My question, Is there ANYBODY here on the forum (who is a serious drag racer) trying to develope a better gear ratio for drag racing the Crossfire?
I know the deminsions of the SLK differential (that the Crossfire uses) limits us when it comes to having enough room to accomodate a more useful differential housing. But surely there has to be some other car makers differential that could be swapped in place of what we have now.
I know Rudy would have to work his magic and talk the computer into accepting a different gear ratio, and
I realize new axles would need to be fabricated, or our current axles would need to be modified. As would the drive shaft mounts. But we aren't talking rocket science here guys.
I mean if some back yard yah hoo's can build a "Rat Rod" with an XKE rear suspension, how hard would it be to come up with a better geared, stronger rear end for the Crossfire?
You don't think those 9 sec Supras are running "Stock" 3.07 gears do ya?
Do you realize, that a SRT6 with nothing more than a Neeswings Dual CAI, a tune, (maybe a pulley) should be capable of high 10's with a 4.44 "limited slip" gearing and slicks?
It's all been done before on a similar car, I don't see why it can't happen with the Crossfire.

Just a suggestion I'm throwing out there. http://www.1speedway.com/irs_quickchange.htm
I know there's an abundance of technological and mechanical talent in the Crossfire community, I would think this small hurdle could be cleared with ease.
Mercedes gave us the H.P. they just forgot to supply the right gears for the average American "performance" enthusiasts.

 

LOL....yes, it is possible. But, like most drag racers, giving out our secrets are slow to come. But, something is in the works. There have been successful 3.07 to 3.27 changes already.

 

Axles would not be hard, I would do like the older corvettes did and instead of the small shaft make two driveshafts to go from the rear end to the tires. More then strong enough only downside there would just b 4 grease fittings to maintain (fine with me) which would u rather have a 1" shaft on small u joints or a 2.5"-3" tube with bigger u joints?

I am thinking about changing to a single driveshaft instead of the double driveshaft we have now. Less resistance in the drive line.

 

Changing the rear end out isn't as easy as you would think, and would be costly. Ring and pinion is one thing, total change out is just too expensive. I guess if you want to strip it down and drag race it, that would be fine. My experience with the NHRA hasn't been a good one. You would be thrown to the wolves in an 8-9 second class of cars. Been there done that. Sportsman is a good class for us, and that is about it... If I had to do all that kind of modifications, I would be back in an old Camaro... Not worth it, now the ring and pinion is affordable, and of course you do need to figure out the right TCU tune...and hope it works...

 

Doc, I fully agree, a ring and pinion is naturally the way to go. But Summit Racing, and Mercedes Benz hasn't returned any of my phone calls.
Now if you know of somebody who's secretly forging new ring and pinions for our painfully unimpressive differentials, but you've taken an oath of silence, then I won't push it any longer.
But I don't think using a completely new housing is impossible.
To be honest, I've never even been under my differential to exam how much space it actually takes up, or even how it is fastened to the chassis, but I'm not suggesting replacing it with a 9 inch, a 12 bolt, or even an 8 3/4".
There are several "Asian" differentials I think could be modified to work. Yes it would take some money for R&D, but their diminitive size should fit under a Crossfire.
Doc, you know I'm not a Drag racer any more and I don't own an SRT. But I don't need 150 mph capability either, and I have ALWAYS thought all my car needed to wake it up would be a 3.73 gear.
As I said, for those serious SRT drag racers, a 4,44 ring and pinion and some DR's should be dipping into the 10's with the SRT's H.P. It's been done before.

 

we are working on it
and there are two ways to do it, and if neither of them work out then you will see a 1968 ford 9:,31 spline and Detroit locker..

I am sure I could install Challenger rear,, axles,, and hubs with a few drilled 2" holes and a bracket or two. and some welding into a crossfire
we already put a Challenger 391 posi rear into a charger . The charger has the same rear set up as the crossfire, No the charger and crossfire do not interchange, even though they look they would, if you go to e bay and look at the Mercedes diff. a lot of them look like the crossfire diff. but when you have 10 to 15 of them laying on the ground and try to match one with the crossfire diff it just does not work. jim

Note:::within a year I will have a rear in my car, around the 371 ratio if it can be driven on the street (some of you will understand that) it stays if not i will try another way.

 

Thanks Jim, I'll be lookin forward to hearing how it all turns out.

 

I know I've been dying myself for some better gearing options ...I've thought about the 3.27 and I've also thought about ripping it out and going with a ford 9inch like Jim said and even thought about doing his Challenger option question is can Rudy or euro charged get the tcu to work with it I'm about to try it soon lol getting the itch to hurt some feelings at the drag track lol I'd love to have anywhere from a 3.91 to a 4.56 or something lol

 

very soon I may have a 327,( with about 8 to 10000 miles and 25 to 30 1/4 runs on it , wavetrac and a tcu all set up for a srt ,the cost was tcu $500, the 327 $350. the wavetrac $1150, total $2000.00 make me an offer. jim

 

Just a little reminder Jim, what your SRT550 will be capable of with a really "GOOD" gear.


With an automatic too.

 

Honestly I want the 2.6 MB rear.

 

bumping this.... my diff is starting to whine really bad

 

if u need a 307 right out of a srt6 let me know. jim
https://www.crossfireforum.org/forum...7970-sale.html

 

OK, it's been nearly a year since I started this post. I'm a patient man. Is there any progress?
NOBODY has broke into the 13's with an NA car, (on just the motor alone) that I'm aware of.
The Crossfire has been around for a dozen years now. There have been all kinds of H.P. #'s tossed out there, what with CAI's, tunes, injectors, pulley's, headers, things that you would think (in the right combination) should be enough to put the XF thru the 13 sec. barrier, yet nobody has laid claim to the bragging rights. Oh sure I've read a few post's over the years where some people claim their cars are "capable" of running 13 sec. 1/4 miles, but unfortunately, talk is cheap, and calibrating a butt dyno is not something many people want to do. Time slips, and (better yet) video speaks volumes.
I know, lot's of people are going to say, why bother? The NA's aren't drag cars, let it be. If you want to race, get a 6. Well to those people I say, car enthusiast don't want to hear that. Every car can be made to accelerate faster and that's the name of the game. Besides that, anything that makes an NA perform better, would make a 6 perform better. Right?
From day one after purchasing my Crossfire new in 2005, my intentions was to install a lower gear ratio. I soon found out there was no easy, inexpensive way to do it, but I figured surely in time somebody would come up with the right formula. I've always said it's going to take a much better gear to see the 13's. How much longer is it going to take.?

 

Mike, my helper got married and has all but retired...lol. I am researching with another group, and may have to go south to pursue the rear gear change. There is a ring and pinion out there that will bolt up in our housing, and the big problem is the TCU. It won't be as high as a 3.70 or 3.73, more in the 3.58 area...and doing the math, that is perfect in order to still drive it down the road and enjoy it.... I will know more once the weather breaks and I talk with Rudy, if he is available. I need to get my hands on the ring and pinion, then off to the south to work with another company. Like I stated, if you go to a 9 bolt Ford, or anything else, you are looking at a lot of work. Too much for me. I like keeping mine stock to satisfy the NHRA or it is pointless.. You modify in any other manner, you are thrown into a class of "race" cars...front wheel pulling monsters. Now, if you don't race legally, who cars, right? ..... It isn't dead yet....

 

I was at Jim's last week and he has something "special" in the works. I'll leave it to him to comment further.

 

Can't wait.....lol

 

got some testing to do with pulleys, one down,, one up,, both up,, one 327,,,,,then being built now is a 346
being my lower pulley cracked, i am starting all over with pulleys and the gearing

one of the these will be the gears in the car,,307,,,327,,,346,,,373,,
pulleys are 185 ,,or ,185 stacked with a 84 super charger pulley or 180 stacked with 84 s c p,, or 84 only or 185 only
or well lots of testing to do. but that is the sum of it. jim

 

Jim, is the 3.46 the one that will bolt right up in our housing... trying to get a part # from Rudy...so I can find a ring and pinion....thanks....

 

if you find something in the 2.6-2.9:1 range let me know please. Want to make 1st usable.