Transfer Case - Slipping?

[Opie]

There are often times that I have to drive up a hill and need to leave the truck in a lower gear in order to make any progress without lugging the engine. Frequently the Hi-Low transfer case will (with accompaniment of loud noises) slip (?) into the neutral position, forcing me to stop/re-engage/start up the hill again.



Is this normal behavior?



Do I need to fab up some kind of mechanical bar across the cab floor to keep the shifter from popping down into neutral or could something more sinister be going on? The clutch on the main transmission seems to be holding well.



What else do I need to check/consider?

 

[rdixiemiller]

You could have some wear in the transfer case. The old manual transmissions used to pop out of gear when the shift drums and the roller bearings started to wear out. Popping out of gear under a load can be several things on a mechanical setup. The transfer case shifter could possibly be out of adjustment and not fully engaging into high range. The detent ball and spring on the shift rod could be bad, bent shift forks are also a possibility.
This is something to look at soon. Popping out under a load can take a tooth off a gear in a hurry. Rigging a lock bar will not cure the problem. If it is trying to come out of gear, you will just trash the shift forks.
I will look in the manual and see what it says, but I would imagine you are going to see the insides of a transfer case soon. Is this an air shift?

 

[rdixiemiller]

OK. According to the troubleshooting manual, check the shift linkage. Make sure the linkage is not bent or binding. Make sure it is properly adjusted and that the shift rod is going fully into position. Take out the tunnel cover to do this.
If the trouble persists, overhaul the transfer case.
That is the extent of the work that can be done externally. I would make sure the lever is not hitting the tunnel cover and not fully engaging.

 

[Opie]

RDM,

The TROUBLESHOOTING MANUAL!

D'oh!

Good thing I'm not in a combat zone. Yes it is an air shift. I'll check out your suggestions and report back.

 

[rdixiemiller]

This is the manual I used: TM 9-2320-209-20-2-2, chapter 33. I am afraid the info is limited, if adjusting the linkages does not cure it, rebuild it!

 

[Opie]

Well, finally found time to remove the transmission tunnel and sadly all the exposed parts look fine, so I'll apparently move towards a having a transfer case rebuild.

 

[rdixiemiller]

Thrill a minute. Get a really heavy workbench.

 

[Deuce-bigalo]

Personally I have removed a Turbo 350 & a NP203 out of my blazer. However with the considerable size difference of these 6x6's, what is the true proper way to remove a really heavy transmission and transfer case? Are these like a 3 person job or 2 people and a good floor jack??

Just curious, sorry for deterring the thread!

John

 

[Armada]

Contact Adelmans trucks if you're near Canton, OH. They have some gov. rebuilt transfer cases. Don't know for how much though.

 

[rdixiemiller]

The transfer cases and transmissions are separate items on a deuce. The main issue I see looking at mine is the top heavy nature of the beast. I'm sure there is a transfer case jack especially made for deuce, probably a $10,000 item for Uncle Sam.

 

[ken]

I just swapped my sprag for a air shift. Since the bottom of the t-case is odd shaped, i used I-bolts in the top cover of the t-case and lowered it to the ground with a chain fall. The whole swap took about 2 1/2 hours. No biggie!!!

 

[rdixiemiller]

Did you pull the rear body to get to the top of the case?

 

[Opie]

I pulled up the two floor plates that cover the transfer case in the cab. Per the troubleshooting manual I didn't find anything amiss with the linkage on the exterior. This section of the manual leads me to the part where it tells me to report the vehicle to a higher authority. Perhaps I should just pray? (Thinking of the old Hebrew National hot dog radio commercials...)

 

[ken]

Rob. All i had to do was Remove the Pass seat and brackets, and both floor pan covers. I even left the shifter is place. I just pulled the lincage. I removed 2 of the top cover bolts on the t-case and used 2 3/8 eye bolts then hooked up my chain fall. It's really easier than it looks. After lowering it to the gound i pulled it out from under the truck with my ATV. After removing the spare tire.

 

[rdixiemiller]

That sounds like a plan. It is easier to lower it with a chain rather than supoport it on a jack.
Safer too.

 

[Opie]

Update:

Long-haul truckers in my extended family seem to think that my issue is with the "blocking ring" (or whatever Uncle Sam may call it) which holds the shift lever in place once set in high or low drive. The adventure continues....

 

[Recovry4x4]

I'm having similar issues with the M275A2. Never pops out of gear under load, it happens when I depress the clutch. I've noticed an abnormal amount of shifter movement as well. I'm going to swap it out when time allows. Looks like I'll finally get to use the way cool gov't transmission hoist.

 

[rdixiemiller]

Usually a worn shift drum in a manual tranny shows up as a "popping out of gear" when you back off the throttle, or de-clutch. After it does this for a while, the gears are damaged enough to allow it to pop out under load. When it first starts to drop out of gear in no-load, you can usually replace the tranny bearings, the shift drum, and the fork, this will sometimes correct the issue.
Considering the low prices of deuce tranny's and t-cases, I would just swap them out.

 

[Recovry4x4]

Yeah, I'm just gonna swap it out. i'm running low on transfer cases though. I think I'm going to figure out how to do the airshift nose to the sprag swap. I know Lance had major issues with his but a friend of mine has done the swap. I just wanna know for myself.