[quote=HotRodDave]They don't need any flashing to change gear ratios. The tone wheel is on the ring gear and is not affected by gear changes, it still turns the same rpm as the tire no matter what gear is in it. However changing tire diameter will change your speedometer. The actual rear end may have different number of tone wheel teeth but I have never counted them and never been asked by my mac, snap-on scanners or the old DRBIII what diff is in one when programing the "pinion factor" as they call it so I would suspect they are all the same.
Are you sure you got a dana in it? I have two of those vans and they both have 9.25 rear ends in em. Also both of them have 3.92 gears, ones an 01 and ones a 92.
Dave is right as I appoligize as I actually do know that but was not thinking in the right mode as I just forgot about that. As Dave said it reads off the tone gear thats behind the ring gear in the rear diff and dumb me should have remembered thats why the scanner asks for the type diff and not a gear ratio. Just tire size or changing to a different style diff may affect it as like Dave I dont know if the tone rings from one style diff to the other have different number teeth. Course you can have the tire size or revs per mile set. Do have any friends with a scanner that could set it for you or maybe if you know a Mopar tech you can slip him a couple bucks to do it on the side ? Good luck with it and again I am sorry that I just forgot about the sensor reading the tone wheel which dont change when you change ring and pinion. All I ever used was the Mopar DRBIII scanner since I worked at a Dodge dealer and could use it whenever I liked but as Dave said many other scanners should be able to do it. Ron
Don't be hard on yourself, you responded to my post and I appreciate it. I wouldn't hesitate to ask you more questions in the future. At this age we all have a little brain fade, sorry to say. LOL
Mike
Thank you as I appreciate that. At 61 I sure do get a little brain fade once in a while.
There is another speed sensor in the trans tail housing and its for just the trans shifting as far as what I was taught. I guess it could be used as back-up for the PCM if it lost the rear diff speed sensor. Thats important for the PCM to know the trans output shaft speed so it can control gov pressure for proper shifts. I actually had a few go south on me over the years that came in the shop. I remember one truck I had that was doing all kind of crazy shifting and it had not set any codes. A few guys said I should replace the Gov pressure sensor and duty cycle solenoid but I decided to watch and record all the sensor when I drove it acting up. And I saw right away it had to trans tailshaft speed rpm for that sensor and of course it worked fine after I replaced it. I could be wrong but I was always told at training that speed sensor in the trans tail housing is just for the electronic gov so the PCM knows driveshaft speed to control the Gov pressure duty cycle solenoid and that the rear diff sensor hats for the ABS is for ABS operation of course and speedo operation.
It was great at the Dealer as when I got weird problems that did not set codes I just put our Co-Pilot (data recorder) on the vehicle and drove it and then when back in the shop just download the info to the shop computer and then I could just take my time to looks it all over and see if I see the problem. It was so much better then have someone trying to look at the scanner info while driving. Ron
