I had a bit of a look at the gear ratios for the SLK32.

GEARS
Diff Ratio..........3.07

Gear Ratios.....Tran ratio...overall ratio...kph speed @6000rpm
1st Gear...........3.59.........11.0..........67 kph.....42 mph
2nd Gear..........2.19..........6.7..........110 kph....69 mph
3rd Gear...........1.41..........4.3.........171 kph...107 mph
4th Gear...........1.00..........3.1.........241 kph...151 mph
5th Gear...........0.83..........2.5.........291 kph...182 mph
Reverse............3.15..........9.7..........77 kph.....48 mph

TYRES
Section Width:mm........225mm
Section Width: inch.. 8.9inch
Profile ................45%
Rim Dia inches..........17inch
Rim Dia mm..............431.8mm
Sidewall Height:........101.25mm
Overall Diameter:.......634.3mm
Circumference:..........1993mm

I'm guessing the wavetrack wont change this unless you actually change the spline and pinoion gears at the same time....I currently have this opportunity - so looking for some advice/comments.

Given the torque available (and soon to be improved) from this beasty
1) should I go for a taller diff ratio if I'm eventually going to 21psi & 330rwhp?

I noted from someone already running in this area (11.7/117) that 2nd>3rd gear change is at the 4.1sec/62mph point. A 2.8 ratio'd diff may push this out to >70mph (calc 76mph on the calcs above).
2) What are the "standard" bolt-on pinion/spline ratios available - if any - or is it a special/machine job?
3) what do I sacrifice (if anything given the extra grunt from the pulley etc.)

b22b

 

Are you asking if the 3.07 can be changed?

 

Well I've got a Wavetrak internal ready to go, but of course the spline needs to be swapped when the deal is finally done....
Everythings a WIP....I think some will understand here.....

If the spline off and pinion out - there's an opportunity to lengthen the ratio from 3.07 out to maybe 2.8 in line with the hp/tq increase.

I have read since posting there might be some ECU/TCU considerations if done - not sure yet.

 

leave it alone at 330 rwhp no need to mess with it. get 500 plus rwhp then you might want to go taller for the 1/4. 355 guys have moved from a 2.82 to a 3.55 and tcu tuning by e/c. it works by their account so it can be done. richmond gears froma srt 8

 

in the interest of thoroughness ... I thought I would add the top speed for reverse in winter mode (dont try going this fast in the snow )


GEARS
Diff Ratio..........3.07

Gear Ratios.....Tran ratio...overall ratio...kph speed @6000rpm
1st Gear...........3.59.........11.0..........67 kph.....42 mph
2nd Gear..........2.19..........6.7..........110 kph....69 mph
3rd Gear...........1.41..........4.3.........171 kph...107 mph
4th Gear...........1.00..........3.1.........241 kph...151 mph
5th Gear...........0.83..........2.5.........291 kph...182 mph
Reverse............3.15..........9.7..........77 kph.....48 mph


"W" (winter mode)
Reverse............1.93..........5.9..........125 kph.....78 mph woo hoo!!

Chris

 

I was just thinking that a new goal of mine was to do 48mph in reverse, to add to my records; and then you came up with that one. I had a good laugh at that.

 

I'm confused, are you saying that you want to change the "final" drive ratio to something like a 2.80:1 instead of 3.07:1?

AMX1397 (Jim) tried running an NA's 3.27:1 differential (in place of his stock 3.07:1) at the drags, and the traction control noticed the dicrepency in the RPM's and put him into limp mode by 3rd. gear.

I totally agree, with you, a ring and pinion change (and Wavetrak) is really all that's needed to wake ALL Crossfires up, ( I would prefer a lower gear ratio) but I don't know where you would get a ring and pinion, or how to defeat the computer. (Well that's not entirely true, I just don't know how to do it with an automatic).

Do you possibly have access to another ring and pinion that would fit our differential housing?

32krazy, are you saying there's a 3.55 gear that will fit our housing?

 

think of the challenge now ...

best 0-60 in reverse time .... requires a shift near 48
perhaps you could be the first to discover that the car upshifts in reverse (from "summer" to "winter") at the rev-limit



if its dry out tomorrow, I may see if it will let you shift from summer to winter in reverse (observing rpms for "the shift", of course)

top speed is likely to be a tic over 80 at 6200 ....

Chris

 

Can you pull the ABS fuse and try it on a frozen lake?

 

How can we have two different gear ratios for reverse? I have never seen that before.

 

one of the many reasons a Mercedes (or crossfire) costs more than a neon ...


Chris

 

LOL.....reverse

But my original question was going "taller" in the spline/pinion....2.8 against the stock 3.07.
32Krazy was commenting that others have gone the other way....3.55

1) I originally thought longer legs were in order here given our torque etc.... although I'm hearing it will "broaden" the gear spacing and would be a little less "flexible" for racing. Hence 32's note re 3.55 would would bring the spacing in and possibly "add" flexibility in shifting out of corners. I guess longer (2.8) would reduce a little wheel slip as well, but obviously you wouldnt power out as quick compared to a 3.55.

As stated my long legs were to keep the drive through the full 1/4
The data I'm looking at 11.7/117mph finds a 3rd to 4th redline shift at 9.4seconds through the 1/4 at 100mph, I'm guessing that that equals time off the pull and could be worth 0.1 or maybe more....???
Going to 2.8 would push this shift out another 10mph. So it would be changing at the flag - well 1 second later anyway.

2) if anyone knows of any off the shelf kits for the SLK32 bolt on diff - much appreciated.

 

your thinking about the gear change all wrong. a taller gear is going to make the car much slower comming out of the hole. We make a 3-4 shift at about 107-110mph at 6200rpm and hit the traps around 4800 rpm. If we could swap to a 3.27 or even a 3.55. I could see us dropping a couple tenths easy.

 

I noticed that back last winter.. backing up towards the house with the car.. "normal" would spin in a hearbeat.. W mode she wouldn't..

Everybody thought I was full of myself.. hmm..

 

And pics or it didn't happen!!

 

SRT8 gears can be changed by using a Predator, our car has to have the tcu changed. jim

 

I would have thought with the added torque we could sacrifice some gearing, however what I'm hearing is that....more is never enough...."Drove it like you stole it"....and who cares if she changes twice in the quarter....or is limited to 180mph down the straightaway, .....quick is best and hence a 3.27 or 3.55 is the most popular call.

Mind you top speed comes in from 180 down to 169 to 156mph respectively....
whereas a 2.8 lengthens her legs to 197mph (316kph) at 6000rpm* and if you have an extra 40kW from mods - you chould possibly get there. As long as your tyres are good for it. And for the 1/4 she changes 3rd to 4th at 116mph....about 20m before the line.


*based on 6000rpm and SLK32 setup17x245/40's 1972mm circ. - SRT6's are slightly larger with 19/255/35's at 2077mm circ. - so multiply the above numbers by 1.053.
So 180mph becomes 190 and 197mph becomes 208

 

So we install our TCU into an LX car. They flash the gear change, and higher shift points onto the TCY with the Predator. Remove the TCU and reinstall on the Crossfire. Now you've got the gear and RPM's you wanted.

Is that what they're doing? That's exactly how I did it in my Jeep (at least the shift points).

 

I just swapped 3.27 gears in my srt6 EV tcu tune utilizing same yolk and car is a beast down low still early stage of testing will get to track soon. Plan on adding killer chiller kit and 100 shot for 2nd and 3rd gear if all goes well.

 

I was running a 3.46 in my black V8 crossfire Sold it
i have a 3.46 for my gray srt6+2 may or may not install it.