Auto Parts: 1993 GMC dually w/4L80E swap, series transmissions, pep boys

Question
This is a 1993 GMC 1 Ton 6.2L Diesel with a 4L80E Stock.  I purchased a remanufactured tranny, new torque converter and replaced the cooler.  After the exchange, the tranny went into rev and backed out, I put it into OD (as always) and it started shifting erradically after about 10-15mph.  The speedo was bouncing as well.  Thinking that I had the spd sensors reversed, I switched them, and the truck would not go out of 1st.  Any help would be greatly appreciated.  Thank you in advance, Jarod

Answer
Hi Jarod,

The E-series transmissions used the speed sensor to aid the computer in shifting instead of a modulator. If the speed sensor is not turning smoothly, which it sounds like is your issue, then the computer will get bad readings and will place the TCM in limp-mode which will make it shift erratically if at all. Check that the gear on the output shaft is not loose and that the turned-gear is not out-of-round.

Looking for a reputable service technician? My advice on finding a good technician is: Steer clear of the dealership and 'chain' stores like Firestone, Sears, Pep Boys, Monro Muffler/Brake, Midas, etc. as they usually only employ ONE ASE Certified Tech just so they can say they do and chances are, that guy is the asst. manager or manager and is not in the store to diagnose/repair vehicles anyway. Find a service location in the link below or get some names out of the yellow-pages and do a drive-by. Garages that employ ASE Certified Technicians will be marked with the 'Blue-Seal' insignia. If unsure about whether a place employs Certified Techs, just ask to see their credentials. ALL ASE Certified Technicians will be PROUD to show and display their certificate(s).

Thanks for the question, I hope this information was helpful to you.
Fred
Knucklebusters Used Auto & Truck Parts, Inc.
www.knucklebusters.us
570-453-0910
"Re-use is the best form of recycling" Help us recycle by purchasing used parts from us!
Looking for an ASE Certified shop near you? ASE Certified Technicians are the BEST of the BEST!
Click here: http://www.ase.com/bluesealsearch/locator.php