School me on 1st gen RX-7 transmissions.

[lateapex911]

Ok, so I done blowed it up, LOL. The PP and clutch that is, at about 7K in 4th at Pocono. I left all the Humptey Dumptey parts there, so there's no crazy gluing the 100o bits back together.

I have a couple transmissions, but they all have syncro problems.

So, the good book says we have ONE choice in ratios, which makes that part simple. My car is an 84.

I've never rebuilt a trans before, and haven't really wanted to. How hard is it? Special tools? What tricks need to be done? Are there certain years/cases/parts I should use instead of others?

What am I getting myself into?

Finally, does anyone sell set up for racing transmissions? Buying might save me a lot of time, time that could be spent welding the holes in the firewall back together!

[ddewhurst]

Jake, contary to what some on this site think of me had you needed a transmission two weeks ago I would have forwarded one to you for the cost of shipping. A guy picked up 5 transmissions, a motor, 2 drive shafts & some other stuff two weeks ago. This past Sunday a guy purchased my rust free 1982 RX-7 including motor/transmission.

Do you have a clue as to what went wrong causing the pp to go south? Loose pp bolts?

[lateapex911]

Thanks David, timing is everything! The PP and clutch were about 12 events old. I last checked the clutch for wear about 5 events ago when the motor was out, things seemed fine.

As of now, I have no firm idea.

[mustanghammer]

Jake, what kind of clutch was it? I have been using the same Center-Force for 6-7 years w/o issues

No experience with transmissions either. So far I have had good luck running used boxes out of salvage cars. We do pull them apart and inspect them. I want to see good bearings and good 3-5th gear syncro's. 1st and second don't matter

[lateapex911]

ACT (Advanced Clutch Technology). 4 puck, with matching PP. I understand they do not make the PP anymore.

[dickita15]

Jake if you need a rebuildable core or two let me know. I have quite a few but they all went thru the great flood of 05 and I have not touched then since.

[lateapex911]

Thanks Dick, I have two cores that have bad syncros that haven't been thru a flood. I'm thinking they'd be better donors, right?

[Chris Taylor]

I installed an ISC box in a 80 ITA car, very nice box. When the owner's vigorous shifting bent the forks in it, too, I took it apart and found out that Mike does/did quite a bit to the insides. After looking at the forks, I'm surprised the owner was able to bend the one he did, as they were all brazed and beefed up, in addition to safety wire.

If you feel like spending the money, and ISC still offers the service, I highly recommend their transmission rebuild. I put a stock fork back in it and plan on running it in the next car.

[joeracerx95]

I installed an ISC box in a 80 ITA car, very nice box. When the owner's vigorous shifting bent the forks in it, too, I took it apart and found out that Mike does/did quite a bit to the insides. After looking at the forks, I'm surprised the owner was able to bend the one he did, as they were all brazed and beefed up, in addition to safety wire.

If you feel like spending the money, and ISC still offers the service, I highly recommend their transmission rebuild. I put a stock fork back in it and plan on running it in the next car.

Oh, oh, oh, let me be first?!?

"they were all brazed and beefed up, in addition to safety wire."

And where in the IT rules does it say you can do that?

Thanks, I enjoyed that. :happy204:

[Chris Taylor]

Oh, oh, oh, let me be first?!?

"they were all brazed and beefed up, in addition to safety wire."

And where in the IT rules does it say you can do that?

Thanks, I enjoyed that. :happy204:C'mon, you know if people can't see it they can't protest it, and therefore you can do whatever you want. Right? Right?:dead_horse:

[Weaver7]

Just keep in mind that the 79and 80 trans are different.

Bill Weaver

[lateapex911]

My dumb response, huh???

Really? How so? I honestly didn't know that, and I just dropped off two identical appearing transmissions at the shop for rebuilding, ...both have been run in this car, an 84 before. One was the trans that came with the car, I think.

Are the differences internal or ??

Thanks Bill.

[ddewhurst]

Jake, the 79/80 have the shifter in the tail housing proper. The 81 plus have the shifter in the extension that's added to the tail housing proper.

[Weaver7]

My dumb response, huh???

Really? How so? I honestly didn't know that, and I just dropped off two identical appearing transmissions at the shop for rebuilding, ...both have been run in this car, an 84 before. One was the trans that came with the car, I think.

Are the differences internal or ??

Thanks Bill.


I think it is just the tail shaft Jake nothing different a far as the ratio's go. I remember someone telling us we could use the 81-85 tranny in our car if we modified the tunnel.

[dickita15]

That’s right Bill the only difference is the shifter placement. When I built the new car, a 79, I updated the tunnel to 81-85 because all the trannys I have laying around are late ones.

[joeracerx95]

Keep in mind that there is a small difference in ratios between 79-83 and 84-85.

79-83 3.674 2.218 1.433 1.000 0.825
84-85 3.622 2.186 1.419 1.000 0.807

See link below for lots more info.

http://mrmazda.no-ip.com/garage.html

[kbailey]

Lots of shops do the rebuild. Kearney Racing did mine. A friend is running an ISC box and another is running an SDJ box (that tells you how long it has lasted.....). Lots of the parts are still available new, but shift forks don;t seem to be so good used forks are a must.

The .825 fifth is the way to go if you have an option. It's interesting- I have seen a different ratio chart that puts the 84 and 85 tranny at a .765 fifth gear which seems to match my cores. Anyway I have been told the third gear hub and output shaft bearings are common failure points so you might want to replace them even if they seem good.

My Chilton's manual actually has the detailed instructions and lists the tools needed (there are some oddball sockets). The only tool I used was a Visa card so I can't speak to the level of difficulty...

[mustanghammer]

Jake,

If you don't mind, can you elaborate on the failure a little more? Did the clutch die and kill the transmission or was it the other way around? And am I reading some of your other posts correctly - you had parts come through the tunnel?

Are you considering any foot protection as a result of this? The 1st gen EP guys in KC have armored the foot box area of their cars with .125 plate steel or .250 aluminum. Your failure has me thinking about doing something similar.

Thanks

[lateapex911]

Here are the gory details.

I can not tell you what I did wrong. All the PP bolts are present and accounted for in the flywheel, albeit sheared at the surface. The flywheel is perfect, not a mark on it. The pressure plate is a shredded mangled mess. The clamping surface is gone. bits were left in the car, other cars and mostly on the tunnel turn at Pocono.

The collateral damage was comprehensive:


exhaust system
cooling system
Guages (mech versions had the connections destroyed)
EGTs
body work (firewall slashed)
engine damaged (Bolting brackets ripped off back plate)
flywheel damaged (sheared bolts)
starter (front MIA)
wiring
fuel lines
fuel regulator
misc brackets and clamps
and of course, the transmission
the clutch and the pressure plate.

Failure occurred just before a 3 -4 shift, about 7500 or so. typically I shift at 8 or under, sometimes a few hundred RPM more. There was no odd vibration at any point, and I am pretty good at feeling those. I've felt wheel bearings getting a bit loose, and a driveshaft vibration is like an earthquake to me. Data showed the engine revved to 8700 right after the incident, then to idle.

The good news is the fact that the RX-7 engine is so compact and short that the PP lives just ahead of , or in line with, the firewall, so the parts were thrust into the engine compartment. No tunnel intrusion whatsoever.

here's some pictures. Starter, PP, transmission, firewall slash (1 of 2) , overall scene.

[mustanghammer]

I'm guessing you did nothing wrong.....

All I can say is WOW and I'm sorry this happened to you. Thanks for sharing the pics this will help everyone.

[Eagle7]

here's some pictures. Starter, PP, transmission, firewall slash (1 of 2) , overall scene.
Ouch!!! Glad you're safe.