hey guys i was wondering if you guys could help me confirm that i just blew somthin in my tranny?
i was driving home from work and i got on it in first shifted hardish into second and bam there was a huge crak and my car started bangin and clunkin and wouldnt move with the cltuch pedal out. (it felt like when u dump the clutch down shiftin)
i limped it literaly into the nearest gas station and started eliminating things like the drive shaft, clutch, and rear end, you can push it in nuetral and not hear any clunkin from the rear end like if was blown but when you put it in first and go it moves about a foot and then stops and moves backwards like a rear end promblem. but you cant start it in nuetral with the clutch pedal out or else it clunks and bangs and kills itself. so i have a pretty good hunch its the tranny but the thing only has 41000 miles on it. im gonna have it towd to a friends house to drop the tranny and confritm what i need but i just wanna hear what u guys think. my manager at work is big into rx7s and he even came out and messed with it some and thinks it might be that the tail shaft is broken. but he said he has a realtive thats got a bunch of trannys lyin around i could pick up for like 50-100$ so i would alos like to know which trannys will bolt up to a 12a with out modification or least as little as possible. any help would be much apprechiated.

 

Sounds like the trans is toast. As for what will fit, any FB or N/A FC trans will bolt up to the engine. The FC trans uses a different rear mount, and the shifter is about 2" further back. A simple tailshaft housing swap will eliminate both of those issues. However, the FC trans has a much higher 5th gear ratio, and will cause the RPM to be much lower. The 12A lack the grunt at lower RPMs that will be needed to effectively use 5th at any speed under ~70MPH or so.
All 81-85 12A 5 speed trans have the same gearing, and the 84-85 SE trans has nearly the same gearing. Either would work fine.

 

hey thanx man but as for the tailshaft swapp i think thats what went byebye, but i have a good connection for tannys so i think i might be able to pickup a good SE tranny for cheap and if i remeber right that would be better than a 12a tranny

 

SE trannies have smaller teeth in the gears so in my humble opinion are worse than '81-'83 trannies.

 

The SE trans does have slightly different gearing. Most notably 5th. It's just a bit taller, and will lower the cruise RPM somewhat, but not enough to be detrimental.
The SE had a lower diff gear, and the O/D ratio was raised to compensate, giving the SE nearly identical RPM at any speed in 5th.
Just be sure to use the speedo gear attached to your speedo cable. That *should* keep the speedo correct, assuming it is now.

 

Never had a major problem with a tranny in any of the 7's I have ever owned.
The standard front countershaft bearing failure has been the norm. I don't know how these guys are breaking trannies on low HP applications unless when shifting hard they are missing the shift alot of times.

Rogue, On the N/A Fc transmissions you can swap out the tailshaft on the S4's only. The S5 will not swap with a FB tailshaft.

 

D'OH! I knew that, just forgot to add the S4 in there. Thanks for pointing that out, Doc.

I thought that the FB & S4 N/A FC trans were relatively unchanged, other than minor gear ratio changes in the 1-3 area, and a major ratio difference in 5th.
I thought the different style gears weren't added till they modified the FB/FC trans to use in a Miata.

 

well it is wied that the tranny went cuse i rarely miss shifts especialy into second and the car only has 41000 miles on it the only thing that couldve happend is the tranny fluid ran low cuse i never checked it i saw no reason to cuse its never leaked anything but a lil engine oil every now and then. The reason why i was thinking why the se tranny would be better is the lower cruising rpm but i guess that doesnt change much unless i get a 5th gear from a 2nd gen tranny. and i do know that the first gen trannys are supposed to be pretty tough so i dont know how i managed to bust it when my engies stock except for gutted cats. the only other thing thats not stock is i have 15 inch rims with a 60 side wall on the back, but the tires spin easily enough so that there isnt too much stress going to the clutch or tranny.

 

the first gen trannys are tough. if you dont miss shifts your ok. i have never broken one and i drive like a maniac. same with the rear ends there indestructible. you cant break them if you try. even with a 350 in them they still hold. just my 2 cents. you must have broke it good!

 

ohhh yeah i shure did break it good , i guess i just have a habit of obeying murphys law what can go wrong will go wrong. the clutch went out about this time last year lol and now its the tranny dangit. i know i was driving it hard every now and then but i never thought it would go like that with stock power.

well somtime in the next week ill be able to see what went wrong on it so catistrophically