Gearbox self destructed for Christmas - thanks Santa. Sound like circlip failure?

[_Wing_]

I didn't check the circlipped-box that blew. One thing is for certain, I'd rather be rebuilding gearboxes than rotarys! But I do have a soft spot for FD's :smitten:

Let me know how your gearbox woes go, I'm always interested in this stuff

 

[I-nearly-bought-a-batty]

Well I finally got my car back with the gearbox intact and my wallet $3.5K lighter. Rebuilt back to stock specs. Fortunately my clutch still had more than half it's life left so I was able to retain the stock clutch and flywheel. This should ensure I get another 73,000kms from the gearbox - or maybe more! Now I can sit back and think of what kinds of modifications I could have made for $3.5K!! GTRS upgrade.....

 

[mitto]

I first used a z32 gearbox + a mazworx copy kit + a OS GIKEN twin, then went to rb25 gearbox + a pt kit + a FULL CARBON twin, now back to z32 gearbox + alpha omega kit + FULL CARBON single. Other than the gearboxes, all parts were brand new... which is scary because I reckon the money I spent on these lessons is enough to buy me another s15 :annoyed:

One thing that will destroy boxes is a twin plate clutch, but to be blowing Z32s like that you must have outrageous amounts of power and drive like a hooligan. I'd check you diff backlash and drive shaft CV joints for play, because i'd assume that you are getting transmission shock issues. I avoid running anything other than nismo super coppermix clutches tbh, at least never an un-sprung clutch. Gear oil might also be an issue, running a "race" oil will do nothing for a nissan box... redline heavy shockproof all day!

 

[Benne]

Helical cut gears by design are always forcing each other apart which loads and unloads the circlip until it fails.

So no more circlip failures if I use a straight cut gearset like the PAR?


Then it makes sense what Nismo says about their box:

"By changing the gear ratio and increasing gear diameter, strength has been improved. Where the gear ratio has not been changed, changing the module by reducing the number of both counter and main gear teeth and increasing the size of individual gear teeth also increases gear strength. By reducing the torsion angle, the thrust power shock to the front of the counter-shaft caused by the input of shock torque is reduced, helping to reduce potential damage to the end face of the counter-reverse gear."

They decreased the tooth angle from 32 to 24° (3rd gear) and 33 to 26° (4th): http://www.nismo.co.jp/en/products/competition/mission/silvia.html

 

[_Wing_]

Pretty much but then the problem is moved on to the next weakest link - the gearset itself, and there have been numerous reports about PAR gearsets breaking.

Nismo actually do know what they're doing and they do it properly. They don't cut corners. You don't get that much in this day and age when price is what most people care about and will do anything to save even $5, which I think is a real shame. And what you've highlighted isn't marketing fluff it's engineering in everyday words.

The reduced tooth angle also increases noise, not by much but something to keep in mind. Nismo recommends their coppermix clutch kit with their gearbox for a reason and it's not just to make another sale. The issue now is, 10 years later, we're all demanding and pushing much more power than the nismo gearset was designed to cope with and we're also doing much crazier things with it - like 3rd and 4th gear clutch kicks with aggressive clutches on wide sticky tyres.

 

[_Wing_]

One thing that will destroy boxes is a twin plate clutch, but to be blowing Z32s like that you must have outrageous amounts of power and drive like a hooligan. I'd check you diff backlash and drive shaft CV joints for play, because i'd assume that you are getting transmission shock issues. I avoid running anything other than nismo super coppermix clutches tbh, at least never an un-sprung clutch. Gear oil might also be an issue, running a "race" oil will do nothing for a nissan box... redline heavy shockproof all day!

I never got to the point of breaking those boxes, it was an issue with the (lack of) proper engineering and endless endless endless endless endless endless amounts of problems. I wish I started working here earlier so I wouldn't have wasted all this money and headaches of trying to fix stuff. Do it once, do it right! I have to test out a nismo supercoppermix for work by which time I think I will have used half a dozen or so clutch kits / gearboxes / gearbox conversions in the s15 lol

PS - the coppermix clutch is actually an unsprung solid centre and solid flywheel. The ingenious part is nismo used a mercel spring to make it nice and drivable, at the expense of a bit of bite and responsiveness. It's really all a bit of give and take, I rate it high... but I think I'll rate my carbon clutches higher

 

[_Wing_]

Well I finally got my car back with the gearbox intact and my wallet $3.5K lighter. Rebuilt back to stock specs. Fortunately my clutch still had more than half it's life left so I was able to retain the stock clutch and flywheel. This should ensure I get another 73,000kms from the gearbox - or maybe more! Now I can sit back and think of what kinds of modifications I could have made for $3.5K!! GTRS upgrade.....

Wowsers!!!!!! In Australia you can walk into a NISSAN stealership and buy a brand new one for that sort of money! Better yet, you could have bolted in a good quality z32 gearbox conversion kit for that! Oh well, the main thing is that it's back on the road where a car belongs

 

[I-nearly-bought-a-batty]

Wowsers!!!!!! In Australia you can walk into a NISSAN stealership and buy a brand new one for that sort of money! Better yet, you could have bolted in a good quality z32 gearbox conversion kit for that! Oh well, the main thing is that it's back on the road where a car belongs

Yeah tell me about it mate; if only I had driven to the garage rather than get the tow - the bill would only have been around $1200 - $1500 max; instead the tilt truck caused the shaft to slip on unloading and ended up lunching my counter shaft. The price you pay for a 6 speed eh?!

Do you think there is any merit in changing out the oil after 2000 - 3000k's? I reckon the new counter shaft mating against the old gears may cause metallic flecks in the oil (as they bed in).

 

[ichi-go]

Hills motorsport in NSW sells the full Z33 gearbox conversion kit and everything to bolt on to s15 for.... AUD8k not delivered. They supply brand new Z33 box with that price as well... I've a mate who's looking into it but it's alot of money!

 

[_Wing_]

Yeah tell me about it mate; if only I had driven to the garage rather than get the tow - the bill would only have been around $1200 - $1500 max; instead the tilt truck caused the shaft to slip on unloading and ended up lunching my counter shaft. The price you pay for a 6 speed eh?!

Do you think there is any merit in changing out the oil after 2000 - 3000k's? I reckon the new counter shaft mating against the old gears may cause metallic flecks in the oil (as they bed in).

I would recommend to change it out after a few hundred KMs. Use an average oil so that it acts as a flush, drop it and then put in the good stuff. That's what I do for all of my work.

 

[Fruitbooter]

So whats the best solution to having a nice 'working' 'reliable' gearbox in an S15 guys?

I have the standard 6 speed with no major bhp upgrades atm and havent used it for drifting yet.

But when i want to start messing with power and having a play now and again whats the best setup?

Nismo super coppermix + Redline shockproof?

 

[I-nearly-bought-a-batty]

I would recommend to change it out after a few hundred KMs. Use an average oil so that it acts as a flush, drop it and then put in the good stuff. That's what I do for all of my work.

Thanks mate - we're thinking along the same lines. A few hundred you reckon? I thought maybe 2000k to give it enough time to shed all the metal? I've already put in the Amsoil ($$$!) and bought more for post flush; but I'm thinking of running another flush cycle too. Maybe 1 at 1000k and again at 2000k. I have to preserve my 3.5K investment haha! Apparently a new Nissan box ex Japan is 15K so a local dealer told me. Given my parts bill - I believe it!

 

[I-nearly-bought-a-batty]

So whats the best solution to having a nice 'working' 'reliable' gearbox in an S15 guys?

I have the standard 6 speed with no major bhp upgrades atm and havent used it for drifting yet.

But when i want to start messing with power and having a play now and again whats the best setup?

Nismo super coppermix + Redline shockproof?

It's a lucky dip I'm afraid. The more power / abuse you give the box - the less lucky you become. The best set up is the stock standard car; anything you do from there will only compromise reliability. Sad but true.

 

[Fruitbooter]

Well whats the best way to prolong its life?

No clutch kicks

 

[I-nearly-bought-a-batty]

Well whats the best way to prolong its life?

No clutch kicks

Well I bought my car with less than 40,000km's (genuine k's / NZ new) and have never clutch kicked it. I don't dump the clutch and run a stock driveline; power is 210rwkw. I never apply full power until my engine oil temp gauge reads normal operating temp; and treat my gearbox with respect. I also use quality synthetic oils in my driveline. I also know how to shift gears properly without missing shifts and graunching gears. However at 73,000ks it shat itself whilst I changed from 4th to 5th. So it boils down to a matter of "when" rather than "if". RX7 owners bank on replacing engines; and we bank on replacing gearboxes. I've just paid my dues so I get to play for another 70,000k's. It's definitely not cheap retaining the 6spd; but I prefer to keep the car original in that sense.

 

[_Wing_]

Take it out and put in on your garage floor - my 6 speed gearbox is still going strong there

 

[_Wing_]

Thanks mate - we're thinking along the same lines. A few hundred you reckon? I thought maybe 2000k to give it enough time to shed all the metal? I've already put in the Amsoil ($$$!) and bought more for post flush; but I'm thinking of running another flush cycle too. Maybe 1 at 1000k and again at 2000k. I have to preserve my 3.5K investment haha! Apparently a new Nissan box ex Japan is 15K so a local dealer told me. Given my parts bill - I believe it!

You don't want it in there for 2000km's for the first change as the oil is contaminated and carrying bits of metal from 1km, so those bits will be doing damage for 2000m's. A few hundred, like 500km's, or 1-2 weeks driving for me, will be plenty to wash off the assembly lube, dust, dirt and crap when the box was opened, and of course for all the new bits of metal to get to know each other.
After that dump it and re-fill. If I wanted to go one step further I'd change it out for a second time after another 1000km's. There is the magnet in there and that'll give you an idea how things are going. I recently wasted $150 worth of oil... put it this way, it's better then wasting $3,500.

 

[craig8585]

I know this is a bit different, but when we change a gearbox on our helicopters at work, we do 3x drain and refill's with a ground run inbetween before it even leaves the deck to remove the inhibiting oil and any build debris.. That's a lot of oil when a gearbox holds 24ltrs too

 

[I-nearly-bought-a-batty]

You don't want it in there for 2000km's for the first change as the oil is contaminated and carrying bits of metal from 1km, so those bits will be doing damage for 2000m's. A few hundred, like 500km's, or 1-2 weeks driving for me, will be plenty to wash off the assembly lube, dust, dirt and crap when the box was opened, and of course for all the new bits of metal to get to know each other.
After that dump it and re-fill. If I wanted to go one step further I'd change it out for a second time after another 1000km's. There is the magnet in there and that'll give you an idea how things are going. I recently wasted $150 worth of oil... put it this way, it's better then wasting $3,500.

Thanks Wing - I'll go with your shorter term plan . You're right though, I'd rather dump the oil than the gearbox!! Still, my gearbox oil bill is currently sitting at $400 for less than 2000k's of driving!

 

[kingtal0n]

I just read all of this and wow. Do you think using a Sprung Disc, like a cheap exedy S14 sprung disc, will help preserve the life of the OEM 6-speed?