Chrysler Repair: Trans limp-in issues: code 0733, hydraulic control valves, hydraulic pressures

Question
QUESTION: We have 1997 Concorde with a 3.5L 4 speed auto.The trans.won't upshift to fourth gear and has two codes that keep coming back after being cleared and a trans quicklearn has been done,Also both the input and output sensors show speeds on the screen.What could be doing that??Also what years and engine sizes does this trans. fit?Any help is appreciated.

ANSWER: Hi Dave,
What are the numbers of the transmission codes? That would best explain what is going on. Of course they will return until they are addressed. I am not certain what you mean by "show speeds" on the screen. What are the numberical values of 'speeds' and in what gear were these taken? On the interchangeability question, a dealer parts counter would be best able to help you with that.
Please let me know the answers to my questions if you want to move forward.
Roland

---------- FOLLOW-UP ----------

QUESTION: The two codes are p1790 fault immediately after shift and p0733 error in third.The input and output sensors both show rpm while driving in drive.Not sure what the readings are though.it goes about a half a block when the codes are cleared then shifts really hard and the codes come back.Fluid has been changed and no debris was found.

Answer
Hi Dave,
The issue is that the ratio between the speed of the input and output sensor is not what would be expected for third gear, indicating some slippage. This could either be a mechanical issue with the clutches (od/ud)* used for that gear or the fluid hydraulic pressures that operate the clutches are out of the normal range due to the hydraulic control valves involved or the overall hydrualic pump pressure not being correct. So the first thing to do is a 'third gear clutch test' for slippage using a diagnotic test box, and then measure the pressures when those valves are called into play and if that passes then you pretty much are faced with opening up the trans and dealing with mechanical wear of the clutches/associated components. The valves can be replaced as a 'solenoid pack' without removing the transmission if they are found to be at fault.
Roland
*The od clutch is involved in only 3rd and 4th gear, while the ud is used for 1,2,3 gears.