Attention: TDR Forum Junkies 
1992 w250 automatic Cummins 5.9l
The problem " Down shifting from 4th to 3d/ randomly " sometimes not for several days then it could happen 6 times in six miles . I spent 19 years on and off thing to solve the problem. The dealer said they could " replace " the throttle position sensor " $$$$. I found some information that the sensor could be calibrated using a 10 mm open end wrench and a volt meeter which I did as per instruction. Problem solved for a few weeks and then it was not. Here is the easy way: take the 10mm wrench and find the adjuster on the the throttle position sensor ( located under the sensor and no you can't see it unless you remove the sensor ) turn the adjuster to a full stop counter clockwise very small movement possibly 15º don't use force . Worked for me just saying.
The problem " Down shifting from 4th to 3d/ randomly " sometimes not for several days then it could happen 6 times in six miles . I spent 19 years on and off thing to solve the problem. The dealer said they could " replace " the throttle position sensor " $$$$. I found some information that the sensor could be calibrated using a 10 mm open end wrench and a volt meeter which I did as per instruction. Problem solved for a few weeks and then it was not. Here is the easy way: take the 10mm wrench and find the adjuster on the the throttle position sensor ( located under the sensor and no you can't see it unless you remove the sensor ) turn the adjuster to a full stop counter clockwise very small movement possibly 15º don't use force . Worked for me just saying.
