Just got 3.73's installed today with a new posi and cover. The mechanic said he changed a reluctor ring I think, and said that I would not need to reprogram the computer because he changed that part out. he also said that he was able to do that because the speed sensor was in the rear axle. I was hoping you guys had an idea as to what he changed and if I should tell him to take it out. Just from driving around easily, I think the speedo is correct. I have a 3 series carrier with 3.23's previously. There are no codes present

Looking in the FAQ I found this:
15. What's the difference between a 3 channel and 4 channel rear?

A three channel rear end has ABS. On a 3 channel rear end, the two front wheels have sensors, and there is one sensor on top of the rear end housing that reads for the whole rear. 3 channel rears have one big reluctor ring on the differential.

Since he said he changed the reluctor ring, I shouldn't have to do anything PCM side should I? Speedo and Odometer will be reading correctly?

 

Im not sure why changing that would make your speedo and odo right, on mine I had to get the pcm redone, 2.73's 2 series. One other things, you mean 3.73 not 3:73

 

you will need your pcm programmed to correct the speedo,, the rear end speed sensors have nothing to do with your speedometer, they are for abs

 

ok, that makes sense because the VSS is on the side of the tranny. So if they didn't change the reluctor ring, how would that have affected the abs? (just an fyi for myself). Ill get the PCM tuned asap. Thanks

 

As long as you kept the 3-series carrier, there was no need for him to do anything with the reluctor gear. The simplified ABS system in these cars seems to work primarilly by looking for a wheel speed approaching "0" when all the others are still turning at higher velocity, and kicking in the modulator to prevent the "slow" wheel from locking up. It doesn't seem to be very sensitive to differences in tire diameters, gear changes, etc.