electric pump in the M1008 might be cheaper, easier and quicker option. Especially since the fuel lines are already at the back of the engine instead of the front.

 

[Back40ent]

Thanks for the reply and info Barrman. The 95 is a 4wd dually without airbags. I'm not swapping the 6.5 over to the M1008 just the turbo related parts and the serpentine drive if my theory works. Is it possible to use the serpentine drive from the 95 with a dual voltage alternator from a 6.5 humvee on the drivers side and replace the 12 volt alternator on the passenger side with the A/C compressor from the 95?

 

[Barrman]

The serpentine system is nicer to live with than the V belts in my opinion. However, the dual alternator, 12/24 volt system is kind of hazy with the serpentine set up.

2 CS130 alternators, no problem in a 12 volt system. GM did that with both the single and dual thermostat 6.5 engines. Making it work in a 12/24 system has been talked about, but not done that I have found. I would like to do it myself. I finally collected enough spare CS130's to try taking one apart and try to convert to isolated ground. They are not as serviceable friendly as the Delco 27SI units on the CUCV trucks.

I have never seen the HMMWV serpentine belt brackets. So, I can't comment on how it would work on a square body truck.

 

[Keith_J]

Great info here. Now that I am single again, I have disposable income to do the 4L80E conversion to the 1031. This is a bit more as I need to preserve the PTO for the Lima MAC generator. Which means moving the engine forward 1-9/16" to keep the transfer case in the original position. Offset motor mounts will need fabrication plus all the hydraulic lines etc but it makes access to the rear of the engine a bit easier. Yes, plenty of clearance with the fan to radiator and it moves the fan into the heart of the shroud for best efficiency.

Moving the engine also means no driveshaft modifications. Worth the effort. What I don't know is how the transmission will react to the PTO load. It works with the TH400 just fine, frequency drops for just a second with load, the governor kicks throttle up perfectly to recover 60 Hz when I put an 8 kW load on the generator. I imagine the lockup converter clutch should stay engaged as the generator is only a 30 Hp load at max. Lima MACs can take huge overloads, meaning it could draw as much as 50 Hp.

 

[Barrman]

Look at the ORD cross member Keith. It might be the answer you didn't know you were asking for.

Nice to see you back.

 

[Jozseph]

Did you research using motor mount used on the Chevy diesel van that had a 6.2 from the same year?

Has been posted on this and other sites those motor mount will move the motor forward and up when used on a pick up frame.

Regards

Joseph

 

[Keith_J]

Did you research using motor mount used on the Chevy diesel van that had a 6.2 from the same year?

Has been posted on this and other sites those motor mount will move the motor forward and up when used on a pick up frame.

Regards

Joseph

Very nice idea. I like fabrication but something commercial off the shelf is a time saver. I'm looking into it..off to Rock Auto..