3 - 4 crunch!

[VAI]

I was wondering if anybody else had this problem and how to solve it.
When I shift from 3rd to 4th at WOT above 6K RPM Its hard to go into 4th gear and results in a crunch/grinding. Even If I shift slowly!!.
- It doesnt do it under 6K.
- It doesnt do it in any other gear.
Are we talking syncros???
RM:csmile:

 

[garllo]

I would try a shifter alignment first. Follow this link for directions http://rpmtransmissions.com/files/c5shiftlinkageadjustment.pdf
(RPM transmissions' website) if not, there is a possibility that the 3-4 shifter fork is worn-not uncommon. Again check out RPM'S site. they do a pretty resonable rebuild but I would try the alignment first. I had a nasty grind going from 4-5th if I didn't shift carefully and if you're "into" it who's paying attention? The realignment cured it.
Good Luck!