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1st gen RX7 solid rear end in 240Z?


Guest 73TPIZ

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Guest 73TPIZ

I've been toying w/ the idea of putting a solid axle under my Z. I have a borg warner rear w/ posi and disks from a '86 TA but i'd have to shorten it and buy new axles, etc, etc. Fabbing the suspension wouldn't be a prob for me but it would still cost a lot of money. Anyway i did some research and saw that a rear from an 84-85 RX7 w/ the 13B motor is pretty close to the Z.

 

1. 55" track is only 2" wider than Z

2. 4 on 4.5 bolt pattern is same as Z

3. Already has 10" disk brakes

4. Has LSD

5. Most have 3.9 gear (i'm running 3.7 now and want to go to 15"

wheel so it would still be close)

 

Anyone tried this or know of any inherent probs w/ this setup.

It wouldn't have to be bulletproof as i prob won't ever push more than 300hp to it and my trans is automatic.

 

any help would be appreciated. thanks

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Guest 73TPIZ

Yea, i thought as small as the rx7 is, the rearend was probably weak.

 

Since they race the RX7's in the scca? and spec? events, would there be a chance that someone makes stronger rear ends for a reasonable :rolleyesg: price?

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Since they race the RX7's in the scca? and spec? events' date=' would there be a chance that someone makes stronger rear ends for a reasonable :rolleyesg: price?[/quote']

 

Doesn't that statement invalidate you goal to do this cheaply? If you're going to start buying new stuff, and want to go solid axle, then just shorten the one you have?

Tim

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Guest 73TPIZ

yea Tim, seems to be major cash either way.

 

When i said race rear end earlier i meant stronger internals. i was just thinking i could get away with stock internals for awhile since i'm only running a 305 w/ automatic then upgrade later. But $100-shorten my housing, $400-new axles, $200-ring & pinion in ratio needed (3.7-3.9), $200-rebuild kit, $100-setup at rear end shop, and ?-redrill rotors for new axles just seems hard to swallow at one time. $100-200 for bolt/weld in mazda rear and throw $400 at it a year from now doesn't turn my insides so much.

At least with the borg warner i'd know what i had. Still $1200+ for the rear when i don't even have that under the hood seems a little ridiculus. I could prob get a 'vette IRS and shorten it for that.

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Guest 81na ZX

Where'd you find ring and pinion for $200 :shock: Racing Beat is one of the only places I've seen them and everyplace has them for ~$600

 

One plus to this setup - Mazda rear ends are almost all interchangeable, so the internals of a Miata w/ a Torsen LSD will bolt right into a FB rear axle.

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Guest 73TPIZ

81naZX,

 

Those were prices on shortening my GM rear. I knew Mazda would be higher but geez :ugg:. Thanks for the info on interchangeability if and when i go with that setup.

 

How much can be swapped out from later Mazdas to upgrade once i have the RB housing installed. you mentioned the posi unit. How 'bout rotors, calipers, etc. or is the posi about it? Everything else aftermarket? i have access to several salvage dealers around here is why i ask. later.

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Guest 81na ZX

IIRC quite a bit of brake stuff. But I'd suggest checking out the RX-7 boards ( http://www.rx7club.com ) for the best info on that kind of stuff.

 

Mazda was preatty good about it, but once Ford got their hands in there, stuff began getting totally redesigned.

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