Transfer case slips to neutral when shifting

[glj]

Sorry folks. I've spent two hours looking but can't find that this matter has been addressed. I'm sure it has, but I'm only a Corporal. The problem is this: T136-27 air shift transfer case, rebuild about two years ago. During an 8000 mile round trip to the Yukon the transfer case lever began to slip (disengage) from high into neutral when shifting the transmission, usually from 1st to 2nd or 2nd to 3rd. Doesn't usually occur when shifting under a load, but with the "relaxed" shift it is occuring with increasing frequency. It never shifts to neutral while in low range. Any thoughts, please? I did find a small piece of bearing race casing (or whatever it's called) on the magnet plug when I changed the lubricant, thinking I might find something.

Gary

 

[212sparky]

Rebuild time. If you found race material, I would deadline the truck untill I found out what it is from.

 

[Ferroequinologist]

Common problem, Angie's M109 has been doing it for years. I strapped it up and have driven it many miles that way, but from what I understand it is hard on the gears.

I have a rebuilt transfer ready to go in, just need the time to do it!

I would also deadline the truck until the source of the metal was located.

Sometimes searching using Google under this website has better results.

http://www.steelsoldiers.com/deuce/90156-transfer-case-mounts-high-range-pop-out.html

 

[73m819]

The SYNCO is worn out, needs a new SYNCO SET. It will only get worse, you can as ADEM said hold it up but will become harder and harder to do, very hard on the engaging gears

 

[gringeltaube]

Holding the lever up with a bungee or strap is a common fix but will quickly wear out the shift fork, too. See pics below...

If you already found bearing-cage pieces that's a clear red flag; time for new ball bearings, at least, for the input shaft. See this recent thread.


G.

 

[Ferroequinologist]

looks like I better move my transfer case replacement up on my list!

Maybe I'll do it in my new 'shop'? lol.

 

[glj]

Thanks to all for this very useful info. It is certainly helping me to learn to use this site, and find information more easily. I also have noted several inches of forward travel of the TC shift handle under acceleration. This was present before the first rebuild (I was not present. It was done by one I thought had the experience) and continued after the rebuild. Brand new mounts were installed during the rebuild. This work was done before I retired and before I had time to "participate" and before I discovered this web site. I don't even recall precisely why the rebuild was done except that the "popping out" of high was a problem for awhile and then one day I just couldn't drive it. (I'm not a mechanic. Any surprises?) Anyhow, the rebuild "worked." No more popping out of high, but the forward movement of the handle was always present. Well, let me say it "worked" for about 10,000 miles. Now it's back.

So, from the above I infer the following (correct me if I'm wrong): 1. The forward motion of the handle may be expected due to "inertia" and is not necessarily abnormal, but one should check mounts, etc. 2. Poor design results in only half gear engagement and we probably should expect to encounter popping out of high sooner or later, especially if we drive it a lot. 3. I do have a military (Ft. Riley) rebuild around the garage, so that is going to replace the original unit, which will be rebuilt if possible. The TC mounts still look very good, but I will replace those as well. OK, well thanks again. Reminder question: Is it really "expected" that the TC handle moves forward under acceleration? Is this a normal finding? Or does it occur as the gear teeth begin to wear?

 

[glj]

abc

 

[73m819]

Thanks to all for this very useful info. It is certainly helping me to learn to use this site, and find information more easily. I also have noted several inches of forward travel of the TC shift handle under acceleration. This was present before the first rebuild (I was not present. It was done by one I thought had the experience) and continued after the rebuild. Brand new mounts were installed during the rebuild. This work was done before I retired and before I had time to "participate" and before I discovered this web site. I don't even recall precisely why the rebuild was done except that the "popping out" of high was a problem for awhile and then one day I just couldn't drive it. (I'm not a mechanic. Any surprises?) Anyhow, the rebuild "worked." No more popping out of high, but the forward movement of the handle was always present. Well, let me say it "worked" for about 10,000 miles. Now it's back.

So, from the above I infer the following (correct me if I'm wrong): 1. The forward motion of the handle may be expected due to "inertia" and is not necessarily abnormal, but one should check mounts, etc. 2. Poor design results in only half gear engagement and we probably should expect to encounter popping out of high sooner or later, especially if we drive it a lot. 3. I do have a military (Ft. Riley) rebuild around the garage, so that is going to replace the original unit, which will be rebuilt if possible. The TC mounts still look very good, but I will replace those as well. OK, well thanks again. Reminder question: Is it really "expected" that the TC handle moves forward under acceleration? Is this a normal finding? Or does it occur as the gear teeth begin to wear?

ON a new, tight, t/c the shift lever won't move, as things ware it will move more and more, the design of the t/c with the shift lever in high, the weight of the lever puts weight/load on the shifting fork, collar, syncos, ect.

These trucks were designed for 75% off road, 25% on road, this means that 75% of the time the t/c will be in low ( shift lever down) hence NO load on the shifting components, notice that the 900s that are designed for 75% on road, 25% off road have the t/c shifting lever reversed with high down, low up.

 

[glj]

Yes. Have an M923 and that is correct.

 

[sigo]

If the weight of the handle causes wear as the t/c ages, do we suppose that strapping the handle in the maximum up position might decrease the wear over time and extend the life of the t/c components? Or will constant upward pressure cause other problems?

 

[Blueduce]

If you have a good working T/C and are driving 90% on road with your truck is there anything you can do as far as preventive maintenance.

 

[gringeltaube]

The pure weight of the lever alone doesn't cause any wear at all: the spring loaded detent ball in the shift shaft groove(s) is strong enough to overcome that relatively small force.

What causes wear to the shift fork's groove is the center disk of the synchronizer hub resting against one or the other side, while in gear and turning. That axial force will gradually increase, the more the small dogs on gears and the synchro unit itself, wear out. Finally comes the point when that force - PLUS the weight of the lever, YES; + eventually loose mounts; + maybe inertia effect; + excessive axial movement of the whole input shaft assy. (from bad bearings) - all combined is simply too much for the detent mechanism to hold fork & shaft in place and it pops out of engagement into neutral position.

If the lever moves Up & Down during acceleration/ deceleration in high gear, that comes mainly from loose mounts but also from the shaft being forced forward (OUT) just before the detent ball jumps out of the (foremost) groove.


G.

 

[glj]

The moderator, Gringeltaube, seems to have best stated, in the most concise manner possible, and with greatest attention to physics the explanation of the issues I have queried. I was suspicious that the weight of the handle would be of any consequence. But, "G," you are the one that used "inertia" to explain the handle movement in one of the associated threads to which you referred me (unless I am mistaken). I inferred from that that inertia was the principle reason for the lever to move forward under acceleration, and that this might be a normal circumstance. You have now clarified that it is not normal. In reference to the mounts, these are new in my application and have been checked and rechecked, and do not appear to be causal. The forward movement of my TC handle occurs under acceleration at highway speed in 5th gear and is not associated with the slipping of the TC handle from high to neutral. So I'm not sure how it could be associated with the shaft movement. But remember, I'm a neurologist, not a mechanic (except gasoline Studebaker race engines). I really liked your tight summation, although I think the "experiment" (i.e., replacing the TC) is the only way for me to go right now.

As an ancillary question, on a military rebuild that has been sitting dry for about 9 years, without any lubricant contained, need I be concerned about anything other than replacing the outer seals? Do bearings, surfaces, etc. rust internally in these rebuilds over time, without contained lubricant?

Oh! One more, if your patience permits. I have owned my Deuce for about 4 years and always, when turning sharply left the PTO has attempted to engage in the play out position (winch). There is gear chatter with the metal lever position lock plate in down position, and on one occasion with sharp left turn, torquing the M35 over a steep ridge it actually engaged the winch in play out position. The lever was very loose and imprecise. On tightening the linkage the situation improved, but now the only way that I can avoid this gear grinding effort to get the winch in REV is to flip the metal lever holder up and out of the way. No problems in this position. Just wondering whether there may be any association. Many thanks.