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M8xx series vs m9xx series off roading
- Thread starter cwedge411
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Hey with the interlock on gimpy can almost drive it off my trailer and into the back of my 5 ton that wasn't part of the plan. It may have aerial acrobatics.
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I think he meant M939 series trucks.
I actually would prefer the M939 series trucks off road, specifically the A1s or A2s. The 1400s, with the air shift front axle, would be preferable and I can't think of a situation where that would not be the case.
sandcobra164
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I'm not sure why a M809 series truck would be any better than an M939 series truck off road. Same heavy 14 Liter Cummins so lots of weight on the front axle. M809's have a sprag type transfer case which engages automatically once the rears tires slip if it's working correctly. M939's have the dash switch which couples the driveline once engaged. That should be a positive if everything is working correctly. One problem between the two models when trail riding is how high the cab of an M939 series truck sits. It hits branches the lower trucks don't have to worry about. The CTIS you mentioned is only available on the A2 models of the M939 series but honestly, I can inflate and deflate my tires at a standstill. It just takes a little longer. Some say the 14R20 tires on most of the M939 series trucks hinder it in the mud. I've seen both dual G177's and single 14R20's on both variants so that may be the real issue. I've heard that singles are better in sand, duals are better in mud.
Now my personal experience which is apples to oranges. My M923 on older goodyear singles has climbed every hill at Durhamtown Offroad park, site they hold the GA get together at in October. My Deuce had some Firestone T831's dualed in the rear and it climbed Slippery Nipple as well. Two of my friends tried with their deuce's, 1 on NDT's, 1 on G177's but they didn't make it. I went up with no problem after them without engaging my front axle switch. My M1028 with it's very old original firestones climbed the same hill as well but to be fair, it has lockers in both axles and I went up fully "locked up". Just to the left of Slippery Nipple, there's a hill that I have watched alot of trucks try and fail. My 923 and CUCV went up that hill as well with no real issues. I've not watched an M809 series truck make it up that hill but that's not to say it's never happened.
Now my personal experience which is apples to oranges. My M923 on older goodyear singles has climbed every hill at Durhamtown Offroad park, site they hold the GA get together at in October. My Deuce had some Firestone T831's dualed in the rear and it climbed Slippery Nipple as well. Two of my friends tried with their deuce's, 1 on NDT's, 1 on G177's but they didn't make it. I went up with no problem after them without engaging my front axle switch. My M1028 with it's very old original firestones climbed the same hill as well but to be fair, it has lockers in both axles and I went up fully "locked up". Just to the left of Slippery Nipple, there's a hill that I have watched alot of trucks try and fail. My 923 and CUCV went up that hill as well with no real issues. I've not watched an M809 series truck make it up that hill but that's not to say it's never happened.
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I doubt the 809 to 939 comparison has a clear winner either way. Presuming we have the same wheels/tires, the differences should be negligible.
A bigger difference would be cargo truck to truck tractor, where the shorter wheelbase makes a difference in high centering. Or a winch truck vs nonwinch where the approach angle matters.
My off the cuff opinion is the M931A2 should have a slight advantage over all the other 5tons due to less weight on the front axle, shorter wheelbase, and optimized approach and departure angles. However, I speculate that the instances where it would go and the others would not are not that common.
A bigger difference would be cargo truck to truck tractor, where the shorter wheelbase makes a difference in high centering. Or a winch truck vs nonwinch where the approach angle matters.
My off the cuff opinion is the M931A2 should have a slight advantage over all the other 5tons due to less weight on the front axle, shorter wheelbase, and optimized approach and departure angles. However, I speculate that the instances where it would go and the others would not are not that common.
red
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Most of the difference would just come down to preference on transmission, manual in the m809 or auto in the m939. One big trait of that is when going slow up a hill/rock ledge. The gearing in the m809's will let it idle or low rpm up/over the obstacle whereas the auto in the m939 will slip the torque converter until you raise the rpm's high enough.
M809 has a lower center of gravity with the cab/body sitting lower on the frame. If you have a locker in the front axle (most don't) then the sprag tcase in that series has the benefit of basically only engaging it when needed, compared to in a m939 truck you would have to flip the air switch to the tcase when you want it active.
Front fenders on m809 are stronger/cheaper to replace when damaged.
M809 has a lower center of gravity with the cab/body sitting lower on the frame. If you have a locker in the front axle (most don't) then the sprag tcase in that series has the benefit of basically only engaging it when needed, compared to in a m939 truck you would have to flip the air switch to the tcase when you want it active.
Front fenders on m809 are stronger/cheaper to replace when damaged.
gimpyrobb
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When it comes to the difference in trucks, it will be negligable. I bet you'd have more difference in drivers, skilled vs not.
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Careful what kind of question you ask here, might start a battle between the 8xx and the 9xx's. So far it has been civilized in responses, but could change
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As far as ability's I'd say fairly equal. In my case came down to what was available at time of my purchase, and the primary fact is that I wanted a standard
transmission of the 800 series over the automatic of the 900. I really like the 2 speed transfer case on my 813a1 as well. You can put it in low range first gear
and creep along and 1/2mph up a 40 degree slope, if you can keep traction.
.As far as ability's I'd say fairly equal. In my case came down to what was available at time of my purchase, and the primary fact is that I wanted a standard
transmission of the 800 series over the automatic of the 900. I really like the 2 speed transfer case on my 813a1 as well. You can put it in low range first gear
and creep along and 1/2mph up a 40 degree slope, if you can keep traction.
red
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All m939 are trash and should be sent to scrap metal!! Something like that? hahaha.Careful what kind of question you ask here, might start a battle between the 8xx and the 9xx's. So far it has been civilized in responses, but could change
As far as ability's I'd say fairly equal. In my case came down to what was available at time of my purchase, and the primary fact is that I wanted a standard
transmission of the 800 series over the automatic of the 900. I really like the 2 speed transfer case on my 813a1 as well. You can put it in low range first gear
and creep along and 1/2mph up a 40 degree slope, if you can keep traction.
The differences are minor and even fewer with trucks that are privately owned. Different front body, transmission, tcase, and brakes (but all that can be changed)
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The 809 series does not have this problem.
When stuck and rocking a 939, it adds a shift and it's counterintuitive which makes it easy to forget, resulting in split transfer cases.
The 809s' sprag makes for its own set of problems rocking. You can't just let it roll back while in a forward gear , or forward while in reverse.
Csm Davis
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Because off road is all about traction, if you take the tires out of the equation, the 809 will pull the hardest then 939, and 939A1, then the 939A2 but if you are talking about sand or mud the 939A2 will be better because of less weight on the front end and it will make a difference if you are running super single tire, not so much with dual tires.
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