Diagnose this for me.

4wd locks in reverse easily at a stop. When I put 4wd in and move forward it does not lock in and popping noises come from the lock in mechanism like the collar is not moving over the gear. Why would it lock in reverse and work fine, but not when moving forward. The splines on that gear on the shaft are a little roughed up on the end also.

What would you recommend I do?
How many psi should the vaccum pump be pulling the fork?
Why would it work in reverse but not forward?

Thanks ahead for your input!

 

sounds exactly like my truck it's in the trans case i can't tell you exactly what it is but me and my dad figured it out on mine it worked perfect in reverse but when i would go into 4 low it would lock until it started climbing up something unless i just bumped the hill pretty good. or yours could be an issue in ur axle get someone that trust you to look under there at the front drive shaft and see if it spins in drive in 4wd on flat ground and on a hill if it does it's something in your axle if it don't it's in your trans case.. hope this helps