There seems to be a constant stream of 5 ton transfer case questions/problems that pop up on this site. Any suggestions for a thread addressing the bulk of these questions so when new members ask, they can be directed to one post? Of all the systems on the 5 ton trucks, this one item seems to be the most misunderstood.
We have tried that in the Wkies or however you spell it.... People don't search so it would not matter if we posted it in the main page and you had to look at it every time you logged in... people still would by pass it and ask the same question 1000000000000 times.
The Following User Says Thank You to Westech For This Useful Post:
We have tried that in the Wkies or however you spell it.... People don't search so it would not matter if we posted it in the main page and you had to look at it every time you logged in... people still would by pass it and ask the same question 1000000000000 times.
Now now Westech do you realy think they would ask that many times.?.
I think it would be more like 100000000000 times at most.
The Following User Says Thank You to jasonjc For This Useful Post:
No more M-800 series trucks in our motor pool so I can't speak for them; we've got the M-900 series trucks. Their transfer cases break pretty regularly if you try to use reverse gear while in low range. A big enough problem to have brought on low range/reverse lock-out kits and dash instruction plates.
We haven't had any other problems on an ongoing basis.
We get a pinched or ripped oil pump line now and then but that's usually from not securing them correctly. Air lines leak or electrical connections break down and suddenly the front axle won't engage. Rest of the time it's usually linkage adjustment problems.
Remember that lot of military equipment was deadlined for a month or better even before they went through the screening process and out the gate to GL.
Anything that isn't driven frequently will stiffen up with congealed grease, seals and bearings will dry out, air and oil lines will gum up or crack and leak, exposed parts will rust.
A regular PM program is the best preventative for most problems.
Well, I will give it a try, at least with the issues we have had, and how they relate to the transfer case &/or sprag shifting:
1) All M54/M800 trucks front axles are engaged with the transfer case when running and driving, if there is air to the shift valves on top of the transmission & on back to the shift cylinder located on the front of the transfer case. Some trucks have an added valve like a Deuce so the front axle free-wheels. The overrunning clutches (sprags) in the transfer case allow the front axle to run faster than the rear axles in a turn so there is little to no binding. There is always a slight delay before the front axle will "grab" due to the sprags engaging.
2) The sprags in the transfer case are controled by the shift valves (poppets) located in the shifting tower of the transmission. In any forward gear or neutral the forward sprag is engaged and the reverse sprag is only engaged when the shifter is in reverse. Never allow the truck to roll back with the transmission in neutral or any forward gear. A transmission change to a non-stock unit would require some type of shifting system to keep the transfer case engaged like the stock system. This is just one problem for an updated transmission installation in these trucks.
3) Any interuption to the air pressure in the shift system will affect the engagement of the correct sprag clutch. This was a issue we had with the water truck at first due to tar like oil in the transfer case. The transfer case must select the correct sprag or binding and much damage will happen.
4) An easy check of the sprag engagement process is to jack up one front wheel, make sure you have full air pressure in the tanks (truck off) and place the transmission in reverse. You should only be able to rotate the raised wheel backwards. With the shifter in neutral or any forward gear the same wheel should only rotate forwards. With no air in the system at all, including the shift valves, you should be able to rotate the wheel in both directions. This test assumes that you do not have a locker in the front axle. If so, just jack up both wheels. If you can't turn the wheels as noted something iswrong and the truck whould not be driven without removing the front hubs or drive shaft (completely). Any air leaks in the valves, hoses or the operator cylinder located at the front of the transfer case must be fixed or you risk a much worse problem with the internal parts of the transfer case.
5) The transfer case is nearly three times as large as the transmission, but only holds about 5 quarts of oil. All the gears are engaged when running down the road, so there is a lot of heat and "oil windage" inside the case at 50 mph. Of any compartment on these trucks requiring regualar lube service, the transfer case is the most important. We use a MIL rated GL5 gear oil and change it once a year at least, with checks in between to make sure that it is full all the time. This is very important, especially for guys that run at speed up and down hard roads.
The system as designed and built is really seamless and requires no thought, but you must follow the operators manual correctly.
The Following 4 Users Say Thank You to m139h2otruck For This Useful Post:
5 ton transfer case issues
