Looking at a 2004 XJ8 with transmission issues. Fault codes 0783 and 0785 codes are stored. Anyone have this problem? Does it require a transmission replacement? Looking for a winter project, but I do not want to bite off more than I can chew. Car has 89000 miles. Seller is asking $3500. for it. Seems high for a car with issues.

 

Seller down to $3000 now. Has anyone had these fault codes? 0783 and 0785. Does this mean a transmission replacement or can it be fixed while in the car.

 

Sounds like they are expecting it to need a trans swap for that price. Not sure of the codes meaning.

 

Get him to $2000-$2500 or walk away. You could just have low fluid level. I would check a couple of things. Is the trans pan wet?

I think you could have the sealing sleeve leaking causing a low fluid condition which will give you all those errors.

Also check the two small bolts that hold the shift cable to the transmission. They get loose and can fall out. Be GENTLE! They only need a snug up.

The shift cables can stretch too so I would attempt to adjust the shift cable. If it does not adjust properly that is telling you the cable is most likely stretched and should be replaced.

Be sure and do a pan and filter change when you service the transmission.

Finally check the transmission cooling lines. They are know for seeping where the metal meets the rubber sections. You can fix this easy at home or spend thousands at the dealer to replace the lines. It's much simpler to cut the metal ferrule off and use two worm drive clamps to hold the rubber hose onto the steel lines.

I would get the car in then air and inspect the above. Do you have a transmission shop you could take it to for an estimate?

Don't give up yet!

If you do get it and fix the above be sure and get the TCM flashed at the dealer with the latest software. It does make a difference.
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Hi noterman,

P0783 indicates a problem with the gear 3 to 4 shift due to a problem with the Engine Control Module (ECM) torque signal, or a transmission malfunction. You can download the Jaguar Diagnostic Trouble Code (DTC) Summaries Manual here:

https://www.google.com/url?sa=t&rct=...03388427,d.cWw

A problem with the ECM torque signal could mean corrosion on an electrical connector, water ingress to the main ECM electrical connector under the cabin air microfilter housing at the rear right corner of the engine compartment (the ECM is behind the glove box on LHD cars, but its connector is on the other side of the firewall). Another very likely cause of transmission-related error codes is fluid contamination of the transmission electrical connector that tbird6 mentioned, and corrosion on ground studs can also cause erroneous fault codes.

The manuals I have do not show P0785 as a code that was implemented by Jaguar on 2004 models, but the list of Ford codes shows that it indicates a malfunction of the Shift Timing Solenoid 'A'. I'm attaching the list of Ford DTCs for your reference.

Worst case, you could probably find a good salvaged transmission because the 6HP26 was used in lots of cars but demand for replacements is low given how robust and reliable they are.

Cheers,

Don

 

Thanks to everyone who has helped me with this. The car recently had the transmission cooler lines replaced. Maybe that has something has something to do with the codes. Or maybe the fluid level is low. Thanks again

 

A transmission swap with a rebuilt unit at a Jaguar indie in my area runs about $7K. So that is what you are looking at worst case. Say he is down to $3k + $7k you are looking at $10K which is a lot of money for that car. Now if you get it at $3K and all you do is a transmission fluid job and it works, then you are ahead of the game.

You like to gamble? Personally, I do. I don't always win, though...

 

I offered the owner $2000 he is now at $2800. I plan on holding firm at my price. As everyone in this hobby knows its easy to get upside down on these cars.

 

Count on being a certainty!

 

I don't see these sales on their website, but our forum sponsor Coventry West recently sent an email advertising a sale on salvaged transmissions. If the gearbox is truly bad and you are capable of doing the swap yourself, it's an affordable option:







Cheers,

Don

 

Definitely an affordable alternative. Elbow grease required.