This is an old thead. anyway,
Budman67, the first 2 1/2 tons had a sprag in the transfer case to help out with engaging the front axle if there is slip between the primary drive (rear axles). So if you were in snow or mud and the rear axles started to move more than the front axle the sprag would engage to give some power to the front axle helping to get you moving farward or backward. only issue was that if you let yuor vehical roll backward on dry conditions the sprag would engage and rip itself apart. Therefore you would have no engagement of your front axle until the sprag is reajusted or replaced. The military changed to the air engagement system to elimiate this issue. the air system works like it should and you also have an indication that the front axle is engaged. The older system has no indication that it is working until you realy need it and it is not.
Hope I got it right. I have a sprag setup and I think its not working but I only use my duece for parades and when it nice out.
41cl8, that's about how Gringletaube explained it to me, with only 1 minor difference, you rolled back while the transmission was in a forward gear with foot on the clutch you got sprag windup. in that case you had problems.
The way it was explained was the problem was not so much just rolling backwords, it was the fact that the transmission would be in a forward gear and even with the clutch depressed, the way the system was designed, it would make no difference because of the spring loaded shift rods that "inter connected" with the transfer case. mine were way out of adjustment and right now they are working again as Gringle instructed me so im good there now.
this problem would happen regardless of going forward or reverse, so just remember, if your going to depress that clutch in the old M35's, just take the transmission OUT OF GEAR FIRST. put it in neutral or reverse if youre going to roll backword, or low gear if going to roll forward. dont have that clutch depressed like you do on civilian jeeps and 4wd systems.