2002 Manual Transmission Shifting Issues

[RPM23]

2002 Ford Ranger 4.0L V6 4x4 5 Speed Manual: Cannot shift into gear regularly/periodically when engine is on. Shifting when engine is off is easy, with rare binding or getting stuck but generally easy. While engine is on, shifting up to other gears and back to first sometimes allows it to get into gear, but sometimes all fears are locked up and engine needs to be turned of and then shifted into first before restarting the engine and driving. Clutch has engagement, the rear has been jacked up and shifted into first and there was no lag when clutch is released from the floor, no suspected air in the system, but the fluid may be old. When car has been driven for a while or is warm, little to no shifting issues. What could the possible issues be and what are the solutions? New ATF mercon 5 was drained and refilled ~6k miles ago

 

[franklin2]

The transmission locks up sometimes after shifting? If that is the case, that tells me someone has been into the transmission, and did not re-install the shifter interlock pins and springs.

What I am familiar with is the earlier 5 speeds around 1984-86. I bought my BII cheap because the 5 speed was bad and pulled out. I investigated what happened, several of the teeth were sheared off on the front two gears. After further investigation I found the shifter interlock springs and pins where not installed. This allows the transmission to be in 2 gears at once, and that locks it up. Must have happened at speed on this trans and sheared the teeth off.

What trans do you have?