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Looks like they moved away from the Chevy differential to the Ford 8.8 for the LFX Totality swap, and in typical Andrew Keisler style this is so simple and well thought out. If I didn’t already have OS Giken LSDs for my RX8 differentials I would have done this instead. No welding required (on 2004 - 2007 rear subframes), no excessive weight addition of heavy carbon steel parts to paint or rust, just drill some holes for the front aluminum mount, install the new aluminum rear cover with integral mounting ears, and boom; done.
No on the axles because I’m sticking with the Mazda diff/axles for now as stated above. You can also buy 8.8 diff axles from the other RX8-8.8 Ford diff suppliers as far as I’m aware.
Keisler does have a trans support brace, but it was intended for the LFX engine/trans. I don’t see it listed separately, but I know he’ll sell it because I already bought one for the purpose of adapting it to the non-Mazda transmission I’ll be using. You should be able to position it where needed, but the urethane mount between the brace and the trans may need to be different/modified depending on what your combination is.
so for the Mazda diff support I bought the bolt-on mount he previously had for the Chevrolet differential. Which only attached on one side of the differential housing. My intention is to use the PPF mounting tabs on the Mazda diff and fabricate a new bolt-on piece for mounting there and then it having an attachment point out to the side to accept the mount bushing
I just need it to have the bushing mount out from the the side of the structure that bolts on in place of the PPF as you can see on the front nose of this Chevy diff housing picture below:
Thanks for sharing. Is that an early 2008? Because Andrew said in the video that the bolt-on mount only works on the 2004 - 2007 subframes and that 2008 - 2012 will need the weld-on mount instead. However, the subframe difference was likely a running change leading up to the 2009 models that did receive a slight rear suspension geometry modification. So I could maybe see how there might be a transition period in there between the late 2008 S1 and early 2009 S2 models.
So here’s a pic that shows the installed transmission brace. You can see how the mounting brackets fit and then bolt on over the two inner frame rails. So it’s going to allow moving the support fore and aft some for other transmission fitments because those rails are straight and don’t vary a lot wrt their dimensional size. So you can then set it to align for your trans and then drill the mounting bolt holes for that fitment.
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Which I also circled the diff for the previous Chevrolet differential and then on a Mazda diff in the pics below to demonstrate how the piece I’ll make to bolt onto the Mazda diff PPF tabs will extend out to catch the subframe mount bushing.
Is that an early 2008? Because Andrew said in the video that the bolt-on mount only works on the 2004 - 2007 subframes and that 2008 - 2012 will need the weld-on mount instead.
Most likely an early 2008 model, but I can't confirm since my car is with Andrew currently. He gave me the same information when we were still planning things out. IIRC I asked for the weld-in mount instead of swapping to an older subframe, and clearly there isn't any evidence of that being done in the photos I have, so there must be a crossover somewhere in the model year like you said.
none really, the only reason to go there is if you need a taller gear ratio than you can find for the Mazda diff, which these lower peak rpm reciprocating piston swap engines generally
require.
because as I stated on this many times; the OEM axles and CV joints aren’t really the limiting factor. The limiting factor for power level is the splined axle end that goes into the rear RX8 hub. that these axle kits attach to. It’s what ends up shearing off first. So far all these Ford 8.8 kits offer is the axle assembly that reuses the RX8 hub axle.
So until somebody offers that part in a much stronger material then it’s always going to be the weak link in the axle power level chain. I wouldn’t be surprised if Andrew doesn’t come up with something for that though. Because he’s generally thinking on that level, but it may end up not being cost effective/viable to offer.
This 20B RX8 from way back on the forum history archive started shearing those splined ends around 800 whp
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Which is partially why I had decided to pursue reusing the RX8 differential instead after finding the Mazda 8” 3.73 ratio r&p option along with having an extra OS Giken LSD on the shelf. Also because those other kits add a lot of steel plate to weld in on the subframe, that then offsets the weight advantage of the Ford 8.8 aluminum housing.
However, this Keisler kit does away with all that steel plate and welding and in the end it will help knock off enough weight to consider it. I might have given thought to going this route instead for the non-Mazda trans swap then, but going and buying the 8.8 diff, the right r&p, the LSD, the rebuild cost, the 8.8 kit, the axles, etc. still ends up being a pretty good chunk of money. A lot more than I’ll have in my Mazda setup. I’m only shooting for 500 whp. There are people doing more than this on the OE diff/axle parts.
When’s the last time you heard of anyone breaking these parts? For me it was that 20B in the pics above from 15 years ago … I could see an LS type engine cranking out big torque with wide sticky tires doing it.
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to add in to my comment about the splined hub axle piece being the weak link, if you start shearing that off it can’t be purchased separately from the axle assembly
For what it's worth, I sheared an axle this year at the Charlotte Pro. It was at the diff end of the shaft. I haven't managed to kill any at the hub (Mazda) end yet.
I have the Ronin kit... Very happy with it, they replaced the axle free of charge. My car is somewhere around 450-500whp depending on tune.
it’s likely more torque than hp related. I can’t recall what lb-ft the 20B turbo was making. At 800 whp it had to be 500 - 600 maybe.
In your case that would be the Ford 8.8 diff axle end though. Which might imply it’s weaker than the Mazda one?
Unless there was possibly something else going on. Hard to say or be sure.
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The failure looked to me like the original Ronin axle had a groove machined in that didn't need to be there. And the machining wasn't the best quality. I'm also adding a clutch delay valve to soften the initial shock-load, even though mine didn't fail on the initial clutch dump.
They sent me a replacement axle which is a lot nicer looking. They also have some beefier parts coming which will replace the hub (Mazda) end, but those aren't ready yet. I have spares now so I'm ok with where things stand.
The 8.8 axle kit is out, first class job as always from Andrew:
Originally Posted by 1StopJeff
Great write up. Here is a picture of the Ford 8.8 Diff installed in the rear subframe since Andrew has since gone to this configuration. Also pictured are the latest half shafts.
La1rx8.com makes a 33 spline hub for the rx8 so you can have fully overbuilt axels. Downside of that is your now dependent on that guys custom hub. For racing I’m not sure I’m ok with that. Easier to get custom axles made and replace axels and broken cv’s
im moving to the ford 8.8. Gm discontinued pretty much all 5th gen Camaro driveline parts. I recently broke a Camaro inner cv. Was a less than encouraging experience to get up and running again. Only off the shelf option is to go to drive shaft shop which seems terrible or a junk yard for another inner cv. I went the junk yard route and put good grease in them.
aftermarket axels are not made to the same spec so that wasn’t an option.
10-14-2022, 08:29 AM
