Nope... The only diff that will work is from an older, if my memory serves me, late 80's MB wagon 8.7:1 ratio.

I had this guy in Van Nuys "BergWerks" that had the process down to a science and did many of them, but he went out of business before I could scrounge-up the $3k... I figure if he can do it, there's gotta be someone else somewhere that can as well.

 

I'd live to change out the gearing on the rear end of my xf. I have a six-speed and find the 1st gear almost entirely useless. Its a real granny gear, almost like that of a pickup I used to drive. I usually start in 2nd because 1st is so low. Another added bonus, better mileage! Using sixth as a true overdrive instead of a displaced 5th, and the xf could get in the mid to high 30's on the highway. The engine has plenty of guts to do it as well. Fore some reason, every manual I have driven lately has been screwy with a six speed. Kind of like they just threw another gear in for the fun of it, and not for any specific function.

 

First off I LOVE my car, and the compliments are endless, on the road or when it is just sitting in the garage. The only complaint that I have is when I am on a 2 or 3 lane highway I find she revs far to high after 60 miles an hour, which I know is hurting my mileage anyone else feel that way. I know its all about the gearing in the rear end but that's my 2 cents.

 

First off,
If you put in a 4.11, in 1st gear at 600 RPM, you would be doing something like 3 MPH. The higher the ratio, the lower the gearing. I think if you added the speed booster and the SRT rear-end gears, you would get what you are after, as you can stay in 1st longer and really squeeze out the power of the engine, and have more speed when you do shift.

Since I use my Limited as a highway cruiser, I was looking for better mileage and more efficient shift points. I did some calcs, and by swapping the rear end in a limited/base for that of an SRT-6, you would pretty much change things by 6%, across the board. The limited has a ratio of 3.25:1, and the SRT-6 is 3.07:1 (source-Chrysler website). At 70 MPH, we get 2,591.186 RPMs of the engine for the Limited, and 2447.647 on the SRT. 5.9% difference. (using the 29.5" Tire diameter of the Continental ASP Tires).

If we use a standard RPM of 2,500, with the Limited we get 769.2 rotations per minute of the tire, and 814.3 for the SRT. Again, 5.9% difference. The Conti rear tire requires 801 revolutions to travel 1 mile, so the SRT will go 1.016 miles per minute at 2,500 RPMs, and the Limited/Base at .960 miles per minute. SRT will be traveling at 60.96 MPH, and the Limited/Base at 57.6 MPH. If at that speed in a limited, we are hypothetically getting 30 MPG, the swap will result in getting 31.77 MPG.

If we got 350 miles per tank before the swap, after the swap, we would get 370.65 now. At 350, with 30 MPG, we burn 11.67 gallons of gas, and at $2.50 a gallon, thats $29.175. Modified, we burn 11.02 gallons, and at $2.50 a gallon, thats $27.55. A savings of a whopping $1.63.

Hardly seems worth it, being that it would probably cost in excess of $500 to do.

I went to public school , and TWO public colleges so please correct my math if in error.

 

That's right, the SRT6 rear gears will improve on our 1st gear shift to 2nd. I think it's a 3.07:1 definitely be able to stay in 1st longer, and get a higher top speed before redline cuts you off.

If you could actually find a 4.11 and install it, which I doubt it would fit but 1st gear will really be useless then.

 

Did you check to make sure the 1st gear or at least the OD gear ratios is equal in the srt6 auto compared to the Limited? I think your numbers might be off, since I don't know the tranny gear ratios, and I doubt they have the same gear ratios.

 

Mine is an auto, so I won't have the first gear hassles.
Still haven't heard from Kleeman - maybe I'll call them again now.

 

Chrysler lists the AXLE ratios as I had stated above, not the transmission ratios, or even the final drive. My calcs were based only on swapping the axle ratio on the limited for that of the SRT. I'm ignoring the final drive ratios and using shaft speed (assuming 6th gear of the manual is 1:1 for the engine/tranny, as it usually is). I was only trying to get a baseline % of difference if one were to swap the gears in the rears. What you have suggested s is if I were to swap more than that, or compare the two cars. I think the numbers are definitely off, but are close enough for the premise.
I'm still looking, as perhaps I can find an even lower ratio, which would do more for the mileage and 1st gear. (I already start of mostly in 2nd, except for on hills, but there ain't a whole heck of a lot of those in my part of Maryland).

 

A little research shows the SL500 has a rear end ratio of 2.65:1, a difference of 18.5%. At 70, the engine RPM's would be about 2,112.8. That might be TOO much of a difference!!!

 

the whole point of the original post was to gear the car for better acceleration, not top speed. who cares if first is useless because the acceleration would be much greater (kick *** tradeoff).

 

Scraper, I went to a public high school and a state college, and the only thing i found off with your numbers was the one you started with. I believe a Limited has 3.27:1, not 3.25:1.
Switching to the taller SRT6 gears (3.07:1) would make 1st gear a little more useful, but it would hurt your 60' times, and eventually your final ET. in the 1/4 mile.

 

Couldn't agree more.
No offense but who gives a hoot about fuel economy.
If you want fuel economy, there are lots of little rice burners that will do the trick.

 

I'm at work and just dug around in the parts computer. The deepest gear set I can find being used in these housings is a 3.70:1 ratio out of a '95 ONLY SL320. The earlier SL320s used a different carrier and the SL500s used less gear.
The housings were originally from the '86 - '95 E-class and a second one taken from the '96 - '02 E-class.
We're kinda stuck when it comes to MB parts. No joy here.

 

Hi Feets,
3.7 gears are better than 3.27- do you have a part number or something that I can run past the local MB parts guy. Actually, it would probably be easier to get it from you- any idea of price and availability??

The local Kleeman guy said that Kleeman could fit an LSD- no mention of what ratio- the diff would have to be sent to Germany and I would have to sell the kidney of my first born to pay for it- not a good option. If I can get the gears, I can get a local to fit them to my diff.

Now, what about the speedo reading, computer feedback?? Any ideas where to start??

 

The Kleeman LSD does not change the gearing it is simple a limited slip.

Kleeman NA and do the LSD install. Not sure why they are telling you it has to go off Germany.

 

Kleeman are a bit thin on the ground here in Australia - that's probably why.

 

I thought we concluded that there already is a limited slip in the XF?

 

This Is Funny !!! I Give-up And Am Just Going To Concentrate On My Track Car From Now On...

 

I know I'm confused now by some of the information I hear on here, one of these days I'll have to take a look for myself.

 

Sorry did not notice the screen name. Just had a US centric view of the board.