Trans/TCase gone haywire

[kjmclark]

This is my '96 Ranger, MT, 4x4, 4.0L. I'm driving down the expressway today and hear a weird noise - I thought it was something strange on the radio. Kind of a revving sound. Hmm. Turn off the radio. Oh, crap, yes, it's a revving - and it's my truck. For the next mile or so, it revs, then settles back down to 2500rpm (70 on the expressway.) So not right. Finally, it just revs - no power going to the wheels at all. I pull over.

No problems till today, except that this is a used transmission and transfer case, and the TCase eats speed gears. I've had both in the truck for like four years and 4000 miles (I mostly drive the truck on weekends.) But nothing like this at all.

So, I can shift through all of the gears, use the clutch like normal, no strange feels or sounds - but no power to the wheels. Then it gets really crazy. I try shifting to 4wd, which doesn't work, but then I try 4W Low. That totally works. The truck starts moving. So I stop, shift back to 2wd, and drive like that for about 1/4 mile, then back to revving. I put it back to 4W Low, try to switch back, but woah! The lights on the dash change saying I'm back to 2wd, but the TCase is stuck in low! And it seems like it's 2W low! What?!?

And that's where I'm at now. I have all five gears in low, and I would swear it's only rwd. One of my autohubs is aftermarket, and doesn't work quite right - it clicks a lot before it engages. Right now it's silent. Also, usually in 4WD if you make a turn on pavement you'll get bucking. None of that either.

But like I said, I have all five gears, just in low range. Drives completely normally, just no faster than about 25mph. Seems like it has to be a buggered-up transfer case, right? If it were clutch, it wouldn't work normally in low. But what could happen to a transfer case that would do that?

 

[adsm08]

It is probably something very wrong in the T-case. You probably are in 2 low, operating as a front wheel drive vehicle.

The first clue that something is wrong in that T-case, even before your current woes, is that is eats speedo gears.

 

[RonD]

Yes, +1 ^^^^ transfer case issue for sure

Transfer case is just like a manual trans in that it has a shift fork that puts it into its various gears, and it also has a Neutral just like manual transmission.
Manual transfer case shift knob picture here: http://www.explorerforum.com/photopost/data/3553/medium/transfercase_012_Medium_.jpg

So you have 2WD--4WD--Neutral---4Low

Here is picture of transfer case electric shift rod with motor removed: http://s972.photobucket.com/user/jds3403/media/bw 1354/1354transfer.jpg.html

You can see where Neutral should be, opposite 2H, it is just not an available selection on regular electric shift systems, it can be added on some models, so vehicle can be towed behind motor homes or ??

So when you select 2WD electric motor moves shifter clock wise all the way back to 2H, selecting 4WD would cause motor to move counter clockwise to 4H, then selecting 4Low would cause motor to move counter clockwise more to move shifter past Neutral and to 4L.
The shift rod is moving the shift fork inside to engage front driveshaft and to select ratio change for 4Low.

The electric shift motor has a contact wheel inside, this wheel moves with the electric motor, the 4WD control module knows which contacts should be closed and open when electric motor has moved to the correct position, 2WD, 4WD, or 4Low

First step would be to pull the shift motor off and manually change gears see how shifter feels.
You will most likely have to drop transfer case since as adsm08 said the speedometer gear issue means tail shaft is not stable, it is moving around chewing up the plastic speedo gear

 

[4x4junkie]

I imagine if this were NOT a clutch issue, there would be some nasty banging and/or clanging noises present, because there isn't any place other than the clutch for it to transition smoothly from a drive to a no-drive condition (engine revving) and then "settle back down" to normal (2500rpm @ 70mph) with a manual transmission.
Because of the lowered gear ratio in 4-low, it is possible for a truck with a badly-slipping clutch to still move, though this may also be short-lived.

If other noises were infact present, then indeed that speedo gear, and the fact it's sticking in low, are good indicators of where you should look first (and warrants a look regardless of whether you have a separate clutch issue or not). So no matter what, I'd start by pulling the T-case since you'd have to pull it anyway to eventually get to the clutch.

 

[kjmclark]

Yep, that was it. Luckily I still had a previous transmission/transfer case pair laying around. Don't have time to work on the truck right now (still have a car thrust bearing project sitting in the garage), so I took it to a local shop. TCase had partly blown up inside, took out shift fork, a set of bearings and one of the gears.

They pulled the spare transfer case and it looks usable.

Thanks for the help!