I'm going to go out on a limb here and say that a 5-speed wouldn't have survived 10 track days at 300+whp. Can we put this "quaife boxes aren't stronger than stock 5-speeds" thing to bed now?

 

QFT - Like I said 8 years ago when I was working to get this gear set to market, Quaife would not have manufactured this gear set if it couldn't stand up the rigors of track use in the OE 5 speed case.

 

That's never been my point. The point is that Quaife makes no claim that they are stronger and - in fact - says: don't expect them to be stronger. We all know that - by design - they are, or I wouldn't have invested in it. No one knows how strong exactly.

 

Quaife employs too many lawyers.

 

lol. Or too few.

 

How many hours per weekend?
The reason for asking is that I for example run less time in a season (6-8 hours) than some others does in a weekend.

 

Varies greatly per weekend and I'm not intending to provide statistical evidence on rwhp*hours of Quaife longevity.

 

I suspect it’s just that they did no analysis or testing to determine how much stronger it was. They used tribal knowladge and the design philosophy “when in doubt make it stout” Then let the customer find out where the limits are with no warrantee expressed or implied. In reality the Qaife internals make the 5 speed hugely stronger than stock at handling high torque. And likely more robust than the 6 speed by a good bit.

Having said that I’m coming around to the 6 speed. The Mazdaspeed box I put in at Laguna after stripping 4th gear in the standard 6 speed shifts much better than any other 6 speed I have had. With a 3.636 rear end it is usable for autocross as long as you set your rev limit over 8000 rpm and the course isn’t too fast. You hit the rev limiter a bit but it is nicely in the power band most of the time on course.

 

Mr. Owl, how many hours will a Quaife gearset last in a OE 5spd case?

 

just thinking - after reading hundreds of linear feet of posts on this subject - it seems to me that, re the 6 speeds:
a) they break sometimes 3rd but 4th or 5th almost always except maybe the guys drag racing and we're not counting them.
b) very seldom (or at least much less frequently) 1st, 2nd or 6th.
c) can we say almost always 4th or 5th - no problem if you want to correct me. Probably cuz most tracks are spent w/ more time in 4th and 5th existing corners than any other gear.
d) the breakage is bending fatigue related, not lube or contact stress related
e) so could the problem be solved for most by a strong set of 4th/5th gears for not near as much money as a quaife or other solution?

 

Problem, getting the 4 gears you would need to do a 4/5 gear set custom made in a small batch will cost more per set than a qualife 5 speed set.

Potential problem. 6 speed gears may be permanently on the shafts like many other cars making partial gearset changes impossible.

 

A/B/C appears to be true, at least within the scope of this discussion (there is a separate subset of broken 6-speeds from regular race use, typically shift fork/synchro failure). My broken 6-speed was 4th gear, and I know of a few others broken in the same way (under power in 4th gear). Not sure if Bob Bundy has broken one in another way yet.

D is an educated guess, but still a guess. Keeping the fluid cooler might go a long way towards 6-speed longevity, but I don't know of anyone running a cooler yet.

E would be penny wise and pound foolish. If you're going through the expense of opening the gearbox, you may as well do the entire set (or at minimum, a 3-4-5-6 set for roadcourse use). If another gear were to fail, you run the risk of damaging the upgraded gears as well, which is just silly.

 

so am i rite in thinking that there has not been a failure due to excessive torque/power of a 5 speed quaife box that anyone knows of?

does anyone know of a car (preferably a race car) running ~400bhp using a quaife box on a regular basis and has been for some time without any problems?

i have another 6 speed to go in the car on Monday then it is back to the dyno on Tuesday. lets see if this one lasts the day... was starting to wonder if i should limit the power/torque for the time being but then thought stuff it. all or nothing!...

 

Ran across this thread looking for something else. FWIW, 330rwhp (380-400ish bhp), autocrossing for 2 seasons on a Quaife gearset, no sign of anything bad so far. Lots of hard launches and not-so-soft rollins in 1st and second. Only 260rwtq peak, though (supercharged).

 

Rite that's it... Blew yet another 6 speed at the weekend! That has to be like 5 or 6 now. I am not prepared to throw any more at it. so as far as i can se these are my options:

1. I have a guy that will make me a custom 5 speed dog box in a 6 speed casing but it is a little expensive.
2. Buy a quaife gearset and see what happens at 400whp+ but if it doesn't take it i wasted my money.
3. Put a box in from something else like an rx7 or whatever. I can fabricate everything myself so cost should be reasonably low but i suspect the ratios are going to be less than ideal.

I really want to go with 1 but if i do the car is going to be sat for most of the season whilst the box is made and i will have blown most of this years budget. on the plus side though the ratios will be custom and it should easily take anything i can throw at it.

I am still not convinced on the Quaife box and have yet to find anyone putting as much power as i have through 1. on the other hand i have not heard of anyone breaking 1 either.

Putting another box in is going to be cheap but what to use to get the best reliability and ratios? Fair bit of labor but that's free...

The box is what is holding me back now with both power and reliability.

Decisions decisions.... What do you think?

 

To the guys blowing up $900 AZ6 6 spds left and right. It appears the only solution is a one off adaption or a Quaife. Unfortunately, those conversions all seem to start at about the price of 3-4 AZ6's. There is probably no way around that.

The only potential lower cost option is a readily available OTS OEM trans with the right form factor, ratios, weight and cost that one can make a billet adapter plate/driveshaft/clutch disc for. A <100lb trans for <$1500 that will hold 300lbs tq with the correct ratios is the unicorn.

I know, that's all obvious. Just wanted to condense it down to it's root factors.
I think we should all be hunting for that unicorn trans and just plan on adapter/driveshaft/disc. If such a trans is found, I'll get the kit made and offer it on our site for less than $750. I need the trans myself so that's where it would start.

 

Lets look at some options and dismiss the ones that are no good:

RX7 FDTII or FC TT
RX8 or nc
Ford type 9
T5
Nissan S15

there must be 100's more

 

Let me know if I can help with the reverse engineering & design work, if needed.

 

RX-8 tranny is a no-go.

The FD box is good to about 370-380wtq.

 

FD box may 1 for the list then. Pull clutch though.... Ratios + info:

Transmission type Type R152, 5-speed manual
Clutch type Single dry plate, diaphragm spring, hydraulically operated with pull-type mechanism
Clutch diameter, outer x inner, in. (mm) 9.3 x 6.3 (236 x 160)
Gearbox type All synchromesh, with double-cone synchronizers on 2nd and 3rd gears (R type)
Gear ratios
1st 3.483:1
2nd 2.015:1
3rd 1.391:1
4th 1.000:1
5th 0.719:1
rev 3.288:1
Final drive type Hypoid
Ratio 4.100:1