Will changing diferentials throw off the speedometer?

[Rukus]

I am in the process of a 3.64:1 ratio to a 3.91:1 ratio differential swap in my car. i know the speedometer reads from a sensor inside the differential. Will my speedometer get thrown off at all? or will it read accordingly?

 

[bahnstormer]

no it'll be the same

edit - of course rpm's at highway speed will be increased

 

[wood_e]

yep, the only tihng that will be different is your higher speed RPMs. Your top end will also be decreased.

 

[Rukus]

yeah i am not too worried about that, i usually don't drive 190km/hr too much anyways.

haha

 

[OreoGaborio]

3.64??? this a 4-speed?

 

[Rukus]

no, its a 5 speed. 318i's prior to november of 83, were equipped with the 3.64. after that they got smart and threw in the 3.91.

Prior to MFG date of 83. and not 84... technically 84, but you get the idea.