Second opinion wanted on transmission woes

[Magic_Wond]

After 14 month's respite from the previous gearbox troubles I had on my '97 4.2QS, they are back with avengence. Struggled to get the car home in limp mode this evening as even the slightest gradient caused it to almost grind to a halt. Engine just revs its nuts off and won't change up to 4th/5th. I changed the fluid/filter etc in June last year and this seemed to cure the same problem back then. Could the same issue have returned after only a year? (< 20K miles since then). Or has my torque converter finally surrendered? Difference this time is that the engine just revs in 3rd (I think) whereas last time it still went in to 4th/5th even in limp mode. Here are the codes :-

17118 P0734 Gear 4 - incorrect ratio

17119 P0735 Gear 5 - incorrect ratio

17114 P0730 Gear Ratio Control - incorrect ratio

17087 P0703 Torque converter/Brake Switch B Circuit - Malfunction

Could a fault in the F125 switch generate the P0730 and P0703 codes?

Any advice welcome - at my wits end with this gearbox and car's fate hangs in the balance as its going in for another fluid & filter change this Wednesday.......

[Magic_Wond]

Just a thought -any chance these symptoms and fault codes could be caused by a faulty F125 switch???

[Architex mA8tey]

From Ross Tech Wiki if this helps -

17118/P0734 - Gear 4: Incorrect Ratio

Possible Causes

Wiring and/or connections faulty

Sensor Gear Position Indicator faulty

Gear Solenoides faulty

Mechanical failure

Possible Solutions

Check wiring and connections

Check Sensor Gear Position Indicator

Check Gear Solenoides

17119/P0735/001845 - Gear 5: Incorrect Ratio

Possible Symptoms

Clutch Slipping

Reduced Power Output

Possible Causes

Gear related Clutch slipping/faulty

Gear related Solenoid Valve dirty/faulty

Overloaded Clutch due to continuous high Torque or Tuning

Wiring and/or Connections faulty

Sensor Gear Position Indicator faulty

Mechanical Failure

Possible Solutions

Check Engine Values for Plausibility, especially Torque related ones.

Check Wiring and Connections

Check Sensor Gear Position Indicator

Check Gear Solenoides

Special Notes

The gear monitoring of the transmission control module checks the gear ratio by comparing transmission input and output speed in regard of the currently selected gear. This fault code is being set when recognizing an implausible transmission ratio.

17114/P0730/001840 - Gear Ratio Monitoring: Incorrect Gear Ratio

Possible Symptoms

Malfunction Indicator Light (MIL) ON

Possible Causes

Transmission Fluid contaminated

Transmission faulty (Mechanical Problem)

Possible Solutions

Check Transmission Fluid (Color and Contamination)

Replace Transmission Fluid when necessary

Check Transmission Mechanics

Special Notes

Transmission Damage may be caused by Engine Problems, make sure there are no other/relevant Fault Codes stored in Engine Control Module.

17087/P0703/001795 - Brake Switch (F): Electrical Malfunction

Possible Symptoms

Malfunction Indicator Light (MIL) ON

Possible Causes

Wiring and/or Connector(s) from/to Brake Switch (F) faulty

Brake Switch (F) faulty

Possible Solutions

Check Wiring and/or Connector(s) from/to Brake Switch (F)

Check/Replace Brake Switch (F)

Special Notes

When found in Vehicles with Drive-by-Cable (DBC) the Brake Switch (F) is connected to the Transmission Control Module. On older Models this Code is stored automatically after Terminal 15/Ignition is switched ON. If the Brake Switch (F) is OK you can avoid this Fault Code by pressing the Brake Pedal after switching on the Ignition and prior to checking Fault Codes. The Code should automatically be cleared then.

When found in Vehicles with Drive-by-Wire (DBW) the Brake Switch (F) is connected to the Engine Control Module In this case you should check the Engine Control Module for Fault Codes as well and the Data Bus Wiring between Engine and Transmission Control Module.

[Magic_Wond]

As feared the gearbox is toast. Fluid was fried and full of metal particles, and after one short drive on new fluid & filter the fluid was burnt and filthy again and the magnets covered in metal. Appear the box has a serious internal problem and is effectively grinding metal. I've decided to cut my losses and call it a day, so if anyone is in the market for a 1997 4.2 QS (pre FL) with 149K on the clock for spares or repair I'm open to offers (collection only!!). Car is in excellent condition for year bar the knackered gearbox (pics available).

Gutted at this outcome but c'est la vie.....if someone is willing to either take on a project or spend £1500 on a gearbox overhaul then they will have themselves a great car. Otherwise its up for spares/breaking.