Is my syncro-mash taking leave?

[R33]

Guys, it's not same anymore. Before, cruise at 140kph, saw a Supra/or anything else approaching fast, step on the clutch, downshift to 3rd, declutch, step on the loud pedal and voooooosh!
Now, cruise at 130kph, see a Supra/or anything else approaching fast, step on the clutch, downshift...err...try harder...shytte...it won't downshift...grrrr....Supra flashes headlight...hv to go to the left and Supra goes voooooosh!((
Why is it that I am finding it difficult to downshift (upshifting is not a problem though!). I have found a cure now...I have to step on the clutch and blip the throttle and then only I could downshift...without the blipping of the throttle, I cannot downshift while cruising at more than 80kph (anything below 80kph, I can downshift even without blipping the throttle).
I think my syncro is taking leave. Am I correct?

[Moppie]

Yes.

My Civic did exactly the same thing with 3rd, and sure enough the teeth on the gear and the ring where worn away.
Triumph did similar things before I had the g/box rebuild as well.


Time for a new g/box!

[RazorGTR]

If it didn't grind or graunch then I would say you hit the gate. I've done that at the drags missing third gear 5 times! thought the same thing but it was my shift lever position.

[R33]

Nope. I didn't do anything...it's like...dead! No grinding, no crunching...nada! Blip the throttle and it will downshift. If I hit the gate, what does it mean? My box is gone and needs changing?
To change is not a problem. A good condition 2nd hand R33 box (without the diff) is just about 200USD over here!
If I need to change, do you know of any place in the OZ or NZ or Japan where I could buy a box with strenghtened gears or close ratio gears?
Thanks.

[Moppie]

Synchro wear is a funny thing, it can manifest itself in a variety of forms, grinding gears is just one of them, and occurs when there is wear on the face of the cone that acclerates the gear, as it wears it is unable to acclerate the gear to exactly match gear speeds and you get a grinding crunch as the syncrho teeth come into contact.

But if the teeth themselves wear, or the selector wears, then will get the exact symbtoms described.
The selector ring either won't line up the synchro teeth correctly, and it simply won't go into gear, or the teeth themselves won't line up and it simply won't go into gear.
This can often cause a grind in one direction, and a difficult shit in the other, or start as a difficult shit, and become a grind as the teeth are forced together inccorectly.


Doe it still do it at low speeds? and is it a constant thing? or just when your hammering it?

I have no idea how the Skyline gear shift is set up, but similar problems occur in FWD cars when shift linkages suffer worn bushs etc, and I know some of the old RWD Ford G/boxs suffer wear in the shift mechanism in the g/box and do similar things.



As for missing the gate, well unless you have a ferrari style "gate" mounted around the gear stick, then the gate is just a term used to describe the total shift mechanism, its a some what meaningless term however you get into the spefics of what has failed, and is better used to metaphiricaly desribe the action of changing gears.

[RazorGTR]

When you say it is dead you mean no movement from the car at all? If that is what you are saying sounds like you've sheared the teeth off the constant mesh gear #4 or snapped the input shaft.

Mopie yes it has the ferrari style gate so to speak but instead of being at the top it is just above the trans.

[Moppie]

Originally Posted by RazorGTR

Mopie yes it has the ferrari style gate so to speak but instead of being at the top it is just above the trans.

Got a pic?



Just re-read your post to R33,

Why is it that I am finding it difficult to downshift (upshifting is not a problem though!). I have found a cure now...I have to step on the clutch and blip the throttle and then only I could downshift...without the blipping of the throttle, I cannot downshift while cruising at more than 80kph (anything below 80kph, I can downshift even without blipping the throttle).

Sounds to me like a failed synchro ring, at high speeds it is unable to do its job, but by bliping the throttle your giving it just enough help to get things lined up.

I would forget about racing supras for a little while, otherwise you will do more damage. At the moment you should be able to get away with replacing just the synchro, but if you keep driving it hard you could easily damage the rest of the gear as well.

[R33]

Ok...here comes the Hollinger!

Seriously, I think it needs replacing. It will happen even without hard driving. Anything above 80kph, I would have to blip the throttle to downshift. Otherwise, I can't downshift.

As for Supra chasing, well I don't do that coz most of the time they will chase me....

Well, while I change my g/box, is there any place in the Oz or NZ which can strenghten my current box and change the ratio etc?

[Moppie]

Originally Posted by R33

Well, while I change my g/box, is there any place in the Oz or NZ which can strenghten my current box and change the ratio etc?

g/boxs are funny things, you can't really strengthen them as such.
You can replace things like the gear sets with parts made from harder material, but how much hp one can stand is often dictated by the strength of the casing and shafts, all of which can't really be reinforced.

Also the problem you are having is not from a weak g/box, its simply normal wear and tear, and 3rd gear being the most often used, its usualy the first to go.
My guess is your extensive time at the track, by the sound of it hard time street driving combined with prehaps a slightly lower quality than normal (and were talking unmesuable differnces) synchro have ment its worn a little prematurly.



If you are serious about the holinger then either do nothing, or simply replace the 3rd gear synchro (assumings it all thats wrong, but sadly, as I have found out in the past the only way to tell is to pull the box apart), to keep the car drivealbe untill you can arrange for the holinger.

If you not so serious about it then I recomend a full g/box recondidtion, bearings and synchros all round to being it back to as new condition, and what should be another 100,000kms of pleasure.

[R33]

Thanks very much Moppie for the insight. I agree with you. It is actually normal wear and tear. That g/box has had to endure 26 mths of 600+ hp and about 250-280 laps around the track plus 10-12 times sprint launches at anything between 5500-7500 rpm! And of course, everyday drive plus the occasional over exuberance on the highway! So, I think it is about time for the inevitable!

I am semi serious about the Hollinger, finance permitting of course. But does anyone here know how long the Hollinger will last before I need to service or replace any parts in it? I heard it is around 10k km. Correct?

In the meantime, I will slot in the second hand g/box into the car. I got it just for USD200!

Moppie, how much do u think a full re-cond would cost?

Thanks.

[Moppie]

A hell of a lot more $200!!!!


Damn, thats bloody cheap, I was quoted that much for a used Box from an 89 Sentra for a friends car, and most late model g/box here in NZ are about the $4-800 for the average car, something like a skyline GTR box would be several thousand.



A rebuild could cost you maybe US$1,000? Thats a very rough estimate based on what the average high peformance 6cyl g/box rebuild would cost, with an allowance for the rarity of the GTR. It makes some parts like synhros very expensive, you might pay as much as US$200 just for one hub (and you will need 3, plus bearings which can be that much again, and you need at least 4). Plus a days labour from a specialist.


The Holingers life span will be dictated by how race or street orintated it is. From my own limited experiance 10,000ks sounds about right for a mild race box, but I have seen things like Quiafe straight cut gear sets last much less.
Regular maintiance is of course much more important, make sure you use the right oil etc.

But the best advice can only come from someone with one in a car, prehaps Vince knows someone?

[R33]

Yup, that's dirt cheap. Actually i have got a friend who dabbles in half cut engines. He owns a GTR (with monstrous T88 - he's a dragster - you can see him in last weekend drag final at http://terato.com/cars/event/sepangd...03/default.asp ) and he has a couple of half cut RB26 lying around. That explaines why it's so cheap. The market price for second hand GTR g/box around here is around USD800.

The lifespan of the Hollinger is one of the reason why I have not really saved up for it! Considering the GTR is my daily driver, I surely would not want to open up the Hollinger every 10k km or so regardless of the performance advantage it affords me. I would appreciate it if anyone from here could enlighten me on this.

Sky/Razor?

[Moppie]

With the HP levels your running it dosnt really sound like you need it either, your current problems certianly don't sound like they are related to any weakness with the stock box.

If you were however going to use the car in an enduro then I guess the hollinger might be worth the extra expense, but then being non-stock it also might be another potential weak point.

Is there any differnce in the ratios to give you enough of a performance gain to make it worth while having? or is the only advantage its extra strength?

[SkylineUSA]

R33,

Moppie has covered all the bases. He is looking at the same way I would.

[R33]

Thanks guys. You, I absolutely agree with you all.

Yesterday, I had a conversation with a guy who replaced his 1st 2nd and 3rd gears with OS Giken's part. He chosed a shorter ratio for the 1st three gears and he said it's good...costs him about USD2250 after sourcing the aprts through Thailand. Sounds interesting to me, especially on the shorter ratio...OS Giken apparently offers some ratio for you to choose from. Price is also reasonable compared to Hollinger or HKS or Quaife. The only thing is that the gears will stay at 5!
There's also a 5 gear set from OS Giken...apparently another guy is using it...costs about USD3000. Shorter 5th gear...his rpm would be 3400 at 110kph as compared to stock gear which is at 2900rpm for 110kph.
Perhaps I would do that.