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RX7 rear axle ???

nomad

Yoda
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Just curious about fitting an rx7 rear axle to a spridget. Are there any tech articles on this??? Know that a 81 to 83 axle is preferred. I can get a 84 which, according to wikipedia, has a different wheel bolt pattern than the earlier axle. Mainly wondering if the earlier pattern is 4 inch and will bolt up to spridget wheels and how much work is required to narrow the axle?

Kurt.
 

Jim_Gruber

Yoda
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Kurt, I may be wrong but I think the guy that built The Mite used an RX-7 Axle. Google The Mite if you've never been there before. He used something to keep the turbo Miata engine from breaking rear axles. Maybe he adapted a Miata Rear End and a 4 link. Now I've got to go back there and look.
 

aeronca65t

Great Pumpkin
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There is a guy on the MGExperience that is going to narrow a ford 7.5" since they are cheap and have a wide range of gear ratios. I think he said the shortened axles were going to cost $300, but when he is finished he'll have LSD and disc brakes. He said he'd try to weigh it when he gets it finished.
 

Westfield_XI

Jedi Warrior
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Follow the link in the article on the Mite to Moser and give them a call. They have probably done this conversion several times before. This sort of work is their speciality.
 
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nomad

Yoda
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Thanks much folks, I've been busy or would have been back quicker. Just daydreaming about building a spridget with a lot more power. Knew I had seen some of that stuff here before. Wish I had a lathe!

Kurt.
 

regularman

Yoda
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I wonder if it has to be an rx-7 diff. I is it that much tougher than others? Some of the Mustang II models with the 302 engine had the 9 inch rearend, as did a few with the V6(my 74 model did). I also have a Kia sportage and it has a pretty marrow rearend with a solid axle in the back and weighs in at about 3000 pounds with a 2 liter engine and has been through hades and no diff problems.
 
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nomad

Yoda
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I imagine it could be a lot of different axles but the RX7 axle has limited slip and disc brakes and is light and tough. One has to consider unsprung weight or handling will go away. I know of a bugeye with a hot rotary and a 9 inch ford rear that goes like stink in a straight line but gets whooped in autocross.

Kurt.
 
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apparently, the gearing of most rx-7 diffs is somewhere around 4.11
 
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nomad

Yoda
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Ah, good call, Trevor. The Mazda wankel would be a high revving engine which would explain the low rear gears. So would the ford be light and make for a good swap? How about other suggestion's--someone mentioned a rear axle from a Subaru. Early 80's is getting pretty old for japanese stuff. Nissan at least does'nt support any of the old stuff. The guy with the bugeye that a friend told me about may have other handling problem's. Higher unsprung weight should only be a factor on rough surface's.
Any pictures from the MG experience guy? I'll see if I can find the site.

Kurt.
 
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He hasn't made the swap yet, but based on his other work ... it'll get done and he'll post pictures.
 

JPSmit

Moderator
Staff member
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I haven't seen Phil on the site recently but he runs an RX7 rearend on his Sprite.
 

regularman

Yoda
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nomad said:
Ah, good call, Trevor. The Mazda wankel would be a high revving engine which would explain the low rear gears. So would the ford be light and make for a good swap? How about other suggestion's--someone mentioned a rear axle from a Subaru. Early 80's is getting pretty old for japanese stuff. Nissan at least does'nt support any of the old stuff. The guy with the bugeye that a friend told me about may have other handling problem's. Higher unsprung weight should only be a factor on rough surface's.
Any pictures from the MG experience guy? I'll see if I can find the site.

Kurt.
The Subee would be an independent rear. That gets a a lot more complicated. I am trying to think of something that might work and have a higher ratio, yet still be light.
 
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