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Gearbox Syncros Or Clutch?

Ant97GTR
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Ant97GTR Grand Master

Ant97GTR

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Posted

Hey All,

Recently during the SAU vic DECA day last year and yesterday while taking the car for a 'shakedown' run, I have had the situation where I have been stationary, engaged the clutch (well the clutch pedal was all the way to the floor) and gone to put it in 1st and it has crunched (same sound as if the clutch wasn't engaged). Each time it has engaged 1st gear and everything seems fine after that. I should note that this only happens rarely...probably 1 in every 50-70 times I have gone for 1st gear if that...and I don't have this problem in any other gear. Also the clutch is not slipping and can still hold up on a heard launch.

I have had my car for about 5 years (95' Gtst), 3 of which has been in a modified state and over the past couple of years have taken it to track days. As such I am aware that some syncros are wearing heavily, particularly 2-3rd. I should also note that I change the gearbox oil fairly reg. with top quality fluids.

My question is whether this is a sign that the syncros in the 'box are severly worn or that my clutch is on the way out.....

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wrxhoon Grand Master

wrxhoon

Posted
Posted
Hey All,

Recently during the SAU vic DECA day last year and yesterday while taking the car for a 'shakedown' run, I have had the situation where I have been stationary, engaged the clutch (well the clutch pedal was all the way to the floor) and gone to put it in 1st and it has crunched (same sound as if the clutch wasn't engaged). Each time it has engaged 1st gear and everything seems fine after that. I should note that this only happens rarely...probably 1 in every 50-70 times I have gone for 1st gear if that...and I don't have this problem in any other gear. Also the clutch is not slipping and can still hold up on a heard launch.

I have had my car for about 5 years (95' Gtst), 3 of which has been in a modified state and over the past couple of years have taken it to track days. As such I am aware that some syncros are wearing heavily, particularly 2-3rd. I should also note that I change the gearbox oil fairly reg. with top quality fluids.

My question is whether this is a sign that the syncros in the 'box are severly worn or that my clutch is on the way out.....

Try engaging reverse while you are stationary if that crunches it means the clutch is not totaly dissengaging , then try to adust the pedal under the dash .

Make sure when you do it that you push the clutch in and wait a few seconds for the input shaft to stop turning .

Topaz Grand Master

Topaz

Posted
Posted

I have a gearchange problem but mine I think is the selectors in the gearbox because I don't get a crunch, its just very hard to push into gear and sometimes won't go in at all. I have to jerk it back forth into 3rd and 4th for a bit to make the shifter 'free up' a bit before engaging 1st or reverse....is this a similar problem to ant's?

Does syncros = selectors?

Ant97GTR Grand Master

Ant97GTR

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Thanks wrxhoon...reverse seems to engage with no dramas and no crunch. Trouble is I can't do it when the gearbox crunches as it has only happened (recently) at a set of lights and like I say it engages the gear it just crunches while doing it.

The input shaft thing might explain it as it is usually a fairly quick hit the pedal and engage gear movement....maybe I'm too impatient :) but it never used to do this in the past.

Topaz.....I think you have a slightly diff problem and def. sounds like your syncros are on their way out. Simply put syncros are gears that accelerate or decelerate parts of the gearbox to match the speed of the turning bits with the next gear. So if you are struggling to get it from one gear to the next that is probably your problem. You can tell when syncros are worn between gears when you change gears the movement feels very cluncky rather than being a smooth action.

wrxhoon Grand Master

wrxhoon

Posted
Posted
Thanks wrxhoon...reverse seems to engage with no dramas and no crunch. Trouble is I can't do it when the gearbox crunches as it has only happened (recently) at a set of lights and like I say it engages the gear it just crunches while doing it.

The input shaft thing might explain it as it is usually a fairly quick hit the pedal and engage gear movement....maybe I'm too impatient :) but it never used to do this in the past.

Topaz.....I think you have a slightly diff problem and def. sounds like your syncros are on their way out. Simply put syncros are gears that accelerate or decelerate parts of the gearbox to match the speed of the turning bits with the next gear. So if you are struggling to get it from one gear to the next that is probably your problem. You can tell when syncros are worn between gears when you change gears the movement feels very cluncky rather than being a smooth action.

If you no problem selecting reverse and it doesnt crunch then your clutch is doing its job , totaly disengaging .

The fact that you crunch when you are trying to get it in to first gear when you are quick is a synchro problem . Yo will find that it will be crunching even when you are moving unless you match the revs , you probably do by toe and heel . When the synchros are worn out and you dont match revs you will get a cruching sound all the time on especialy on high rpm changes and when the box is hot .

On normal say 3-4000 rpm upchanges you wont notice any crunching unless the syncro is totaly stuffed .

Synthetic oils dont do the synchros any favours either , mineral oils work better ..

Ant97GTR Grand Master

Ant97GTR

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I kind of thought it would by syncros but wasn't too sure. In regard to the box being hot, the only 2 times it has happened has been on days pushing 30+ degrees after a lot of driving. I must say though that even when it was this hot and doing high rpm changes (1-2nd around 7k, 2-3rd around 6k etc etc) it doesn't crunch...sometimes I heel-toe but not always. Like I say it has only happened going into 1st from neutral when stationary.

Also the fluids used has mainly been redline shockproof which came very well recommended and up till recently has done the job very well.

It sounds as though it might be a combination of a worn syncro and not waiting long enough for the input shaft to stop moving....

wrxhoon Grand Master

wrxhoon

Posted
Posted
I kind of thought it would by syncros but wasn't too sure. In regard to the box being hot, the only 2 times it has happened has been on days pushing 30+ degrees after a lot of driving. I must say though that even when it was this hot and doing high rpm changes (1-2nd around 7k, 2-3rd around 6k etc etc) it doesn't crunch...sometimes I heel-toe but not always. Like I say it has only happened going into 1st from neutral when stationary.

Also the fluids used has mainly been redline shockproof which came very well recommended and up till recently has done the job very well.

It sounds as though it might be a combination of a worn syncro and not waiting long enough for the input shaft to stop moving....

If the synchros are working as they are designed to work then it doesnt matter if you wait or not for any forward gear as they all have synchros, only reverse doesn't.

The fact that you are not crunching in other gears i good , it means the synchros are working .

Each to their own on the oils but i like to use mineral oil in synchro boxes, i have found that synthetic oils slow the sychros, but thats just me. Everyone seems to be happy using them , like i said each to their own ....

Topaz Grand Master

Topaz

Posted
Posted
Topaz.....I think you have a slightly diff problem and def. sounds like your syncros are on their way out. Simply put syncros are gears that accelerate or decelerate parts of the gearbox to match the speed of the turning bits with the next gear. So if you are struggling to get it from one gear to the next that is probably your problem. You can tell when syncros are worn between gears when you change gears the movement feels very cluncky rather than being a smooth action.

crap, it does sound like my synchros then :D. Its fine when I'm moving and the been driving for a while, but only when I am stopped at lights or just starting the car in the morning. But I only get crunches into 1st and changing from first to 2nd sometimes...

ok, how much is a new GTR gearbox? :)

Ant97GTR Grand Master

Ant97GTR

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I guess I'll run it till something breaks.....then I'll definiately know what it is :D Considering it is only selecting 1st, if that goes I have the other gears to get me home :)

Topaz....I'd forget about getting a new box and get your one rebuilt by a pro....a lot cheaper and I'd hate to think of the cost of a new 32 box!! A mate got a new 33 r box from nissan...cost him around 5k and the thing had heaps of problems.

T04GTR Grand Master

T04GTR

Posted
Posted
I guess I'll run it till something breaks.....then I'll definiately know what it is :D Considering it is only selecting 1st, if that goes I have the other gears to get me home :)

Topaz....I'd forget about getting a new box and get your one rebuilt by a pro....a lot cheaper and I'd hate to think of the cost of a new 32 box!! A mate got a new 33 r box from nissan...cost him around 5k and the thing had heaps of problems.

hmm iff you reif it in quickly it will crunch as the gears are still spinning in the box for a short time :P .

i dought yuove got a colapsed or broken clutch diaphram spring. can have the same efect

2rismo Grand Master

2rismo

Posted
Posted
Also the fluids used has mainly been redline shockproof which came very well recommended and up till recently has done the job very well.

I think you'll find it's STILL doing the job well. Look elsewhere. Good luck.

Adrian

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