I have changed the differential gears to 2.45:1, a great improvement. However, since the speedometer and the odometer read the driveshaft revolutions, both speed and distance show 2.45/2.90 less than before. Speedometer and odometer are in kilometers, not miles.
So, the solution is to change the odometer gears to those of a car that uses the 2.45 differential. Now the question:
What are the part numbers of the odometer gears that match the 2.45:1 differential ratio?
This is important because I use the car mostly in classic car regularity rallys, and acurate odometer (and speedometer) readings are crucial.
Any help here will be greatly appreciated.
- Site Admin
- Posts: 28925
- Joined: Tue Sep 14, 2004 12:23 pm
- My E21(s): '81 323i Baur
- Location: The Netherlands
Of course there are ways to get to a shorter final drive by changing out internals, but if that's the case I do not know of any factory stock possibilities to adjust the odometer to that. However, there must be mechanical odometer specialists that should be able to solve this for you.
My E21 is 320, 2 liter engine. I fitted a Weber 40 twin body carburetor, IrishEngineering forged "high head" pistons to increase the compression ratio and dimensioned down pipes in stainless steel, all the way to the back. The car gained around 30 to 40 in power just with those modifications.
This engine now handles very well the 2.45:1 differential ratio. The car is much better now.
The issue I have, is to correct the odometer reading to reflect the difference between the 2.45 and the 2.9 ratios. That can be done by changing the small gears that drive the odometer cilinders. However, I need to identify those gears that will exactly match the 2.45 diff ratio.
- E21 Mad
- Posts: 2957
- Joined: Mon Nov 04, 2013 9:49 pm
- My E21(s): E12 520-6
- Location: nederland , Weert
Haha, thats a realy long diff ratio. With a 2.45 diff your car would do 145km/hour in second gear easily. Could you confirm that?
We do classic car rally's and regularity's also. We do not rely on the speed and odometer in the car, therefore we have fitted a period correct rally trip meter, which is verry accurate.
Megasquirted '77 E12 520-6
Aspen Silver '96 E39 523i
Sort of a hybrid between Bertje's solution and the original.