Gearbox Shift Quality - R32 Gtr

[Scooby]

Guys;

I've had my gearbox rebuilt (was catching on 1-2 too often) with new synchros and bearings and I'm running Motul oil. Problem is that it still sometimes catches 1-2 and 2-3, doesn't matter whether it's cold, hot, hi rpm or low rpm. Only way to guarantee it won't catch is to pause briefly during the shift but that means losing pace. 3-4, 4-3, 3-2 are no problem.

Tried different oil and Slick 50 but no change. I know that heavy duty (compared to most other cars) gearboxes like the GTR tend to be a bit clunky due to the sheer size etc of the internals and I don't expect it to be ever be as smooth as a Camry or WRX ie 'hot knife through butter, but I'm not happy about this happening in mine so soon after a rebuld. It doesn't get thrashed and I expected that the shift might be heavy but still smooth with no catching - ever. Rebuild was done by Award in Sydney.

Is this just the way they are or should a rebuilt box be like silk? Thanks for any feedback.

Regards

[djr81]

A couple of things come to mind.

Firstly, make sure the clutch is not dragging.

Secondly, the viscosity of the oil in your box will make a big difference to the shift quality & to the synchro's. First stop is to make sure you have the right grade.

The second step is to use the ubiquitous Redline oil. This often helps old/tired boxes, but I'm not sure about new ones.

Beyond that it may require the gearbox out again.

[someonestolecc]

Just out of interest in regards to viscosity.. too viscous means you tend to drag stuff right? and if it's too thin what happens then?

I've been running redline shockproof heavy in my box and now it's seized in 3rd so I'm wondering if that may have done it?

[slow13dude]

Just out of interest in regards to viscosity.. too viscous means you tend to drag stuff right? and if it's too thin what happens then?

I've been running redline shockproof heavy in my box and now it's seized in 3rd so I'm wondering if that may have done it?

Too thin means Crunch!

[Sydneykid]

Guys;

I've had my gearbox rebuilt (was catching on 1-2 too often) with new synchros and bearings and I'm running Motul oil. Problem is that it still sometimes catches 1-2 and 2-3, doesn't matter whether it's cold, hot, hi rpm or low rpm. Only way to guarantee it won't catch is to pause briefly during the shift but that means losing pace. 3-4, 4-3, 3-2 are no problem.  

Tried different oil and Slick 50 but no change. I know that heavy duty (compared to most other cars) gearboxes like the GTR tend to be a bit clunky due to the sheer size etc of the internals and I don't expect it to be ever be as smooth as a Camry or WRX ie 'hot knife through butter, but I'm not happy about this happening in mine so soon after a rebuld. It doesn't get thrashed and I expected  that the shift might be heavy but still smooth with no catching - ever. Rebuild was done by Award in Sydney.

Is this just the way they are or should a rebuilt box be like silk? Thanks for any feedback.

Regards

Mmmmmm, gearboxes do take time to run in and you haven't mentioned how many K's it done since the gearbox was rebuilt. Personally i don't find GTR gearboxes to be overly heavy or slow to shift. We use exclusively Castrol synthetic lubricants (Syntrax 75W90 in the gearbox) so I have no experience with other oils.

If it were me, I would have a talk to Award and see what they have to say:cheers:

[Scooby]

Thanks SK;

It's probably done about 6000km since the rebuild. I'll talk to them, have already spoken to the shop that took it out and they were full of words like 'size of internal parts, mass, old technology' etc but they didn't give me a definitive answer.

In particular I don't see why it would do it sometimes and not others.

Regards