M931 driveablity

[acesneights1]

What is top speed on an m931 with a 250na cummins ? Realistically
How driveable is one on the highway say a two or three hour trip ?

 

[doghead]

If you plan 4 hours for a 2-3 hour trip, you'll be fine.

Oh, and if this is a new purchase with no history known, add 3 hours pre trip, and plenty of cash or plastic, JIC.

And, 3 hours the night before, reading the TMs.

 

[doghead]

And if your idea of driving is to get in and just floor it for 3 hours, read this first.(easily found with a google search for M931).

Safety
The safety of the M939 series of trucks has been criticized, especially braking performance and stability when loaded. In 1999 the US Army began refitting anti-lock brake systems to the M939 trucks. Until the trucks were modified, they were limited to a 40 mph (65 km/h) top speed by an Army-wide safety order.
Prior to that improvement, 26% of all Army vehicle accidents and 53% of all Army vehicle accident fatalities were in M939 series trucks. From 1987 to 1998 the series made up 9% of the total US Army vehicle inventory, but accounted for 34% of all fatal accidents.[2]
The problem seemed to be that the torque converter would "lock up" in 2nd gear, and would not unlock easily. When the driver attempted to brake hard, often in a sudden or 'panic' stop, and accidentally locked the brakes (no wheel movement, tires skidding), this would kill the engine; this also killed the power steering, and the driver would suddenly be unable to steer. Too often, the truck would veer sideways and either hit something or roll over.

 

[USAFSS-ColdWarrior]

Ah, yes.....


.... Be ye warned !

 

[acesneights1]

Thanks. Yeah I realize the trip home would be an adventure. I was just wondering about overall drivablity once I got it and made any nessicary repairs like If I wanted to travel with it a little. I was thinking of making a camper out of one but I think a Deuce is a better candidate. I saw one of these going cheap.

 

[doghead]

I just noticed this inside the door of one of the M923 trucks, here in my yard.

 

[wreckerman893]

I drove my M927 towing a trailer using a converter dolly to last year's GA Rally......about a 4 hour trip and about all I want at one time. I have used the truck for recoveries at Redstone which is about a 4 hour round trip which I usually enjoy.

These are tactical vehicles.....not designed for speed, comfort or driveability. They are designed to haul heavy loads over various terrains while being driven by 18-25 year olds that may or may take an interest in maintaining them.

You can't gold plate a turd. (well......you probably can, but then it just becomes an expensive turd)

 

[USAFSS-ColdWarrior]

I just noticed this inside the door of one of the M923 trucks, here in my yard.

Eric,
Something concerns me when you say, "I just noticed..." How long have you had this truck? And why might you ave NOT notices a HUGE WARNING STICKER like that one before now? ... Just wondering. Thanks.

I drove my M927 towing a trailer using a converter dolly to last year's GA Rally......about a 4 hour trip and about all I want at one time. I have used the truck for recoveries at Redstone which is about a 4 hour round trip which I usually enjoy.

These are tactical vehicles.....not designed for speed, comfort or driveability. They are designed to haul heavy loads over various terrains while being driven by 18-25 year olds that may or may take an interest in maintaining them.

You can't gold plate a turd. (well......you probably can, but then it just becomes an expensive turd)

Words of wisdom from our illustrious and beloved Possum-ophile

 

[doghead]

It's not my truck! I started it today, just to run it a bit. They were both tow barred here.

I do not own one of these trucks.

I just wanted to share the sticker with everyone.

 

[USAFSS-ColdWarrior]

It's not my truck! I started it today, just to run it a bit. They were both tow barred here.

I do not own one of these trucks.

I just wanted to share the sticker with everyone.

Ah, I'm relieved
I wasn't trying to you. It just seemed out-of-character for you to have missed something like that.


"We got us a CONVOY ! ! !"

 

[Scarecrow1]

The truth is as stated by the others yes you can drive it but, it isn't made for comfort. You can drive it 55 if the tires are in good shape and in balance but, you have about a foot on each side of the road to play with. Not being familiar with the truck and it's quirks you need to take it slow and take the time to get used to it. If your in a hurry then you need to allow more time for the unexpected .......

 

[quickfarms]

The cruising speed of a 931 is about 52 and the A1and A2 variant are a little faster. The terrain and weather will have a lot to due with your actual speed. This is a semi tractor with air brakes and if you are not used to driving this type of vehicle you should consider having it shipped for safety's sake.

 

[GHall]

All depending on the tires as well.. I'm new to this hobby but I did read this. http://www.militarytires.com/
My M932A1 will cruise 70 MPH if you really want to but the tires are only rated for 56. I wouldn't push it with these trucks.

 

[hankstrucks]

My bud drove a 9 series tractor this summer from Nellis air base Vegas to N.Y. 3200 miles alone with the front windows open a i pod in his ears . He said that the most ground he could cover was 50 miles each hour at best. Put any load to it & ad some hills and the 250 cummins just does not have it period. Now the tire size makes a difference 1400 20 empty tractor top end is almost 68 mph. He said that each truck is different as he has 5 9Series. The GPS tells the speed . The thing most guys do not know when they want a 9 series or after they buy one is that you can not use LOW RANGE IN REVERSE. So as a off roader you would have to keep that in mind. This is the reason why the older 5 tons where better for off roading The auto tranny just will not go when the truck has a load on it so low range is needed. But in the 5ton 8 series kicked Ass because you could shift your way out of trouble not the case with the auto tranny.

 

[hankstrucks]

The trip back from the G.L. At the air base in Nevada that truck had 1100 20 and was pulling a boulten trailer, the 1400 tires make a difference. The truck I think looks rough and ready with singles.

 

[sandcobra164]

The reason you can't shift a 939 into reverse in low range is simple. The torque converter multiplies the torque sent through the driveline. Something is going to give and in the M939 series, it's the transfer case. In the M809 series, same basic driveline layout, they have a clutch which can't mulitiply the torque. Same motor in most cases', I understand that the A2's have the 8.3 6CTA Cummins but the basics still apply. A torque converter will apply more force on the input shaft than a clutch for getting things moving when something is "stuck" or "doesn't want to move"

The M939 will move fine in reverse as long as it's rolling free and there's not a load connected. It can roll free in reverse if a load it attached as well, but if it can't move it backwards connected in High Range, you'll kill it if you reverse it in low range.

 

[flibob]

The thing I don't like about these trucks is doing 25-30 mph up a hill with Buba roaring up behind me at 70. The rear lights are terrible also. I'll admit I am a wimp. Are you legal? You bet. But I have done it and I didn't like it.

 

[Interapid]

To the OP,
We have now retrieved two 939's from Jeff City to STL. About 120 miles. They ran along at 55 the entire time. Hills would drag them down but we had no problems or scary times on the highway. They are WIDE and paying attention at any speed will be greatly appreciated by those on the left. Try not to wear out the drunk bumps. I would consider some clamp on battery operated red tail lights for all these trucks as the original lights are dim and if you are going to have a problem it will be from the rear as you are the slowest thing out there. We always had a chase vehicle follow us which helps. When considering the military's drivability problems with this truck consider that it was often driven by very young people of unspecified gender with questionable driving/mechanical aptitude during periods of less than optimal weather. For a mature person on a Sunday drive your results may vary. Enjoy.

 

[jonsm114]

just drove a M931 back from Jeff last week...no issues..nice truck.

Jon
St Charles

 

[73m819]

The reason you can't shift a 939 into reverse in low range is simple. The torque converter multiplies the torque sent through the driveline. Something is going to give and in the M939 series, it's the transfer case. In the M809 series, same basic driveline layout, they have a clutch which can't mulitiply the torque. Same motor in most cases', I understand that the A2's have the 8.3 6CTA Cummins but the basics still apply. A torque converter will apply more force on the input shaft than a clutch for getting things moving when something is "stuck" or "doesn't want to move"

The M939 will move fine in reverse as long as it's rolling free and there's not a load connected. It can roll free in reverse if a load it attached as well, but if it can't move it backwards connected in High Range, you'll kill it if you reverse it in low range.

TWO very simple ways to fix the reverse low range transfer case breakage problem
1--- Drive the truck like YOU own it and YOU have to pay to fix it, NOT like if you break it, someone else (tax payer) will fix it.
2--- Disconnect the automatic front wheel engagment when going into low.

It eaiser to put a lockout for low reverse and stickers saying "DO NOT PUT INTO REVERSE LOW" then to train young GI truck driver how to drive a big truck.
The problem is that the truck goes from 2 axle drive in high to 3 axle drive in low, the young GI truck driver thinks that there is only ONE throttle postion most of the time and that is on the floor boards, the truck is having trouble in high so he drops to low, since it is now in low, it will need ALL the power it can get, so NOW all 3 axles are pulling with traction and with a lot of instant horsepower, SOMETHING HAS TO GIVE, the transfer case TAKES THE HIT.

Bet I could break something putting any 5t into low forward/reverse, crank the rpms up and dump the clutch, the ONLY difference here between the 900s and the older 5ts is the when starting out with a clutch you have to eze into it on the throttle, where a automatic you can just floor it and go.