Ratio gear monitoring or my tranny slips

Tom Technical Support Specialist Commack, New York Posted   Latest  
Tech Tip
Driveability
P0783 - 3-4 Shift

Tip O the day,

RATIO GEAR MONITORING

A possible fault code for a late model Land Rover may be P-0783-64 (for example). This code is set for Input/output shaft ratio too high during shift. There are many other fault code numbers that indicate this condition. I'm just using this one for now. Clutch does not open or close.

So what does this mean? 

Well in other words , the transmission is “slipping” between shifts. 

This can obviously be caused by low fluid.

However if the fluid level is at the correct level (and clean) and the filter is clear, then we may want to consider that the actual clutch material is worn away enough to not allow the next gear to fully engage. This can be felt, while driving, in the form of “flair” in RPM while accelerating.

We must also take into consideration, is the supply voltage to the transmission TCM (for electronic transmissions) correct?

Is the TCM up to date ,as far as programming?

Is this a high mileage vehicle?

Is the Mechatronics (electronic valve body) functioning correctly?

Are there other fault code involved here?

If all of the above checks out, the grim news here , is that the transmission will have to be removed and either replaced or rebuilt. It is not a reasonable plan of action to tear down an automatic transmission to replace a single clutch pack. You’re going to have to do the whole show!!!!

ADDITIONAL TIME SAVING TIP

In some cases a USED transmission will be fitted. FOR ELECTRONICALLY CONTROLLED TRANSMISSIONS you will have to re-use the original valve body.

In the common ZF configuration, the TCM is on the back of the valve body (Mechatronics ). This TCM is ‘”VIN specific” to the vehicle it came out of. So therefore it will not be able to be programmed to work in another vehicle.

Either a new TCM or a “ wiped clean” TCM will be necessary. (or any other backyard skullduggery thereof).

Happy and Safe motoring.

+1
Mickey Owner/Technician
Gainesville, Florida
Mickey Default
 

Hi Tom and DN group. Just wanted to throw my .02 cents at this scenario. Technically this transmission is designed to slip. Yes. It works that way. It is a ” controlled slippage”. Closely “ monitored“ (gear ratio monitoring) in order to overlap every up and downshift. Excessive and uncontrollable slippage is what causes the faults to set. Let’s take for example your example. Gear monitoring

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