M939 series towing procedures

[M1075]

I need some input on proper towing procedures for M939 series trucks.

The operators manual Indicates that damage to automatic transmission will result from towing unless transfer is in neutral. That is surely common sense and I have towed many M809 series trucks this way. However, the manual then goes on to say that normal towing procedures require removing the prop shaft.

My questions are as follows:

1. Is the auto tranny more susceptible to damage while towing than the spicer (assuming transfer in neutral) thus requiring removal of driveshaft?

2. Would a front driveshaft need to be removed if doing a lift tow with rear wheels suspended?

 

[Andy1234]

When I flat towed 2 of them, I removed both driveshafts. If towing w/ the front in the air, then I would only remove the rear driveshaft.

I can't comment on the transmission question, as I am still a novice w/ these trucks.

Andy

 

[R Racing]

In a nutshell if the output shaft on the trans spins it does not turn the pump in the trans ( which would move fluid thru the clutches and bearings ect ect). The old Mopar auto trans that had the push button selector had 2 pumps. 1 front and 1 rear. Those you could safely push start those cars like a manual trans.

 

[M813A1]

James I would just for the sake of safety to your truck take the flange apart at the front rear axle that way the transfer and trans will not spin . Good Luck

 

[73m819]

NO on pulling the front shaft, the transfer has a air shift not a sprag, can not answer the trans question

 

[Coldfusion21]

In a nutshell if the output shaft on the trans spins it does not turn the pump in the trans ( which would move fluid thru the clutches and bearings ect ect). The old Mopar auto trans that had the push button selector had 2 pumps. 1 front and 1 rear. Those you could safely push start those cars like a manual trans.

But with the transfer in neutral the output shaft of the automatic transmission shouldn't ever spin right?

If the transfer gets oiled properly with just the rear output shaft turning you should be fine. I know some designs need a certain shaft or gear turning to fling oil or drive a pump.

 

[73m819]

]But with the transfer in neutral the output shaft shouldn't ever spin right? [/B]

If the transfer gets oiled properly with just the rear output shaft turning you should be fine. I know some designs need a certain shaft or gear turning to fling oil or drive a pump.

the output shaft is connected to the drivrshafts, the front has a air disconnect

 

[fasttruck]

With m939s with straight airbrakes either use two airlines between towed and towing vehicle to release brakes or install caging pins in rfear brake chambers to keep brakes released with no air in towed vehicle. Hope caging pins are in their recepticles on brake chambers or you have extras in your tool box.

 

[M35A2-AZ]

When we picked up my M923A1 we towed it with a M916. We hooked up the air lines and I took off the drive shafts from differentials. Not sure if needed to remove it from the front, but I did. I tired the ends up out of the way.

The Story..
http://www.steelsoldiers.com/conversations/77359-m35a2-azs-m923a1-recovery.html

 

[powersmoke18]

you must remove driveshafts. front and rear to prevent damage. just unbolt the front from the axle flange and remove the rear from the transfer case and axle flange. cagerear brakes if not hooking up front airlines. or start engine and leave parking brake disengaged.

 

[Nonotagain]

I need some input on proper towing procedures for M939 series trucks.

The operators manual Indicates that damage to automatic transmission will result from towing unless transfer is in neutral. That is surely common sense and I have towed many M809 series trucks this way. However, the manual then goes on to say that normal towing procedures require removing the prop shaft.

My questions are as follows:

1. Is the auto tranny more susceptible to damage while towing than the spicer (assuming transfer in neutral) thus requiring removal of driveshaft?

2. Would a front driveshaft need to be removed if doing a lift tow with rear wheels suspended?

1. Parasitic rotation of the drive line is possible even with the transfer case in neutral. Since the automatic transmission does not lubricate without the front pump operating, there are bearings and sleeves that would not be lubricated. Is the rotation enough to cause damage, I can't say for sure, but I always pulled the drive shafts or axles to keep from having someone come back at me and claim damages.

2. Pulling the front drive shaft would be easier than pulling a front axle shaft if towing from the rear. Watch your axle weights since the tires are going to be close to maximum weight rating.

 

[skidunits4you]

As a general practice I remove both front and rear if flat towing or rear if lifting front. Just good to be safe. cheaper to pull shafts than rebuild. Good luck

 

[M1075]

If I were to pull the rear axle shafts, how many would need to be pulled? 1, 2 or 4?

 

[M35A2-AZ]

If you are going to flat tow I would remove all four in the rear and the front drive shaft from the front axle.
If you need to you will need to cage the brakes on the rear axles.
Here is a link to when we towed my M923A1 home. I just unbolted the front and rear drive shafts for the axles and tired them up.
http://www.steelsoldiers.com/conversations/77359-m35a2-azs-m923a1-recovery.html

Good luck with your towing and be safe!!!