Hello everyone. I have a 1999 F350 SD 7.3L Auto 4x4. My trans has just started shifting weird. It will shift from first to second to third very fast if I am just starting out slowly. It shifts up into the higher gears before I am hardly getting going. Then it will shift back and forth from 3rd and 4th about a dozen times. After that the OD light will start flashing and it will stay in 3rd.

Also, the speedo doesn't always work correctly. Sometimes as I'm heading down the road at 65 it will drop down to 0. Sometimes it will drop down to 55. Sometimes it bounces around from 45 to 55. I have replaced the VSS on the rearend with a new one from the auto parts store. If I have the cruise control set when the speedo starts to drop, the truck will start to speed up.

I have a Diablo Programmer that came with the truck when I purchased it. When I used it to check the codes I got the following:

P0733 Gear 3 Incorrect
P0603 Powertrain Control Module
P1728 Transmission slip
P0732 Gear 2 Incorrect
P0715 Turbine Input Shaft

I was also watching some of the live data while I was driving. I'm really not sure what I should be looking at but one thing looked out of place. The TPS reading was 0.0v.

From what I understand so far, 0733 and 0722 could be from the engine rpm being higher than expected. 0603 could be related to my speedo problem. 1728 could be because the torque converter isn't locking. 0715 is probably the ISS sensor on the front/top of the trans.

I am looking for suggestions on what to replace first. I'm thinking of 3 different things. TPS, ISS, and the gauge cluster.

Thanks for any help or suggestions on other things I can check.

 

Try this in the 7.3 forum 1999 - 2003 7.3L Power Stroke Diesel - Ford Truck Enthusiasts Forums too, but the TPS can be cleaned, maybe you got a bad VSS it sure sounds like it is still the issue at first glance if not transmission failure? the p0603 is probably from the programmer

 

A lot of those could be caused by a bad VSS signal. Even if you replaced the VSS, the wiring could be rubbed through somewhere. I would inspect all of that wiring as best as I could and if possible try to look at some live VSS data while you're driving, if it's available.