RB25T Box 3rd gear gone

[180 wanabe]

Hi guys

Went drifting yesterday and managed to loose 3rd gear.

Now that sentience alone would normally be a no brainier as to what went wrong only there are a few things about my car that makes this strange.

My car is a S15 with a SR20 making 300 hp @ the wheels, I broke the 6 speed about 18 months ago and decided to just bite the bullet and pay the extra to upgrade to a RB25 box conversion and not have to worry about breaking a box again in the future. 

When I broke the 6 speed I lost gears 3 and 4 + reverse would sometimes want to randomly go forward...

With the current gearbox all of the gears apart from 3rd seem fine. The strange thing is when you move the stick to what should be 3rd gear it seems like there is nothing there at all. There are no noises, crunches or grinding sounds. You can have the clutch fully engaged with the box in neutral and move the shiftier to 3rd and its like there is nothing there/the same feeling as if the clutch was disengaged?

Could this be a broken selector fork? 

I'm a little stumped, I will admit that this happened during an entry into a corner. I had pulled the hand brake to kick the car out and was either in 3rd gear at the time or had just shifted from 2nd to 3rd and did a clutch kick to break traction. 

My thoughts were that the RB25 box was good for 400+hp and that 300 should be a cakewalk for the box to deal with. Since doing the RB25 box upgrade I have only done 1 previous drift session and on the day that I lost 3rd "yesterday" had only been on the track for about an hour. I have been trying to smash my mortgage not more gearboxes which is why the car has seen very little use.

The only other things worth mentioning is that after the conversion there was noticeable vibration in 3rd and 4th gear when coasting/decelerating which the shop that did the conversion blamed on my diff as it was getting tired. I also have alloy slip in diff-subframe mounts/collars which would probably also cause more noise. 

Anyone else had this happen with their box and what was the solution?

 

[niZmO_Man]

Off topic: There was a theory with the RB26 box (basically the same) that oil starvation kills 3rd gear components. The g-forces pushes oil away from the front of the gearbox? I forgot which thread it was in, but the posts are in this forum somewhere.