First gen rear axle swap

SLUF

SLUF

New member
Looks like I have a good find on a disc brake rear axle assembly for our POS-7. Any one swapped out a drum rear to a disc rear on a first gen? Any trouble spots beyond R&R? I need to do a bit of research on the existing braking system to see what else needs to be changed (proportioning valve, hard/soft lines and such). Just wanting to see if there is some knowledge to be gained before I start on the project. Thanks!
 
SLUF said:
Looks like I have a good find on a disc brake rear axle assembly for our POS-7. Any one swapped out a drum rear to a disc rear on a first gen? Any trouble spots beyond R&R? I need to do a bit of research on the existing braking system to see what else needs to be changed (proportioning valve, hard/soft lines and such). Just wanting to see if there is some knowledge to be gained before I start on the project. Thanks!
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You had drum brakes??? No wonder you had braking issues!

What year is the Disk Brake rear end?

This matters because there are differences between the rear axle housing and drive shaft flanges depending on year.

Differences.

84-85 models have bigger axles and bigger axle bearings
79-83 models have smaller axles and smaller axle bearings
79-82 models have smaller drive shaft flanges
83-85 models have larger drive shaft flanges

Interchanges

The third member will fit either the big or small bearing axle housing - the side gears in the third member are specific to the size of the axle.

The drive shaft flanges interchange on the pinion.

Mazdatrix list different part numbers for master cylinders for cars with rear drums vs cars with disks. Regarding the prop valve I would check the Mazdaspeed web site. You can see part numbers by reviewing manuals for 79-85 mazdas.
 
Thanks Scott, that helps a ton. Our car is an 85 and the unit I am getting is an 84 or 85 so should bolt right up as far as I can tell. I found the same info about the master cylinder so that's something I'll need to get. Hoping to have this all done by Gateway in March!

How's your STU project coming BTW? I'll be in STU with Trey in IT7 this time around. I have requested a move from big bore GT/T1/EP to the T2/T3/SSC/SSB/SM group too. The chief steward did this for us last year so I figure it will be OK this time around.
 
SLUF said:
Thanks Scott, that helps a ton. Our car is an 85 and the unit I am getting is an 84 or 85 so should bolt right up as far as I can tell. I found the same info about the master cylinder so that's something I'll need to get. Hoping to have this all done by Gateway in March!

How's your STU project coming BTW? I'll be in STU with Trey in IT7 this time around. I have requested a move from big bore GT/T1/EP to the T2/T3/SSC/SSB/SM group too. The chief steward did this for us last year so I figure it will be OK this time around.
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Glad to help....you'll like having rear disk brakes. It does make a difference.

My STU project is going slow but I knew it would because I am changing....well...everything. My goal is to test in the fall of 2010 and race again in 2011. I am also being held up by the rules a little - the cage rules in STU/STO are not well defined. So the CRB is looking at this.

I like the T2/T3/SSC/SSB/SM run group too but keep in mind that AS may be in that group from time to time. Uiltimately my car would work in either group...it will have EP power with "maybe" better aero.
 
We haven't had any "prepped" STU cars yet in the division so yours may be the first! Trey and I are building an E30 Bimmer specifically for STU and expect to have that on track late next year sometime. The engine we acquired for this is already prepped beyond IT specs for sure! We think once its installed and with a bit of tuning work we should see 200 whp or better. After we get that one done I'll feel better about running with the big dogs. It will also fit nicely in with Brand N and Brand B club racing groups too.
 
SLUF said:
We haven't had any "prepped" STU cars yet in the division so yours may be the first! Trey and I are building an E30 Bimmer specifically for STU and expect to have that on track late next year sometime. The engine we acquired for this is already prepped beyond IT specs for sure! We think once its installed and with a bit of tuning work we should see 200 whp or better. After we get that one done I'll feel better about running with the big dogs. It will also fit nicely in with Brand N and Brand B club racing groups too.
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Nice - should be a good car. Hopefully there will be more cars in the class as it catches on. I expect to see allot of Honda with Acura engines in the future.

If I do another car it will be a 12A powered Miata or 2nd gen RX7. Gotta stick with a rotary......

There is an ex World Challenge Lexus IS out of Oklahoma - Ron Pawley is the driver. His lap times are comparible to mid pack EP.
 
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