New M998 Project looking for input.

I recently purchased a 1985 M998 6.2, open top (canvis) in excellent condition.

Im looking to do the following and any ideas or possible improvments to my ideas would be greatly appreciated.

1. Putting a shell on top, prob a slant back from California Gold kits...
Home

Pic of slantback
Mil SlantBack

or Wagon
Military
Note there will be seems on eaither

2.Paint GunMetal Gray, with rhino line for parts of the interior.

3. Hard doors. These seem hard to come buy any ideas...
http://www.calgoldproducts.com/ use to sell them but dont.
Will the two door M998 doors fit on the four door?

4. Engine, I was sugjested a cummings, Durmax, or CAT motor, any particular motors that people have used for swaps...etc

5. Transmition....wide open

6. Tires, any advice on what to stay away from...

7. Winch. What if any winch can be mounted.

Interior Mods, another post

Thanks, allready for any who reply

I've been doing the same research after buying a Humvee last week. I've also been talking to a number of friends and clients in the industry. Their recommendation: the Cummins 6BT conversion from Predator Motorsports. The guys at Platt Mounts speak highly of them, and tell me their Humvee will do 120mph with new rims/tires, tranny, brakes, and the Duramax conversion. Of course, their Humvee was $$$.

The Platt Humvee is on the Predator Motorsports web page, in the gallery section, near the bottom. Good looking truck.

I too wanted a hard roof, and liked the idea of a turret top. Everyone says they leak. Your end goals may be different than mine, but I want to actually shoot off my Humvee. I'm thinking a roll cage with built in turret ring that gets covered entirely by the soft top. Not quite sure what to do there.

Can't imagine driving without radial tires, even though my truck currently has 8 bolt bias ply. Others can speak on rims and tiresl but I learned a lot from this page. Complete with pics:

Wheels/ Tires for Hummers

PBR

Thanks for the reply,

I think youre post may have helped with the wheels, I like the 24 bolt ones. My M998 will be a dark gunmetal so I might use the the 20 bolt 2-piece forged Hutchinson with a runflat and a Goodyear MTR tire, but for 2k a piece has me with second thoughts .

Ill deff check out the Cummins thanks
Ill be chatting it up with my mechanics the next few days.

What type of Hwwmv did you get?

Info thread on cummins swap ; New Cummins HMMWV project in the works!

I would do a cummins 12v swap. It has pracitcally no electronics, and less to go wrong.

I put the 6.5TD and paired it with the 4L80E and it gets plenty of power for me and plenty of speed (as fast as the truck is really rated to go). The best part is I really had to do no modifications to put any of this in since it is all current military equipment. I use the Goodyear military HMMWV tires and so far I have had zero problems with them. As for your question on slantback vs. wagon I think it comes down to one thing; that is whether you are going to put a lot of things in the back or not. The slantback restricts what items will fit in the back whereas the wagon offers much more room. I have two winches from warn (from the HMMWV models), the front hydraulic and the rear electric. So far they have worked great. Hope this helped.

Front doors are the same on 2-door or 4-door trucks. Front and rear doors are not interchangeable. The non-armored "X" doors and the lightly armored doors (which are just "X" doors with thin armor plates riveted on) hang on the same hinges as the vinyl doors, but the door strikers need to be changed when switching between soft and hard doors.

If you go with a 2 door configuration, there is a newer style of those rear filler panels (commonly called "half doors", even though they aren't doors) that has a hinged section at the bottom to give outside access to the rear footwells. I have a set of those on my truck. The newer style could probably be fabricated by cutting up older ones if needed.

usmc81301 said:

I put the 6.5TD and paired it with the 4L80E and it gets plenty of power for me and plenty of speed (as fast as the truck is really rated to go). The best part is I really had to do no modifications to put any of this in since it is all current military equipment.

Click to expand...

I was under the impression that mods to things like frame crossmembers were needed to retrofit a 4L80E into an older HMMWV that originally had the TH400? I don't recall whether there are also issues with using the original transfer case with the new transmission, too.

I wouldn't mind having higher cruising speed and more power in my truck, which is particularly sluggish with that heavy shelter on the back, but upgrading the engine and transmission seems like a project that would involve substantial effort and expense. I'm still rolling on the bias ply tires, even.

usmc81301 said:

I put the 6.5TD and paired it with the 4L80E and it gets plenty of power for me and plenty of speed (as fast as the truck is really rated to go). The best part is I really had to do no modifications to put any of this in since it is all current military equipment. I use the Goodyear military HMMWV tires and so far I have had zero problems with them. As for your question on slantback vs. wagon I think it comes down to one thing; that is whether you are going to put a lot of things in the back or not. The slantback restricts what items will fit in the back whereas the wagon offers much more room. I have two winches from warn (from the HMMWV models), the front hydraulic and the rear electric. So far they have worked great. Hope this helped.

Click to expand...

Thank you so much for the post, ill look into the 6.5.

I made contact with Preditor motors but its a bit expensive....

Have to do some more research....

couple questions, what do you think your MPG is and overal top speed with out running at 3k rpm?


opcorn:

Some updates, Ill looking to keep the vinyl top and just paint it. (black) too off set the gunmetal gray body paint.

I am being told by a well known and respected mechanic that he could change the gearing in the diffs and keep the 400 TH and the 6.2 as is, and achieve

Freeways rpms at ~2k at 65-70 MPH
~12mpg
and only change the diff from 510 to ~450.

Does this sound about right.

We were just going to throw an allison tran in and call it a day but the above might be less expensive.

I also am looking to put a roll bar in...any ideas?
I’ll be starting the upgrades soon, after the mechanics check out the truck.
opcorn:

Cummings?

Durmax?

Crauly said:

I recently purchased a 1985 M998 6.2, open top (canvis) in excellent condition.

Im looking to do the following and any ideas or possible improvments to my ideas would be greatly appreciated.

1. Putting a shell on top, prob a slant back from California Gold kits...
Home

Pic of slantback
Mil SlantBack

or Wagon
Military
Note there will be seems on eaither

2.Paint GunMetal Gray, with rhino line for parts of the interior.

3. Hard doors. These seem hard to come buy any ideas...
http://www.calgoldproducts.com/ use to sell them but dont.
Will the two door M998 doors fit on the four door?

4. Engine, I was sugjested a cummings, Durmax, or CAT motor, any particular motors that people have used for swaps...etc

5. Transmition....wide open

6. Tires, any advice on what to stay away from...

7. Winch. What if any winch can be mounted.

Interior Mods, another post

Thanks, allready for any who reply

Click to expand...

where did you end up getting your hmmwv from?

Nf6f you are right. I had to upgrade the transfer case to the NP242 because the old one can't Handel the speed or heat. The crossmember to hold the tranny in was easy and cheap to get. I can say it was a little pain in the butt but it was worth all the effort in the end. Much nicer on the motor.

Derrickl112 said:

Cummins?

Durmax?

Click to expand...

I have been told that the 12v cummings 6bt is the way to go, but I think for now untill i find something wrong with the 6.2 ill prob stay with it....or untill get restless.....

motas2002 said:

where did you end up getting your hmmwv from?

Click to expand...

I got mine from LA. I have been looking for a while and one night on a whim I checked EBAY motors and found it.

Attached are the pics of it.....

Nice looking truck. Drive it around for a while and see how you like it and what you are looking to get out of it. More power? Keepig up with traffic etc? Then think about a motor swap. Maybe give thought to the Optimizer 6500 (6.5TD GM Motor) General Engine Products This is what is being put into HMMWV now. That and the 4L80E transmission will give you very good road speed with out much changing of the motor mounts exhust etc.

I was pointing out your spelling. There is no G in cummins

nattieleather said:

Nice looking truck. Drive it around for a while and see how you like it and what you are looking to get out of it. More power? Keepig up with traffic etc? Then think about a motor swap. Maybe give thought to the Optimizer 6500 (6.5TD GM Motor) General Engine Products This is what is being put into HMMWV now. That and the 4L80E transmission will give you very good road speed with out much changing of the motor mounts exhust etc.

Click to expand...

I have been speaking with a well known custom off road mechanic.

My goals are
1. 65-70 with ~2k rpm Freeway speed
2. ~15mpg
3. Maintain Off-road abilities

His recommendations are to replace the transmission to the 700 R4. He stated there are two different types of transmission and one is the ****s and the other (later one) is “bullet proof” I will ask him about the 4L80E.

With some minor changes with drivetrain it should be an easy swap and if needed later I could upgrade from the 6.2 to either the 4bt or 6bt Cummins.

I believe the year’s best for the 6bt are 97-98? What would be the better years for the 4bt?

How would the Optimizer 6500 engine compare?

Thanks for all the reply and input. J

After Mechanic

After seeing the Mechanic

Well under the advice of the mech I’m going to have install the 700r4 and see that set up is enough with the extra drive.

If not I’m leaning towards a turbo 4bt with probably an allusion transition. Not sure which 4bt but the one with no computer as well as the Allison. If anyone knows which Allison is the one that has less electrical, ie no need for computers and will fit the Cummins 4bt, please let me know . AT542 or AT545?

As for the body, I will be installing a roll bar and having a slant back fabricated.

Hard doors are on the way , along with some cosmetic parts.

Ill post pictures once we start installing.

Thanks for all the input its been helpful.
Crauly

Well,

Had a few minor set backs but things are beginning to pick up. I have been able to get my Slant back. Im looking in to having a quick removable option for the rear half, but leave the top from the c pillar forward.

opcorn: