For those of you interested in jack rabbit speed 0-120 with your manual tranny, take a look at replacing the rear end gears and changing the ratio from the current 3.27 to 3.46 or 3.69... http://www.bergwerks.com/differential.jsp http://www.bergwerks.com/different_appli.jsp

I am in the process at BergWerks here in LA because I race the car quite often at many CA road courses and have found the gearing is too low for all of the tracks I race on. And also too low for average freeway driving 65-70 mph.

I rarely get into 5th gear on the freeway at 65-70 unless I'm travelling long distances, which is rare. And I never use 6th gear at all. (it is a wasted gear unless you routinely drive at 110 mph + for long distances).

And on the track the OEM gearing inhibits fast launches from the tight turns to the straights because it is geared so low.

Yes, this will bring your average RPM up at 65-70 mph, decrease your gas mileage and increase engine wear, but for tight road courses it is IMO mandatory to make the car more competitive. For regular freeway driving it will keep your engine in the power band range of 3,200 rpm in 5th gear.

I'm glad to have found these guys and so close to my house makes it even better.

PS: I need everyones help in locating the Eibach Anti-roll Kit for the SLK320 standard model. It seems they have discontinued the mfg. of this part and is no longer available from Eibach here in the US or Germany. If you run across one during your internet searches, let me know ASAP so I don't have to pay through the nose for a custom sway bar system.

 

Wow! This is reminiscent of our discussion on that other post RACING.
Let us know how you make out with the gears. Are you going to try both ratios? How big a job is the switch (crown & pinion gears??)?

 

You're right MBEPIC we did discuss this a few weeks ago after my run-in with the RICERS at Willow Springs, but last Sunday I spent the day at Button Willow and confirmed our opinion about the diff gear change.

Ok ! I admit this is a post that belongs in both (RACING & TECH MODS) categories and was going to post in both, but got lazy. Debated which I should post in first and decided that I would go for the Tech. Mods. because It seems to get more views and also this modification pertains to highway driving for those of us who own MAN. TRAN.

I'm in discussions with the mechanics at BergWerks which ratio will be more effective on the track, but still give me some comfort on the highway and not kill the engine and my gas mileage. Obviously the 3.69 ratio would be perfect for the small road course at Willow Springs and Buttton Willow, but impossible for the Highway. The 3.46 ratio would be great for the big road course at Willow Springs, Button Willow and Laguna Seca and much easier on the car on the highway, but still geared too low for the small road courses which are very tight turns with short straights.

HMM !!!

I am leaning toward the more conservative 3.46 gear ratio change at first. This is the same OEM stock ratio on the SLK32 AMG and the SRT6 which represents a 7% change from stock.

The 3.69 ratio is a 13% change from our car and a 6% change from the SLK32 AMG / SRT6, but I think I would be running somewhere in the 3.5k RPM range in 6th gear at normal highway speeds. That would probably limit my top end at somewhere around 130 mph before the rev. limiter kicks in at 6.2k RPM.

BergWerks says the differential swap out is a DIY 2.5 - 5 hours, but I am going to have them do the install since I want their warranty if it F's up. Appx. cost will be 2.2k...

Will keep you guys posted...

 

That should work nicely, I know guys that did the same in V-8 MBs for more power. The lower ratio in a stock auto would probably put it in 6 sec 0-60. Ask them what they think on that! I drive my car around in 3-4th all the time because it feels stronger.

 

By the sound of this, your swapping complete differential housings. Did you talk to them about just getting the necessary gears and changing those within the existing housing?

 

Yes it is a full diff housing swap. Don't know if they can do just the gears. That would be much better because I could keep the OEM gears in the car until I get to the track, then swap out for the 3.69 ratio during races. Thus saving the engine a bit during my normal driving.

I'll inquire.

 

I wonder if the 3.69 gears would put an auto in the 5's, 0-60? I never drive over 100 mph so, I'd prefer the quickness. Then all those other Mods for power wouldn't be needed.

 

Doubtful. And 2200 for a gear change! I almost threw up. LOL At least someone is modding their car though. But that is was too rich for my blood. 2200 for an Chip, intake header exhaust, gear swap, fuel pump and injector package, i could do that. Ouch 2200 thats over a half a years of payments.

 

Yeah but that's cheap for real 0-60 gains if it puts the XF in the 5's without any other engine mods it's still under warrenty to. I'd pay that for real gain.

 

Steve, the owner of Berg Werks did the math for me yesterday based on the current gear ratio of 3.27 and my man. tran. The car runs the following at 65mph, 3550 in 4th, 2750 in 5th, 2400 in 6th.

He estimates that with the change to 3.69 ratio is a 13% change and will run 2700 +/- in 6th, 3100 +/- in 5th, 3900 +/- in 4th. This will definately keep the car in the power band that we have all felt in the 3500 rpm range.

It will decrease top end by 13%, so if the car hits rev / speed limit at 155 mph in 6th, it will now cut at 138 mph.

This is perfect for the road courses I run the car on. and won't seem to effect my highway driving. The percentage of gearing increase 13% should reflect in the same increase in 0-60 times and 1/4 mile times. Within relative terms...

I am a little concerned that first gear will be extremely short now and will have a shift point somewhere around 12-15 mph. But I would assume I could launch the car in 2nd during normal street driving without buzzing the clutch too much.

PS: total cost for the new diff, gears and install is going to be $3,100. Pricey, yes, but I think it will give me the performance I need in the car.

Based on my conversations with Berg Werks, All standard MB cars are over-geared to help create a much quieter, smoother ride at highway speeds. And to help with gas mileage.

I have ordered the diff. and since it is custom made, I won't see it for 6-8 weeks. Will keep you all posted.

 

Did you price the SRT6 Diff.?It's should be easy to get that.And MBenz might make even lower ones that would fit .

 

The SRT6 diff ratio is 3.46, I've purchased the 3.69 ratio, I'll keep you posted.

PS: You'll love this one Dan, I'm still waiting for the SRT6 that I ordered to be delivered. But I have decided to take delivery and swap the super charger and intercooler with my car then give the SRT6 minus SC & IC to Jenny since she can't drive a man tran anyway.

 

it seems like it would be easier to swap the whole engine.the dealer in Valencia offered me a SRT6 for invoice he has a Graphite and SSB.and 1 Convt.

 

I know, that is where I ordered the Black SRT6 from in July. They called and offered me the other colors and I declined about a month ago.

They still have mine on order and I have not taken delivery on it yet... It is Power Chrysler in Valencia where I ordered my first Crossfire...

 

They said they have more coming in soon.

 

Instead of putting in an entire new set of gears, why dont you just reduce your wheels size, and get the same effect for a lot cheaper?

Plus you could also change the driving back to stock, simply by putting the stock wheels back on.

I imagine some 16s or even 17s with low profile tires would do the same trick as the gears. It might look strange at first, I mean we are used to seeing 19s in the back, but some 17s couldn't look THAT out of place. You'd have a little bit more wheel gap but 17s are big enough to not look like you have a lowrider. However you'd get a lower center of gravity for cornering, versus stock wheels, and the faster accelleration that comes with reducing wheel size. This car would fly with 17s in the back, those 19s look good but have to slow it down a bunch. 16s would just be ridiculous but I think thats more what your going for.

Ok heres another idea, coilovers. If you go with 16s or 17s, you can drop it at the track with coilovers. Then you get the accelleration you want, super sharp handling since the car will be so low, and no ugly wheel gap. Then when you wanna go back to stock, raise the car back up and put the stock wheels back on.

 

yeah but getting a 16 to allow a wide enough tire to keep the grip we have because of the width of the rear tire would probably require getting a custom wheel made, which would be super expensive as well. HDDP, you said that it would increase 0-60 and qm times by 13%. did you mean decrease, or will those times actually raise?