Transmission not working unless it’s in 4x4

[Freshfish]

Hello. I have just done a frame swap and used the same engine and transmission. I drove the truck before the frame swap so I know it’s a good transmission. I cannot get the truck to move unless the front differential is engaged. I have checked the fluid(good) linkage(good) and cable(good). I need some guidance on where to start diagnosing that while sitting the transmission decided to fail. Thanks in advance

[tmoore4512]

Hey brotein, ran into this same issue.

 

What I found was that the T case linkage was too short to get it to engage properly.

 

Disconnect the linkage and move it manually, then check it. 

 

I had to extend my linkage and tack weld it once I got it right, then pull it off and weld it up.

 

No problems since.

[Slartibartfast]

The first thing I would do is make sure that the shifter goes through its full range of motion (from 2H to 4L and back again). I've heard of similar issues where people have swapped in a transfer from a different platform (made for a different floor pan) or mixed and matched the linkage and the lockout plate. Either the shifter hits the floor, or the lockout stops the shifter in the wrong place. Given yours is all WD21 parts, and worked previously, I would guess something didn't go back together quite right (assuming you had that linkage apart?), so you're shifting from neutral to 4L when it looks like you're shifting from 2H to 4H.

 

I can take a picture of the linkage on mine for reference if that would help.

 

I've also heard of people having the console apart, moving the shifter to get it out of the way, and being shocked to find no drive afterwards--because they forgot they put it in neutral. I may have done this myself at some point.

 

If the transfer is in neutral, putting the auto trans in park (or leaving a manual in gear in gear) will not hold the truck. This is both a way to rule out the transmission, and something to watch out for if you're working on uneven ground--don't run yourself over with your own truck.

 

I am of course assuming that your rear driveshaft isn't sitting in the corner laughing at you.