New M998 Slantback owner, admittedly ignorant, seeking guidance

[A New Guy]

Hi and thanks for letting me join the group. I have recently acuired an M998 with an installed crate P400 mated to a 4L85E trans and a customized suspension set up to carry an aftermarket armor solution. Approximately 100 miles on the swap. I'm completely new to HMMWVs in general. Im decently mechanically inclined but this thing is currently a real charlie foxtrot in terms of what's there and what isn't.
Example, trans stays in somewhat of a "limp mode" which is second gear (tops out about 42mph) and refuses to shift. That's not even the weird part... the OEM shifter [R-N-D-2-1] is still in place with the mechanical linkage connected to the trans but the transfer case is missing the shifter and linkage and has an Arens shift by wire t-case power box installed. Stranger still is an Arens 4L80E trans power box was in a box of "new" (2011) parts that also came with the truck. The transmission harness is wired for the Arens controller and all the terminals are intact. However, there is no actuator whatsoever on the trans aside from the OEM shift linkage. Also noteworthy is that I have yet to locate a transmission control module on the vehicle, just the Arens that was in the box. Truck was originally equipped with a 6.2L diesel and HD trans and transfer case (also on a pallet that came with the truck). Purchased and converted by an armor manufacturer as a marketing rig to showcase a heavy armor package, unfortunately none of the original project team is still with the company. The truck sat in storage for the last 6-7 years before I acquired it (minus the armor package).
Questions: what type of Frankenstein project have I gotten myself into? Anyone else running this powertrain combo? (weird controllers or not). Any suggestions on the tranny issue? Should I hook up the controller and try to test it?
I welcome any and all feedback and will answer any questions to the best of my ability.
Thanks in advance ,
Confused in Colorado

 

[TOBASH]

Welcome!... AND :




First of all, your shifter seems like a TH400 tranny, and not a 4L85E. Is it possible the shifter is set up in such a way as you're literally in 2'nd vs. being in limp mode?

 

[USAFSS-ColdWarrior]

Welcome aboard

Find a bunk, stow your gear, and prepare to get underway

You're questions are a bit out of my league - My wife and I have an M35A2 and an XM818 along with a couple of trailers.
I'm sure others with insight into your situation will be chiming in soon.

Again, WELCOME!


John
SS Chaplain
San Angelo, Texas, USA

 

[Crapgame]

Did that truck happen to come from the SOT in Colorado Springs that was making armored (and Dillon M134 Minigun) equipped Suburbans and other vehicles, often for foreign customers in the Middle East?

 

[A New Guy]

Welcome!... AND :




First of all, your shifter seems like a TH400 tranny, and not a 4L85E. Is it possible the shifter is set up in such a way as you're literally in 2'nd vs. being in limp mode?

The transmission is definitely a 4L85E, stamped on the side of it. The shifter however is original to whatever transmission the truck started life with. Here are a few pics

 

[A New Guy]

Did that truck happen to come from the SOT in Colorado Springs that was making armored (and Dillon M134 Minigun) equipped Suburbans and other vehicles, often for foreign customers in the Middle East?

No sir, this one was the only one the company had built as it was just the display of a ceramic armor package. Was shipped around to tradeshows for bit and then put into storage when the next gen solution was developed.

 

[A New Guy]

Welcome!... AND :




First of all, your shifter seems like a TH400 tranny, and not a 4L85E. Is it possible the shifter is set up in such a way as you're literally in 2'nd vs. being in limp mode?

And missed that last part, that's an excellent question, there are a couple ways I can test that out. Current roadblock is a massive undercarriage plate that's blocking any access to any of the transmission components other than what can be accessed through the top inside the motor hatch.

 

[osteo16]

 

[Retiredwarhorses]

you have a FrankenProject....I get one a month in the shop that requires an “unf***ing”

 

[TOBASH]

You need to deal with one problem at a time... First is that mismatched 3 speed shifter on a 4 speed tranny. Then a custom mount for the shift for the transfer case.

Might be worth going back to standard transfer case and shifter. You need to modify the current shift or purchase the correct shifter for a 4L80E and get the linkages for the transfer case.

Interesting vehicle.

 

[A New Guy]

You need to deal with one problem at a time... First is that mismatched 3 speed shifter on a 4 speed tranny. Then a custom mount for the shift for the transfer case.

Might be worth going back to standard transfer case and shifter. You need to modify the current shift or purchase the correct shifter for a 4L80E and get the linkages for the transfer case.

Interesting vehicle.

Bottom blast plate is coming off tonight, hopefully I can shed a little more light on what's going on in there

 

[Crapgame]

Do you think they mothballed the project because they couldn't get it to run at road speeds? Was just good enough to drive off and on the trailer and into whatever expo center? Old enough to be from the early days of "hot rodding" HMMWVs when there was limited knowledge or was attempted by a small shop or individual who thought they knew what they were doing.

And I'll state it right here before somebody says the kettle calling the pot black, or when you point your finger at someone else you have three fingers pointed back at yourself, I'm just a parts changer, I can read the TM, research a part to its manufacturer to the mil-spec etc, but I can't listen to poppet valve cover and say "Oh yeah, your #3 is a bit loose" In my 2 years assigned an M1026, the worst I ever had to do was replace a transfer gearcase because the truck was hauling a severely overloaded trailer in support of a REFORGER exercise. And that I still did most of the work, with a Support Bn mechanic in Illesheim telling me to unbolt a few things at a time then go find him when I got them done.

 

[A New Guy]

I've got a few videos of them running it through a trial's course in Vegas and also demo in Moab. A couple high speed runs included so I'm certain it worked at least once haha. It's been bothering me all day with the "what ifs" but im going to try something tonight. I have a theory that the oem shift linkage is right and is putting the trans in "drive" but without the Arens controller plugged into the harness the transmission is missing its brain and defaults to limp mode because the speed sensors have nothing to talk to. I'm removing the giant blast plate tonight to get full access to the tranny to unhook the linkage and manually check how many shiftable positions the trans has available. Then hook up the wires for the controller, reassemble the linkage and test whether or not the trans can shift automatically. Fingers crossed, the shift points have remained stored and are at least close if it works at all. The main thing that makes me think this is that I have seen the videos but also I just found a custom console in a box of stuff that came with it and its built specifically for both Arens controllers. I'm told the interior was stripped and repainted in a hurry before its last tradeshow and was flown back and parked in storage right after that. The company I work for builds the armor and had the truck built. Unfortunately most all of the guys on the project no no longer work there and people that still know anything about it seem to know nothing at all other than they though it cool haha. I run large teams of mechanics (industrial not automotive) and know just enough about vehicles to do basic service type stuff and changing a few parts here and there. I'm either going to learn fast or fail miserably with this thing lol.