I'm going to re-gear my transmission when I get the opportunity. The engine is a JDM B18C Type-R with a Garrett GT2860RS...maybe 300hp.

It's in a classic Mini that weighs 1700 lb's so gearing it correctly will really help.
I talked to Gearspeed and they recommended the ratios.

However, it looks like there is a choice between helical and straight cut gears. King Motor sports has entire sets of most ratios in helical.

Any reason to go one way or the other? Or (maybe this is a silly question) can they be mixed?

 

Are you going to have Gearspeed or Synchrotech build it? Seems like you're going back and forth. Whichever you're going with talk to them about it.

Semi-helical is stronger than straight cut given the same tooth profile. The advantage of straight cut is less friction for more power and less heat. Straight cut will whine (I can make a quick vid if you would like) much more than semi-helical (helical will not whine). They can be mixed without problems. Just remember the noise. Most will not want a quiet 1/2, whine 3rd, slight whine 4th, whine 5th.

 

I am going back and forth...I mentioned Synchrotech and then got a more than a few private messages saying to use Gearspeed...so at this time I have pretty conflicting opinions on who to do this.

Please do make a video. Any help or advice will be greatly appreciated. The overriding requirement is that I either use the gear case I have that already has a Houseman 3.47 FD or obtain an LS and put the House 3.47 in it. However, I don't know if that's do-able.

I want the LS gear ratios, with the exception of 1st. I want that to be 3.07 from MFactory or some other reputable gear maker. Since it's being opened it makes sense to rebuild it and put in carbon fiber synchros and whatever else makes sense.

As I understand it, these are the widest ratios I can go with a hydraulic transmission. The cable transmissions seem to be higher with the exception of 5th but are different and not interchangeable with the hydraulic gears.
I wouldn't mind having the 2nd, 3rd and 4th from the cable transmission with the MFactory 1st gear, 5th gear from the hydraulic and Houseman FD.

1st 3.07 MFActory
2nd 1.90
3rd 1.269
4th 0.966
5th 7.14
FD 3.47 Houseman

Cable
1st 3.07 MFactory
2nd 1.857
3rd 1.259
4th 0.935
5th 0.742

As far as this whole idea, including helical vs straight. With my situation, I need a genuine, "here's what you need to do" expert advice."

The broader gear ratios will really help make this car far more drive-able.

 

I was just informed that MFactory makes a straight cut 2.85 1st gear. I'm wondering if that would be even better than the 3.07 in this case.
1st and 2nd would be straight cut and the rest would be helical or semi-helical...not sure what semi-helical is.

1st 2.85 MFactory
2nd 1.90
3rd 1.269
4th 0.966
5th 7.14
FD 3.47 Houseman

 

Not sure if it was a typo on your part, but it is a 2.785 1st. Semi-helical is just a steeper angled gear than stock (helical). I'll make that vid for you tomorrow.

 

That would be great...thanks

 

Here you go. Straightcut syncro set.


H series 5th gear pull 9K 750


http://www.youtube.com/watch?v=q2mn553xRec




BTW, Dave at Sycrotech is the man, whoever is PMing you needs to quit.

 

WOW! that was a great video. I'm really thinking about going with:
1st 3.07 MFActory
2nd 1.90
3rd 1.269
4th 0.966
5th 0.714
FD 3.47 Houseman

I believe it was Dave at Synchrotech that recommended these ratios. We never got into the discussion of straight cut vs helical. He was looking at what would work and what would cost the least amount to do, offering to swap out good stock gears of one ratio for stock gears of different ratios they had on had for pretty much nothing...hard to beat that.
And if some of those are straight cut gears....I just don't think the whine would bother me. If it happened to be in 5th and I had to cruise constantly with it, I guess it could. However, my car is so loud that I doubt even that would bug me.
I'm not sure what a rebuild with a few straight cut gears and all carbon fiber syncros would do for tightening up the shift feel, it feels a bit sloppy now. But I don't think it would hurt. Much of that may be due to the fact I have to use a very long shift lever.

I'm really hoping the turbo acts to muffle the whole thing down a notch or two.