205 T-case that just doesn't lock in 4wd?

[mountainexplorer]

We put a TH400 and NP205 T-case from an '83 K30 dually, that worked fine according to the previous owner, and put it in an '84 K5. At first, the shifter was acting strangely but it worked in 4-low and 4-high.

Now, without any noises and with the shifter and shift rails working just fine (visually extrenally), it just doesn't engage the front driveline.

What can go wrong with a 205?

 

[8_YOUR_H2]

I bet the shift rails are worn where the detent balls go and the front rail will not sit properly.

 

[mountainexplorer]

Hmmm... sounds like something that the t-case would have to be pulled out in order to fix (at least easiest).

 

[pvfjr]

Well if it feels like it's shifting fine, but doesn't engage, there's probably something wrong with the fork. Maybe the roll pin that holds the fork to the rail has come out? Have you checked to see if rail for the front is moving in and out of the case properly when someone shifts it?

 

[mountainexplorer]

Everything externally that can be seen from outside the t-case (shifter handle, little linkage piece, and shift rails) is all working fine. You can watch and feel it solidly click into each different position from 4-high; 2-high; Nuetral; 4-low. Whatever may be wrong has to be inside the case. But theres no bad or irregular noises coming from it at all. It's just that the front driveline (front output) will not solidly engage when it's supposed to.

 

[BadDog]

The outboard shift rail (nearest the front output) controls LNH for the front output. And the stock 205 shifter uses a see-saw linkage and hard interlock pins to make the "shift pattern" work right. Sounds like maybe that rail is stuck in the N position. Low is all the way forward, H is all the way pushed into the case. First thing is get under there while someone shifts it to see if it moves, then go from there. Either way, if there is not some visible interference externally, you are going to have to pull the case.

The onlything you might try if it is not moving is remove the spring detent. Look for a screw in plug on top, right above the rail. Remove th spring and the ball, then see if it moves. I guess it could be rusted or otherwise jamed in there, locking up that rail...

 

[mountainexplorer]

That's the thing I don't understand. I've had alot of 205s before, and know how the linkage works as far as positions of the shift rails... at first I thought it was the linkage being screwy, but we have the floorboard open to where I can literally watch each rail click in and out as they are supposed to in each position. I shifted it a dozen or more times watching every part move and theres nothing I see out of place.

 

[tolovana]

If everything on the outside of the t-case is working, the problem must be internal. It is most likely a busted shift fork or the pin connecting it to the shift rail. The only way to know for sure is to tear it down. Shouldn’t take more than a day if you have a good source for parts.

 

[pvfjr]

Yep, my vote is for the fork, or the pin holding it on. The one right under this freeze plug. Not the one with the punch in it, but the one with the arrow pointing to it.

 

[BadDog]

Yeah, I figured you knew most or all of that, but I gave a full run down of everything I could think of just in case. Lots of folks treat the tcase almost like a non-serviced component (just pull and replace) without knowing the details. And even if you've worked on it before, it's easy to miss some detail or overlook something. I know I've overlooked "the obvious" before... Let us know what you find, I'm kinda curious about what happened.

 

[mountainexplorer]

Well, I tend to be one of those people that just swaps whole things rather than fixing them sometimes... which is why I've never actually gone down into the internals of a 205 before... that and usually I never have 205 problems.

This one is in a Blazer I traded off to a friend and it's a 400 version so not so easy to just grab another and throw it in.