Wagon Owners... food for thought, rear axle

Suspension, including wheel, tire and brake.
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DMS
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Wagon Owners... food for thought, rear axle

Post by DMS » 21 Jul 2009 08:46

So I own several other Datsuns models. Because of this I do a lot of reading on other forums.
One of my other models is a 68 2000 Roadster that is in the middle of a frame up resto. Ive been watching a thread over at 311s.org about rear axles for the Roadster. The Roadster has as very similar axle to the 510 Wagon. They have the same spring mount positions. The e-brake pivot is on the opposite sides from each other. The non-adjusting brakes are pretty much the same. The spring packs are interchangeable, though they arent the same load rating.
So in this other thread has been sourcing a new axle to swap in.

Check this thing out.
"
Mazda RX-7 GSL-SE Rear End Swap by Spriso Motorsports


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So, the SR swap is done, the car is running great, is a hoot to drive, but the lack of a limited slip differential is frustrating, and no matter how much you water them, the money trees in the back yard never seem to grow fast enough to purchase the unobtainium factory limited slip. Even if the factory limited slip differential were to magically show up, there are very few service parts for it available… so what to do?

There are several alternative limited slip carriers available out there, but they are either very expensive, fragile, or locker-style spools—not the best thing for the street. There is an alternative that is worth exploring however! I thought that I would share our take on the Mazda RX-7 rear axle conversion that we are doing in our Datsun Roadsters up here at Spriso Motorsports.

While not as exotic as a four-link conversion like what Alvin recently had built, the RX-7 conversions that we are building are bolt in upgrades to the existing roadster rear leaf springs.

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In 1984 and 1985, Mazda offered the GSL-SE model which had the upgraded 1.3 liter 13B rotary engine. The GSL-SE had more power, so the Mazda engineers made suspension and brake upgrades to the aging RX-7 chassis to handle the extra power. While Mazda had previously offered a rear-disk brake setup, the GSL-SE had upgraded axles, a new 4 x 4.5 bolt pattern (same as our Datsuns!) vented rear disk brakes, and an upgraded limited clutch type slip differential.

With a little searching at the local wrecking yards or Craigslist, GSL-SE’s can be found, usually with the rear end intact. You will want to pull the entire axle assembly from the car (but you can leave the crazy control arms for a fellow RX-7 enthusiast—we won’t be using them!

Once you have your donor, set up the axle assembly up on the bench, drain the differential fluid and disassemble the axle assembly. When you are done, you should have a bare axle housing that looks like this:
http://farm4.static.flickr.com/3605/33 ... 89.jpg?v=0

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Hmmm. Not so sexy with all those brackets and stuff welded to it… We won’t use any of this bracketry, so out with the plasma cutter or a cut off wheel and let the sparks fly! We won’t have to worry too much about the first 4-5” of the ends of the housing, as these will be removed when we shorten the housing to fit the roadster chassis.

Now it is time to measure and ask yourself what your plans for rear wheels and suspension are. This is a perfect opportunity to allow you to narrow your rear end a bit to fit larger wheels and tires and still get them to fit under the stock roadster sheet metal.

In my case, I wanted to have a housing that was ¼” narrower on each side than the stock roadster wheelbase of 48.5”. I have a 15x7 15mm offset wheel stuffed under my 66’ rear fenders that very occasionally would rub the outside fender. By shortening the housing just a bit, they will now clear without rubbing.

Others wanted to put even more rubber under the stock fenders and we were able to shorten the housing even more to a 47.5” width. By playing with wheel and tire combinations, this car has a 225/40/16 stuffed under the rear wheel wells with on a 7.5” wheel.

Once you have measured once, twice, and three times, cut the end flange assemblies off of the housing. This is easily done with a cut off wheel by cutting through the weld at the end of the casting. If you do it right, you can knock the flange assemblies off with a hammer once the weld has been cut. This leaves the finished edge at the end of the housing that we can now measure from.

Once you have determined how much you are going to shorten the housing, cut the ends off in a band saw (or suitable cutting device). Dress the ends of the cut with a slight chamfer to remove any burrs.

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The axle end flange assemblies won’t fit the now-shortened tube, so they will need to be opened up on the lathe so they will fit.

Since we are going to bolt the Mazda axle assembly to the roadster chassis, we need the original spring pads off of the original axle housing. These are easily removed with a cut off wheel. We cleaned and dressed the edges and put them in the bead blast cabinet to get the 40-years of patina off of them.

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We set the axle housing up on two blocks on a level surface and put the original roadster spring pads onto a specially built jig that spaces the spring pads correctly. The Mazda axle housing was placed on the spring pads and the pinion angle was set. Datsun set the original pinion angle at 6-degrees and we copied that here.

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We triple checked that the housing was sitting centered on the jig, with the same amount of material sticking out both sides. Once satisfied that the housing was centered on the jig, the pinion angle was set and the spring pads were tacked to the Mazda axle housing. Again, the angles and measurements were double checked one last time, and then the spring pads were welded onto the housing.

Our JIG has the location of the original traction bar bracket built into it, so the traction bar was welded to the housing after being ground to suit the Mazda axle housing. The brake T-fitting was cut off of the original roadster housing and welded on as well.

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Now that the axle was sitting on the spring pads correctly, the end flange assemblies can be welded on. Since we used the original RX-7 rear brake calipers (with the built in emergency brakes) we welded them on in the same position that they were on from the factory.

To make sure that the end flange assemblies were welded on square, special centering quills were machined which fit inside the flange assemblies. A 1.25” bar of TGP (Turned, Ground and Polished) bar stock was run through the center of the quills to keep everything nice and aligned. It is critical that the flange assemblies are welded on square and straight to the housing to keep everything nice and happy.

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The end flange assemblies were TIG welded on and the quills and centering bar were left in the flange assemblies until the assembly had fully cooled so we would be sure that everything is was nice and square.

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The axle housing was then sent out for powder coating!

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The RX-7 axles were sent up to Dutchman up in Portland, Oregon and were shortened and re-splined to match the Mazda differential. At this time, Dutchman charges $45 per axle.

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New brake lines were built and the axle assembly fully built with new calipers and rotors. This one is being installed in Eric's SR20DET project.

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There are a variety of gear ratios and LSD center sections that can be run depending on what you want to do with the car. The Miata Torsen limited slip carrier can be used (which several of us are going to be using in our personal cars) or the factory LSDs can be rebuilt with new clutch packs from Mazdaspeed.

This project would not have come together without the talents of Dave Jolliff, Mike Braaten, and Eric Straw. We have a great crew that is all getting these rear end swaps into their cars this summer. Every one that we are building is a little different to suit the needs of the individual owner, but I thought that I would share the process...

Michael Spreadbury
Spriso Motorsports

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Spriso Motorsports
http://www.spriso.com
SR20 Powered Roadsters
Kits Available! See Vendor Section!
"

"We have done 5 axle housings at this point, the race will be to see who gets theirs in their car first!

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More soon,

Michael
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Sorry 311s.org doesnt have an easy way to link to their pages so I copied the whole thing.

Im not looking at this for my roadster. I believe the roadster axle has a shorter length than the 510 axle but I am to lazy to actually walk out the door with a tape measure and spend the time to find out... I know lame. I am considering this for my Wagon and thought it was some good info to pass along to other wagon owners to consider. Maybe someone will get to it before me and critique it...lol


Ray

Benzo
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Re: Wagon Owners... food for thought, rear axle

Post by Benzo » 21 Jul 2009 09:15

that would be a great upgrade? if I had some money I would do this as I have been looking for at least a gear upgrade at least for my wagon but this would open up doors in other ways. wonder what they charge for this mod?

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vgwagon
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Re: Wagon Owners... food for thought, rear axle

Post by vgwagon » 21 Jul 2009 10:22

http://www.the510realm.com/viewtopic.php?t=4766#p41853

I've done this already.

I have since twisted the left axle at spline engagement but I still run it.
Other than that it seems to be holding up very well to my VG.
Denis Gagné
AKA VGwagon

69 510 VG30e swapped
73 240z VG30et swapped
86 300zx na2t VG30et converted

tornadom
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Re: Wagon Owners... food for thought, rear axle

Post by tornadom » 22 Jul 2009 10:58

Wow, the finished product looks amazing!
Last edited by tornadom on 23 Jul 2009 16:50, edited 1 time in total.
2009 Honda CBR600RR | 2006 Ford F150 4x4 | 2002 Yamaha YZ250 | 1972 Datsun wPL510

tornadom
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Re: Wagon Owners... food for thought, rear axle

Post by tornadom » 23 Jul 2009 15:09

What is the ring gear size on one of those axles? I would love to find a stouter rear axle for my wagon, one that could handle more power, provide options for a limited slip and even accept disc brakes. To that end, I have looked into narrowing an 8.8" Ford rear axle out of a '96+ Ford Explorer. These axles are plenty beefy (Mustangs can launch hard enough to pull the front tires off the ground with few axle upgrades), offer a ton of after market support and are already equipped with disc brakes and leaf springs under the axle.

With that said, I am always open to new options (like the one presented in this thread).
2009 Honda CBR600RR | 2006 Ford F150 4x4 | 2002 Yamaha YZ250 | 1972 Datsun wPL510

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okayfine
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Re: Wagon Owners... food for thought, rear axle

Post by okayfine » 23 Jul 2009 15:47

tornadom wrote:What is the ring gear size on one of those axles? I would love to find a stouter rear axle for my wagon, one that could handle more power, provide options for a limited slip and even accept disc brakes. To that end, I have looked into narrowing an 8.8" Ford rear axle out of a '96+ Ford Explorer. These axles are plenty beefy (Mustangs can launch hard enough to pull the front tires off the ground with few axle upgrades), offer a ton of after market support and are already equipped with disc brakes and leaf springs under the axle.

With that said, I am always open to new options (like the one presented in this thread).
Spriso tends to install SR20DET swaps into Roadsters as well, so the durability should be there for a stock-to-mild SR turbo hit.

That said, the Ford solution would be how I would go about things. It's also the route Anthony Schwislow went with his Supra turbo 510 wagon.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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Re: Wagon Owners... food for thought, rear axle

Post by tornadom » 23 Jul 2009 16:55

okayfine wrote:That said, the Ford solution would be how I would go about things. It's also the route Anthony Schwislow went with his Supra turbo 510 wagon.
When all is said and done, my wagon should be sporting a mildly built 302 Ford and is probably better served by the 8.8" axle. Searching the Internet I came across an olive drab green Wagon with an MK3 Supra Turbo motor, I didn't look into it too deeply, but it may have had an 8.8" rear axle swapped in.
2009 Honda CBR600RR | 2006 Ford F150 4x4 | 2002 Yamaha YZ250 | 1972 Datsun wPL510

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rnorrish
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Re: Wagon Owners... food for thought, rear axle

Post by rnorrish » 23 Jul 2009 18:03

that would be Anthony Schwislow's wagon, mentioned above.
richard norrish
'68 'goon resto / '71 ice racer / '72 'goon project / '70 4-door rust pile / '67 520 project
----------------------------------------------------------------------
shardik wrote: My swap will be made of solid gold and it will run on puppy farts.

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Re: Wagon Owners... food for thought, rear axle

Post by tornadom » 23 Jul 2009 22:30

rnorrish wrote:that would be Anthony Schwislow's wagon, mentioned above.
Good to know. I visited his Car Domain page on a few occasions - it seems like a nice car.
2009 Honda CBR600RR | 2006 Ford F150 4x4 | 2002 Yamaha YZ250 | 1972 Datsun wPL510

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