M35a2 6x6

[RollingThunder19]

Hi I own a deuce and was noticing some possible 6x6 issues while off road. Since I live in indiana its snowed recently and I was driving offroad noticed my rear tires spinning but nothing from the front. I noticed the front wheels would engage sometimes but not all the time even if rear wheels were spinning. While going through a ditch that's 1 ft to 1 ft and a half deep the front wheels wouldnt spin only rear and after going 1 to reverse I would look out and see the front would spin in reverse and pull me out like it should but I couldnt get it to do it all the time. This is my first winter with the truck and didnt know if anyone has came across this or know what's going on

 

[Scar59]

Need a little info about the truck, is it equiped with the air shift lever/switch located under the dash? Or, is the truck equipped with the sprag equipped transfer case?

 

[gimpyrobb]

Sounds like a sprague t-case. Often what happens is the forward clutch wears out before the reverse.

 

[RollingThunder19]

The truck has a sprag tcase

 

[RollingThunder19]

I was driving in the snow today and noticed the front axle would engage in 1st and reverse but not everytime. It seemed like if I turned the wheel a certain way it engaged dont know if that's just by luck or has anything to do with it. I probably engaged 1st and reverse maybe 6 times and reverse engaged 2 out of the 6 times

 

[Tracer]

I you can afford to, replace the sprag transfer case with an air shift.

 

[RollingThunder19]

The truck only has 14k miles on it and I find it hard to believe that anything with the tcase is bad already. I saw some posts say there might be an adjustment for the tcase? Dont know much about that or if that could fix the issue

 

[fasttruck]

Check to organizational maintenance manual, TM 9-2320-209-20 and see if it says anything about adjusting the sprag. Otherwise changing out the transfer case is an animal job.

 

[RollingThunder19]

I thought about replacing the tcase before but figured everything with my current truck was fine till I started noticing the front axle would engage only sometimes.

 

[RollingThunder19]

I have a manual that I found online not sure which one it is but it's pretty informational and I can see what I find about adjusting it

 

[Scrounger]

The sprague could have been damaged from coasting backward when in a forward gear. The sprague may also be “gummed’ up. The inside of the transfer case and gears can develop a film of old oil. This film can cause the sprague to act erratic. Drain the old oil out. Fill the transfer case with ATF or kerosene. Place the transfer case is neutral, start the engine, run thru the gears in the transmission, then idle the engine for a while with the transmission in gear. Don’t place any load on the transfer case. Drain the ATF or kerosene out, then refill will the proper gear oil. This usually frees up the sprague.

 

[porkysplace]

The truck only has 14k miles on it and I find it hard to believe that anything with the tcase is bad already. I saw some posts say there might be an adjustment for the tcase? Dont know much about that or if that could fix the issue

Your more likely to get the truth out of a politician than the correct hours/miles on a military truck . The government just swaps gauges out they don't fix them.

 

[RollingThunder19]

The truck did sit for a while possibly 7 years before I bought it so that sounds like a good possibility. When you say run through the gears and let idle in gear there is no movement of the truck during this period right? Just hold clutch in and let the fluid work through the gears while shifting in each

 

[tobyS]

Remove the front and rear driveshafts, then do above. Holding the clutch in doesn't make the tranny or TC turn.

I took the TC case out of my M817 and it's really not too bad if you are mechanically inclined. Getting to know the inside of that part is not a bad idea. Where are you in Indiana?

 

[RollingThunder19]

Okay that makes sense. I've taken the front and rear driveshaft off before so it shouldn't be bad now. I would say I'm pretty mechanically inclined I could probably take it out fairly easily. Is there a way to fix the sprague or is it just trashed out? Also the thought of an air shift crossed my mind but that is not a priority of mine at the time do to other projects. I'm in south bend, indiana

 

[tobyS]

There are a lot of parts if you take the sprag tooo far apart to clean and inspect. I don't know if new ones are available, but I liked mine when it worked right. I think the sprag could come off with the TC on, but working overhead seems harder than taking the entire TC off to R&R it.

I used aviation form a gasket for putting mine back together...good thing...3x splitting the case and 4-5 for the sprag (take the sprag off but do not disassemble)(don't misplace a snap ring like me).

Mine was 5 ton 809 series, do you have air engagement for your sprag unit, can you take any photo's? someone with one like your (M35A2) will come along

 

[gringeltaube]

.....I would say I'm pretty mechanically inclined I could probably take it out fairly easily.

If so, then why not just pull the front output section off of the T-case? Then, disassembling it and inspecting these sprag clutches is no big deal at all.
(all covered in TM 9-2520-246-34, Section VIII, Fig. 4-46 or TM 9-2520-246-34-1, Table 2-39)



So far, all of the (known) low-mileage sprag units that I have checked, were all still in very good shape.
Most often the whole issue with these -21 sprag T-cases is just a matter of a proper working, well adjusted shift rod, in between transmission and transfer.

(You may refer to this thread... , also the links posted in #3)

 

[tobyS]

RT....Gringeltaube is the man. ALL good info and the last link is great. Notice the spring holds it to the normal position and is shifted by the linkage to the reverse position.

G...is the T1138 the same....except air shift? I don't see a neutral (at least a location intended to be neutral).

 

[RollingThunder19]

There are a lot of parts if you take the sprag tooo far apart to clean and inspect. I don't know if new ones are available, but I liked mine when it worked right. I think the sprag could come off with the TC on, but working overhead seems harder than taking the entire TC off to R&R it.

I used aviation form a gasket for putting mine back together...good thing...3x splitting the case and 4-5 for the sprag (take the sprag off but do not disassemble)(don't misplace a snap ring like me).

Mine was 5 ton 809 series, do you have air engagement for your sprag unit, can you take any photo's? someone with one like your (M35A2) will come along

Mine works every once in a while. I figured something like once it goes out it goes out and wont work but it kicks in sometimes. If I were to work on it I would probably take it completely down. My sprag unit isnt air engaged

 

[RollingThunder19]

If so, then why not just pull the front output section off of the T-case? Then, disassembling it and inspecting these sprag clutches is no big deal at all.
(all covered in TM 9-2520-246-34, Section VIII, Fig. 4-46 or TM 9-2520-246-34-1, Table 2-39)

View attachment 754017 View attachment 754018 View attachment 754019

So far, all of the (known) low-mileage sprag units that I have checked, were all still in very good shape.
Most often the whole issue with these -21 sprag T-cases is just a matter of a proper working, well adjusted shift rod, in between transmission and transfer.

(You may refer to this thread... , also the links posted in #3)

Should I try to drain fluid in TC first and see if getting the TC cleaned out helps first before dropping the whole unit and disassembling the sprag? I would like to not make more work for myself than needed. You mentioned a shift rod and adjustment to it. Where is that adjusted from?