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1996 M1078 - Just purchased and have questions.

Greekpete

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Hello all! Thanks for adding me! Just purchased a 1996 M1078 and have some basic questions. I'm totally new to this, so bear with me..
1. When driving, it takes pressing the gas pedal to the floor to get it going and to shift gears. Transmission fluid level seems fine. Is this just how they operate?
2. When accelerating quickly, in 3rd, 4th, and so on gears, it sounds like there's air coming out of the turbo. Normal?
3. This vehicles max speed is like 45-50, sound right?
Thanks,Pete
 

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GeneralDisorder

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That's typical of the 90's trucks with the 3116. They don't have a ton of power. You can install high speed gears and get them up to about 65 or so. But acceleration will be (if anything) worse since you have taller gears. These are still light-years ahead of the old M35's, 800 and 900 series trucks though. I have many memories of driving M35A2's over mountain passes at 20 mph.

3126 and C7 trucks fetch more money because the more powerful engines (especially the C7 that can be flash tuned to 370 HP) and they can easily do 65 in stock form at WOT and handle taller gears for best economy really well.

You will definitely hear the turbo when it's on boost.
 

Green Mountain Boys

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I have a 1998 M1078 and the stock 3116 with the self recovery winch so I am carrying an extra 1,000 lbs and I can do 58 MPH on level ground if I push it. If your truck is unloaded and fully warmed up you should be doing more than 45 0r 50 MPH on level ground. My truck cruises very nicely at 50 MPH either loaded or unloaded. These trucks take a long time to fully reach operating temperature. In cooler winter weather, say around 32F, it takes at least 25 miles at highway speed to get close to fully warmed up.
 

GeneralDisorder

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That's true - the cooling system on these trucks is gigantic with a monstrous capacity and the engines run pretty cold unless they are loaded. Mine will stay at 165 pretty much indefinitely unless cruising at highway speed for a while. They were designed for operation in extreme environments such as some of the hottest places on earth so the cooling system was likely designed for at least 130 to 140 degree ambient temps. Vehicles sold in places like the Middle East have considerably beefed up cooling systems compared to what is typically sold in North America.
 

Ronmar

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The cooling capacity isn’t the warmup issue on the A0, the plumbing is. On the normal bypass type cooling system, cat sent the warm water exiting the head out the bottom of the thermostat housing and right back to the waterpump and back thru the engine. This loop recirculates until the engine warms the coolant enough(178F) and the thermostat opens.

On the A0 they diverted this bypass flow out the bottom of the thermostat housing and sent it to the transmission heat exchanger. So untill the trans becomes a heat source and all that extra mass is warm, the engine will never warm up… Basically you have a large unregulated aluminum radiating surface to contend with.

The 3116 is mechanically governed, so you need to insure that full pedal depression is rotating the linkage on top of the governor to the high speed stop. The governed RPM on the top label sticker on the engine is 2600RPM. You then need a photo tach or a volt meter that reads frequency to determine that the engine is reaching 2600 RPM when the linkage is against the high speed stop. There is a tach sensor on the top left bellhousing that senses the 133 tooth flywheel ring gear, so a freq counter or a multimeter that reads frequency measuring the output of that sensor can get you a reasonably accurate RPM. 2600 RPM X 133 teeth divided by 60 seconds = frequency in Hertz/cycles per second(5763HZ./5.76Khz). The reverse is freq in hertz X 60, divided by 133 for RPM… That RPM determines top speed and if the linkage is mis-adjusted or the engine is not reaching fully governed RPM then there is your top speed limitation…

The engine has a throttle position sensor on top, right above the primary fuel filter/primer. That TPS sensor is hooked to the throttle linkage at the governor and is solely for the trans controller to use to help determine a shifting scheme. If the throttle pedal to governor is out of wack, then this is also out of wack. IE, the governor and TPS being low, the trans thinks you are cruising so doesn’t want to upshift Untill it hits a high limit RPM for a given gear.

Even if the pedal to governor linkage is correct and the engine reaches full governed RPM, if the TPS is out of wack, it still may not predict a shift and wait till max RPM for the current gear is reached before shifting. If the throttle linkage and governed RPM is OK, you can reset the TPS. You also need to check for any stored transmission fault codes. press up and down arrows simultaneously to reach code/diag mode which will display D1 and either dashes(no code) or a pair of numbers Will be displayed. Press mode to step thru 5 memory positions D1-D5 And record the numbers for all 5 locations. Switch off or press both arrow buttons to exit. Press and hold both arrow buttons for 10 seconds to clear stored codes…

To recalibrate the TPS and relearn the shift points do the following:
start the truck and drive it till fully warmed up.
stop the truck and shutdown. Then turn the main switch on untill the trans display appears, then turn the switch off. Do a total of 5 complete power-on to power off cycles. This clears the TPS info and the stored shift information. Switch the main switch on for the 6th time and once you have a display on the trans controller, depress and release the pedal once or twice to set new min and max TPS throttle positions. Press the start button and go drive the truck for a while thru all the gears to allow the trans to relearn it’s shift points.

of course this won’t work right unless you first confirm that the pedal givs full governed linkage position and that full governed is at the correct RPM…
 
Last edited:

Mullaney

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Charlotte NC
Hello all! Thanks for adding me! Just purchased a 1996 M1078 and have some basic questions. I'm totally new to this, so bear with me..
1. When driving, it takes pressing the gas pedal to the floor to get it going and to shift gears. Transmission fluid level seems fine. Is this just how they operate?
2. When accelerating quickly, in 3rd, 4th, and so on gears, it sounds like there's air coming out of the turbo. Normal?
3. This vehicles max speed is like 45-50, sound right?
Thanks,Pete
.
Pete - Welcome to the Outfit!

I hope you enjoy your new-to-you truck.
Pretty much the questions you asked got answered, so about all I have to offer is a warm welcome to Steel Soldiers.


Tim Mullaney
 

BERZERKER888

Well-known member
Steel Soldiers Supporter
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892
93
Location
Daytona, FL
The cooling capacity isn’t the warmup issue on the A0, the plumbing is. On the normal bypass type cooling system, cat sent the warm water exiting the head out the bottom of the thermostat housing and right back to the waterpump and back thru the engine. This loop recirculates until the engine warms the coolant enough(178F) and the thermostat opens.

On the A0 they diverted this bypass flow out the bottom of the thermostat housing and sent it to the transmission heat exchanger. So untill the trans becomes a heat source and all that extra mass is warm, the engine will never warm up… Basically you have a large unregulated aluminum radiating surface to contend with.

The 3116 is mechanically governed, so you need to insure that full pedal depression is rotating the linkage on top of the governor to the high speed stop. The governed RPM on the top label sticker on the engine is 2600RPM. You then need a photo tach or a volt meter that reads frequency to determine that the engine is reaching 2600 RPM when the linkage is against the high speed stop. There is a tach sensor on the top left bellhousing that senses the 133 tooth flywheel ring gear, so a freq counter or a multimeter that reads frequency measuring the output of that sensor can get you a reasonably accurate RPM. 2600 RPM X 133 teeth divided by 60 seconds = frequency in Hertz/cycles per second(5763HZ./5.76Khz). The reverse is freq in hertz X 60, divided by 133 for RPM… That RPM determines top speed and if the linkage is mis-adjusted or the engine is not reaching fully governed RPM then there is your top speed limitation…

The engine has a throttle position sensor on top, right above the primary fuel filter/primer. That TPS sensor is hooked to the throttle linkage at the governor and is solely for the trans controller to use to help determine a shifting scheme. If the throttle pedal to governor is out of wack, then this is also out of wack. IE, the governor and TPS being low, the trans thinks you are cruising so doesn’t want to upshift Untill it hits a high limit RPM for a given gear.

Even if the pedal to governor linkage is correct and the engine reaches full governed RPM, if the TPS is out of wack, it still may not predict a shift and wait till max RPM for the current gear is reached before shifting. If the throttle linkage and governed RPM is OK, you can reset the TPS. You also need to check for any stored transmission fault codes. press up and down arrows simultaneously to reach code/diag mode which will display D1 and either dashes(no code) or a pair of numbers Will be displayed. Press mode to step thru 5 memory positions D1-D5 And record the numbers for all 5 locations. Switch off or press both buttons to exit. Press and hold both buttons for 10 seconds to clear stored codes…

To recalibrate the TPS and relearn the shift points do the following:
start the truck and drive it till fully warmed up.
stop the truck and shutdown. Then turn the main switch on untill the trans display appears, then turn the switch off. Do a total of 5 complete power-on to power off cycles. This clears the TPS info and the stored shift information. Switch the main switch on for the 6th time and once you have a display on the trans controller, depress and release the pedal once or twice to set new min and max TPS throttle positions. Press the start button and go drive the truck for a while thru all the gears to allow the trans to relearn it’s shift points.

of course this won’t work right unless you first confirm that the pedal givs full governed linkage position and that full governed is at the correct RPM…
Yeah ..what he said !
 

BERZERKER888

Well-known member
Steel Soldiers Supporter
414
892
93
Location
Daytona, FL
Hello all! Thanks for adding me! Just purchased a 1996 M1078 and have some basic questions. I'm totally new to this, so bear with me..
1. When driving, it takes pressing the gas pedal to the floor to get it going and to shift gears. Transmission fluid level seems fine. Is this just how they operate?
2. When accelerating quickly, in 3rd, 4th, and so on gears, it sounds like there's air coming out of the turbo. Normal?
3. This vehicles max speed is like 45-50, sound right?
Thanks,Pete
And the most important note when owning a FMTV…..they are absolute money pits…..just a heads up..
 
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