Help! Crusing @ 60mph 5th gear 4000 revs

[Bahama325]

i think this may help
"The speed sensor gear is typically mounted on an eccentric to accomodate
installing different gear sizes to account for changes in the ring and
pinion gears. If your car had 3.07:1 gears, and you wanted to change to
4.10:1 gears, then you would need a new speed sensor gear so your
speedometer and odometer remained in proper calibration. Since this would
require speed sensor gears with different tooth counts, then the speed
sensor gears would necessarily be different sizes, and would need to be
mounted differently in order to maintian the proper gear mesh."

http://newsgroups.derkeiler.com/Archive/Alt/alt.autos.bmw/2005-09/msg00512.html

[supkev]

my redline is 7k also.

[LJ851]

i think this may help
"The speed sensor gear is typically mounted on an eccentric to accomodate
installing different gear sizes to account for changes in the ring and
pinion gears. If your car had 3.07:1 gears, and you wanted to change to
4.10:1 gears, then you would need a new speed sensor gear so your
speedometer and odometer remained in proper calibration. Since this would
require speed sensor gears with different tooth counts, then the speed
sensor gears would necessarily be different sizes, and would need to be
mounted differently in order to maintian the proper gear mesh."

http://newsgroups.derkeiler.com/Arch.../msg00512.html

The speed sensor in a BMW diff is mounted to be triggered by a chopper wheel on the output of the diff. It doesnt know what the gear ratio is nor does it care. Tire diameter is the only thing that affects its reading.

[nando]

My red line is 7gs, after reviewing the two sensors there is a big difference, i think that is the culprit, i am going to replace, on the stock diff the sensors are uneven and on the 4.10 they are even.

No. all bmw diffs use a 9 tooth wheel. It doesnt matter what ratio you have, the culprit is you have the wrong coding plug for the instrument cluster.

[o.d.]

hook up an external tach just to check the rpm's

[kamotors]

definitely tach, not even a 4.27 revs that high

[supkev]

alright I'm gonna buy another tach since my odo and stuff don't work I could use it

[Zesty Bonanza]

your tach is probably not reading correctly

I think the Euro Tach is reading the RPM incorrectly. I test drove an e30 that had a tach in which the RPM wasn't correct because the redline gas cutoff was about 2k higher than the 6.5k rpm. His tach would increase and then get stuck at 7k while the car would still accelerate. his car also read the speed wrong, but it was in MPH instead of KM/h.

Then I test drove another guy's e30 and described the issue of the previous car that I test drove and this guy said that the euro tach has the problem of not reading the speed and RPM correctly.

I think both of those people are (or were) on this forum.