Rear axle ratios?

[tdw6974]

Ok have accumulated 2 extra Diff assemblies plus one in car all LSD. Are the housings marked any way to determine ratio with out counting gears ? I know about the 5:12 ratio (with some work) but a 4:88/4:90 has been mentioned. Thanks TW

[lateapex911]

Are they set up?? Can't you just turn the input and count the revs?? Or am I missing something?

[C. Ludwig]

All 5-speed cars had a 4.10 ratio except the GTUs which had a 4.30. All auto cars had a 3.90. Turn and count like Jake said or count teeth and divide if they're disassembled.

[Eagle7]

Yes, the most common non-stock ratios for racing are 4.88 and 5.12.Both are pretty expensive because they're not manufactured for the 2nd gen. You have to buy a 1st gen gearset and have a very good shop cut the shaft off and weld a longer shaft on.

[billf]

Marty,

Where are those ratios sources from? I only knew of them from various tuners who had actually done the work.

Good racing,

Thanks,

Bill

[Eagle7]

IIRC, you can buy either gearset from Mazda and have it sent to your shop. You also send them a donor diff. They cut the shafts of both the donor and the new gear and weld the long shaft to the new gear. Then they'll assemble the diff with the new gearset. I think ISC and maybe SpeedSource will do the work for you. I don't know if there are others.

[Andy Bettencourt]

Marty is right. You can buy a 4.10, 4.30, 4.44, 4.88 and 5.12 R&P from Mazdaspeed. The 88 and 12 need cusomization to work on the 2nd gen RX-7.

We are working with a partner to get these built as suppliers around teh country have dried up. Call Mike at ISC but I think he is done with them...

[gruff]

I realize that I am a little late to this thread. Any word on new suppliers?

Thanks,
Jason

[mbuskuhl]

ISC has (1) 5.12 in stock listed for $2450 on their site.