M1078 gear change transmission program

[ragingbear]

Newbie questions; I would like to find the information on gear changes and transmission programing for higher highway speeds. In both of the 1078's I have, it seems like 45 MPH is great and 50 MPH is stretching the envelope. I want to make a camper unit out of one for cross country trips, 50 MPH just will not do. Please show me the way to people that sell or can do what I need. I have a fully capable person to do the work, but lack the knowledge of a parts supplier or computer program for the truck.
Thank you

 

[NDT]

Welcome. I toured the Stewart and Stevenson plant years ago, and I remember as we careened around the test track, the driver telling us that the truck CAN be reprogrammed to go faster. Since that plant is now closed, those people that knew how to do this have been scattered to the wind. I would think that the reprogramming involves the CAT engine software only. Maybe start with someone who is familiar with the Caterpillar code.

 

[expeditionimports]

I just purchased 2 LMTV's as well as Surplus Axles to gut and use the 3rd members for higher road speed. It ran about 4K per truck, but gives us a 70+ mph cruise. We will be starting the change out in the next couple of weeks. Pretty common stuff. I purchased the axles from a retailer with experience in the vehicles. About 7 days after the new axles arrived at 2K each a batch of them went off on GL for about $300 each. Ouch......

Cheers,
Scott

 

[CARNAC]

Ouch is right. And with more and more of the LMTV/MTV's getting ready to hit the market, it makes you wonder if any of the early entry folks will be missing even more ROI.

There is a reason I tell folks to be patient. There are more coming....lot's more. Every single soft skin is going to get sold off in the next few years.

As for the program, I was told there is a computer commercially available and it runs about $3-4K. I will try to contact the guy to find out who mfg it.

 

[Oxyacetylene]

Unless you have an A1 variant, the engine is manual injection, no computer for it. At highway cruise the transmission is already in 7th gear. You will want to investigate the axle gearing options. If your truck is the A0 manual injection model then it should also have Rockwell axles. I would be curious how the higher gearing which makes the truck more highway friendly would affect offroad performance. Also, I would be curious how well the manual injected models like mine would pull hills/grades on the highway with the higher gearing.

 

[runk]

The computer on the Allison transmission has a lot of computing power (based on digging through an Allison TS2480EN [1998] I located), including the ability to run a bunch of stuff external to the transmission, including things like governors and engine brakes. With a fairly cursory review of the parts TM, there seems to be a fair amount of wiring between the transmission controller and other part of the truck, although it was unclear to me what was A0 and A1 variants. It was pretty clear all the road sensing and engine speed sensing is done by the transmission. I can't find anything in the TMs that talks about how RPM is governed or limits adjusted, but maybe I just haven't found it yet. One report on a recovery (in a different thread), noted how slow the truck was, but didn't talk about if it was RPM limited or power limited, but of course there is no tach in these trucks, you have to have a diagnostics computer plugged to know RPM (and it plugs in to the transmission controller !). I also haven't been able to find the gear ratios in the transmission to calculate what theoretical speeds should be possible.

I wouldn't give up yet on computer changes increasing the speed limits of the trucks.

 

[Oxyacetylene]

Mine has a tach (part of the winch package). At 50MPH (clocked on my GPS) the engine is turning about 2250-2300 RPM. In TM 9-2320-365-10, table 1-6 (System Data) it lists the governor as Auto/Mechanical. When the PTO is engaged it locks the transmission in Neutral, and the Mode button controls the power split for front/rear through the transfer case. Maybe all the wiring you are seeing has something to do with these features? I have been meaning to take a closer look at the governor itself. Maybe it can be adjusted or modified to provide more fuel for pulling hills and stuff; just not sure how many more RPM you would want to turn the engine?

On a related topic, I would like to get more information on the transmission also. Maybe you or I can give them a call . I would like to get their opinion on the best fluid to run since the military ran them with 15w-40 oil just like the engine. Others on here have advised to change that out for ATF, possibly the Allison branded Transdyn. It's a little tough to find much info on their website. If I can get the serial # off mine I will try plugging that into their website.

 

[THE MACHINIST]

Scott which axle assemblies have the higher gears and how can one tell? I am looking at the m1079's for a camper conversion and I would like better fuel economy but wonder if the motor will have adequate power for hills when loaded.

Thanks

jamie

 

[Oxyacetylene]

Scott which axle assemblies have the higher gears and how can one tell? I am looking at the m1079's for a camper conversion and I would like better fuel economy but wonder if the motor will have adequate power for hills when loaded.

Thanks

jamie

He may mean he purchased two additional axles just to regear those third members, so he could keep the originals if he wanted to switch back? The data plate which lists the third member / center section ratio is on the center section of the axle, on the driver's side of the housing, turned sideways. I tried to get a picture of the data plate on mine, but it's hard to make out. I may try cleaning the data plate and/or see if the front one is more readable for a picture. I am pretty sure all of the military trucks are geared 7.8. The center section is geared 3.9, then the 2:1 outers gives you the 7.8.

 

[auctionaddict]

Mine has a tach (part of the winch package). At 50MPH (clocked on my GPS) the engine is turning about 2250-2300 RPM. In TM 9-2320-365-10, table 1-6 (System Data) it lists the governor as Auto/Mechanical. When the PTO is engaged it locks the transmission in Neutral, and the Mode button controls the power split for front/rear through the transfer case. Maybe all the wiring you are seeing has something to do with these features? I have been meaning to take a closer look at the governor itself. Maybe it can be adjusted or modified to provide more fuel for pulling hills and stuff; just not sure how many more RPM you would want to turn the engine?

On a related topic, I would like to get more information on the transmission also. Maybe you or I can give them a call . I would like to get their opinion on the best fluid to run since the military ran them with 15w-40 oil just like the engine. Others on here have advised to change that out for ATF, possibly the Allison branded Transdyn. It's a little tough to find much info on their website. If I can get the serial # off mine I will try plugging that into their website.

I called Allison and they recommended changing it to the Transdyn or similar approved makes on there website.
He told me it would shift better and last longer !!

 

[jtron79]

There is great info around about the governor on the 3116. I believe it won't be very hard to make an adjustment there. Perhaps a removal of a shim. But I'm not sure encouraging a higher rpm will be productive. Our dump trucks at work have almost this exact drive train I need to check and see what kind of ram's we are running.

 

[jtron79]

After checking our trucks at work they run 2000 rpm at 55 mph with the 3126 and 7 SPD Alison. I bet you could boost the governor up to 2500 rpm and be OK.

 

[steve6x6x6]

The LMTV's came with a (3.90) 7.80 final drive axle. There are many other FMTV's that use the same axle with a (3.07) 6.14 final drive axle. All you need to do is change the chunk assembly with a 3.07 chunk. I have been working with these axles for 14 years.

 

[THE MACHINIST]

I wonder if allison makes a different 7th gear overdrive that way no lower end would be lost just a gain in fuel economy on flat ground.

 

[NDT]

The LMTV's came with a (3.90) 7.80 final drive axle. There are many other FMTV's that use the same axle with a (3.07) 6.14 final drive axle. All you need to do is change the chunk assembly with a 3.07 chunk. I have been working with these axles for 14 years.

Finally! Thanks for the post. Can you estimate when Rockwell became Meritor or Axletech or whatever the evolution has been??

 

[Rodney Lough Jr]

These guys did mine: http://www.mtpdrivetrain.com/

 

[steve6x6x6]

Finally! Thanks for the post. Can you estimate when Rockwell became Meritor or Axletech or whatever the evolution has been??

Rockwell changed their symbol to the twin rivers around 1973, becomes Meritor in 1997 and them Arvin Meritor in 2000 and then Axletech in late 2002. The LMTV- M1078 and the FMTV- M1083 did their feild trials in 1992 and failed, the big brass said we need a stop gap truck and in 1993 the M35a3 were built under the E.S P. program. About 10,000 M35A2 were rounded up and disassembled for parts to build 5,600 of the M35A3.

 

[ALEX2005]

M1078 im planing to buy one in gp but not sure about max speed , is there out there a cheap way to increase it?

 

[Suprman]

Larger tires

 

[Overdrive]

The LMTV's came with a (3.90) 7.80 final drive axle. There are many other FMTV's that use the same axle with a (3.07) 6.14 final drive axle. All you need to do is change the chunk assembly with a 3.07 chunk. I have been working with these axles for 14 years.

Do you have fluther details on which "other FMTVs" ran the 3.07 gears (models/years)? Just wondering without actually checking the axle data plate.