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strenthing my IRS

1350 Views 27 Replies 11 Participants Last post by  M.P. Cobra Fan
Strengthening my IRS

so i have a 99 cobra and its got pretty much every bolt on possible except pullies for now. im about to put a 4.10 in it to liven it up a bit but i dont want to blow my irs setup. i was thinking bullitflow irs brace and front and rear bushings but i thought id take a few opinions from the pros. my questions are 1. are pulleys even worth getting? and 2. how much of a difference should i be seeing going from a 3.27 rear end to a 4.10. thanks guys!! btw heres a vid of it with the slp loudmouth 1's before i switched them out with magnaflows for the people who are wondering what loudmouths sound like. my hair is also alot shorter now hahaha;)

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You'll see a HUGE difference w/ the 4:10's in there.
yeah great mod!
i did some research on the cost of having bushings installed and its about 800 dollars so i was wondering if its a bad idea to put the 4.10 gears in w/o a bushing kit and maybe just with an irs brace. atleast for a little while. i dont really launch the car so im not sure what i can do. i really want to get some AFS wheels for it but i dont think ill be able too with the bushing kit. whats your input on it guys?

yes you can just do the 4:10 swap, however the torque multiplication will amplify the wheel hop (in theory)
I get less hop now with the 4.10's. More spin though.
i guess what im trying to ask is do i really need bushings to put my 4.10 in and if i dont would i have to worry more about breaking IRS?
No, you really don't need bushings, but it is a very smart move. You might as well replace atleast the IRS Differential bushings while you have the diff out of the car though. This will only add a couple of minutes to the total install time, and the ones from MM are not a bad price either. I would HIGHLY recommend atleast doing that. FTB or MM your choice, but do atleast on of them. I would also highly recommend getting one of the braces installed at the same time. Putting it in later is just going to cost more money in the long run.

As far as breakage, you will only have to worry about it if you are dirving the car hard.
Best Cobras to buy 90 percent of time are old guy Cobra owners lol. Than theres the 10 percent which are just like the young people who buy it from the old guy.
i guess what im trying to ask is do i really need bushings to put my 4.10 in and if i dont would i have to worry more about breaking IRS?
If you read the article on Full Tilt Boogie Racing Homepage they attribute most if not all the breakage to wheel hop. if you're careful to not stay in the throttle while it's hopping you shouldn't have to much to worry about.
It's not just wheel hop. You can control wheel hop with the right set of springs and throttle control. However, if you have sloppy diff bushings, your diff will still shake like Oprahs thighs. Your diff shaking is bad bad bad.
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