Dog/straight cut gearsets - PAR, PPG, Quaife etc or Tremec?

Eeyore · Postby **Eeyore** » Wed Apr 10, 2013 9:33 pm

Hi I'm looking for advice or anyone's personal experience with MX5-based dog boxes. I did search but I mainly found information on gearbox conversions such as RB25 or FC RX7 units, the latter of which I am considering.

I am looking to build a turbo 1.8 combo for drag racing and Powercruise events. I would like to stick with a manual so the car can be used for other applications. I'm aiming for 250rwkw but I wouldn't rule out searching for more in the future. I would like a dog set a) for their stength and b) the purposeful and aggressive shifting ability. PAR haven't been overly helpful via email correspondence and PPG list their power rating at 400hp. I'm worried that I might find the limitations of these gearsets considering they are quite expensive.

Othe options; a standard or Faceplated Tremec TKO with a QuickTime bellhousing. These boxes are quite big so they might be a tight fit and I believe they don't have a speedo pickup. I've also considered the FC RX7 idea and possibly using an Albins or PAR dog gearset although I'm not sure if the gearbox adaptor plates are easily available from what I've read on US forums. Being a rotary enthusiast I know the FC box can take a fair bit of punishment particularly in a lighter car. Should I forget it all and stick with an SE 6-speed?

Thanks.

plohl · Postby **plohl** » Wed Apr 10, 2013 9:39 pm

http://www.holinger.com.au/index.php?

Postby **NitroDann** » Wed Apr 10, 2013 9:41 pm

FC adaptor kits for BPs are now off the shelf. I'll link you when I get home.

Dann

Magpie · Postby **Magpie** » Wed Apr 10, 2013 9:47 pm

http://www.ppgearbox.com.au/page.asp?productid=12

Also look at this thread http://mx5cartalk.com/forum/viewtopic.php?f=29&t=15539

16bit · Postby **16bit** » Wed Apr 10, 2013 10:09 pm

i think for power wouldn't the rb25 box be the best bang for buck?

i have read of drift cars with lots more hp handling that fine with rb25 boxes in the.

manga_blue · Postby **manga_blue** » Wed Apr 10, 2013 11:33 pm

From what I've heard MX5 gearboxes fail under heavy power because the case buckles, not because the gears break. That's why people convert to RB25 boxes.

Postby **NitroDann** » Wed Apr 10, 2013 11:41 pm

The case takes the load when the diff is mounted quite solidly and the engine twists on stock or freshly broken stock rubber mounts and the gearbox takes the torsional load.

Then the gears strip.

The other issue which somehow seems to be related is because the gears are helical cut they push away from each other and a particular locking circlip gets overcome by this force.

Solid mounts are ok for the US guys who track at 350whp every weekend, however a gearbox becomes a wear item at these levels and needs replacing every 2nd season at least.

This is for 6 speeds.

As promised heres the link for the bolt in FC TII solution.

http://www.miataturbo.net/miata-parts-s ... ata-71777/

Dann

Eeyore · Postby **Eeyore** » Thu Apr 11, 2013 6:59 pm

Thanks for the opinons guys.

manga_blue · Postby **manga_blue** » Thu Apr 11, 2013 8:18 pm

BTW Eeyore, welcome to the forum.

I had a Mazda 1300 wagon, bought new in 1971 I think. It had a bad start when the front suspension virtually fell out in Glebe Rd on its first drive. Mazda hadn't tightened up any of the bolts. :shock:

After that it was a great car. Light years ahead of any small car we'd dríven before. Nice little free spinning motor. We revved the guts out of it for years.