Getrag difficult 3rd to 4th shift ?

[Merc4me2000]

Hi all ,
Has anyone here had experience with a Gettag that won't select 4th from 3rd ?
The Synchro is fine and all other Gears shift perfectly .. the shifter just locks out when trying to select 4th everytime .. if you release the pressure on the stick and then try pulling 4th again , it drops in perfectly ??
Must be wear in shiftrail or detent issue but I have never had a getrag apart before to really know what it can be .
Hoping there is a Trans Guru out there that can offer some advice ..
Thanks in advance for any help ...
Dave

 

[Immortality]

Tried new fluid first?

Stock shifter sits in a nylon cup in the shifter linkage if I'm not mistaken, might pay to check this first. Stock shifters are fairly sloppy at the best of times...