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Road race guys have problem with the gearing. I never make it out of second gear, and the 5 speed was perfect with that ratio for me.
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First is basically useless in both the 5 and 6 speed. An overdrive option would be nice...
I do agree that the price point is going to be rough though. The issue is that from a mass production scale, it's far easier to make a kit that can use something already available and use that instead. Most turbo miatas are between 200-300 in terms of hp/tq at the rear wheels. There are so many cars out there today that are mass produced that are in that range and can take more abuse than just that on their stock gearsets. Why reinvent the wheel when it's cheaper to just use something cheaper that can be mass produced? |
For the 5spd: If we only make a 3rd/4th/5th, this is very economical. It's 1st/2nd that's the expensive part to make due to having to make a new mainshaft
For the 6spd: We "may" only need to make you guys a 3rd/4th/5th, as we already have a 1st/2nd/6th for the GT86 that we made for Toyota Motorsports which, I believe, uses the same transmission. However, the ratios may be completely unsuitable, so would need to double check |
The thing with the 5 speed is that they're so weak I figured you'd need to do 9310 shafts to help it hold together.
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Originally Posted by Leafy
(Post 1394192)
The thing with the 5 speed is that they're so weak I figured you'd need to do 9310 shafts to help it hold together.
It really just depends on what you guys are breaking (i.e the gears, or the shafts) |
What have the gears in the GT86 stood up to? Power levels? Road race usage?
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Around 500hp on our UK GT86's, Road/Race
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Do you not have to upgrade the 3/4/5?
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No. The gears didn't have an issue with breaking, and the ratios worked well with our 1st/2nd/6th combination
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Odd. Because our 6th speeds break 4th at 300-350 ft/lbs on the track.
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Originally Posted by aidandj
(Post 1394300)
Odd. Because our 6th speeds break 4th at 300-350 ft/lbs on the track.
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Thanks Ken!
I have a spare 6 speed coming that I'm going to take some measurements on to see how close we are to the BRZ parts that MFactory currently offers. I am also going to contact Jacks and see if they have any familiarity with our AZ-6. |
If anyone has a failed gearset can you take photos? If there is some truth to what's Jacks claims the fix may not require much beyond modifying the countershaft with a stronger 4th gear clip.
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@bbundy has about 20. And not all broke 4th gear.
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Originally Posted by Alternative
(Post 1394500)
If anyone has a failed gearset can you take photos? If there is some truth to what's Jacks claims the fix may not require much beyond modifying the countershaft with a stronger 4th gear clip.
@ everyone - The loss of 4th gear in the AZ6 (at least in the FT86 twins, Miata, and S15 versions) are usually related to one of two things: pure torque zipping the teeth off, and a misalignment of input and output 4th. The first one is unavoidable at high TQ on the OEM gearset, the second can be held off for a while with our thrust washer modification. There may indeed be some shaft deflection making a contribution, though it would be comparatively minor against the amount of thrust wear behind the input 4th bearing sleeve. The thrust wear can be measured in whole millimeters, and once the gears are that far apart axially the contact patch is terribly compromised and it all goes to sh!t. As for difficulty shifting into 4th causing breakage, it is not a direct cause and effect, but we feel that it can speed up the process if there are already thrust washer problems. For that matter, once the thrust washer moves down the shaft, the fork, synchro sleeve, synchro, and sleeve detent ball/spring assemblies all become liabilities, and the combination of problems is death for 4th gear, even on a low to moderate power car. Side-stepping the clutch into 4th (or any gear) will shock load the trans and can also break gears; that of course is less related to the synchro than it is the loose nut behind the wheel As for gear ratios: I think the stock ratios with a 3.6:1 (which is standard for EUDM) works quite well for boosted cars. |
Reply from Jacks
Hi Dan, One of my techs actually owns one and has played with it. Most of the stuff is the same so we should be able to do the same work for close to the same price. It will just come down to any of the parts that are different and what their replacement cost is. Thanks, John |
@bbundy Can you come in and chime in with pictures and the sorts of failures you have seen?
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AZ6 clip
https://cimg9.ibsrv.net/gimg/www.mia...d28381f96f.jpg Similar modification better explained better: GTR Retaining Clip Modifications ? Jacks Transmissions |
Interesting....Paging B Bundy, Just sent him a PM to this thread.
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6 speeds mostly break 4th gear. note that an RX8 box has all the same gears in it accept 4th. and it is a strange ratio jump for 4th on the rx8, I suspect it was done for strength. I have broken multiple 4th gears and some were probably related to thrust bearing problems and one second gear in Miata 6 speeds.
I do not believe at all that the 6 speed case is inherently stronger. It has more gear pares between the bearings and more unsupported shaft length than the 5 speed. Basically only two sets of support bearings on the main shaft where the 5 speed has 3. the five speed gets away with much lighter shafts mostly because it has a stiffer case than the six speed. The six speed is stronger because the shafts are much larger and the gears have wider faces. All the weight difference between the boxes is shafts and gears I can't remember if it was 12 or 14 lb's more rotating steel bits in the six speed. That extra weight is there to make it live with a weaker case design and deal with the shaft flex. The Quaife gear set in the five speed is not bullet proof either. I have broken the input gear, second gear, and had 5th gear seize onto the main shaft in three separate occasions. Bob |
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