Manual transfer case 4hi issue

[Dave18]

Okay, so I have finally made progress on my B3000 off road project... truck started as a manual 2wd with a worn transmission, so I've swapped in a remanufactured M5OD and added a manually shifted transfer case. Anyway I drove it for the first time today, and while low range works, when you shift from 2wd to 4hi, there is a rotary grinding noise and the t-case front output slowly rotates, as though it is not quite engaged (no front driveshaft as of yet). Notably, when you shift from 4low to 4hi through neutral, the 4hi seems to work normally. No weird sound or anything.
At first I assumed the shift linkage was misaligned, but I followed the adjustment steps (lining up the chamfered edge of the gate with the shifter shaft in 4low) and the problem persists. Could this be a fault in the transfer case? The unit is a remanufactured one from Zumbrota drivetrain.

 

[franklin2]

You are completely stopped while shifting the transfer case correct? And you have the 5 speed in neutral?

Does your clutch seem to work ok? If it's not releasing that great, as soon as you drop the transfer case out of 2wd, the trans may start turning and cause the grinding. Try doing it quickly before it gets a chance to turn.

 

[Dave18]

One other detail... if you shift from 2wd to 4hi while moving, it will grumble and not lock in the front output as described above... if you come to a stop though, there is a soft "clunk" and the front output seems to lock in and behave normally in 4hi. It seems as though the shift collar (or however that works internally) is just not quite able to engage the front output, and when you stop it can. I can feel the 4hi detent as I move the shifter so it doesn't feel like it is mis-adjusted.

 

[Dave18]

Sorry Franklin2, you beat me to it. I was shifting between 2wd and 4hi while moving (slowly)... Is that the problem? Does the manual 1354 not allow for that? I thought it was shift-on-the-fly but will feel like an idiot if the manual version is not...

 

[Dave18]

Also since I have no front driveshaft, I suppose there would have been a big speed differential between the front output shaft (stationary) and the rear one turning at road speed. Maybe that was too much for the case to compensate for?

 

[franklin2]

You can only shift on the fly if the manual hubs are locked in. When they are locked in, the front tires will turn the front diff and the front driveshaft as you are moving, and the transfer case will go right in as you are moving, since EVERYTHING is turning. In your case, you do not have the driveshaft in place, so even if you lock the hubs in, the front output of the transfer case is not going to be turning in 2wd. So when you go to 4wd you will get grinding. So for right now you have to be stopped. When you get it all together, make sure the hubs are locked in, and then you can shift back and forth between 2wd and 4Hi. You always have to be stopped or creeping very slowly to get into 4 low.

 

[Dave18]

Great, thank you for replying, that makes me feel a lot better! Totally makes sense; that would explain why it locks in as soon as you stop too. Phew!