differential ratios

[b3robbo]

Hi,

I'm having a problems with the diff on my auto 1992 190e 2 litre petrol.

I have located a s/hand diff, which is ok but the ratios are not the same as the current one. s/hand 3.46:1, current 3.23:1. The dealer that I bought s/hand from is adamant that the 3.46:1 is correct, as his computer says so!
However I know the car and it has never had a new diff before. Where can I get further info on the ratios? I do not anticipate fitting the 3.46:1, does anyone know which model it is for?

Thanks

 

[Sprint'n'Go]

If you were to go with the new s/h diff it would improve your cars off the mark performance and acceleration across the range but the trade off would be higher engine revs for a given speed.

For instance if you currently get 3000rpm at 70mph then with the replacement diff you will be at 3214rpm also at 70mph, or looking at it the other way if you drove at the same 3000rpm you would only be travelling at 65.3mph with the replacement diff.

 

[b3robbo]

True,

I supose I would also need to re-calibrate the speedo and have less ecconomy.

Thanks

 

[Sprint'n'Go]

True,

I supose I would also need to re-calibrate the speedo and have less ecconomy.

Thanks

If you have the speedo altered get them to do it accuratly as in my experience most cars are a little optimistic. My van seems to read a consistent 3-4 mph high across the speed range and this has been similar in most cars I have checked recently. I check it against a GPS like tomtom which I have tested over a measured mile and found to be spot on.

 

[SomethingRattling]

Do you need to recalibrate the speedo? I have a C240 which I am looking at replacing the diffs on and recently had the back axle on axle stands to run the car and confirm the whining was coming from the diffs. One thing I noticed was when the drive was running there was was no indicated speed which sort of suggest that the speedo is connected to the front wheels? Not sure if its the same with your van?

 

[C220GJS]

Do you need to recalibrate the speedo? I have a C240 which I am looking at replacing the diffs on and recently had the back axle on axle stands to run the car and confirm the whining was coming from the diffs. One thing I noticed was when the drive was running there was was no indicated speed which sort of suggest that the speedo is connected to the front wheels? Not sure if its the same with your van?

The signal for the speedo is derived from the ABS wheel sensors, of which there are three on earlier models and four on later models. The ABS control unit takes the average speed from the wheel sensors and this is fed to the speedo.
Don't know why you don't get a signal when running the back wheels only.
Geo.

 

[clive williams]

The signal for the speedo is derived from the ABS wheel sensors, of which there are three on earlier models and four on later models. The ABS control unit takes the average speed from the wheel sensors and this is fed to the speedo.
Don't know why you don't get a signal when running the back wheels only.
Geo.

If your right about using the ABS sensors then not having a signal from two of them (front wheels stationary) would confuse the poor thing and think its on sheet ice! hence no reading.

Clive

500E
E320CDIT210