Sorry to highjack a thread but im going through the same problem. I have a 2wd sapphire at stage 1 to and my 4th gear i have to go to engage it twice for it to select the gear then with 3rd i can go up the gears like from 2nd to 3rd but cant come down gears like 4th to 3rd or 5th to 3rd.

2 of my mates have got 2wd cosworths and they have a spare T5 between them that 4th gear cant be engaged atall.
We have had a 5th gear puller made to remove 5th gear and stripped this spare box down to find the 3 slipper pads inside the 3rd/4th synchro hub to be worn and the C clips that hold these in were snapped. We have replaced these and rebuild the box. I put this spare box now in my car on sat and i can now select 4th but it sometimes struggles to engage 4th when coming down the gears.

So at the moment its driveable but a newsence to be honnest. So as we have the 5th gear puller i thought id ask people on here their opinions as to whats wrong with my origonal box and also what parts are required.

Also where's the best place to buy good parts for the T5 gearbox. I dont want to put cheap aftermarket parts in my box and them not be up to the job of fixing it.

Thanks Dale