4 Th Gear Crunching

[JKR34S]

Hi guys I have a gearbox problem

As the topic states everytime I change from 3rd to 4th it crunches unless I really take my time shifting is there anything I can do to fix this oil change perhaps or is it just stuffed and time for a rebuild? Any help or thoughts would be much appreciated

[Moodles2]

Has the gearbox had an oil change anytime in your ownership? I used to get a similar crunch changing from 2nd to 3rd at the track which was solved with redline shockproof lightweight (the oil which came out was completely black)

[JKR34S]

Yea I have about 10 000 ago I'm thinking may be wrong viscosity what viscosity did you use?

[10 4]

Just get lightweight shockproof, will "fix" the crunch but long term will be rebuild unless the oil in there is simply incorrect.

[GTR_JOEY]

dunno about 34 GTT but the reason alot of GTR 5 speed boxes crunch when tryin to select 4th is becasue there isnt sufficent grooving within the syncro ring to allow oil to pass through it when sliding over the cone

when u shift quickly itll crunch cause the syncro cant match the speed of the engine to road speed quickly enough, though if u shift slowly the oil has enough time to move the oil from the insufficent grooves within the syncro ring and it works fine

it doesnt necessarily mean ur syncros are worn out, but they can be modified with new grooves to work sweetly again

thats what i can recall from the explanation that i recieved from someone whos done a lot of skyline boxes