4 speed trans conversion

[racingjoe66]

Hi guys, I purchased a 1986 HMMWV M998 A0. It has a rebuilt detuned 6.5 in it already and still has the 3 speed trans. I am wanting to update it to a 4 speed trans and leaning towards a mechanical non computerized 4 speed. I was wondering if anyone has done this and has any pointers for me. I am planning on having a local guy go through the trans for me and put a kit in it as I want it built for towing as I plan to put a receiver on the back so I can pull a small trailer with it and also pull m 1967 Jeep Kaiser M715 behind it when mudding and also my boats from time to time and also to gain some cruising speed.

any and all help would be greatly appreciated.

thanks

 

[parklandtrans]

If you are going with the 4L80E trans, which is the only 4spd overdrive trans for the HMMWV.....You will require the stand-alone computer brain box. This replaces your conventional computer in your POV. Very simple plug and play set up...doesn't get any easier then that my friend. You will also need the shifter Assy with the "Park" position, specially for the Overdrive transmission. Any other questions feel free to PM me and I will answer as soon as possible.
Parklandtrans/ Bob

 

[racingjoe66]

Thanks Bob. I was told the cross member needed to be moved back some also for the 4L80E and possibly a different transfer case? Will send you a pm

 

[Retiredwarhorses]

Thanks Bob. I was told the cross member needed to be moved back some also for the 4L80E and possibly a different transfer case? Will send you a pm

Yes and yes....plus several other things. I find it funny how folks say it's just as easy as 1,2,3...
the crossmember is not moved back, it's replaced. The 242 tcase mates to the 4L80E, your also going to need drive shafts too. To be fair...I don't do after market conversions....I do factory OEM work at my shop.
I am sure these non factory conversions are cheaper then an OEM conversion....

 

[racingjoe66]

Which crossmember is it replaced with? And I didn't think it was as easy as 1 2 3, from everything I have been reading up on it. As for the driveshafts, are there some that work or do some need to be made? I am thinking this will be a conversion I want to do this winter, so any help is great

 

[Retiredwarhorses]

Which crossmember is it replaced with? And I didn't think it was as easy as 1 2 3, from everything I have been reading up on it. As for the driveshafts, are there some that work or do some need to be made? I am thinking this will be a conversion I want to do this winter, so any help is great

sorry Joe, I didn't mean you thought it was as easy as 1 2 3....this thread topic is not new.

 

[99nouns]

Thanks Bob. I was told the cross member needed to be moved back some also for the 4L80E and possibly a different transfer case? Will send you a pm

Can you guys keep your conversations on here so we all can learn please, unless you planing to patent your findings...

Thank you and carry on...

 

[racingjoe66]

No worries I didn't take it as you were meaning me I will do some more research

 

[Action]

Which crossmember is it replaced with? And I didn't think it was as easy as 1 2 3, from everything I have been reading up on it. As for the driveshafts, are there some that work or do some need to be made? I am thinking this will be a conversion I want to do this winter, so any help is great

The crossmember is replaced with the one made for the 4l80e. Propshafts do not need to be made. You just buy the correct ones.

 

[parklandtrans]

Warhorse,
thank you for the correction on the 4L80E swap for Joe...if you've never done the conversion..it will not be as easy as "1,2,3"...however, after the first one is done successfully you will feel like you can do anything on the HMMWV...I think a lot of the other folks would agree..!!! Joe, the real key is to obtain as much info as possible prior to starting project..information is power and is the best tool in your toolbox..!! Bob

 

[racingjoe66]

I will do a lot of research and part searching before I proceed with this swap this winter. Are there any upgrade kits out there for the trans or torque converter made more for pulling heavy items? If anyone can copy & paste links to some good write ups on this swap, I would greatly appreciate it.

Thanks again Bob & Warhorse & Action!

 

[Lionel]

"the real key is to obtain as much info as possible prior to starting project..information is power and is the best tool in your toolbox"

Information and about $6,000 + in parts.

 

[nattieleather]

Just a dumb question here, but a 700r4 would not work in place of the 4L80? I thought they were basically the same case, length etc.?

 

[racingjoe66]

Nattieleather---- check this out http://g503.com/forums/viewtopic.php?f=101&t=204902

 

[racingjoe66]

Does anyone have the #'s to the driveshafts that are needed for the 4L80E swap?

thanks

 

[Action]

Does anyone have the #'s to the driveshafts that are needed for the 4L80E swap?

thanks

Are you going to install a 242 transfer case with it?

 

[racingjoe66]

Yes I think I would be doing a NP242 with it as I am looking at a trans that comes with the 242 already. Is the 242 a better one?

 

[Action]

It is better than the 218 that comes with the old 3-speed. The 242 has two cooling line ports on the front of it. A revised version will have a blue band on one or both of those tubes. That is the preferred one to find. The non-banded one had some issues with leaking the cooling fluid into the transfer case. So the trans would run low and the t/c would get high.

 

[racingjoe66]

by chance do you have a pic of what the bands look like? also are those cooling lines suppose to be solid steel or spliced with a rubber hose & hose clamps?

 

[racingjoe66]