Speedometer and Differential Ratios

HB Chris

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The e9 coupes came with three differential ratios and could be found both open or unlocked and locked or LSD. The speedometers were matched to the car based on which differential was fitted.

Differentials

The differential ratio is expressed as a fraction and is stamped on the right lower side of the differential on a flat boss. The presence of a stamped or painted S indicates locked or LSD.

3.25 = 39/12
3.45 = 38/11
3.64 = 40/11

These differentials were typically found on these models:

3.25 Open - CSi
3.25 LSD 25% locking - CSi and CSil
3.45 Open - Euro 3.0CS/CSA
3.45 LSD 25% locking - CSL, Euro 2800CS/CSA and 3.0CS/CSA and US 2800CS/CSA
3.45 LSD 40% locking - Euro 2800CS/CSA and US 2800CS/CSA
3.64 Open - Euro 2.5CS/CSA and US 3.0CS/CSA
3.64 LSD 25% locking - 2.5 CS/CSA

The LSD could be ordered as an option as well.

Speedometers

The speedometer ratios are as follows (numbers stamped on the speedometer are rounded and include a mm/yy build date):

3.25 KPH W= 0.679
3.25 MPH W= 1.078
3.45 KPH W= 0.7125
3.45 MPH W= 1.14
3.64 MPH W = 1.2164

Note: MPH includes not only the US market, e.g. the 3.25 MPH speedometer

7E8E2DF0-6EF6-4EA3-8475-78BB055A15E6.jpeg


3.45 Locking differential identified by the stamped S

s-l1600 (6).jpg


Internal S 25, sometimes visible through the vent hole
 
Last edited:

rsporsche

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for those interested in the speeds of a given diff ratio with the getrag 265 (5 speed) see the charts below. as i understand, the 262 (4 speed), the gearing is the same for the first 4 gears.
 

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  • e9 - 3-64 diff speeds.pdf
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  • e9 - 3-45 diff speeds.pdf
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  • e9 - 3-25 diff speeds.pdf
    116 KB · Views: 112

HB Chris

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Perfect. Users should note that this is with 16” wheels/tires but should be very close. The numbers match my experience.
 

Markos

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Love the activity in the FAQ! The dogleg pattern is below if anyone is up for generating more PDF's. I can always do it later.

Ratios for the G265/5:
  1. 3.72
  2. 2.40
  3. 1.77
  4. 1.24
  5. 1.00
 

rsporsche

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okay, here are the speeds / rpm for the CR dogleg box. the combination of a CR box and the 3.25 diff looks intriguing ... but i am happy with the 3.45 and the standard 5 speed.
@HB Chris i checked with the 16" tires and the 195/70-14 tires ... and the numbers were basically the same at 3000 rpm
 

Attachments

  • e9 - 3-25 diff speeds - rev 1.pdf
    116 KB · Views: 106
  • e9 - 3-45 diff speeds - rev 1.pdf
    116 KB · Views: 91
  • e9 - 3-64 diff speeds - rev 1.pdf
    115.9 KB · Views: 91
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rsporsche

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Love the activity in the FAQ! The dogleg pattern is below if anyone is up for generating more PDF's. I can always do it later.
i think this FAQ section is / will be invaluable to all members. much easier than searching through all of the forum sections trying to find the most common things to all coupes - colors, sources, vin numbers, stickers, etc. really cool guys - thanks!
 

rsporsche

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here are a couple of other charts with different rear tire sizes - all with the 3.45 diff. 205/70-14 ... 215/60-15 and 225/45-17. all are basically the same but its worth seeing
 

Attachments

  • e9 - 3-45 diff speeds - 205-70-14.pdf
    116 KB · Views: 86
  • e9 - 3-45 diff speeds - 215-60-15.pdf
    116 KB · Views: 87
  • e9 - 3-45 diff speeds - 225-45-17.pdf
    116.6 KB · Views: 91

Markos

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okay, here are the speeds / rpm for the CR dogleg box. the combination of a CR box and the 3.25 diff looks intriguing ... but i am happy with the 3.45 and the standard 5 speed.

I’ll be running a dogleg and 3.25. Technically my carb CSL tribute should be a 3.45LSD but the 3.25 behind a B35 sounds ideal to me. :)

I’ll delete this post later.
 

Oldbmwcoupes

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I was planning on transplanting my m90 drivetrain from one of my early euro 635 cars in its entirety. It has a 265/5 close ratio box. However, I believe that it’s a 3.07 ratio in the side loader LSD. Has anyone had this combo, and if so, what might be the best remedy to speedo error. Thanks mark
 

rsporsche

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i may have the solution. i have a speedo that was thought to work with a 3,07. i would have to look and verify. the other scenario is to put it in and have a speedo shop change the gear in the speedo.
 
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