Hi all,

First time poster, but long time Jaguar admirer and now owner of a JRG 03 S-type. To start with, I've done my due diligence in reviewing other posts before starting a new thread, but I do apologize if I missed this being asked.

I bought this Jag about a month ago with 77k miles in unbelievable condition- freshly detailed, new tires, brakes, suspension components, all fluids changed etc, including transmission with OEM ZF replacement. The issue I'm having is when it's cold, the transmission likes to judder very mildly between 30-40 mph, like the TC should be locking up, but can't. After 5 minutes of driving it's completely fine with no issues. A fault code has never reared it's ugly head and if I modulate the pedal properly during those first couple min, it won't act up. I'm curious to know if anyone else has experienced this and what the culprit could be? I've driven brand new cars that shift funky until they reach normal operating temp, but with something this delicate I don't want to chance a bigger problem developing.

Any suggestions would be most welcome.

Tim

 

The ZF is programmed to cycle the converter between unlock and lock when cold. This is done for emissions purposes.
as the Torque Converter wears out this becomes noticeable and you'll see RPMs fluctuate. Common issues not just to jags but BMWs and others who use the same ZF.
Some people let it be, some hold down a gear while the car warms up.
I have the same issue and the TCM flashed with an updated firmware. This greatly improved this issue for me.
The car now holds the gears a bit longer during warm up than before thus minimizing the lockup cycle. The lockup cycle is now non-noticeable by feel. The RPMs do still fluctuate but nowhere near as much as they used to.
Next option would be to rebuild or replace torque converter. Rumors have it the converter rebuilds have not been that great, maybe others can provide feedback.

 

Oh wow, did not know that. I looked up a reflash, and don't think I'm at that point just yet. There aren't any gear change issues or stumbling, and it's only when sitting overnight. Growing up, I was always well aware of GM slushboxes shuttering almost violently when the the TC locked at 50, but knew that's just what to expect since it happened in every vehicle they made.

Thank you for your insight! I'm glad it's not anything too too expensive at this point should the need to replace arise.

 

Unfortunately, that is a "feature" although it does an excellent impersonation of a "bug."

Just put it in "4" for the first 5-10 minutes and it won't do that.

 

Back in the 90s I had a T-Bird that felt like going over rumble strips as the TQ converter went into lockup in top gear. Ford said it was due to fluid degradation. The car was only 1k miles out of warranty (37k miles) so they replaced the converter for 80% of the cost (I paid the other 20%)

 

Maybe see TSB S307-14