So, most folks know i broke the torsen, carrier, ppf delete, and trans in the miata this spring. It was ugly.
I just picked up an aluminum housing 8.8 from an 04 explorer with the axles, 3.73 and track lock for $100
Doing a Google for 8.8 swap is quite overwhelming, and contradictory.
I k ow custom shaftes will be needed for the miata outers and ford innners, as well as some fab to mount it.
Can y'all enlighten me on rolling my own swap here? Or did i grab the wrong diff?
I'm proud of you for stepping up. Still going to egg you on to do a burnout on the new setup. You killed the trans also?
Look at Monster Motorsports, I think they're the originators of the 8.8 swap. Axles you might be able to get from DSS.
In reply to Stampie :
Yup. Broke the tailshaft it appears. Oh, and the shifter only finds two gears now.....
In reply to Dusterbd13-michael :
Did the 8.8 in the Molvo
I went with the Monster Miata solution for axles and rolled my own pumpkin install.
The axle assemblies are pretty much Ford parts with a custom shorter intermediate axle and a "broached" Miata hub. I imagine you could buy the shorter axle only from MM or other sources.
From what I can tell, "broached" means that the ford outer stub axle damn near fits the Miata hub and just needs a bit of a tweak to fit.
In reply to NOHOME :
Have any pictures of the mount you did? Give me some ideas of how this lays out. Because honestly, comparing the new diff to what was left of thw old, its massive.
In reply to NOHOME :
I think broached is a normal machining term for how you make splines. Probably a slightly larger OD on the Ford parts and maybe a different spline count.
I would hope the 8.8 is beefier, nobody goes to a Miata 7" for a strength upgrade unless they're starting with a 6" :)
Broaching is graunching a long doohickey (called a broach) kind of like a stepped file, or stepped cutting tool, through the part to cut the shape you need. If you follow Project Binky, they used a simple broach to make the keyway for their front pulley.
Detroit used to machine the flat surfaces of engine blocks with broaches! They rammed the casting through one and it came out sort of the right dimensions on the other side. Because iron is springy, this is why the decks would be saddle shaped or taller at one end than the other... but it was good enough for mass production at the time.
Broaches for axle splines are pretty expensive, so you may have to go to a specific shop who happens to have that size. I know a certain Mazda employed rallyist actually bought the broach to be able to use CX9 axles on his rally car, he never said how much they cost other than ouch!
I owned the old Mongrel Miata which had a Ford 8.8 with custom made(GRM special) axles. They took the inner CV and 1/2 the Ford axle and the other CV and 1/2 of the Miata axle. They then sleeved and welded them together. It worked for a while. One "custom" axle broke at or just prior to the 2003 GRM Challenge and the other broke on me during a glorious burnout while test driving the car with a potential buyer. I ended up calling Martin and getting a pair of his axle shafts. He told me that even they are a bit pricey, he has never had one returned that failed.
DIY axles are possible.
so this is the version i have. Its far bigger than the old.
How does ground clearance work?
Any pictures of brackets?
Anyone use the dutchman axles and the old joints?
Not gonna lie, the size difference is intimidating.
In reply to lotusseven7 (Forum Supporter) :
Possible, but all the ones in the Mongrel broke :) I had a friend with a bike-engined Locost and similarly modified axles, and he broke a few (with sub-1000 lbs and sub-100 hp) before he managed to get a set together that would hold up. So I'd file them under "possible but more difficult than you'd expect". All that gearing multiplied torque goes through the axles and they're a small diameter.
The monster axles are intended for use in 28 spline differentials (I believe all explorer stuff is 31 spline). You'll have to find a junkyard (from Ford, not from FLAPS) set of 7.5" axles then buy the center bar/boots/hubs from Martin. Last I spoke to him he was working on a version using 8.8 axles, its been awhile I wouldn't be surprised if he has them for sale now. After hemming and hawing about the price for awhile and spending some money trying to think of a better solution, I am very happy that I bit the bullet and bought the monster kit.
So, conversion axles are $650 for the shaft only. Then, driveshaft and mounts, boots, and fiddley stuff.
A 3.63 torsen from Britain should theoretically bolt in for 725 to my door.
I already broke one stock rear. Granted it had hundreds of drag launches on it, and was rough when i got it.
What to do?
Are you getting wheel hop? That's hard on a diff.
I couldn't resist.
Plenty of pics in the Molvo build. But I see you are using the Exploder diff, so the mounts will be a bit different.
And yeah...this was one of the areas that I spent a lot of time trying to figure how to same $$$$ and came to the conclusion that there was no easy way. Bit the bullet and got the axle assemblies with new hubs from Martin at MM and it suddenly got easy.
In reply to Keith Tanner :
A little. It was a lot better after platting the carrier.
Would wheelhop account for spitting the spider gears out of it? How much should a stock rear take?
A Torsen shouldn't have spider gears, but I assume you mean you disassembled the internals :) They're good for 400-ish without wheel hop. If you hop them, you have pulled the pin in the hand grenade because you're hammering it with shock loads. I'm not a drag racer but I would be looking at bushings and shocks if I were looking to avoid hop.
Keith Tanner said:A Torsen shouldn't have spider gears, but I assume you mean you disassembled the internals :) They're good for 400-ish without wheel hop. If you hop them, you have pulled the pin in the hand grenade because you're hammering it with shock loads. I'm not a drag racer but I would be looking at bushings and shocks if I were looking to avoid hop.
So that information does not make my decision easier. And I will do my best to take a picture of the gears laying in the bottom of the housing that came out of the carrier that I broke. Regardless I broke internal bits into external bits. Car is primarily an autocrosser and Street beater. I do like to launch it hard though because a Miata with torque is a whole lot of fun.
Nothing wrong with hard launches, but hard launches with hop are a problem :)
Axles are always the surprising cost when you're doing an alternative diff. You could try contacting Driveshaft Shop directly to see what applications they have.
One of the features of the MM rear axles is that the outer CV is smaller than the stock ford part. The original Ford part has some clearance issues with the CV boot and the shocks. Resolvable, but just one more detail.
If you do fab your own mounts, keep in need that exhaust tubes need to get around your work. Boss Frog used to make a nice 8.8 mount kit but getting an exhaust past the hardware was near impossible; it gets kinda tight at the pumpkin.
This was a very helpful resource for me when building mounts for the diff (along with the many examples here on the site).
http://miatav8.blogspot.com/2014/01/rear-subframe.html
You'll definitely want to check if the monster/other axles are compatible with 31 spline differentials. I believe that dss has a set that is compatible but they were very expensive when I last checked.
Shavarsh said:This was a very helpful resource for me when building mounts for the diff (along with the many examples here on the site).
http://miatav8.blogspot.com/2014/01/rear-subframe.html
You'll definitely want to check if the monster/other axles are compatible with 31 spline differentials. I believe that dss has a set that is compatible but they were very expensive when I last checked.
I leaned heavy on that website when building the Molvo. The front subframe in the Molvo was actually designed and built by the site owner ( Mike) and allows for off the shelf headers.
In reply to NOHOME :
If you know Mike please pass along a thanks from me, his documentation across the site was incredibly helpful for me.
The Zoomboni has a 4.3 torsen diff living behind a 5.0 SBF and seems happy so far.
My turbo Miata has one of those euro/Aussie spec 3.63 diffs and is dialed up to around 230 hp.
Eric Anderson ran a 4.3 torsen in his SSM Miata for YEARS until it finally gave up behind 450+ hp and too many pro-solo launches.
My monster Miata came to me with an open 7.5" t-bird rear diff with 3.27 gears. It was comically bad at autocrossing (one tire fire EVERYWHERE). So I found an 8.8" pumpkin from a 93 SuperCoupe with 2.73 gears and Track-loc. Even trading one ford diff for another was a bit of a PITA. Eventually it was easiest to pull the rear subframe to work right side up. Sorry I don't have any pictures.
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