Kenku

Figured I'd throw this out to you guys because it's a road racing thing and... well, just lemme know if it should have been somewhere else.

Background: my dad and I race an '83 RX-7, prepped to ITA specs. We're not professionals or anything, just out to fun. He races wheel to wheel, I do high-speed autocross.

Well, last year the tranny started getting pretty balky... it didn't want to go into 3rd or 4th. So we rebuilt it; all new synchros from Mazda Motorsports, etc. One weekend race at Blackhawk farms, and one partial day of autocross (goddamned rain!)

Last weekend we were at Elkhart Lake, and halfway through the race, he lost 4th. And a lot of other gears were not working either; I couldn't get it into 1st at all to drive it into the garage, and reverse was crap.

Yesterday we pulled it and opened it up. We were running Amsoil GL5 synthetic oil in the box... it turned this nice marbelized color (instead of red) with metal shavings, the works. Got it partially apart and the problem's already obvious... a quarter of a synchro ring dropped out, with even half the teeth on the ring sheared off! I don't think my dad was especially abusing the thing, though I won't rule out the possibility of a missed shift.

We have spare transmissions but... anyone have any tips on making them last longer?

blackbirdzach

Wow dude, I've got no idea. Hope I don't run into the same thing!

Gene

iTrader: (1)

My mechanic (J&R in Elmont, NY) was recommending getting a transmission cooler for serious track duty.

It's also possible that some of the parts used for your rebuild weren't up to proper tolerances.

Kenku

I don't know how a tranny cooler would work really... the stock boxes are just splash lubricated.

As for proper tolerances and stuff... well, we checked it, and LIS it was all brand new bits. *shrug*

GT3_racer

Does he flick the throttle before shifting down, i.e. heel and toe, or push it in to gear and let out the clutch. This has remarkable effects on tranny life.

C. Ludwig

iTrader: (27)

A tranny cooler would need a pump. It would help the situation with these gearboxes being rather fragile. The problem is that if you're racing in an IT class it's not legal.

Kenku

Yeah, heel toe pretty much exclusively (in car camera is nice for finding things like that out for sure) and I know that I did when I was autocrossing it. Synchro's in some fairly even chunks too, actually.

Strangely, only lost about 6 seconds on lap times on Road America for not having 4th.

Ah, okay... didn't think of that. External pump would work but yeah, as you said, legality. Darn IT...

Gene

iTrader: (1)

Yes, he did mention a pump would be required. We weren't discussing an IT car though, we were discussing making my FC into a tank for use at driver ed events.

SPiN Racing

Granted they are fairly local to me.. (1 hour drive) I am going to go with Mike to re-build a couple of mine. It is just not worth the time to me to try it myself and maybe get it right.
I keep razzing Evil Aviator that he needs to consider trannies disposable like tires for the 20B, and just buy em outright.
http://www.iscracing.net/clutch.htm
295.00 plus hard parts.
550.00 for a 1st Gen tranny outright..
695.00 for a FC..

He does some things to it.. things like.. makes it a bit harder to engage first.. so you dont accidentally go into it.. same with reverse.. you have to "PLACE" it in 1st and reverse.. and the rest of the shifts are real nice.

I see on the page he is making a EP tranny based on a TII tranny... dunno.. just saw it.

That is what I will do when my current stock of spare trannies is depleted.

Kenku

Making it harder to engage first is an idea... I'm actually going to make a little lockout lever for 1st-2nd since we never use them. Not completely sure if that's legal, but it would be in a place that's easily returnable to stock, so.

We've been advised that going to a 4-puck clutch is a very bad idea (we're using one of the better ACT street ones and upgraded pressure plate) if we're breaking synchros... though it's tempting because the 4-puck clutch disc is cheaper.

TrentO

I've been roadracing an 84 RX-7 for the last five years. I now consider transmissions as wearing parts, just like brake pads. The truth is your stock gearbox was never meant to shift at 8000 rpm all the time. The stress on the synchros from the rotational speed difference when you make a shift is much greater at higher rpms. I've seen two major types of failures in my road racing, the first and most common is the 2-3 synchro going (where can you use first on a road course?). The second mjaor failure I had was the rear bearing supporting the driveshaft drive yoke simply wore out. The result was a hammered out rear seal and a loss of all the gear oil out of the gearbox. If you are going to rebuild a gearbox I would suggest starting with a good condition used gearbox from a street car. Any serious time in a race car seems to seriously overstress the weak first gean gearboxes. For a second generation car we've had great luck with the 626 gearboxes. The 2nd gear ratio is much better and the 626 family car gearboxes often come from the wrecker in excellent shape.

Hope this helps,
-Trent

Kenku

Hm. We're running 4.88 rear gears, so 2nd is about as useful as 1st. Heard about the rear bearing problem before though. I guess, overall, it's a good thing we have a lot of spare trannys.

What's stronger on the 2nd gen boxes? Uh... just out of curiousity... not that we'd go and put one in...

31rx7

From my experience, the 1st gen tranny is reasonably reliable for ITA racing, but you do need to be somewhat gentle with it. Speed shifting and the like without using the clutch will kill it. From talking to guys that run EP and GT3, the stock transmission will only reliably handle about 150 or so horsepower, so in ITA trim we are at the edge of reliability.

My 1981 ITA car had 25 or so weekends on it, and the transmission was the original according to the owner. I use Redline MTL in the tranny and always have with my race cars. I put another 12 weekends on it and it started to get a bit noisy (but it worked fine) so I put in a 100,000 mile spare which works fine. I heel and toe when needed, avoid banging the gears (except on starts), and change the fluid every season (it always looks fine).

Also, make sure your clutch master and slave cylinders are good. If there is air in the system it will cause shifts to be more difficult and accelerate wear on the tranny.

I think this was discussed on the Improved Touring board, but I would not bother rebuilding a tranny simply because good used ones are so cheap.

cpa7man

iTrader: (2)

I seem to have a little issue on the 2-3 shift once and a while. This is my first season to run ITA and I have not heard a lot of issues with transmission failure. As 31RX7 said, they seem to wear out slowly in spec7 and ITA. The transmission im my car is on the 5th season and about 8 scca schools.

I just purchased an e-prod car RX-7 so I'm curious to find out how long the transmission will last in it. It's coming with a spare.

Kenku

Hm, well guess we'll see. New (to the car) box going in for next weekend so... yeah.

Another issue is that I realized the shifter is really loose compared to one of the other 7s we have handy. Going to try swapping around shifters to see if that helps anything.

Blake

That could be your problem right there: shifter bushings! Remove the shift lever and look in the extension housing. There should be both upper and lower shifter bushings (white plastic). Very cheap and easy to replace. Without them, there is a whole lot of slop.

cpa7man

iTrader: (2)

Is this right? I just changed my clutch in the first gen ITA car. No shifter busing at all. I have a lot of slop as well. It's one reason I keep missing the 2-3 shift. THe other is I just can't drive. I know my third gen has a shifter busing. I better pull the parts diagram and look.

SPiN Racing

Go to www.mazdatrix.com they have a nice section about it in the FAQ area..

TrentO

We run ported 12A's and most of the people are shifting from 8000-8500. I'd guess the fastest guys are probably running around 165-180 hp at the crank. My shifts are mostly smooth heel toe affairs, with the odd botched shift and the infamous 2-5 shift once or twice a season. With our season we run 6 or 7 events, with a two hour mini-enduro on the first evening and three 20+ minute races on the Sunday. I'd ballpark it all slightly above 4 hours of track time per event. My gearbox experiences have all begun with some gearnoise or a really reluctant 3-2 downshift.

-Trent

31rx7

The 2-3 shift is where I noticed weaknesses. You just can't rush it too much, and it seems that it doesn't like to be rushed no matter the mileage on the tranny. Whenever I do, it ends up missing totally or in 5th. Fortunately, with 4.88 gears, you generally only need it on the start.