Boss Frog Differential Subframe and Axles
 

They finally released some details and pricing on these items. I think I will be placing an order in a month or two. Will definitely be a step in the right direction for me and when I do eventually do an LS swap I won't need to worry about messing with the rear end at all. Any thoughts or opinions?

Here's a link to their site if you aren't familiar with the kit:
http://www.bossfrog.biz/Miata_V8_Swap.html

Interesting. $350 for the "kit", but then axles are $1750! :eek5: I might would buy the stuff to bolt in a 8.8 and then make my own CV joints.

And funny thing is the t-birds had a 7.5" IRS diff, not the 8.8 IRS IIRC. 8.8's were for Cobra Mustangs and Lincoln Mach VIII's. I think, anyways.

v8 birds had a cast houseing 8.8, the marks have an all aluminum housing.

Interesting since I can get the same axles made for 500$, I guess a 1250$ profit isnt bad.

My 87 turbo bird has a 8.8 solid, with disk brakes from the factory.

Pretty sure the Supercoupes 89+ had 8.8 with IRS.

Hmmmm. I thought all the T-birds and Cougars had the solid axle till the mid to late 90's, when they went to the 4 cyl FWD. I belive I pulled a solid axle 8.8 out of a 93 cougar.
I'm not for sure about the Supercoupe. It was a beast of it's own.

all 89+ birds had IRS IIRC

Apparently the setup they are selling really limits the size of the exhaust that can be used, time to start looking at the competition.

Limits it how much? If you can fit 2.75" or so you should be fine considering you'd probably be running duals with a V8 anyway.

The biggest he said was the 2.25" that they are currently running. I could fit duals, but I don't really want to unless I don't have any other options.

The more I look at the costs involved with any of the rear ends offered, the more I really want to just forget buying a kit from someone and just have it all custom made.

And that is why the v8roadsters kit uses the CTS diff. It is new, available for around $5-600 on car-part.com and much smaller than the ford diffs. I believe they are using up to 3" exhaust on their car. Still extremely expensive, but the boss frog kit doesn't come with the diff either. Both kits are exactly the same price when you get the complete conversion.

I'll have a 3 inch single with the v8roadster kit. My diff is already mounted. Just waiting on other shit. I could probably run dual 2.5s if I need to.

Frank

Do you think you could post a few pictures of that setup actually on the car? I'd really appreciate it.

Here's the pic of the diff mounted without the brace that runs under it:

http://forum.miata.net/vb/attachment...chmentid=63836

Here's a pic of the diff with the pipe mounted. This is a v8roadster pic:

https://publish.comcast.net/rpath/Kd...GgZ0Xb4zyBiso/

Frank

In the first pic, I don't have the front mounting point welded on and I don't think I have the bolts torqued all the way up, so it sits a bit lower than when it is bolted up completely.

Frank

Something is wrong when its cheaper to go out and buy all the tools + axles you need then to buy BOSS axles!!! I found 3 places that all could custom make CV axles to just about any conversion you wanted for 225$-250$ per side


BOSS AXLES - 1750$

Custom made axles - 500$
MIG welder 500$
Torch 400$
total 1400$

Do you think it will handle the the abuse that a 500+ hp car would give it while drag racing on slicks?

I doubt many will be running a 500hp+ car with slicks. Wheel hop seems to be the demise of the CTS diff in the highly tuned CTS-Vs out there. I'll be traction limited most of the time so I don't see a problem in killing the rear end.

FWIW, FM is doing a few LS3 swaps so they're starting with cars closer to that power point.

Frank

First H.p. doesnt matter. Its torque that breaks axles. And the last place I checked said they ran the same CV joints behind a modified 460 big block.

I think a better question would be how much torque do you think the diff will take.

I think everyone here knows this and the number was thrown out there just to give an estimate of the overall power level I am talking about. :jerkit: