Just a curious question

Suicidex · Dec 4, 2004

I have a 99 Cobra with IRS, and I am doing the wonderful job of having it totally repaired after a slight grenade from a co-worker driving it.

Since im having it repaired I figured I would go ahead and change the gear ratio to 4:10's. My curiosity is, should I be putting any type of support bars on the rear of my car at all or will this gear ratio be just fine from me possibly slamming the gas and racing here and there on the speedway?..
If I can wait on bracing or what not I will and just Drive it easy and no racetracks till I can get a lil more money as this isnt the cheapest venture in the book. Anyhow any thoughts would be awesome on the subject. The mechanic thinks I should be ok, with it at only 415 hp, do you guys think it should be ok?

Thank you for any suggestions.
-Sui X

COBRA90GT · Dec 4, 2004

What kind of racetrack are you talking about exactly? Roadracing or quarter-mile stuff?

4.10s are a good upgrade from the factory 3.27s but many people would lean towards 4.30s instead of 4.10s, because with 4.10s you would shift right before the end of the traps whereas with 4.30s you won't have that issue.

As you probably already know, wheel hop is the main culprit for IRS cobras when trying to "launch" at the dragstrip.

If this is your main concern and you plan on spending a good deal of time with the cobra going down the quarter mile, then swapping to a solid axle is probably in your best interest.

However if you wish to keep the IRS you can do a few things to improve it for dragracing. Lower it with some springs, upgrade the axles (ie - GKN halfshafts), get the IRS bushings, a newer crossmember brace ('03 cobra style), perhaps even opt for a 31-spline setup like the 03/04 cobras or an aftermarket diff, etc. It definately won't be cheap to beef up the IRS this way. Wheel hop at the dragstrip will never be totally eliminated after all of the above modifications, but it will help.

I would also suggest running a few searches, as there is plenty of good info in past threads about upgrading the IRS (or swapping to a solid axle). G'luck.

BTW#1 - You might also want to try running a search over on the BON Cobra forum, use keyword "halfshaft" for example. Link to search page: http://warnerrobert.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=search

BTW#2 - What kind of damage resulted when your coworker "grenaded" the car - was it the differential or a halfshaft?

Suicidex · Dec 4, 2004

ok cool some things for me to look into, Usually I try to stay away from the "dragstrip" type stuff we have a group of guys that go out to an area out here that the owners have let us use for a road course type setup.

As for the grenading, it was the differential im having the diff replaced as well as the gears and not sure what else yet as we towed it from the blow up point to the shop I couldnt really see all of the damage on the road just the big hole in the housing and shrapnel in the gears themselves, I'll get that call on Monday.

Now not looking at performance such as the dreaded wheel hop "oh god yes I hate it"
But as far as the car is concerned the new gear ratio won't put so much added stress on the car that everything is gunna break again the first time I hop on it or twist the rear.. (yes this is my first differential blow out, the price tag made me nervous) he's putting in aftermarket not ford stock btw..for housing and etc ..

cwd · Dec 4, 2004

I DID THE SAME THING AND IT WILL HAPPEN AGAIN! THE DESING IS POOR. THE STRESS ON THE ALUMINUM COVER IS TOO GREAT AND THE TWO BOLTS HOLDING THE DIFFERENTIAL IN PLACE WILL SURELY BREAK THE COVER AGAIN. WHEEL HOP IS THE MAJOR CULPRIT. GO TO THIS E-MAIL ADDRESS AND FIND THE SOLUTION WWW.MAFTERBURNER.COM. I HAVE DONE ALL THE OTHER UPGRADES MENTIONED AND THE SET UP IS TO RUN THIS GIRDLE AND THE UPGRADED HALFSHAFTS. IF YOU NEED E-MAIL FOR HALFSHAFTS LET ME KNOW.

Suicidex · Dec 4, 2004

hmm wish i would have known this before I paid to have everything redone on the rear... grr... Interesting to know however. Either way I can't get this right now anyhow even if I did have the money off hand they are out.

But if its gunna be a huge deal I guess I could always put on Hard Launch bracing. But im still not sure if im even putting out enough to worry about it all that much. As I said Im not a die hard 1/4 milest.. so no real need for hard take off's as much as say someone who goes to the drag strip every week. But I think they are right the stock housing sucks

cwd · Dec 4, 2004

WWW.XMSENGINEERING.COM PROBABLY HAS IN STOCK. THE PART IS IN DEMAND FOR GOOD REASON.

Suicidex · Dec 4, 2004

Then again, it's cheaper then I had expected.

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