P0733?

P0733 - Gear 3 Incorrect ratio
P0734 - Gear 4 Incorrect ratio

These codes set when there is excessive slippage in a clutch pack. The transmission computer knows engine speed, (actually input shaft speed), and it knows which gear is activated. The gear ratio of each clutch pack is programmed in. Based on all that information, the computer knows what road speed, (output shaft speed), should be for a given input shaft speed. Those two will not agree when a clutch pack is slipping.

You can get an idea of the cause of the problem by observing when it goes into limp mode. If there is an electrical problem, such as a broken wire or corroded connector terminal, it will go to limp mode the instant you shift to "reverse" or "drive". The check engine light will turn right back on as soon as it completes the six-second bulb test. Code 700 in the engine computer just means there are other codes in the transmission computer.

If there is a mechanical problem with a sensor, such as metal filings built up on the tip, or an air gap that's too big, those will prevent it from developing a signal voltage even though electrically, everything is okay. That will not be detected until the computer sees the vehicle is moving. The check engine light will remain off as long as the van is standing still, even if it is in "reverse" or "drive".

If the check engine light is off when you drive off, and it starts out in first gear, everything electrical is working up to this point. When it bangs to second gear, (limp mode), and the check engine light turns on, look for what is taking place at that instant. Most commonly that is an up-shift under light to moderate load. The clutch plates wear a little each time the clutch pack engages. On older vehicles we had a good two years warning that was occurring by the "engine runaway" between shifts. Engine speed jumped up higher than normal while it was waiting for the next clutch to engage. With your design, which was a Chrysler innovation for the 1989 model year, the computer learns how much fluid volume it takes to apply each clutch pack, and it constantly updates those numbers as the wear takes place. To address that engine runaway, it will apply third gear, for example, a little sooner, and wait a little longer before it releases second gear. The result of that overlap is a nice crisp, solid shift, until it cannot update any further. The drawback is you do not get that two-years of warning that a rebuild is in your future. One day it shifts perfectly; the next day it goes to limp mode.

A transmission specialist can tell if I'm right by reading the "clutch volume index", (CVI), on a scanner. That is a set of four numbers representing the volume of fluid it takes to apply each clutch pack. As more and more clutch plate material wears off, more fluid is needed to squeeze the plates together.

You may be able to bypass the problem for a little while by accelerating a little harder than normal to delay an up-shift, then let off the accelerator pedal to let it up-shift under no load. The reduced torque will reduce the chance for the clutch pack to slip. If it does go to limp mode, you must turn the ignition switch off, then restart the engine to get it out of limp mode.

You do not actually buy a clutch pack. The fiber and steel plates inside each of the four clutch packs are replaced, along with a lot of rubber seals, as part of a rebuild.

Talk with the specialist first. If there is a problem with one of the solenoid-controlled valves, fluid pressure to apply that clutch may not rise high enough to lock the plates together efficiently, but that should set a different fault code as monitored with a pressure switch.

They did have a lot of trouble with this transmission in the early years, but at the mileage you listed, it seems too early to need to rebuild the transmission. I would have more faith in what the specialist has to say if you see him connect a scanner to read the clutch volume index before he suggests a plan of attack.

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

Please let us know what happens.

Cheers, Ken

Hello,

This means you need to replaced the transmission input shaft speed sensor. Here is a video of the job being done so you can see what you are in for when doing the job.

https://youtu.be/f3bETtCIdxM

Here is the location for your car.

Check out the diagrams (Below)

Please let us know if you need anything else to get the problem fixed.

Cheers

Yup, there's two and they are different. Input speed sensor and output speed sensor. They refer to engine speed and axle shaft speed.

Check the picture

Any particular reason why you replaced the CKP sensor, when both the codes refers to the transmission?

P0700 Transmission Control System Circuit. Your transmission control module.
P0725 Engine Speed Input Circuit Error. Possible from P0700 and/or input speed sensor.

Try this diagnostic.

DTC P0725: ENGINE SPEED SENSOR CIRCUIT

NOTE: Crankshaft position (CKP) sensor signal may also be know as EATX RPM signal.

NOTE: Ensure PRE-DIAGNOSTIC CHECK has been performed before proceeding with the following procedure.

Circuit Description

DTC P0725 will set when engine speed is less than 390 RPM or greater than 8000 RPM for more than 2 seconds with engine running.

Possible Cause
Open crankshaft position sensor signal circuit.
Crankshaft position sensor signal circuit shorted to ground.
Crankshaft position sensor signal circuit shorted to voltage.
Malfunctioning TCM.
Malfunctioning PCM.

Diagnostic Procedure

1. Using scan tool, read PCM DTCs. See appropriate SELF-DIAGNOSTICS article in ENGINE
PERFORMANCE. If any crankshaft position sensor DTCs are present, diagnose and repair fault
before proceeding. If no crankshaft position sensor DTCs are present, go to next step.
2. Using scan tool, check STARTS SINCE SET counter. If counter is not set to zero, go to step 8. If
counter is set to zero, go to next step.
3. Turn ignition off. Disconnect TCM and PCM harness connectors. Measure resistance of
crankshaft position sensor signal circuit between TCM and PCM harness connectors. See
WIRING DIAGRAMS. If resistance is less than 5 ohms, go to next step. If resistance is not less
than 5 ohms, repair open in crankshaft position sensor signal circuit.
4. Measure resistance between ground and terminal No. 6 (crankshaft position sensor signal circuit)
at TCM harness connector. If resistance is less than 5 ohms, repair crankshaft position sensor
signal circuit for short to ground. If resistance is not less than 5 ohms, go to next step.
5. Connect TCM harness connector. Ensure PCM harness connector is disconnected. Turn ignition
on. Measure voltage between ground and crankshaft position sensor signal terminal at appropriate
PCM harness connector. See WIRING DIAGRAMS. If voltage is 10 volts or less, go to next
step. If voltage is greater than 10 volts, repair crankshaft position sensor signal circuit for short to
voltage.
6. Measure voltage between PCM harness connector ground and crankshaft position sensor signal
terminals. Ensure ignition is on. If voltage is 4.5-5.5 volts, replace PCM. See appropriate
REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. If voltage
is not 4.5-5.5 volts, go to next step.
7. If not problems have been found, replace TCM. See TRANSMISSION CONTROL MODULE
under REMOVAL & INSTALLATION. Perform SHIFT QUALITY QUICK-LEARN
PROCEDURE and PINION FACTOR PROCEDURE under PROGRAMMING.
8. Conditions needed to set DTC P0725 are currently not present. Perform wiggle test to diagnose
intermittent or poor connections. Repair as needed. If no problems are found, testing is complete.