4 speed trans conversion

[racingjoe66]

I have found some, just the sellers can't tell me much about them but the part numbers. So any info to identify the ones I need is greatly appreciated or a site to run the part numbers

 

[Retiredwarhorses]

How bout post the part numbers you have?

 

[Action]

The 218 uses a u-joint at the rear, the 242 uses a slip yoke. So shortening won't fork.

 

[TacMac2012]

Most driveshaft shops (or at least the one we use regularly for our various other vehicles) have no issue welding on new yokes as needed. A bolt-in shaft would be nice though if the price was right.

 

[linhster]

What's are differences between the th400 and the 4L80e crossmember?

 

[WAGNUM]

I had extra tan...

racingjoe66, Jon0249, Augi, (and pretty much everyone else) helped me with my recent conversion, and I'd be more than happy to pay it forward. I just got mine finished 4 days ago, and all my injuries are still fresh... Did 75mph for the first time, felt like I was trying for the land speed record, but 65mph on the hi-way is awesome.

 

[dilvoy]

Just take your driveshafts and have the front lengthened and the rear shortened at a local driveshaft shop. If you have a decent shop they should be able to do it for cheaper than you can buy a new shaft.

You can do that, but then you will still have all the smallest U joints that were ever fitted to the Humvee. When they went to the four speed trans, the U joints were replaced with the larger ones, even at the diffs.

 

[Action]

Did 75mph for the first time, felt like I was trying for the land speed record, but 65mph on the hi-way is awesome.

Did you use a GPS for that speed reading? When you start swapping parts, things get missed. There is a plastic gear in the transfer case that is specific to tires size, diff ratio, etc. That is a whole different topic.

 

[humvee1035]

i put a gear vendor dual range.

 

[TOBASH]

couldn't agree more on the TH400...they are one of the strongest trannys on the market.
My trans guy told me this years ago....the 4L80E is good, but nothing like a TH400 on durability.

Retired War Horses is on point.

I have personally worked on vehicles with gobs of horsepower and torque (including my old 1967 heavily modified GTO) and the TH400 is awesome. (I procured an MV41 tranny and not an MV40 though.) Easily modified and worked on and improved. Well understood by all tranny shoppes as they have been in use since the mid 1960's. Some people on other forums even replace the parking brake stuff on their HMMWV TH400's so as not to rely on the E-brake. ALSO there were modification kits to allow removal of TH400 bell housing and replacement with a sturdier bolt on unit. Sounds corny but they work for guys drag racing and mud crawling.

If they stand up to that abuse, I'm assuming they will survive the stock engines.

That is why I mentioned in an earlier post that I would prefer to not swap my tranny as part of my planned upgrades. It is entirely mechanical, cheap as borsht to get a mechanic to fix it, and predictable. No limp mode, and no electrical issues.

MHO. Your mileage may vary. I'm sure others love the 4 speed automatics and I respect that.

Best,

T

 

[dhaumann69166]

Built 700r4 and a 241c transfer case is the way to go. Fully mechanical with no need to change drive shafts, crossmembers or anything. People say the 700r4 is junk but there are a million drag racers putting 1000hp to them with a mid level build. Way cheaper and easier than the 4l80 and no computer required

 

[formula223]

Built 700r4 and a 241c transfer case is the way to go. Fully mechanical with no need to change drive shafts, crossmembers or anything. People say the 700r4 is junk but there are a million drag racers putting 1000hp to them with a mid level build. Way cheaper and easier than the 4l80 and no computer required.



If you've done the 700r4 conversion I would love to talk to you. Specifically, I have seen the $3300 kit but I've seen ads for built ultra heavy duty 700r4 for $1700. What did you use? I need to find someone who knows all the little answers like if the transfer case bolts up with no problem, can two wheel drive be selected, what does the TV bracket look like, how is the 3 speed shifter modified for 4 speed use... as on and on.

 

[tomelroy]

I did a "built" 700r4 (level 2) from bowtie overdrive. I wanted to use my np242 which requires an adapter. The adapter is made by advanced adapters, but I did order it with the 700 from bowtie. With the adapter installed,the 700r4, adapter and 242 fit perfect. For the tv cable, just reuse the bracket in the valley. It is basically the same setup as with the 3 speed. Just notch 4 corners in the round hole of the bracket and the tv cable will fit perfect. From there you just have to get every mm of throttle travel you can find. (Take slack out of throttle cable and even remove insulation that limits foot pedal travel.) once you get maximum throttle range set the tv cable . At idle it should just barely have no slack and full throttle the tv cable should be at max range.

The next 700r4 I do, I will weld an extension on the foot pedal arm were the cable connects to make it easier to get max range. That would eliminate having to cut out insulation.

 

[dhaumann69166]

I am getting ready to do the 700r4 conversion in my 93 and have learned a few new things. Since it’s a 27 spline output shaft you either need to change output shafts or t case input. You can get a 32 spline output for the 700r4 but it is a stock shaft cut off with a 32 spline end welded on. It’s extremely rare to break the output on a 700r4 and you can buy HD ones. Some say this could be a possible weak point at the weld and the 32 spline shaft is expensive and not real easy to change. You can get a 27 spline input for your factory NP218 for $90 and it’s pretty easy to install. Some will even bolt up without aftermarket adapters. My 700r4 came from an 87 Suburban and aside from output shaft it’s a direct bolt on fit. The hardest piece to get is the TV (kick down cable) bracket. Some civilian vehicles came stock with a 6.2 diesel and a 700r4 and have the correct bracket if you feel like junkyard hunting. You can use a regular one for a 700r4 and customize it if you are handy with a grinder and welder. Someone a while back on SteelSoldiers had a place making them for him but can’t remember who. The TC lock up is simple to wire in. You can put it on a switch or there are kits for 12v or 24v break pedal switches. The TC lockup is something you need for both tranny’s. There are a few places selling kits for around $100 or less for the 700r4 or you can make your own. Only 4 wires and lots of diagrams online.
In my opinion you will spend less time and money having a 700r4 built up and changing the T case input. No drive shaft mods required. No moving crossmembers or changing gas tanks. Best of all no computer! These tranny’s are used in drag cars and many off road 4x4 vehicles so parts are cheap and easily available. They also have a lower first gear than the TH400 (I don’t know about the gear ratios in the 4L80).
With a 4l80 you need a computer, drive shaft mods, gas tank changed (if 93 or older), move your cross member and many other small things. Parts are more expensive for the 4L80 and there is computer controlled stuff that might not like the off road abuse some of us put our Humvees through. I don’t know if there is a way to make the computer waterproof and handle bumps and bangs but I am sure you could somehow. And for those worried about EMP’s frying electronics when the world falls apart probably want to go 700r4.
I guess it comes down to how much you have to spend, how close to original do you want to stay, what kind of situations will you be putting you vehicle in? I have a functioning deep water ford kit and full marine stereo so I plan on getting stuff wet and I would be nervous about water vs computer. If it wasn’t for the fact that the nearest town is 60 miles away I wouldn’t worry about a 4 speed but that extra gear and being able to do 65 mph without the 6.2 screaming will be GREAT!

 

[Augi]

Just a few points having installed a 4L80:

The gas tank does not need to be changed to install the 4L80. The new style tank hits the driveshaft parking brake rotor so requires the new style parking brake installed if you punch a hole in your old tank and can only find a new one to replace it.

As for the resiliance of the computer, if you install a stock one it comes in a waterproof box lined with foam. It's solid state though, so bumps really don't affect it unless you manage to break parts off somehow. It's been tested for a couple of decades in actual HMMWVs to boot.

EMP survival ability... probably won't have a large impact on your daily commute.

The crossmember and driveshafts can be bought if you don't want to have a shop lengthen the front. In fact the rear must be bought because of the slip yolk.

Augi

I am getting ready to do the 700r4 conversion in my 93 and have learned a few new things. Since it’s a 27 spline output shaft you either need to change output shafts or t case input. You can get a 32 spline output for the 700r4 but it is a stock shaft cut off with a 32 spline end welded on. It’s extremely rare to break the output on a 700r4 and you can buy HD ones. Some say this could be a possible weak point at the weld and the 32 spline shaft is expensive and not real easy to change. You can get a 27 spline input for your factory NP218 for $90 and it’s pretty easy to install. Some will even bolt up without aftermarket adapters. My 700r4 came from an 87 Suburban and aside from output shaft it’s a direct bolt on fit. The hardest piece to get is the TV (kick down cable) bracket. Some civilian vehicles came stock with a 6.2 diesel and a 700r4 and have the correct bracket if you feel like junkyard hunting. You can use a regular one for a 700r4 and customize it if you are handy with a grinder and welder. Someone a while back on SteelSoldiers had a place making them for him but can’t remember who. The TC lock up is simple to wire in. You can put it on a switch or there are kits for 12v or 24v break pedal switches. The TC lockup is something you need for both tranny’s. There are a few places selling kits for around $100 or less for the 700r4 or you can make your own. Only 4 wires and lots of diagrams online.
In my opinion you will spend less time and money having a 700r4 built up and changing the T case input. No drive shaft mods required. No moving crossmembers or changing gas tanks. Best of all no computer! These tranny’s are used in drag cars and many off road 4x4 vehicles so parts are cheap and easily available. They also have a lower first gear than the TH400 (I don’t know about the gear ratios in the 4L80).
With a 4l80 you need a computer, drive shaft mods, gas tank changed (if 93 or older), move your cross member and many other small things. Parts are more expensive for the 4L80 and there is computer controlled stuff that might not like the off road abuse some of us put our Humvees through. I don’t know if there is a way to make the computer waterproof and handle bumps and bangs but I am sure you could somehow. And for those worried about EMP’s frying electronics when the world falls apart probably want to go 700r4.
I guess it comes down to how much you have to spend, how close to original do you want to stay, what kind of situations will you be putting you vehicle in? I have a functioning deep water ford kit and full marine stereo so I plan on getting stuff wet and I would be nervous about water vs computer. If it wasn’t for the fact that the nearest town is 60 miles away I wouldn’t worry about a 4 speed but that extra gear and being able to do 65 mph without the 6.2 screaming will be GREAT!

 

[dhaumann69166]

What year did you do your conversion on? Just curious because I have read multiple places that the 93 and earlier you have to change tanks because the 4L80 being longer causes rub and the 94 and newer A1 models have a slightly different tank. I don’t know that to be fact just what I have found from reading on here. I have ZERO personal experience with the 4L80 swap.

What did you do for a shifter? I am trying to find a 4 speed with Park that doesn’t cost 500 to 700 dollars. Any way to modify the existing one or put an aftermarket shifter in?

 

[tomelroy]

dhaumann69166

You do not need a new bracket for the tv cable. The existing bracket (for the t400 kick down) and linkage to the injection pump works perfect.

 

[dhaumann69166]

dhaumann69166

You do not need a new bracket for the tv cable. The existing bracket (for the t400 kick down) and linkage to the injection pump works perfect.

That is awesome to know! The bracket is ridiculously expensive. Has anyone tried modifying the stock shifter to make it a 4 speed? B&M 3 speed shifters can be changed to 4 speed by changing a piece on the side. Basically looks the same only notched slightly farther for 4 gears. Didn’t know if you could use a dremel tool and make the factory one work. Probably just wishful thinking.

 

[BLK HMMWV]

I think Board member 86humv has some 4 speed shifters for sale in the $350-$400 range.

 

[86humv]

I think Board member 86humv has some 4 speed shifters for sale in the $350-$400 range.

Yes...but a guy is buying all 4 so he says.
$ is pending on them.