RoTARY-ReX

would 2nd gen 4.10 gears fit in a 1st gen '85 GSL?? If so, would it help?? thanks much!!

yayarx7

link:

http://members.aol.com/solomiata/Drivetrain.html

that should answer it.

Pele

iTrader: (28)

Damn. I fucked up my thoughts...

I thought I could take the whole pumpkin out of a 1994 + Miata and stick it in my rear axle housing.

This apparently is not the case as it will fit a 2nd gen housing, but the first gen is not shown.

The ring and pinion will fit, however, as well as the torsen differential package. But then I have to deal with the damn pinion spacers. How do you tell, other than by trial and error, which spacer to use?

I knew it sounded all too easy, especially when there ar so many Miata's that someone has managed to wrap around a pole.

So... Does anyone Know if I can just stick the later Miata pumpkin into the 1st gen rear axle housing?

Pele

iTrader: (28)

Just grab the pumpkin out of a GSL-SE... 4.077 until 12/1984 when they switched to 4.083... Close to 4.10... Damn close.

Not much of a change from your stock 3.909 though.

I forgot to resummarize my plans in my above post.

At first I wanted to build Frankenaxle. Take the stock late rear axle housing wiht large axle shafts, 4.44 ring and pinion gears out of the front differential of a 1987-1988 Mazda B2000 4x4 pickup truck, and the Torsen limited slip unit out of a 1994 + Mazda Miata...

Then I found out that the Miata had 4.3 rear gears. Close enough to the 4.44, and it's one less thing I have to find in the scrap yard. I misread the site and thought you could bolt the Pumpkin straight up to the 1st gen axle... But it was the 2nd gen diff housing they were talking about.

Kill No Cone

iTrader: (6)

Hey Pele,
I just reading Jim Susko's G-Force setup manual and he states that you can bolt the 94+ Miata pumkin into an 84-85 axle housing, and the large Rx7 axles will slide right in.

Now, if you were really going to do the Frankaxle bit, I understand that the next step would be to bend or cut and weld the axle housing to give you 1 degree of negatice camber.

Good luck!

peejay

The pumpkin from the '94-up Miata will work in a '84-85 rearend witrh no problems - it'll work in a '79-83 if you chance the differential side gears.

The gears from a 2nd-gen won't work in either case - the pinion gear is too long.

REVHED

This mx5 diff swap sounds interesting. Does anyone know if all '94+ mx5's have the LSD? If not, which ones do and how can you tell?

Methinks this might be a cheap(er) way to get an LSD in my car.

yayarx7

quote from my above link....

"While the 1990-93 Miata rear had a viscous LSD option, the 1994+ Miata's could have been ordered, based on package, with the superior Torsen type LSD. A poor mans alternative to the Torsen is a clutch type LSD from the '84-88 NA RX-7. They will also bolt into the later 1994+ Miata housing since they are basically the same diff type (the 1989-91 RX-7 LSD will also fit but it is a viscous type, the earlier RX-7's had smaller axle shafts and won't fit). The OEM RX-7 clutch type LSD does have replaceable friction plates and is rebuildable."

Kill No Cone

iTrader: (6)

To find a Torsen rear end you need to look for a 94 to 97 Miata with power windows and a stick.

But, they were not delived to Washington state. (Ok, so maybe they were, but I am still looking for mine). I called a Mazda only recycle parts place in Portland Or and they wanted 1,800 bucks for one. Once I got back up off the floor, I thoiught I would stick with my GSL-SE for a bit longer.

Good luck

Pele

iTrader: (28)

Wouldn't I need U-Joints or CV joints for ANY camber in the rear?

I know you can't put alignment shims ona solid rear drive axle, only the fake solid rear axle on FWD cars.

peejay

You can "fudge" some camber into the rear. Just because it's a solid axle doesn't mean it has to be straight You can get about a degree max of slop in the axle splines. Obviously the closer the "fudging" is to the center the better.

Both of my 1st-gens had about 1/2 degree of toe in on the left side and zero on the right. Bent axle housings. Haven't broke an axle yet!

REVHED

A lot of racers do this to obtain some negative camber but I've heard you need to replace your wheel bearings a lot more often. Don't know if it'd be worth it on the street.

Pele

iTrader: (28)

Would it be easier or harder to fudge that degree of camber if I did the floating axle conversion?

How easy is it to bend the axle housings? Would a sideways slide into a curb at about 20 MPH do it? If so, I'm gonna need a new axle anyhow.

MATRIX XRS

Pele? you still around? In my earlier days I was a regular known as jjbrozak. Its been a while but its good to be back on the forum. Its changed so much, I dont know how to put on pictures anymore. I have a new paint job an am anxious to show everyone. Cheapest rear end mod: I have an 85 gs and swapped the 4.08 out of a gsl-se. It was a noticeable acceleration difference. After it was in I was able to hold a 3 car lead on a 88gxl. We shut down at 95mph. Gears rock!

Kill No Cone

iTrader: (6)

I have heard that some of the Aussies on the forum have spoken about the negative camber mod. (cutting and re-welding rear ends), but I have not been able to find the theard to read their notes.

Have you guys seen that thread before?

theNeanderthol

iTrader: (1)

I want some 4.56 rear gears. Or something around there. Our 5th gear is so steep it doest really screw up highway driveablilty too much. Any cars in a junkyard with some really shallow gears like that?

1st7heaven

Great thread!!! I have been considering having my rear axle bent! Some of the C prepared guys(Camaros, Mustangs, etc.) have done this with success. I have been told a guy here in Dallas has the capabillities of bending axles accuratly....looks like I may do this.

yayarx7

ummmmmmmmmm.....you people need to click on the thread and read it before you post.......


The 1990-93 rear had 4.30:1 gears and there are no factory alternate ratio's available (an aftermarket 4.875 ratio is available). Mazda OEM Gears currently available new for the later 1994+ differential assembly are 3.636:1, 3.909:1, 4.10:1, 4.30:1, 4.44:1, 4.625, and 4.778. The 4.10:1 and the 4.30:1 came on the 1994-97 and '99+ Miata respectivley (4.10:1 on automatic starting in 2000). The 4.44:1 came as original equipment on 1987-88 4x4 trucks on the front axle and some commercial light duty trucks. The 3.909 came as original equipment on the 79-85 RX-7 12a as well as the 99+ 6-speed Miata. The 3.636:1 came on the 79-82 RWD 626 5-speed and is currently available new on the 2001+ Austrailan 6-speed. The 4.625 and the 4.778 come on the Kia Sportage 4x4 on the front axle. The 4.778 is US spec and the 4.625 is unique to the NZ market. Mazda has discontinued the 3.308 (optional on 82-83 B2000 diesel) gears. Steeper 4.875:1 and 5.125:1 aftermarket gears are available. All gears are interchangable as a set. See also Felix's RX-7 drivetrain interchange page page for older model Mazda ratio info. Ring and pinion tooth counts

http://mrmazda.members.atlantic.net/...l#DIFFERENTIAL

peejay

You don't cut and weld to fidge camber. You just heat a small section of the axle cherry-red and let it cool. This shrinks that part of the axle. So to make negative camber you heat a small section of the top of the axle and let it air cool. I've seen it detailed in several chassis/handling books.

twister

To get some negative camber rather than heating you can actually bend the rear end with a custom press (I have seen Rohan Ambose make this press and it works great). Again we do this for our racers here in Oz, but a little far to send your rear-end this far I woud suggest!

A number of us now also use a full floating hub set-up that is cutom made for the RX7 with seperate axles etc, works like a dream! Much stronger, safer, easier to change diffs etc etc and the best I have seen around.

Happy to put the link to the site that sells that stuff if people want it.

Cheers, Twister

Kill No Cone

iTrader: (6)

Hey, Twister, would you add the link to the guys the sell the floating rear end?

Do you have any photos of the press or could you post an email address for Rohan Ambose?

thanks for your time.

1st7heaven

I am in contact with Rohan about becoming a distributor over here?? I have been talking with him for a couple of weeks. He has some great looking stuff!! I will post the web address tomorrow, I have it at work and cant think of it here at home!!!!

twister

hi,

It is from Rohan Ambrose who owns/runs Guru Racing



www.gurumotorsports.com

twister

How are things going with Rohan?

His products are great, he is an excellent engineer and the quality is above anything I have come across before, those floating hubs and Torsens are a piece of art, let alone the gearset.