Regearing the differential.

[elan4me]

As I enjoy driving my 69 S4 on these wonderful fall days on Northern California's great winding roads. I do have to motor along some of our highways to get to them. With the average speed of 65 to 70 mph the engine is turning around 4000 rpms. For a more comfortable drive, is it possible to regear the differential? I had the transmission rebuilt when I rebuilt the engine 9 months ago. So I'm not ready to replace it with a 5 speed. Any other ideas?
Thanks
Stan

[john.p.clegg]

If you change the diff ratio you'll have to regear the speedo drive or have the speedo recalibrated
John

[elan4me]

Are either job very difficult; changing differential gears or recalibrate the speedo?
Stan

[mac5777]

Stan, I too drive the Northern CA roads and I did change the diff to a 3.55 ratio from the stock 3.77. I have a semi close transmission and I drive 65 mph at about 3400 rpm. I have not done anything to the speedo yet but I assume it reads slow. My tire size are stock 145/80/13. The taller tires also keep the rpms down. The 5 speed trans seem to have negative stories if you can find one. That's when I decided to stick with my four speed and have Kampena Motors lotus at Infineon Raceway rebuild the diff with a new 3.55 gears. I'm very happy with the results.

regards, Sarto

[SADLOTUS]

Hi there, years ago i changed my axle ratio for a higher one too. I went for the 3:54 from a Ford RS 2000 escort - straight in no probs- just the usual getting the diff out problem!
There is a plastic gear the other side/inside of the rightangle speedo drive that has to correspond with the axle ratio you are running, different colours depending on the ratio, it's in the workshop or parts manual somewhere. again no prob to get out - just the usual gearbox out first problem!
I think mine is black for the 3:55

Did you have RS200's in northern California?