Differential ratio selection for M156 swap and 6 speed, opinions wanted!

[Brento]

I have (2) 210mm differentials, one I will be rebuilding and installing a Wavetrac LSD centre. One is a 3.27:1 from a '90 300CE24V and the other a 2.65:1 from a 94 E280. I have a brand new CD00A transmission with the following ratios:

• 1st Gear: 3.79:1
• 2nd Gear: 2.32:1
• 3rd Gear: 1.62:1
• 4th Gear: 1.27:1
• 5th Gear: 1.00:1
• 6th Gear: 0.79:1

My rear tyres are 255/40R17.

My quick calcs show say cruising in 6th gear at 1750RPM speed is 63.3 MPH with 2.65 and 50.46 MPH with 3.27.

I have a 2.65:1 rear in my M113K swapped 560SEC with 722.6 transmission and with the 3.167:1 ~3:61 ratio of the first gear it does not take much throttle input to light up the 275 pilot sports.

The car will be just a fast streetcar, it may do the odd tarmac rally. It will barely be used for long distance highway cruising. I'd like opinions on what differential ratio I should run, the 3.27 or 2.65 based on experiences with the M119 or anything else applicable like other M156 powered AMGs. Id assume due to the 6.2L displacement the M156 will have a little more lower end grunt than the M119 also.

 

[gsxr]

It's hard to say without driving each combo. The 3.27 should be snappy around town while still retaining a 2.58 final drive in 6th gear, which is fine for freeway driving. The Wavetrac needs a custom ring gear spacer to fit in the 3.27 diff. As you noted, there may be some traction issues in 1st gear.

The 2.65 will be a little more tame off the line, but have a really low freeway cruise rpm with 6th gear at 2.09 (~70mph at 2000rpm).

You could always split the difference and get a 3.06 diff... that would be a 2.42 final drive (~70mph at 2300rpm). The Wavetrac or Quaife works with the 3.06 gearset.

 

[Markus-MD]

2,65 too long. And 3,27 too short ist too hectic. I wood prefer 3,06 maybee from w210 .You have the bigger 3 arm Flank to conect the Driveschaft.
etc etc and its can handle the power. My choice

 

[Brento]

Great input thanks, particularly the compatibility with the Wavetrac. So the gear sets found in the W210 are compatible? If so they would be much easier to source, I notice on gsxr's differential chart the only W124/R129/W140 fitted with the 3.06 is the 91+ 300CE.

 

[gsxr]

Great input thanks, particularly the compatibility with the Wavetrac. So the gear sets found in the W210 are compatible? If so they would be much easier to source, I notice on gsxr's differential chart the only W124/R129/W140 fitted with the 3.06 is the 91+ 300CE.

The 500E-specific Wavetrac / Quaife are only compatible with the early W210, which have 210mm diffs. think may only be the first year or two of production? Maybe only 210.072 chassis with M119?

Later 210 (as of 1998?) the diffs changed to some oddball size like 198mm, and I didn't pay much attention because those are not plug+play for the 124 chassis. Later diffs eliminated speed sensors at the diff, as the sensors were relocated to the rear wheel carriers instead. There may be a different Wavetrac / Quaife available for later W210 diffs but I've not done any research into those.

 

[gerryvz]

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