Don't Use Low Range Reverse with 939's? Here's Why !!

[emr]

Driver error, Just like the >> Army, Allison and AM General came up with the exact same reason for early failures ... after all the re testing after a rash of cracked cases started showing up many years ago. The facts I have read show after more extensive driver training the problem was severely reduced. And no changes were made because they were and are fine . Now you cant completely fix stupid. These are TACTICAL vehicles and can not be driven like a street truck ... the tire traction alone is enough to put severe strain on the drive train. And no matter how many times a Soldier says " No really I waited for it to shift applied the accelerator slow and steady just like we were taught and the thing just blew up .And No I was not over loaded !!! . LOL) really ? That's like " These tires got me stuck LOL)))) breaking brakes free by ramming it in reverse an forward ..really Sorry that says it all.

Now I see people saying , In theater we had problems. " I need facts .... Well lets say>> with facts these trucks have more than proven them selves . the NJ unit here in conjunction with a PA unit put more miles on these yes they had mostly 939 series More miles than the Red Ball express, I was at one of the ceremony's when the citations were being handed out here in the first gulf war. there were a very mix of drivers in these units, I new or know most from The unit here, They ranged from Vietnam Vets that were drivers then and new guys . ALL the older guys I talked with over the years following said the 939 series outperformed ALL the previous M series trucks they drove. Just an eye witness account from me )))

I just think the facts presented by Me should be taken into consideration, these trucks are NOT fragile. In ALL climates an ALL terrains they have more than proven them selves. But like I said You cany fix stupid.

ALERT DISCLAIMER ALERT >>> I have more than fulfilled my quota's of STUPID LOL))))))))))))))))))))))))) So I speak from experience )))

Drivers that tend to shift from forward to reverse before the transmission finishes shifting will cause this problem , that's driver error period. These trucks can back up fine all day long in low. UNLESS # 1 you do not let the transmission finish shifting before changing direction . #2 do accelerate knowing its in 6 by and just disregarding the fact of just how tough these trucks are, And when the center of the driver s foot and traction explode its >>> Driver error . That is the largest problem and once again proved beyond a shadow of a dought here in this thread.

A very simple fact, This trans is late 1970s early 80s technology. It is exactly what the Army asked for, It is geared as low in reverse as a D 6 Cat . You MUST let this trans finish shifting before you change direction.

 

[6x6junkie]

ok heres one for ya how did you ever get the brakes off? I have a parts truck that the 2 pass side wheels are locked tried unlocking in low range with power of truck. hooked the tire with a backhoe and lifted hole truck off ground you cant pull the drum off because the brakes are so tight on there. yes the brakes are getting the proper air pressure have pounded with big sledge???answers

 

[JohnnyBM931A2]

ok heres one for ya how did you ever get the brakes off? I have a parts truck that the 2 pass side wheels are locked tried unlocking in low range with power of truck. hooked the tire with a backhoe and lifted hole truck off ground you cant pull the drum off because the brakes are so tight on there. yes the brakes are getting the proper air pressure have pounded with big sledge???answers

Hmm.. That's unusual. From what I have been hearing on here the common fix is to smack the drums with a sledge. They are supposed to free up at that point.

 

[Csm Davis]

ok heres one for ya how did you ever get the brakes off? I have a parts truck that the 2 pass side wheels are locked tried unlocking in low range with power of truck. hooked the tire with a backhoe and lifted hole truck off ground you cant pull the drum off because the brakes are so tight on there. yes the brakes are getting the proper air pressure have pounded with big sledge???answers

Start a different thread or do a search for a brake problem and add it there and we will help you get them unstuck.

 

[rivercreek]

ok heres one for ya how did you ever get the brakes off? I have a parts truck that the 2 pass side wheels are locked tried unlocking in low range with power of truck. hooked the tire with a backhoe and lifted hole truck off ground you cant pull the drum off because the brakes are so tight on there. yes the brakes are getting the proper air pressure have pounded with big sledge???answers

A couple good smacks with a 4lb sledge will usually break them loose fairly easily. Hit right on the middle of the drum, maybe top and bottom, left and right (forward and back) sides just for good measure. Usually you can hear them pop loose. (Unless you have a buddy named Mark - in which case you need not waste energy slinging a hammer because you will need to save your strength for replacing a transfer case... Not a sermon MARK, just a thought.. Serious Side Note: Be sure that the truck is aired up and that your parking brake is off before you commence smacking. Also, before you start smacking, I would also strongly encourage the use of a couple of wheel chocks, particularly if you happen to be parked on a hill.

A previous poster had mentioned that if you simply drive them semi-regularly, frozen brakes are typically not an issue. I absolutely agree with this. Just to start them up and run them down the driveway and back every couple weeks or so is good practice for more than just this reason. I try to do this myself, but this past summer has been a bit crazy for me, and i'm sure everyone here knows how that sort of thing goes from time to time - things like the "bi-monthly driveway run" tend to get pushed to page 2 or 3 of the To-Do List, especially when you have 5 of them.. My bad on that, but it is what it is. When I do drive them during the off-season, I try and ride the brakes a bit to knock the rust off the drums. Use your good judgement while doing this - i'm not suggesting that you get your brake drums cherry red, just ride them a bit or come to a quick stop from 55-60mph a couple or few times. I've found that either one works well if done fairly regularly. Also, if you park the truck immediately after driving in the rain/snow (Wet Drums)and expect that she will be parked for awhile, it is a very good idea to go for a quick drive as soon as the roads dry up (next day or whatever) OR ride your brakes a bit before you park it just to create enough heat in the drums to evaporate any water still inside them. You'll thank yourself later.

Update: Transfer case has been replaced with one from a parts truck - she's rolling on her own steam again ! That was not a fun job, and what a shame... Perfectly good Transfer case. (Was, anyways) MARK.

P.S. MARK, YOU'RE DRIVING THE M1008 this Winter !!! You've been demoted - no 6WD for you, buddy... I oughta give you a snow shovel... I love you Buddy, but GOOD LORD I RECKON....

 

[fattboy123456]

So, I thought I would share the result of using low range reverse on a 900 series truck, for those of you who are not clear as to exactly View attachment 590643View attachment 590644why this is a bad idea...

I'll give a short background on exactly what caused this catastrophic failure: We use a number of 900 series trucks for snow removal - they are contracted with VDOT for the winter season. Since they sit all summer, inevitably some of the brakes are seized up by October, requiring a few strategic smacks on the brake drums with a 4lb hammer to release. I had a buddy over helping me with pre-season inspection/maintenance a few days ago. Assuming he was checking fluids, tires, etc., I didn't worry too much about what exactly he was doing outside in the back yard until I heard a huge BANG. Long story short, he had fired up the truck, pulled the t-case down into low range and apparently was attempting to break the shoes loose by rocking it back and forth. Physics 101: When the wheels won't spin, the power must go SOMEWHERE! This pain in the @$$ wasn't completely bad, however - there is a bright side. We've discovered a valuable time-saving maintenance tip that I am happy to share with everyone: This is by FAR the quickest and easiest way I've ever seen to drain the transfer case. Much quicker, easier and faster than having to climb up under the truck with a wrench and a shop rag and a drain pan and all that hassle. This method I will call the "Mark Technique" in honor of my buddy Mark (the guy who did it).

You need to add to your Thread title while the breaks are locked up! thats a big part to the puzzle LOL!!!!!

 

[rivercreek]

You need to add to your Thread title while the breaks are locked up! thats a big part to the puzzle LOL!!!!!

Hey Fat Boy - please advise how YOU would post the title to this thread to better keep it concise and to the point and to easily and in a straight forward way point a user (search) towards their intended target.... ( In my humble opinion a serious problem here on Steel Soldiers) ???? I felt as though I was reasonably concise and to the point with the title to my post. I've learned through experience through my years on this site how important this is.. Any pertinent advice you may have, Fat Boy, would be much appreciated. I thought that the time I took to post my experience may be useful to less extensively experienced "Steel Soldiers" such as yourself. Just for reference, I've spent the time to look up the word "Pertinent" for you, Fat Boy. Merriam Webster Definition is as follows just for your reference: "Having a clear decisive relevance to the matter at hand."

 

[fattboy123456]

LOL nothing else needs to be said on my end enjoy

 

[Csm Davis]

Rivercreek I believe what Fat boy was getting at is that low reverse didn't cause this damage but the locked brakes and operator error did.