when driving with no load
by Visitor in Rio Rancho, NM on April 04, 2011
There is a Technical Service Bulletin to address a similar issue.
SUBJECT: Vibration or Perceived Engine Miss
DATE: Apr. 14, 1995
NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH THE CUMMINS DIESEL ENGINE AND AUTOMATIC TRANSMISSION.
A vibration or perceived engine miss at approximately 1100 RPM as the torque converter clutch engages. This condition occurs in 4th gear at speeds between 42 to 48 MPH.
After duplicating the above condition, verify the part number on the Powertrain Control Module (PCM). For proper repair procedure, refer to the guidelines given below.
If the vehicle is a 1994 MY equipped with PCM P/N 56027303 or 56027304, replace the PCM with P/N 4798745. Proceed to the PCM replacement section of this TSB.
If the vehicle is a 1995 MY, verify that it is equipped with PCM P/N 56028335 or 56028336, and proceed to the PCM reprogramming section of this TSB.
If the vehicle is equipped with a PCM other than 56028335, 56028336, 04798745, or 04856080, replace the PCM with P/N 4798745 and proceed to the PCM replacement section of this TSB.
NOTE: IF THE VEHICLE IS EQUIPPED WITH PCM P/N 4798745 OR 4856080, THE SOFTWARE UPDATE NEEDED TO ADDRESS THIS TSB ISSUE HAS ALREADY BEEN COMPLETED AND NO FURTHER ACTION IS REQUIRED.
(1) 04798745 Module, Powertrain Control (1994 Only)
(1) 4669020 Label - Authorized Software Update
(1) 4275086 Label - Authorized Modification