I have two spare 5 speed SA trannys to use for the T2 project car and I dont know the history of use of either of them. I am considering getting one rebuilt and wondered about the part kit to get

Link below I found courtesy of Stu Aull in a Kenetsau thread

http://www.drivetrain.com/parts_cata...rhaul_kit.html

I understand all 79 -85 Gear ratios are the same from the Mazdatrix web site . But the SA's appear to have smallerfront bearing set.

Can the 20.5 mm dual front countershaft bearing and synchros Kit shown in the parts list for 81-85 be swapped into the SA trans which has parts listed for 15 mm single bearing ??.

there seems to be both a 15 mm and 20.5 mm kit for the 81-85 , but just a 15 mm for 79-80

 

Is there a reason you don't want to use the kit that's appropriate for the trans you have?

 

somewhere I read the 20.5 mm double bearing is better ?

Also have heard the SA transmission wasnt as good as 81+?

Considering I'm hooking more HP/torque to it , figured I'd make it as good as possible

 

Neither one will take much power, and I don't think you can swap to the bigger bearing without modifying the case. It'll last if you baby the shifts, people have broken them with near stock power and a heavy duty clutch. I snapped a counter-shaft in my '85 tranny shifting into 2nd with ~200rwhp on 205 wide street tires. I'd recommend selling those trannys or trading them for a TII tranny. It should last a while unless you're revving past 8k rpm.

 

I doubt they are interchangable, BUT if you look at the last kit listed for an RX-7 on that site it shows a 20.5mm bearing for 79-80.
p/n - DTSBK132(WS)



Id have to agree with the others who say TII trans is the best option though

 

yea , I didnt see that part # on first look . Maybe you wouldn't know which one will fit until you got it open ??

I am really set on keeping the interior true to the SA on this project so want to keep the 79 shifter position and console . Thats the only reason I'm holding off on the T2 transmission. Down the road, if they dont hold up and I go through two of them pretty fast , I'll do the swap . This will be my second fun car in addition to my dd and likely will only put 2000 km on it a year anyway .

anybody else have any idea on the 15 mm vs 20.5 mm ??

 

nope. if you look up the bearing from mazda, it will superceed and you get a different number than in the parts catalog, but no idea if you get a wide or narrow.

the front countershaft bearing isn't the only one that goes bad either, the center countershaft is the big problem, but they dont mention it because they don't sell the good one.

on the center countershaft, they had a double row ball bearing, and with a plastic race, the ***** fall out, and it gets loud.

mazda updated to a roller bearing in 1987, and it retrofits because the roller is narrower than the double row ball bearing. so you need a spacer.

and note that the better bearings make the trans more DURABLE but not STRONGER.

 

Yep, that's the cross we SA'ers bear; probably the single biggest non-swap we face. That and the rear-axle/brake setup, but that's at least do-able invisibly.

 

the B2600 trucks and MPV/929's had a turbo trans, and a tailhousing with a more SA compatible shifter location.

or actually the good one is the Rx8 trans, it wont work in an FB/FC because the shifter is too far forward, but it might fit the SA perfectly.

and the Rx8 trans is beefier than the turbo, its got HUGE shafts and big gears. its fragility and unreliability is just based on internet rumor, its not as bad as you've heard. AND the couple of little things that fail, are actually well documented and there are fixes

the turbo transmissions can handle more power without snapping gears and breaking shafts, but if you put it in a roadracing car its no better than the NA transmissions

 

If you're doing a T2 swap, you should find a T2 trans.

The SA trans is fine for a 12a but that's about it. Best thing you can do is get the iron countershaft bearing plate if it fits your application. I've done a few FB models but don't know the interchangability with the SA versions.

Ask Rob at Pineappleracing.

 

Int'resting... wish I had the money to think over a full Renesis swap, for that matter. Don't, though.

Some day I will have to tackle a trans rebuild or find a swap; one I've got is holding up OK but time worms all gears.