Chrysler Repair: Speedometer error / knocking sound from engine, odometer check, calibration factor

Question
Hi,

My 2001 Chrysler T&C has 120000 miles, the speedometer is not working.  It's running 10 miles over the correct speed.  Also, it's making a knocking noise in the engine when running.  I see small power lose but not much.  What should I change?

Thanks,
Jason

Answer
Hi Jason,
The speedometer error may be just a loss of accuracy with age or it might be an incorrect calibration factor in the transmission controller. The test would be to see if the odometer distance reading is in error or not. If you happen to pass an odometer check section on a highway and compare how far the odometer says you went in comparison to the actual distance and you find that is thinks you went further than you actually did, then that error could be corrected and at the same time the speedometer would be corrected by the same fraction if you went to a dealer and had them change the 'pinion factor' by using a diagnostic reader box so as to make the necessary correction. It might be the result of the tire size having been changed sometime between when the van was new and today that has caused the error. But find out what is going on with the odometer accuracy and if it too is optomistic about the distance travelled then decide if you want to have a corrected 'pinion factor' entered in the controller.
Diagnosing noises is an 'art' when one can hear it, so I can't really speak to a knocking noise except to say that what people describe as a knock is often due to a main bearing or rod bearing that has too much play in it. Were that the case, only a rebuild of the specific area would fix it.
Roland