I searched prior threads and did not find an answer. I left my ignition switch slightly on and completely drained my battery after sitting for a week. Now I have a hard 1-2 shift and a hard 2-3 shift. I suspect the trans pressures went to factory settings when the computer dumped from the dead battery.

background: 1999 V10, 4WD, DRW. I have 165K on my truck, to my knowledge it has the origional transmission. I did an drain and fill on the transmisson a few years ago when I installed a new engine.

Is there a learning process for the computer to adjust shift patterns? Do I need to have a mechanic adjust the pressures with a high end computer? Do I need to get the 5 star tuner that has been on my wish list forever to adjust the pressures? Thanks for your advice.

 

Just drive is the easiest protocol. If there's nothing internal wrong, the PCM will make it's adjustments and the shifting behavior should improve.

Not possible. However, it the (firm? harsh?) shifting continues, it might be advisable to have some diagnostic work done to see if the issue is internal or not.

FWIW, I've had the battery disconnected a number of times on my 01 SD and I've never even noticed any perceptible change in shift feel after any of those events. YMMV.

 

Not for this truck, no. It does not adjust shift pressures.

No, it will not. This computer does not have that ability.

Read the codes. Then we will know how to diagnose this.

 

On the 1st drive after the battery went dead I didn't get a service engine lignt. On the 2nd drive I got a light. The code is P0500, speed sensor. I did see the speedometer being erratic on the 1st trip. Can a speed sensor problem cause hard shifts?

 

Yes, as the PCM is 'guessing' when to shift. It normally uses engine rpm and vehicle speed, and I'm not sure on these trucks but some also use transmission line pressure, to determine the proper point at which to shift. If it is getting erratic or no input from the speed sensors then it doesn't know how fast it is actually going.

 

I believe that there is a mode that the transmission goes into under certain trouble codes that causes harsh shifts

 

The PCM uses pedal position and vehicle speed to schedule the shifts. Engine RPM is only used when the vehicle speed is determined to be faulty.

I have never heard of an electronically controlled transmission that would use line pressure to schedule the shifts. The PCM controls line pressure, so it makes no sense to use line pressure to schedule the shifts. Also, there are no pressure sensors, so the PCM doesn't even know what line pressure really is. It only knows what line pressure it told the transmission to set.

 

Just putting in an update to close out the thread for future users. The problem appears to have been caused by a leaking windshied. It was leaking on the passenger side. down the A pillar. I'm not sure what the water was getting into, but after getting the windshield replaced there is no parasidic draw on the battery and the transmission started shifting normally. No more speed sensor check engine light.