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Brand New R33 Gts-T Gearbox - Crunch Into 4Th?

boxheadmr
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STATUS Grand Master

STATUS

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is it a conversion? i would look at alignment as 4th is straight through.

Its a long shot but i had a r33 come in for an assessment as it was still crunching 4th and no-one could trace it, the customer had it built twice by the shop that did all the work and it still crunched.

I pulled the box and noticed it had no dowels.... for shits and giggles i fitted a set and bang..It turned out to be simply missing dowels... odd as i hadn't seen it before but was a nice 40min fix.

The Dan Grand Master

The Dan

Posted
Posted

Shit yeah, if it's a conversion that could definitely be your problem. Also those are notorious for overthrow of the clutch due to mismatch master/slave cylinders so you get massive throw on the slave causing the clutch fingers to invert on disengage.

I know you are saying it's only in 4th but sometimes its one gear where you'll press the clutch further than normal.

The other problem is 4th is driven straight down the main shaft so sometimes a slightly bent clutch plate or missing/incorrectly installed spigot will cause more problems in that gear than others and especially at high revs when it's critical for the box so slow down quickly for a smooth shift.

For the fans reading at home, what is the history of the car? Why the new box and what's been done to the car?

boxheadmr Mentor

boxheadmr

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interesting around the clutch, running OS Gekin twin. Yes it is a conversion but have checked the input shaft to std box center and it is spot on.

I would have thought the crunching was the clip that has been mentioned in other threads,

The Dan Grand Master

The Dan

Posted
Posted

interesting around the clutch, running OS Gekin twin. Yes it is a conversion but have checked the input shaft to std box center and it is spot on.

I would have thought the crunching was the clip that has been mentioned in other threads,

The shift clip? Not in a new box. It shouldn't be that

It's not a height issue for the clutch. What I meant was you might be getting too much throw in the fork and it over-engages the clutch and reapplies pressure.

There is also the possibility of the gearbox being stuffed from the get go but you'd need to have it apart to check synchro clearance and the action of the shifter

Birds Grand Master

Birds

Posted
Posted

May not be a fix for your issue, but I don't like running synthetic oils in these boxes, they tend to result in synchro issues. Never a problem from plain old 75w90 mineral, which is what they were designed to run on.

As above, gearbox may well be stuffed from the get go, all it takes is a knock in transit to dislodge parts of the synchro hub assembly and presto, you have a crunching gear.

I usually start with the cheapest fix, which is trying a different oil. Did your new box come with a factory parts warranty?

boxheadmr Mentor

boxheadmr

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not 100% sure the issue would not at least in some way show under minimal or even regular load if it was something to do with the clutch and also in any gear under load.

I am going to drain the castrol fluid i put in it with a filter sock to have a good check for parts in it and replace the oil with redline to see if that makes a difference although i am skeptical about oil making a difference. If it was stuffed from the get go then the problem would have presented itself earlier i would have thought.

I am sure i could go back to nissan but the car is not exactly standard so doubt they would be keen to do it "under warranty".

R31Nismoid Grand Master

R31Nismoid

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Well you wouldn't get Nissan to rebuild it... So unless they did it under warranty you'd be up for another one.

If the oil doesn't show anything up - perhaps go talk to Nissan and explain you've hardly used it and see what they say.

If nothing good comes of the conversation time to get a professional (or two) to inspect it and maybe report back, could well be a transit issue as stated.

Birds Grand Master

Birds

Posted
Posted

not 100% sure the issue would not at least in some way show under minimal or even regular load if it was something to do with the clutch and also in any gear under load.

I am going to drain the castrol fluid i put in it with a filter sock to have a good check for parts in it and replace the oil with redline to see if that makes a difference although i am skeptical about oil making a difference. If it was stuffed from the get go then the problem would have presented itself earlier i would have thought.

I am sure i could go back to nissan but the car is not exactly standard so doubt they would be keen to do it "under warranty".

Why put Redline in to mask up the issue? That's what you do with a half dead box that you want more life out of. These boxes should be able to run fine on mineral 75 or 80w90.

boxheadmr Mentor

boxheadmr

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R31Nismoid

Yeah i think the plan might be to do the change and see how it goes, not going to the track again for a bit as funds a little low so might look to do some private testing if possible to see if the problem presents itself. Next option is to pull it down and inspect further.

Birds

i am not currently running a mineral oil, i am running a synthetic currently and thought whilst i drain the fluid to check for any particles i would change to another oil which is meant to be good for fast shifting with synchros.

krzysztof

If the clutch fork was bent i would imagine that this problem would occur across a number of gears and at different speeds and conditions.

boxheadmr Mentor

boxheadmr

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another thought is that the shifter is a little offset from the normal SR box position and more forward, we customized the shifter to get it into a better position and it could be as simple as me needing to change gears better and when i try to change quickly between 3rd and 4th i am slightly off causing the crunch.

Birds Grand Master

Birds

Posted
Posted

Birds, i thought it would be good to check the oil first and at the same time change it.

So change it for a $30 mineral oil instead of wasting your money lol.

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