Going to neautral from drive

[94_C/1500]

I have a '94 C1500 with a V6 and 4L60E. When I drive over rough sections offroad going fast it jumps out of drive and into neutral. This week I ported the throttle body and added 4 degrees of timing and now it comes out of drive when I stall the converter. This is very annoying. The truck has around 208,000 miles. Any ideas why it does this? Any help is very appreciated.

 

[blacked94blazer]

check the bushing on the frame that the shift linkage goes into when it wears and the engine torques to one side the shift linkage will move and make the trans shift itself

 

[91Bluestreak]

yep check the linkage for tigtness. My s15 jimmy does this when I go over big bumps or railroad tracks at speed.

 

[rhino]

Look at the engine mounts.... Take and pop the hood, brake torque the truck and see if the engine pops up.