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Old 10-13-2008, 03:04 PM   #1
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Default 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
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Old 10-13-2008, 04:59 PM   #2
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Interesting. $350 for the "kit", but then axles are $1750! 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.
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Old 10-13-2008, 08:35 PM   #3
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Originally Posted by patsmx5 View Post
Interesting. $350 for the "kit", but then axles are $1750! 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.
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Old 10-21-2008, 02:13 PM   #4
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Interesting since I can get the same axles made for 500$, I guess a 1250$ profit isnt bad.
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Old 10-21-2008, 02:30 PM   #5
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Originally Posted by patsmx5 View Post
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.




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.
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Old 10-21-2008, 02:45 PM   #6
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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.
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Old 10-21-2008, 07:59 PM   #7
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all 89+ birds had IRS IIRC
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Old 10-21-2008, 08:03 PM   #8
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Apparently the setup they are selling really limits the size of the exhaust that can be used, time to start looking at the competition.
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Old 10-21-2008, 08:07 PM   #9
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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.
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Old 10-21-2008, 08:46 PM   #10
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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.
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Old 10-21-2008, 11:26 PM   #11
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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.
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Old 10-22-2008, 07:32 AM   #12
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I'll have a 3 inch single with the v8roadster kit. My diff is already mounted. Just waiting on other ****. I could probably run dual 2.5s if I need to.

Frank
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Old 10-22-2008, 01:34 PM   #13
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I'll have a 3 inch single with the v8roadster kit. My diff is already mounted. Just waiting on other ****. 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.
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Old 10-22-2008, 02:00 PM   #14
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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:



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



Frank
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Old 10-22-2008, 02:01 PM   #15
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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
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Old 10-22-2008, 03:01 PM   #16
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Quote:
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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.

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$
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Old 10-22-2008, 03:02 PM   #17
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Do you think it will handle the the abuse that a 500+ hp car would give it while drag racing on slicks?
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Old 10-22-2008, 03:15 PM   #18
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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
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Old 10-22-2008, 04:02 PM   #19
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Do you think it will handle the the abuse that a 500+ hp car would give it while drag racing on slicks?
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.
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Old 10-22-2008, 04:27 PM   #20
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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.
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