Hi Everyone,

I have only had my Crossfire for a week and I love it. This is not an SRT so I find the car to be a little sluggish - something I realized when I bought the car but am keen to alter.

Reading posts regarding top speed of the Crossfire, it seems they have plenty of speed where you won't really use it so much.

Has anyone changed the diff ratio of their Crossfire to give it a bit more acceleration down low?
Perhaps the gears are already low and the trans ratio gives the big top end.

I would like to give it a bit more kick without buying an SRT. No-one seems to know what the car is around here, let alone how to make it go a bit harder.

Any thoughts or tips would be appreciated.

 

Order the Sprint Booster and it will solve your problem. The thread is in this section. Best money you could ever spend for acceleration down low.

 

I don't think there are many choices for our XF, we have two ratios. And the SRT is numerically lower I think like 3.07 while our stock XF is numerically higher something like 3.27 or about that.

You should do more research on the older SLK maybe they offer more ratios? otherwise put smaller wheels on the back, that should make acceleration a little quicker.

 

actually you should be the first to change gears. trust me i have wanted to, but don't know where to start.

i think a nice set of 4.10 or 4.11 would give the car a nice feel and quite possibly a respectable 1/4 mile time, and alot faster acceleration. all the sprintbooster does is increase the throttle response, which is well just a feeling you receive and wouldn't increase any quarter mile times or 0-60 times ect...

 

I disagree. With SB you should improve time. I agree it does nothing to increase HP but think of it. If I got in your 10 second car and ran the quarter mile but instead I did not give it the gas all the way and built up to my speed by gently pushing the peddle I would have a worse time than if I got in the car and floored it. Same car two different times. The SB allows you to have fast acceleration so faster time.

 

That was all he was asking for..."a bit more acceleration down low." Regardless of how it does it, that is exactly what the sprint booster does, and for less than $300. And it doesn't mess with the high end. Cheap way to get your kicks at both ends. Gearing is not going to do that...and definitely not at that price. I was just offering a simple solution.

 

4.11 gears-That's what I want to hear.
I have an old '73 Chrysler hardtop with a stock 318 and 2.92:1 rear end. I changed the gears to 3.7:1 and it's like a different car. Unfortunately the old 904 trans has no overdrive so it sings a bit at 120 km/hr- no such problem with the Crossfire.

I reckon DynamicS suggestion to research earlier Merc diffs has lots of merit.

I think the Sprint Booster could be nice but probably not enough kick. I need to get the car faster to, say 120 km/hr, than my wife's 300C Hemi. I think a change in diff gears will do it if I can get the right ones. Right now I can stay with her to about 90 but then the Hemi keeps going.

Obviously an SRT will do it immediately but that's not an option.

 

Thanks for your additional comment. I do not see how anyone can logically figure that if you increase throttle response and have faster acceleration, that you would not also have faster times. Of course, once you get to WOT there would be no difference, but it would make sense that if you get there faster...you are faster.

And, downunder...you still have the same top end to keep on going. As an ex-weekend drag racer, I understand gearing very well, but throttle lag in these cars is still going to be there without the sprint booster. Now, if you do both...holy crap, batman!!!

 

Just checked a MB forum- they say the 300SL had a 3.69:1 rear end ratio- that is a step in the right direction.

Being a newbie to Crossfire, I have no idea of model/drivetrain compatibility between MB and Crossfire. Can anyone tell me what year or model Mercedes the Crossfire was based upon- everyone says SLK but isn't that a bit of a broad description when trying to track down diff gears??

 

XF Downunder, You didn't say if your car was a automatic or a 6 speed. If it's an auto, then changing the rear end to what ever ratio you want would be OK. But if it's a 6 spd. going to a lower gear ratio much more than say a 3.55:1 would render 1st. gear practically useless.
This idea has been discussed at length many times hear. HDDP has done alot of research about it because he races his car and as of yet, hasn't come up with any affordable way of doing it. From what I can tell, since our car has SLK "mechanicals" that gives us very few options.
I've mentioned numerous times to at least try the front tires on the rear to see if that would make any difference, because of there smaller diameter, it would essentially give you a ratio of approx. 3.50:1. You would simply need to borrow somebody else's front tires though, because I don't think the rear tires will clear the front fenders.
Good Luck trying to beat your wife's HEMI, they can break into the 13's, and I think it would take at least a 3.91 gear to get a Limited XF there.

 

when i did my reading on it (i used another older mb form) and they had come to a conclusion that it did not improve times by using a 1/4 mile track. i do understand their are alot of factors in 1/4, but he used it and took it off the same night.

think of it this way how bad do you think mb did when designing their throttle response system, hopefully not bad enough that it would drop .2 or even .1 off of 1/4.

anyone have a g-tech and have the sb want to give it a shot.

 

I wonder if any of the larger displacement mercedes vehicles have rear diffs similar to ours?

 

Hi,

First thing to try is a reset of the drive by wire. Turn the key to on/run (don't start the car) Press throttle all the way to the floor and hold it down for 10 seconds. Turn off the key. Wait 2 min. before you start the car. Go out for a cruise and take off hard. Computer will "learn" your driving style and you should get better response when you mash it. This should help and there's no down side. Plus the price is great.

 

I've spent a bit of time looking into it a little more.
A spare parts guy at MB had a good point. He suggested that if the gear ratio was changed, the wheel/engine rev ratio would also change- take care the computer doesn't perceive this as a major problem and put the vehicle into limp mode.
Chrysler service just about had heart failure when I suggested a gear swap - does anyone know if Chrysler are capable of reprogramming the computer if the diff ratio is changed.
I am going to try the MB car club next to see if anyone knows diffs but I don't hold much hope - they tend to breathe different air.

 

Yeah you might have a problem with the computer reading the wheel speeds, Chrysler dealerships are not as technically experienced as MBZ dealerships, so your best bet is to stay away from chrysler techs, that's not meant to be a put down, but the XF is mostly SLK MBZ.
You should contact Kleenman, or another Euro car tuning company that is familiar with MBZ.

 

I have looked into this about a year ago...no luck.
Berg werks use to make gears for the slk but the went under.
HDDP did some serious searching also and the best solution was to have a set made which i believe was around $3,000 and that does not address any computer problems that may arise from the swap.
Good luck and post if you learn any new info as I WANT GEARS!
Thanks.

 

I believe I read somewhere that the SLK's underpinnings are composed of nothing but the S-class and C-class. So you might have better luck getting gears from those two models.

 

Just to save me a whole lot of Googling, what are S-Class and C-class - everyday Merc sedans, 4WDs, ??? I have no idea what they look like- thought maybe a wrecking yard (or as you guys say "junk yard") may have something around if the diff blood lines are old enough.

Still have the computer problem - that could prove a little bit curly.

I work with a couple of guys with Skylines - they have a 200km/hr speed limiter on them - the rear end ratio is in the region of 4.3:1 - damn those autobahns. Without them, the MB reasoning may have been different.

 

Actually, I had a scheduled install at BergWerks for a 3.87:1 and then went to the shop and it was DOA. The owner has since gone back to work for a local LA MB dealership...

 

I am waiting for an answer from the Kleeman distributor here in OZ. Hopefully he can shed some light on it all on Monday or Tuesday.