Transmission front cover difference between 12A and 13B?
 

I want to replace mine, it's a bit worn. The car is 85 GSL-SE, so according to Mazdatrix I should have the cast iron cover, but I pulled mine and it's aluminum, like the 12A ones. Do I have a 12A transmission, then? Which cover should I order? What exactly is the difference between them other than the metal?

http://mazdatrix.com/g3.htm


There is no difference with the replacement parts for the front cover, they are all the same for 81-85 models. The 79-80 model original were different.

Yeah, that's what you'd think, but if you click on the part number itself, it shows the 81-85 is for 12A with THIN BRG, whatever that is, thin bearing I'm assuming, but I don't know of the bearing differences. And if you click on the part number for cover listed for 86-92 it says 84-92 13B CAST IRON. It's tricky like that, so I got confused and called them up and was told that cast iron is for all 13B motors, including 84-85.

But mine is aluminum, so either Mazdatrix info is mixed up or I have a tranny from a 12A car. Does that make sense?

According to the factory parts manual the number for the Se is N204-16-220A

http://www.mazda-parts.com/partscat.html

OEM Catalog
Item Number MSRP Core Price Price
n20416220a $50.00 $0.00 $35.99

COVER,FRT CLUTCH

I did not get the number from the above website but off of the factory parts manual. Gave you the website so that you could get it cheaper through them.


It is possible that the transmission has been changed and I do not know what the difference would be between the 2 of them since the release bearings and the front seals are the same.

When in doubt you just pull yours off and there may be numbers on it.

I guess it might be a safe bet just to get the same cover as the one I have. It doesn't look like it's ever been replaced, so it's probably the right one for the tranny. If I knew why Mazda switched to cast iron and the difference between the two, maybe I could make a more informed decision, but for now it'll probably be ok. I've not found any numbers on the transmission, aside from a torn off sticker that says something like 309 and the rest is missing (I'll double check later).

The cast cover will work on a 12A trans 81-85.

There is a thin front bearing and a thick front bearing. All 4 12a trans I've worked on had the same bearing.

Also the pivot balls are different. There are two sizes that fit the 13b cover. No, your aluminum 12a cover pivot ball will not work on the cast iron one because the cast iron one is thicker, so the ball shaft is shorter.

The cast cover is a more rubust piece and the TO bearing shaft wont wear out nearly as fast as the stock aluminum cover.

the covers come with the pivot balls when you buy them new.

the aluminum cover was installed on the 12a trans thru 85, it was even available as a new part up until a few years ago, when it was superceeded with the iron one.