Airshift transfer, repair or replace?

[LanceRobson]

I've got an M35A2 with an airshift transfer case that developed a problem and I'm looking for advice as to whether to repair it or replace it. I have the parts TM for the transfer but no maintenance TM and if the job needs any special jigs or fixtures I don't have them either.

After exhibiting no unusual symptoms the truck acted like a brake was frozen when it started to move from a parking spot. The truck began to move only very reluctantly and as soon as the clutch was stepped on it rolled back a few inches like it was "unwinding" Then we backed it up a few feet to see if it would move in reverse and it backed OK.

We then shifted into neutral at both transfer and the transmission. The drive shaft from the transmission to the transfer case would not turn until the transfer shift lever was cycled from high to low a few times.

Now it will not shift and the drive shaft had to be disconnected to tow it.

The transfer had recently been taken out of a good running truck with 53K miles and put in the truck it's in now and, yes, it had gear oil in it.

I've got a pretty complete shop and tools so the big question remains, should I overhaul the transfer or roll the dice on a used replacement. I intend to keep this truck and use it often.

Any thoughts from folks familiar with costs of parts would also be appreciated.

Thanks

Lance

 

[jatonka]

Why not take it out, you have to anyway, take it apart and see if the high low shift fork and collar is broken or bad. Or if you have bearings so bad that some gear is climbing out of position. If what is bad turns out to be parts that are also in sprag transfer cases, I will have parts for you, inexpensive. JT out

 

[clinto]

I'd overhaul if for no other reason.................. you don't know what you are putting in it if it's used!

If you overhaul, you know it's right and will last and be dependable. Imagine if you'd been 500 miles from home when this happened.

I know a lot of folks will disagree with me, but it's a lot of work to install a used engine, tranny or transfer and only have it last 6 months or a year or whatever. Plus, every time you take a trip you'll be wondering "Is this used transfer gonna' make it home?".

I have no ideas on the cost or parts.

 

[mikew]

I just finished replacing all the input shaft bearings on my transfer case and the job wasn't that bad or expensive.

The input shaft runs on two ball bearings, one in front and one in back. The low speed and high speed input gears each have a pair of ball bearings in them that allow them to free-wheel on the input shaft when disengaged.

Based upon what you described, if the input shaft won't turn in neutral one of the input shaft bearing has probably failed and jammed.

But.... if you tried turning the transfer case input shaft while the drive shaft was connected to the transmission, you could have a transmission output shift problem instead. You should try it again with the transmission to transfer case shaft disconnected to confirm.

Whether you repair or replace, you've got to pull the transfer case. I removed the passenger seat and used a cherry-picker to lower the transfer case.

Once you've got it out, pop the cover off and figure out what has failed. At that point you know what you're up against and can decide the best course of action.

Transfer case service is covered in: 9-2520-246-34-1

Your "unwinding" symptom makes me a wonder if it is an input shaft issue. I don't see what could "wind up" in the first place with a failure on the input shaft.

Mike

 

[mikew]

Having thought about it a little while, I'd check the front cluch and the air shift mechanism.

My truck has a sprag clutch and if you let it roll backwards while in a forward gear or vice-versa in will "wind-up", the way you describe, when you try to take off.

I don't know if the air-shift can do the same thing, but I'd check it and related parts before pulling the transfer case.

Mike

 

[gringeltaube]

...............................
I don't know if the air-shift can do the same thing........

No, not after only a short distance going straight line. Unlike the sprag-TC the Air-S. front AND rear output shafts are the same ratio and rpm.

I don't see what could "wind up" in the first place with a failure on the input shaft.

It could indeed... if for example a bearing went real bad inside the (small) LOW range gear and is about to "lock" it to the shaft while you are trying to move in HIGH. Its like having two gear sets of different ratio engaged at the same time!

G.

 

[LanceRobson]

If you overhaul, you know it's right and will last and be dependable. Imagine if you'd been 500 miles from home when this happened.

.

Clinto, if the problem had surfaced 5 days later the truck would have been on the way to Aberdeen, 320 miles from home with a full load and trailer! Talk about dodging a bullet!

I haven't touched a single thing with the MVs since Aberdeen. The next 10 days will be really busy then I'll get a chance to pull it into the shop and drop the transfer case. I've got a small time window before we start the next house.

Lance

 

[nk14zp]

I'd overhaul if for no other reason.................. you don't know what you are putting in it if it's used!

If you overhaul, you know it's right and will last and be dependable. Imagine if you'd been 500 miles from home when this happened.

I know a lot of folks will disagree with me, but it's a lot of work to install a used engine, tranny or transfer and only have it last 6 months or a year or whatever. Plus, every time you take a trip you'll be wondering "Is this used transfer gonna' make it home?".

I have no ideas on the cost or parts.

I concur.