Reverse Lockout - Not
 

Installed a Rennshift with automatic reverse lockout a year ago and has worked perfectly since. Yesterday I started to get a major crunch when downshifting to 4th. The lockout pawl seems to be operating flawlessly and the shift rod bushing and coupler bushings are all new and just inspected. I can downshift fine but need to pull into neutral and let the spring gate take it into the 3-4 plane.

Several months ago I did pull the transmission and had some work done on 1st and 2nd gear. I hope nothing is going on there.

Sounds like the coupler adjustment could stand to be fine tuned.

The directions from J West are very straight forward for coupling adjustment, almost fool proof. I guess I could try a tweek in both directions. Odd that it happened so suddenly.

Well, you might also look at the engine and transaxle mounts, it may be allowing the drivetrain to shift a little.

if the tapered pin in the shift coupler backs off just a touch, you will have enough play in the linkage to cause your problems. Check that everything is tight prior to re-aligning the coupler.