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6L80 in my M998

Mogman

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Wow. The rpms do drop in last gear. I most definitely would consider this mod. Is there any concern with offroading and the converter lockup?
To answer this, there was no issue in low range, I was monitoring it on the laptop and it went into lockup in second gear and stayed there as long as I was feeding it fuel but I have noticed that in gears between 2nd and 4th the TC will go out of lock most of the time when the accelerator is at 0%, then as I add fuel it will within a few seconds will lock the converter again.
Rock crawling would really benefit from manual shifting, one of my many upcoming projects.
The 4.030:1 VS 2.480:1 (4L80) 1st gear is awesomely slow.
 

Mogman

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I'm starting to buy the individual items for a swap. I saw this dual brake switch. I know you only needed rpm and tach signal. Is there any added benefit with brake signal? I was thinking one side for 24v and other for 12v.
Not that I can think of, have you received the documentation from Zero Gravity, if not ask them for it.
 

Lkn4luvtx

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Howdy. I may have missed it but how did you wire the zero gravity harness for the tach signal? Currently doing this swap also. Thank you.
 

TOBASH

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Dang, spring break starts this weekend, no bikini's on the beach!!!!
Enough tranny talk. This isn’t G-rinder. Please give us red blooded men the much sought after bikini siting update and consider even starting a dedicated PICTURE thread. :ROFLMAO:

I’ll get the pics going below…

Also and perhaps less important. Your patience and attention to detail re.: this installation is remarkable. Thanks for this interesting multi-year post and follow-up

.IMG_0041.jpeg
 
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Lkn4luvtx

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With the tach I used I just wired it parallel with the crank sensor, IIRC
mine does not have a tach. It looks like it has a crankshaft position sensor in about the same location as a distributor would be on a gas engine, two white wires coming out of it. I can’t find any information on which wire does what, does that sound familiar to you?
 

Mogman

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That is for the Diag port, (its only use) it is a reed switch that closes 1 X crankshaft rotation, I did use that for my 6L80 install until I put in a turbo motor, the turbo motor cannot have that diag sending unit as the turbo will not allow it, nor does it need it as the turbo motor has a crankshaft sensor,
You will need to supply 5V to "power" that reed circuit but that is available on the controller.
 

Lkn4luvtx

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That is for the Diag port, (its only use) it is a reed switch that closes 1 X crankshaft rotation, I did use that for my 6L80 install until I put in a turbo motor, the turbo motor cannot have that diag sending unit as the turbo will not allow it, nor does it need it as the turbo motor has a crankshaft sensor,
You will need to supply 5V to "power" that reed circuit but that is available on the controller.

I wired the reed switch with 5 volts on one side and the other going to the orange/black wire of the tack signal. I have the input pulses per revolution set a 1, trigger level speed set at 5 but still do not have a tack signal. I’ve taken the reed switch off the engine and have rotated it by hand, I’m getting continuity at a few spots during rotation. I’ve also started the engine with the reed switch off and verified that the drive is spinning. Do you have any idea what I am missing? Or am I setting up the module incorrectly? I have continuity from the orange/black wire to the zero gravity module. I am at a loss on why I cannot get a tach signal. I appreciate your help and thank you for your time!
 

Mogman

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I wired the reed switch with 5 volts on one side and the other going to the orange/black wire of the tack signal. I have the input pulses per revolution set a 1, trigger level speed set at 5 but still do not have a tack signal. I’ve taken the reed switch off the engine and have rotated it by hand, I’m getting continuity at a few spots during rotation. I’ve also started the engine with the reed switch off and verified that the drive is spinning. Do you have any idea what I am missing? Or am I setting up the module incorrectly? I have continuity from the orange/black wire to the zero gravity module. I am at a loss on why I cannot get a tach signal. I appreciate your help and thank you for your time!
As far as I can remember that is all I did, I will have to look at the documents (if they are online) and see why you are having the issue.
You should have two opens and two closures per revolution on that sensor, since the cam turns at half the crankshaft speed that works out to one closure per crankshaft revolution.
It should also be wide open and completely shorted as it turns no matter how slow, there were some other sensors used, IIRC the one you want is yellow not black.
It may be the trigger level, how did you decide on 5?
 

Mogman

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You can also contact zero gravity, they were pretty responsive when I contacted them.
 

Rescuediver1982

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Mogman, Can we get an update on 6L with the turbo engine? How are hills and towing with the turbo 6 speed? Thoughts on a BMI turbo kit for the 6.2 with the 6 speed? I basically want to just tow my jeep to go wheeling. Before this thread, I assumed a duramax was the only answer.
 

Mogman

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Mogman, Can we get an update on 6L with the turbo engine? How are hills and towing with the turbo 6 speed? Thoughts on a BMI turbo kit for the 6.2 with the 6 speed? I basically want to just tow my jeep to go wheeling. Before this thread, I assumed a duramax was the only answer.
It was OK, it probably was comparable to a stock turbo diesel at highway speed, there is only about 30HP difference between the 6.2NA and the 6.5TD
That can only be improved to about 50 max and that still costs some money.
I sold that truck because it was just so disappointing, if I had it all to do over I would have left the 6.2L in there, the difference was not that noticeable but the increased heat was, when pushed it ran uncomfortably hot.
Some higher ratio gears may have helped ether that or manual shifting so it could be run in 5th into head winds or slightly up hill.
All in All a 4L80 would be cheaper and easier to do.
 

Rescuediver1982

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It was OK, it probably was comparable to a stock turbo diesel at highway speed, there is only about 30HP difference between the 6.2NA and the 6.5TD
That can only be improved to about 50 max and that still costs some money.
I sold that truck because it was just so disappointing, if I had it all to do over I would have left the 6.2L in there, the difference was not that noticeable but the increased heat was, when pushed it ran uncomfortably hot.
Some higher ratio gears may have helped ether that or manual shifting so it could be run in 5th into head winds or slightly up hill.
All in All a 4L80 would be cheaper and easier to do.
I already have the 4l80 conversion done and it drives down the highway great, but it just falls on its face when I tackle any hill (or slight incline in the roadway for that matter.) Its great in town and on flat roads but I would like to be able to tow a trailer at 70mph reliably. I have yet to find a bmi turbo kit vs 6.5td comparison but I can't see the bmi kit outperforming the factory turbo engine, unless there is a compression difference that helps. So maybe the dmax is the way to go.
 

TOBASH

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I already have the 4l80 conversion done and it drives down the highway great, but it just falls on its face when I tackle any hill (or slight incline in the roadway for that matter.) Its great in town and on flat roads but I would like to be able to tow a trailer at 70mph reliably. I have yet to find a bmi turbo kit vs 6.5td comparison but I can't see the bmi kit outperforming the factory turbo engine, unless there is a compression difference that helps. So maybe the dmax is the way to go.
You need to contact Chris at Twisted Steel. He specializes in Detroit diesel, GEP, and P 400 rebuilds.

Much cheaper and easier than putting in a crap Duramax conversion. IMHO…

He can easily get you 350 to 400 hp for much less time and effort than it would cost you to source and place a Duramax. The advantage is you don’t have to fit the Duramax engine and you don’t have to fit the computer and you don’t have to cut up and cluge together a harness and you don’t have to worry about hooking up the brakes or the transmission.

Mogman has done an amazing job with his Duramax conversion. I’m not trying to throw shade on that. He has done things right where-as most places that advertise this conversion do sloppy horrible dangerous work.

I’m trying to say that for the money you can get a kick ass GEP engine rebuild with 350 to 400 hp and never have to worry about engine size and fitment and transmission and computer. Pure rebuilding and then plug and play.

A more simple option might be to add water injection for $600 and then follow Mogman’s instructions regarding how to turn up your waist gate between 10 and 12 psi.
 
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Mogman

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I had a short conversation with Chris at Twisted Steel Performance, he has no dyno data on the engines he builds, only that some of his customers claim that it performs BETTER than a mildly tuned Dmax and pulls better than a Dmax, a mildly tuned Dmax will make 450-500HP and that platform will make 600+ on a stock platform.

So I am calling BS, what a customer says after spending a Beaucoup amount of money means very little in the real world as pocket book bias takes over.

Considering that GEP had to put a girdle and many other improvements just to get 250HP out of the 6.5L and the known limitations of a indirectly injected engine that is mechanically injected dictate that would be a VERY expensive goal, in one article I read they put over 100 HRS just in head preparations, at a nominal rate of $100 HR that's 10K in labor just in the heads not to mention a large pile of custom valves, springs etc. and there is no performance data on that project.

Add the fact that a stock P400 long block will now set you back around $19,000 because they have been discontinued the numbers do not add up.
And IMHO there is no way anyone is going to get 400HP out of a standard production 6.5L lower end. well for more than a few seconds anyway

And without high pressure computerized rail direct injection (talking 30-40K psi vs 2K psi) there is little one can actually do to improve efficiency which adds up to much more heat in a platform that has trouble getting rid of heat to begin with, I doubt even if possible one would not be able to use most of the available HP. BTW the Dmax flows 1/3 of the cooling water in GPM than the 6.5L (read less HP wasted at the water pump) and I have zero issues with coolant temps.

Now I am not saying getting 400HP is not possible but 50 years experience with mechanically, indirectly injected diesel engines tells me not only would it be expensive it would not be practical on the street.

Going on 25,000 miles with exceptional drivabilty and dependability tells me that this is the best formula for a daily driver at max highway speeds.
I normally cruise at around 82MPH mostly because I don't like being around other traffic and still looking for that "warning" ticket for speeding, also trying for a "exhibition of acceleration" ticket but LE generally just gives me a thumbs up when I do. (sometimes a guy just can't win) :cool:

I built the Duravee for around 10-12K including full stepper instrumentation, all new lights and fully rewiring the truck from tail lights to headlights in my spare time before the Wuhan made my job go away.

Any time you want to pass by and drive the DuraVee you are welcome to do so, then you will have actual experience of which to speak of.
It is completely different cruising @2200 RPM at 75MPH without having the Tasmanian Devil trying to get out of the engine compartment...

MM
 
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