School me on 1st gen RX-7 transmissions.

[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.