Jump to content
SAU Community

Gearbox Syncros Or Clutch?

Ant97GTR
 Share

Recommended Posts

Ant97GTR Grand Master

Ant97GTR

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.....

Link to comment
https://www.sau.com.au/forums/topic/107095-gearbox-syncros-or-clutch/
Share on other sites
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

Posted
  • Author
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.

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

Posted
  • Author
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....

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

Posted
  • Author
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.

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

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • GTSBoy
      After market rear camber arm adjustment

      By GTSBoy · Posted

      Wheel alignment immediately. Not "when I get around to it". And further to what Duncan said - you cannot just put camber arms on and shorten them. You will introduce bump steer far in excess of what the car had with stock arms. You need adjustable tension arms and they need to be shortened also. The simplest approach is to shorten them the same % as the stock ones. This will not be correct or optimal, but it will be better than any other guess. The correct way to set the lengths of both arms is to use a properly built/set up bump steer gauge and trial and error the adjustments until you hit the camber you need and want and have minimum bump steer in the range of motion that the wheel is expected to travel. And what Duncan said about toe is also very true. And you cannot change the camber arm without also affecting toe. So when you have adjustable arms on the back of a Skyline, the car either needs to go to a talented wheel aligner (not your local tyre shop dropout), or you need to be able to do this stuff yourself at home. Guess which approach I have taken? I have built my own gear for camber, toe and bump steer measurement and I do all this on the flattest bit of concrete I have, with some shims under the tyres on one side to level the car.
    • Jarsky
      R33 Fuel Pump & Brakes after alarm swap

      By Jarsky · Posted

      Thought I would get some advice from others on this situation.    Relevant info: R33 GTS25t Link G4x ECU Walbro 255LPH w/ OEM FP Relay (No relay mod) Scenario: I accidentally messed up my old AVS S5 (rev.1) at the start of the year and the cars been immobilised. Also the siren BBU has completely failed; so I decided to upgrade it.  I got a newer AVS S5 (rev.2?) installed on Friday. The guy removed the old one and its immobilisers. Tried to start it; the car cranks but doesnt start.  The new one was installed and all the alarm functions seem to be working as they should; still wouldn't start Went to bed; got up on Friday morning and decided to have a look into the no start problem. Found the car completely dead.  Charged the battery; plugged it back in and found the brake lights were stuck on.  Unplugging the brake pedal switch the lights turn off. Plug it back in and theyre stuck on again. I tested the switch (continuity test and resistance); all looks good (0-1kohm).  On talking to AVS; found its because of the rubber stopper on the brake pedal; sure enough the middle of it is missing so have ordered a new one. One of those wear items; which was confusing what was going on However when I try unplugging the STOP Light fuses (under the dash and under the hood) the brake light still stays on. Should those fuses not cut the brake light circuit?  I then checked the ECU; FP Speed Error.  Testing the pump again; I can hear the relay clicking every time I switch it to ON. I unplugged the pump and put the multimeter across the plug. No continuity; im seeing 0.6V (ECU signal?) and when it switches the relay I think its like 20mA or 200mA). Not seeing 12.4V / 7-9A. As far as I know; the Fuel Pump was wired through one of the immobiliser relays on the old alarm.  He pulled some thick gauged harness out with the old alarm wiring; which looks to me like it was to bridge connections into the immobilisers? Before it got immobilised it was running just fine.  Im at a loss to why the FP is getting no voltage; I thought maybe the FP was faulty (even though I havent even done 50km on the new pump) but no voltage at the harness plug.  Questions: Could it be he didnt reconnect the fuel pump when testing it after the old alarm removal (before installing the new alarm)?  Is this a case of bridging to the brake lights instead of the fuel pump circuit? It's a bit beyond me as I dont do a lot with electrical; so have tried my best to diagnose what I think seems to make sense.  Seeking advice if theres for sure an issue with the alarm install to get him back here; or if I do infact, need an auto electrician to diagnose it. 
    • Duncan
      After market rear camber arm adjustment

      By Duncan · Posted

      Then, shorten them by 1cm, drop the car back down and have a visual look (or even better, use a spirit level across the wheel to see if you have less camber than before. You still want something like 1.5 for road use. Alternatively, if you have adjustable rear ride height (I assume you do if you have extreme camber wear), raise the suspension back to standard height until you can get it all aligned properly. Finally, keep in mind that wear on the inside of the tyre can be for incorrect toe, not just camber
    • V35Newbie
      After market rear camber arm adjustment

      By V35Newbie · Posted

      I know I have to get a wheel alignment but until then I just need to bring the rear tyres in a bit they're wearing to the belt on the inside and brand new on the outside edge. I did shorten the arms a bit but got it wrong now after a few klms the Slip and VDC lights come on. I'd just like to get it to a point where I can drive for another week or two before getting an alignment. I've had to pay a lot of other stuff recently so doing it myself is my only option 
    • Duncan
      After market rear camber arm adjustment

      By Duncan · Posted

      You just need a wheel alignment after, so just set them to the same as current and drive to the shop. As there are 2 upper links it may also be worth adding adjustable upper front links at the same time; these reduce bump steer when you move the camber (note that setting those correctly takes a lot longer as you have to recheck the camber at each length of the toe arm, through a range of movement, so you could just ignore that unless the handling becomes unpredictable)
×
×
  • Create New...