I just put a 6.0 LS in my 89 1 ton square body crewcab. I retained the TH400, I actually never removed the TH400 during the engine swap, didn't even remove the torque converter from it. I just got the engine fired today and when I move the column shifter through the gear range, I get no gear engagement in any linkage position. The trans (and original motor for that matter) had no issues, the engine was just under powered for the 35" tires...the torque converter spacing to the LS flexplate (with use of adapter) was ideal, not too tight nor excessive travel to mate to the flexplate.

The swap took me about a month, so it didn't sit long. I had no fluid loss either. Curious what would be most likely to cause such a condition on?

 

did you hook the vacuum modulator back up?

 

Nevermind me, hilariously; I just accidentally knocked the 4WD shifter into neutral while working under the dash during the swap and hadn't realized or checked it.

I'll leave this here so someone in the future will get a good laugh at me or themselves.

 

everyone has done it. only a few of us have the ***** to admit it. at least it was an easy fix.

 

Been there, done that!!!
Thanks for letting us know!