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Jez

Gearbox strength

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Does anyone know what sort of torque the standard gearbox starts to get unreliable? We're thinking of rebuilding the engine on our GT86 and turning the boost up - just wondered when the 'box will give up!

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25 minutes ago, Jez said:

Does anyone know what sort of torque the standard gearbox starts to get unreliable? We're thinking of rebuilding the engine on our GT86 and turning the boost up - just wondered when the 'box will give up!

I've had to have the 3rd / 4th synchro replaced on stock power

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Deacon: btw, how much did it cost, what was involved?

Jez: IIRC there are few options to make gearbox part stronger. PAR gearset, Velox gearset and recall reading thread about adapter for one more common american gearbox .. my wild guess is that upto 1.5x times should be somewhat safe. BTW, with more power/torque, maybe other parts need stronger variants too .. eg. clutch, axles and so on ..

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24 minutes ago, Church said:

Deacon: btw, how much did it cost, what was involved?

Jez: IIRC there are few options to make gearbox part stronger. PAR gearset, Velox gearset and recall reading thread about adapter for one more common american gearbox .. my wild guess is that upto 1.5x times should be somewhat safe. BTW, with more power/torque, maybe other parts need stronger variants too .. eg. clutch, axles and so on ..

It was covered under warranty @Church but parts alone were around £900

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Those £900 just synchros or gears aswell or maybe even whole gearbox? (by then i wonder if it wouldn't be worth to put aftermarket close-gear set if not the warranty). And it took them long to do the job?

(just that my 2nd gear synchros are a bit crunchy. (not talking about normal trait of twins of hard to engage 2nd when cold, but i wonder if heavy handedly doing w/o rev-maching gear switches may have worn that synchro, as when it was new, despite hard to engage, but it was no different sound wise from rest of gears. So i'm starting to seek info how much it may cost / what parts costs / how much may work cost. I can drive fine, get in gear fine, but that slight crunch makes me think all the time "that's not fine" :) )

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What Jeff reports is very unusual. I'd tend to put syncho issues down to user error. The boxes  do appear to be pretty strong. Unless of course you have the auto which is made of chocolate. 

400bhp+ on a manual box does not seem to be an issue .

Auto is generally limited to around 260bhp though it's the torque that is the issue. 

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21 minutes ago, Lauren said:

Unless of course you have the auto which is made of chocolate. 

Nooo don't tell me that! I have to stop myself from engine braking too much too, feels like once it goes wrong in an auto, it's never not expensive

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1 hour ago, Lauren said:

What Jeff reports is very unusual. I'd tend to put syncho issues down to user error. The boxes  do appear to be pretty strong. Unless of course you have the auto which is made of chocolate. 

400bhp+ on a manual box does not seem to be an issue .

Auto is generally limited to around 260bhp though it's the torque that is the issue. 

Lol. Look on the US forum at the amount of replaced gearboxes. They're definitely not strong.

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RRG also reported having done several when mine was in. The only bit that was unusual with mine was it was third to fourth and most that RRG have done are second to third.

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2 hours ago, Church said:

Those £900 just synchros or gears aswell or maybe even whole gearbox? (by then i wonder if it wouldn't be worth to put aftermarket close-gear set if not the warranty). And it took them long to do the job?

(just that my 2nd gear synchros are a bit crunchy. (not talking about normal trait of twins of hard to engage 2nd when cold, but i wonder if heavy handedly doing w/o rev-maching gear switches may have worn that synchro, as when it was new, despite hard to engage, but it was no different sound wise from rest of gears. So i'm starting to seek info how much it may cost / what parts costs / how much may work cost. I can drive fine, get in gear fine, but that slight crunch makes me think all the time "that's not fine" :) )

There you go @Church the full break down of what was replaced

IMG_20170814_180130.thumb.jpg.8e2dfcc49cce052e9aa6b107b1643f7a.jpg

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But then again there are hundreds still running stock gearbox just fine. Don't get too set on that. Negative/breaking cases are posted about and often very loud, while there actually might be LOT of parts still running fine, just nobody posts about it, as it's "as it should".

Meanwhile if you are really serious on lot of forced induction power and track a lot .. i'd probably would not get another spare stock gearbox, but since beginning one meant for more strength / sport abuse, eg. with straight cut gears. If budget very high, then even sequential one like eg. quaife or holinger.

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The Automatic is stronger IF you can keep it cool. Remember HP doesnt kill gearboxes, torque kills gearboxes.

Manual (Aisin AZ6) has a maximum torque rating of 250nm

http://www.izb-online.com/uploads/tx_tnmexhibitordatabase/uploads/AISIN AI company presentation.pdf

Remember, the AZ6 (derived from the J160/RA6x) is in the s2000/rx8/altezza/mx5/s15 so gernally low torque 4 cylinder engines.

Automatic A960E has a maximum torque rating of 300nm

http://www.atspareparts.com/toyota-a960e-transmission.html

A960E has been in many V6 lexus applications.

Also here's a great blog from Lexus that mentions the evolution of both transmissions.

http://blog.lexus.co.uk/lexus-gearbox-transmissions/

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Having been in other people's cars and witnessed their driving, it seems that most seem quite hard on their gearboxes. Trying to change gear fast is a sure way to wear out your syncros and gains you nothing. Ditto with racing, most tend to try and change gear too quickly. It's the adrenalin and all that. I too have had this issue when I first raced tin tops and I learnt an important lesson in purposefully slowing down my gear change. American's aren't the best it seems when it comes to driving manuals as they learn on automatics. 

Most people IME do not do a good job of changing gears thinking that you should do it quickly when in fact doing it slowly is a far better option, so I would say that of the others that have had issues with syncros is down to user error as well. The typical syncro being shot on second is down to too many traffic light GP's. 

Also the number of those reporting issues with worn syncros is very low, so it probably says more about the drivers than an issue with the gearbox or an inherent weakness itself. 

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15 hours ago, Kaisersalsek said:

Nooo don't tell me that! I have to stop myself from engine braking too much too, feels like once it goes wrong in an auto, it's never not expensive

It's fine with stock power. The only issue seems to be when you go over 260bhp or so with forced induction. So you shouldn't have anything to worry about. I have very little experience with automatic boxes but I don't see why using the 'manual' option would cause an issue if you drive it well, so lifting a bit on upshifts and all that. 

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I'm pretty sure it's me as driver to fault for worn synchros, indeed. Did all cited errors, like switching gears as fast as i could, almost forcing them, started learning heal & toe for downshift rev-match only later on, after already at least year had been tracked.. Well, at least clutch still lives fine, despite lot of clutch-hits due not rev-matching, or sometimes even purposely to initiate drift. When "grew up", decided cut on flashiness, rather keep car more planted if downswitch prior entering curve with proper revmatch, but i guess that is a bit too late, all that time before i put on heavy load & for many times at that.

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It's good to know the design spec of the box is above what the engine can put out by about 40 Nm. They'll probably take more than that, but not for the life of the vehicle. Then it comes down to how you treat any part of the car. If you push it to the limit, it wears out faster.

 

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3 hours ago, Lauren said:

Having been in other people's cars and witnessed their driving, it seems that most seem quite hard on their gearboxes. Trying to change gear fast is a sure way to wear out your syncros and gains you nothing. Ditto with racing, most tend to try and change gear too quickly. It's the adrenalin and all that. I too have had this issue when I first raced tin tops and I learnt an important lesson in purposefully slowing down my gear change. American's aren't the best it seems when it comes to driving manuals as they learn on automatics. 

Most people IME do not do a good job of changing gears thinking that you should do it quickly when in fact doing it slowly is a far better option, so I would say that of the others that have had issues with syncros is down to user error as well. The typical syncro being shot on second is down to too many traffic light GP's. 

Also the number of those reporting issues with worn syncros is very low, so it probably says more about the drivers than an issue with the gearbox or an inherent weakness itself. 

Why is it better to change slowly? Just for gearbox longevity?

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Each application for the AZ6 is customised.

I agree with @Lauren that it does depend on your level of mechanical sympathy. If you literally pull it into gear very quickly and the revs dont match, the syncros will wear quickly on stock power, obviously more power and more mis-match will put more stress on it. 

Generally the box seems to be okay up to 350hp in terms of mechanical strength. 4th gear is the one to go usually. 

I think Adrian @ fensport ran 400+hp but you've got to admit, ten or so 1m30s laps at six or so events a year is not the same as 6 trackdays a year where you spend 2 hours lapping hard on each day. Same applies to running above 280HP with stock internals. 

 

 

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10 hours ago, Lauren said:

It's fine with stock power. The only issue seems to be when you go over 260bhp or so with forced induction. So you shouldn't have anything to worry about. I have very little experience with automatic boxes but I don't see why using the 'manual' option would cause an issue if you drive it well, so lifting a bit on upshifts and all that. 

Ahh ok :-) in theory it shouldn't I guess, think I'm just wary of not knowing how well built it is.

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