6L80 in my M998

[Mullaney]

I have about 300 mi on the transmission and I am extremely happy with it, I still have not resolved the problem being able to read the tune from the TCM.

If I am pushing it as say to enter a highway I still have to lift the throttle to get it to up shift at times, I have not pursued the programming issue at this time because it is actually a minor problem.

Otherwise it is worth every damn cent! with no headwind or a tailwind I can cruise comfortably at 75 MPH with the stock 6.2L, even with a strong headwind (it is always windy down here that is why they are building so damn many of those ugly A$$ wind generators here) I can still push to 75MPH in 5th with no problem, BTW I am running the same RPM at 75 in 5th as I ran at 60 with the TH400, 2900 RPM and in 6th at 75MPH I can barely hear the fan kick in.

Do not get me wrong, I think this was a HUGE improvement but if I was asked about the down side if any I would say that if you are running a heavy HMMWV with a body like the helmet top, (like pulling an open para-shoot and weighs 7400LB) and only had a NA6.2L/6.5L then I would suggest starting with truck with higher gears (273 VS 2.56). But with a 2 or 4 door soft top this combination would be AWESOME!

Of course I am somewhat spoiled by the DuraVee and somewhat crazy, but it is like night and day compared to the TH400, when driving like a sane person it is wonderful to have it shift up through the gears, very much like a late model factory pickup.

As far as operational problems other than the minor shifting issue there has been none, the transmission runs very cool, the highest I have seen is 170 deg F.

I have no doubt that installing the GEP turbo and it's low end torque and extra ponies will will put me over the top..

.
Dang. Sure is nice to hear about having the ability cruise at highway speeds!

 

[Mogman]

I do not plan to do any changes until after the N. Padre island cleanup in Feb. I do plan on doing much more road time until then, they usually put us on the longest run, usually about 40-50 mi of 4WD beach (and back) so that will give me plenty of off road data to work with but I do not have enough time to get the GEP turbo test run, installed and be comfortable on such a long off road trip. Also after that I plan on just trying to download a tune into the TCM which is all I really need to do, as I do not actually need to read it but am going to wait just in case I brick the TCM.

 

[Mogman]

Turned over 1000 mi. on the conversion today and loving every one!

 

[Expedition.HMMWV]

I have about 300 mi on the transmission and I am extremely happy with it, I still have not resolved the problem being able to read the tune from the TCM.

If I am pushing it as say to enter a highway I still have to lift the throttle to get it to up shift at times, I have not pursued the programming issue at this time because it is actually a minor problem.

Otherwise it is worth every damn cent! with no headwind or a tailwind I can cruise comfortably at 75 MPH with the stock 6.2L, even with a strong headwind (it is always windy down here that is why they are building so damn many of those ugly A$$ wind generators here) I can still push to 75MPH in 5th with no problem, BTW I am running the same RPM at 75 in 5th as I ran at 60 with the TH400, 2900 RPM and in 6th at 75MPH I can barely hear the fan kick in.

Do not get me wrong, I think this was a HUGE improvement but if I was asked about the down side if any I would say that if you are running a heavy HMMWV with a body like the helmet top, (like pulling an open para-shoot and weighs 7400LB) and only had a NA6.2L/6.5L then I would suggest starting with truck with higher gears (273 VS 2.56). But with a 2 or 4 door soft top this combination would be AWESOME!

Of course I am somewhat spoiled by the DuraVee and somewhat crazy, but it is like night and day compared to the TH400, when driving like a sane person it is wonderful to have it shift up through the gears, very much like a late model factory pickup.

As far as operational problems other than the minor shifting issue there has been none, the transmission runs very cool, the highest I have seen is 170 deg F.

I have no doubt that installing the GEP turbo and it's low end torque and extra ponies will will put me over the top..

It should make a huge difference once you tune the trans for correct gears and tire size. Mine shifted absolutely terribly until I had the correct tire size/gear ratio tuned in

 

[Mogman]

It should make a huge difference once you tune the trans for correct gears and tire size. Mine shifted absolutely terribly until I had the correct tire size/gear ratio tuned in

So you also have a 6L transmission in your HMMWV?

This system has adaptive programming, I am having no problems at all with shifting now, the only reason I want to program the TCM now is so I can dump a Corvette tune in and activate manual shifting.

I have a hunch I may be able to dump a tune with the EFILive I have now, (Zero Gravity the ones providing the controller are using H P Tuners) I have only tried to download the tune from the TCM, this is not needed as all anyone really needs to be able to do is upload TO the TCM.

There are two reasons I have not tried this, 1 because it is doing VERY well at this time and 2 because I have an event coming up in Feb. in which I will be towing a trailer a total of 80-100 miles down and back on a FWD only beach for the annual cleanup and there is a small possibility I could "brick" the TCM so I want to go ahead and wait until after that event just in case.

The only issue if you could call it that is when running into a head wind AND running 75MPH it will not shift into 6th which is actually correct as the stock 6.2L does not have enough power considering the configuration and weight of this helmet top, but even at 75MPH in 5th I am only turning 2900 RPM which is the same as I was turning at 60MPH with the TH400 and the transmission is just as happy in 5th as in 6th.

If I "coax" it into 6th in these conditions by lifting the throttle and then getting back into the throttle is simply bogs down until it is forced into 5th again, so it is smarter than I am at that point.

This will be remedied by replacing the 6.2L with the 6.5L Turbo GEP I have sitting on the floor in my shop, (again after that event) that extra 50-60HP will change everything I am sure.

If this was a lighter truck like a 2 or 4 door soft top the 6.2 would push it along just fine, that stupid helmet tops aerodynamic property's are horrible, not to mention with all the gear it weighs 2200 LB more than my other M998 the DuraVee.

EDIT, the only caveat is that when I first was working with this transmission I was turning off the batteries on a regular basis and that wipes out the adaptive programming, I finally figured that out and now leave the battery switch alone, it would take 20-30 miles before it would start to level out and work correctly again. If I can manipulate the tuning this learning curve would no doubt be much shorter.

 

[Expedition.HMMWV]

So you also have a 6L transmission in your HMMWV?

This system has adaptive programming, I am having no problems at all with shifting now, the only reason I want to program the TCM now is so I can dump a Corvette tune in and activate manual shifting.

I have a hunch I may be able to dump a tune with the EFILive I have now, (Zero Gravity the ones providing the controller are using H P Tuners) I have only tried to download the tune from the TCM, this is not needed as all anyone really needs to be able to do is upload TO the TCM.

There are two reasons I have not tried this, 1 because it is doing VERY well at this time and 2 because I have an event coming up in Feb. in which I will be towing a trailer a total of 80-100 miles down and back on a FWD only beach for the annual cleanup and there is a small possibility I could "brick" the TCM so I want to go ahead and wait until after that event just in case.

The only issue if you could call it that is when running into a head wind AND running 75MPH it will not shift into 6th which is actually correct as the stock 6.2L does not have enough power considering the configuration and weight of this helmet top, but even at 75MPH in 5th I am only turning 2900 RPM which is the same as I was turning at 60MPH with the TH400 and the transmission is just as happy in 5th as in 6th.

If I "coax" it into 6th in these conditions by lifting the throttle and then getting back into the throttle is simply bogs down until it is forced into 5th again, so it is smarter than I am at that point.

This will be remedied by replacing the 6.2L with the 6.5L Turbo GEP I have sitting on the floor in my shop, (again after that event) that extra 50-60HP will change everything I am sure.

If this was a lighter truck like a 2 or 4 door soft top the 6.2 would push it along just fine, that stupid helmet tops aerodynamic property's are horrible, not to mention with all the gear it weighs 2200 LB more than my other M998 the DuraVee.

EDIT, the only caveat is that when I first was working with this transmission I was turning off the batteries on a regular basis and that wipes out the adaptive programming, I finally figured that out and now leave the battery switch alone, it would take 20-30 miles before it would start to level out and work correctly again. If I can manipulate the tuning this learning curve would no doubt be much shorter.

Ahh I gotcha, definitely understandable to wait until after the trip. 6.5Turbo will definitely fix that issue as well!
Bricking the TCM would be unfortunate! considering its location, just annoying to have to replace lol
yes, I have a 6L90 in mine, along with a 6.0 LS

 

[Mogman]

Ahh I gotcha, definitely understandable to wait until after the trip. 6.5Turbo will definitely fix that issue as well!
Bricking the TCM would be unfortunate! considering its location, just annoying to have to replace lol
yes, I have a 6L90 in mine, along with a 6.0 LS

Ah, ok you installed it as a set, so you already had a "controller" to talk to the 6L80 TCM with the ECM, yes it would be a pain to change the TCM
I was thinking I was the first to put a 6L behind a DETROIT diesel in a HMMWV

 

[Expedition.HMMWV]

Ah, ok you installed it as a set, so you already had a "controller" to talk to the 6L80 TCM with the ECM, yes it would be a pain to change the TCM
I was thinking I was the first to put a 6L behind a DETROIT diesel.

Yeah, I just had to have the TCM and ECM programed to ignore the tcase and BCM commands. I've pulled the TCM before, its a mess and annoying lol.
that I know of, you probably are the first to put it behind the original engine. I saw that Phoenix Hummer just came out with a "Kit" recently

 

[Mogman]

Ahh I gotcha, definitely understandable to wait until after the trip. 6.5Turbo will definitely fix that issue as well!
Bricking the TCM would be unfortunate! considering its location, just annoying to have to replace lol
yes, I have a 6L90 in mine, along with a 6.0 LS

I am curious what transfer case you used and how you adapted it to the transmission.

 

[Mogman]

Yeah, I just had to have the TCM and ECM programed to ignore the tcase and BCM commands. I've pulled the TCM before, its a mess and annoying lol.
that I know of, you probably are the first to put it behind the original engine. I saw that Phoenix Hummer just came out with a "Kit" recently

Also do you have a link to the Phoenix site, seems there are a ton of folks using Phoenix in their name.

 

[Expedition.HMMWV]

Also do you have a link to the Phoenix site, seems there are a ton of folks using Phoenix in their name.

It came with an MP1626 but I didnt feel like making the electric shift work so I swapped it for a MP1226, so it bolted right up.
They dont have the kit listed on their website yet, they have talked about it on their instagram, they just arent ready to release it yet, but here is their website https://phoenixhummerrepair.com/

 

[Mogman]

It came with an MP1626 but I didnt feel like making the electric shift work so I swapped it for a MP1226, so it bolted right up.
They dont have the kit listed on their website yet, they have talked about it on their instagram, they just arent ready to release it yet, but here is their website https://phoenixhummerrepair.com/

OK that is what came on the 6L90 (1626XHD) I used as a core for the 6L80 and the MP1626XHD is also what I used in my Duramax conversion, without the data from the ECM there was no way to make the TCCM work on the Detroit, but you could have and I am pretty happy with the MP1626XHD in the DuraVee.
I also have a MP1226XHD and that was the plan but after pulling the pan and seeing the 6L90 was trashed I saw the opportunity to use the original TC with a 6L80.

 

[Expedition.HMMWV]

OK that is what came on the 6L90 (1626XHD) I used as a core for the 6L80 and the MP1626XHD is also what I used in my Duramax conversion, without the data from the ECM there was no way to make the TCCM work on the Detroit, but you could have and I am pretty happy with the MP1626XHD in the DuraVee.
I also have a MP1226XHD and that was the plan but after pulling the pan and seeing the 6L90 was trashed I saw the opportunity to use the original TC with a 6L80.

There ya go, I like the 1226, little less wiring and I was able to just keep the original shifter in the truck and not put in a selector switch which was nice

 

[Glider]

I'm still researching this swap. Found this pic on a fb forum. They are saying it's the tps for the 4 speed. Could I use this setup for the 6l80 swap? I figure it is 12v. Looks like it should be a factory fit.

 

[Mogman]

I'm still researching this swap. Found this pic on a fb forum. They are saying it's the tps for the 4 speed. Could I use this setup for the 6l80 swap? I figure it is 12v. Looks like it should be a factory fit.

Yes it should work, all common TPS sending units are just variable resistors, you connect the 5V buss to one side, ground to the other and the "wiper" is the TPS signal to the TCM

 

[Mogman]

I'm still researching this swap. Found this pic on a fb forum. They are saying it's the tps for the 4 speed. Could I use this setup for the 6l80 swap? I figure it is 12v. Looks like it should be a factory fit.

If you do not have a TPS, it's just as easy to use the GM version that is referenced in the other posts, if you have a 4sp IP then by all means use it.

 

[Mogman]

I have about 1500 miles on the transmission now, still loving it!!
The annual beach cleanup is the 26th, that will mean 80-90 miles on 4WD beach pulling the M1102 and half of that distance will be with a loaded trailer, should give the rig a good workout, then because I have not wanted to make any big changes before that event I will get the GEP turbo engine installed and the manual shift control, the gears are a little too tall (2.56:1) in 6th for the bone stock 6.2L given this truck weighs 7400lb and that helmet top is not going to win any aerodynamic awards, but that is also not a big problem, the trans is just as happy in 5th as 6th and 5th gives me the same RPM at 75MPH that the TH400 gave me at 60MPH , AND the same damn hills I could not maintain 65MPH with the TH400 I can do no problem at 75MPH with the 6L.
So I am pretty confident the GEP will give me that small amount of extra power that will make what is great as far as vastly improved road-ability even better...
If this truck was a 2 or 4 door soft top at about 5200lb I would not change a thing!

 

[Mogman]

Gee, can't believe I waited all year for this weekend and the annual FWD beach cleanup, it is going to be nasty, Low 47, high 57 wind NNE 18MPH and 65% of rain..........

 

[Mullaney]

Gee, can't believe I waited all year for this weekend and the annual FWD beach cleanup, it is going to be nasty, Low 47, high 57 wind NNE 18MPH and 65% of rain..........

.
Well yeah. That seems to be how it is. A nice warm day - no events - cold, wet, and windy and everything happens. Kinda like 2021 in the spring... We had a weekend MV show and a berzerk honey bee stung me in the corner of my eye.

I have plans this year again - and come hell or high water - I plan to be there. Probably end up with a monster Snowfall this year.



Best of luck out there on the beach in the cold and wet in Texas.
That ain't supposed to be that-a-way!

 

[Mogman]

.
Well yeah. That seems to be how it is. A nice warm day - no events - cold, wet, and windy and everything happens. Kinda like 2021 in the spring... We had a weekend MV show and a berzerk honey bee stung me in the corner of my eye.

I have plans this year again - and come hell or high water - I plan to be there. Probably end up with a monster Snowfall this year.

View attachment 859843

Best of luck out there on the beach in the cold and wet in Texas.
That ain't supposed to be that-a-way!

Yes, I will miss this Saturday when it is 105 at 90% humidity with a stifling 0 MPH wind and no rain it sight!!!