Transfer Case Troubleshooting

[degride]

So I've had some grumblings going on with my t-case for a while. Mind you, this has been going on for over a year and while the truck ('03 D2) is drivable, there is something not quite right about it.

Spoke to Will last week about a potential t-case replacement but before I go down that path I wanted to make sure that it's something related to the t-case and not just throwing parts at it. Again, the truck drives, in Hi and Lo and locked (at least I thought - stay with me here) or unlocked. And yes, it does have a locking t-case in it.

This past weekend I dropped the front driveshaft (GBR) to road test it with an attempt to eliminate load being transferred from the t-case, through the driveshaft and into the front diff (one of the areas I'm troubleshooting). Ultimately i was trying to rule out the front output shaft on the t-case being bent just enough to introduce vibration at various RPMs and when under load or possibly the preload being off if the t-case had ever been rebuilt (limited history on it). I replaced the output bearings and resealed it but the gears looked good.

So, with the front driveshaft removed, I proceeded to start it, lock the t-case, and put it into "D". Nothing. Would not go forward. Would not go backward. Went to put it into "P" and I then heard grinding (like what you would hear when you miss a gear in a manual transmission). Quickly moved it into "N", tried again, same sound. Moved it back to "N", unlocked the t-case, moved it back to "P", same thing. I turned the truck off while in "N", moved it into "P" and started the truck. All good regarding sound but still no movement. It didn't matter what gear I was in (1, 2, 3, 4(D)), it exhibited the same behavior.

I climbed under the truck disconnected the CDL linkage and manually locked it. Climbed back in and repeated all the steps above with the same outcome. At this point I'm stumped. Decided to grease the driveshaft while it was out, put it back in and reconnected the CDL linkage.

Got back in the truck, started it with t-case unlocked and shifted through all the gears and the truck would move (again, driveshaft is back in). Would also move when t-case was in "locked" position. Went to put it in "P" and no grinding sound. Took it for a spin around the neighborhood and all is good or as good as it was before I removed the driveshaft.

So my question is:

1. Even with the t-case manually locked, why wouldn't it move
2. With the front driveshaft removed, why would the transmission make a grinding sound when trying to put it into "P"?

 

[discostew]

It does sound like your t case isn't locking. A couple things could be going on in there to cause that. I guess the easiest way to tell that is to see if the rear drive shaft is spinning when its not driving in gear. I think you would have bigger issues if that was the case. The reason you hear the grinding when you put it in park is because all that shit is spinning, it would normally be stopped by the drivetrain.

If its just the transfer case not shifting to locked even with the lever in that position then the shift dog is most likely broken. I think if your dif was blown out then you would have other issues also.

 

[degride]

Rear shaft is not spinning. I'd have to go out in the garage and look at the old case, but IIRC there is no way to inspect the shift dog even coming through the console is there? The CDL was definitely in the locked position when I moved it manually. That much I'm sure of.

When I resealed it, everything worked as it should so interesting to think how the shift dog could have snapped.

 

[discostew]

the shift dog is inside the t case. Its the weakest link inside the t case. Just a guess from 1,000 miles away
.

 

[degride]

Yeah I know the shift dog is inside the t-case. I just can't remember if there is a way to get to the diff-lock housing from inside or under and remove to inspect versus having to drop the entire t-case. Would prefer not to but it sounds like I'm gonna have to regardless.

I guess ultimately I need to sync back up with Will and get a t-case from him.

 

[discostew]

If you had both prop shafts in the car you might not have noticed the center diff didn't lock. Maybe it was never right. Without the front prop shaft you are seeing what it would look like if you had a broken axle.