I bought a 2003 STR with 77K on the engine. It's in good shape but the second day I owned it I noticed that at highway speeds (~50-60mph) the transmission seems to be flipping back and forth between gears like it doesn't know which one to be in. It flips about once per second. It is very subtle but if you pay attention to the RPM's the needle bob's a bit and you can feel the car surge like you're quickly but gently goosing the accelerator rapidly.

I took it to a local mechanic who said the transmission fluid was low and he put in more. He used Merc 5.

Since then, I am still having the issue. I called the dealer and he said the mechanic used the wrong fluid in the transmission.

I called the mechanic and he assures me that the Merc 5 is appropriate for the car.

I can't seem to find anything to clarify this on the web (though I'm finding much to confuse it). I know that Jaguar recommends their specialized fluid but I can't imagine my mechanic would have messed this up. He's been very good with all of my sports cars for years.

Can anyone clarify this for me before I start making more calls?

Someone else suggested it could also be the fuel pump making it do that.

 

I just put a new gearbox in my 03 STR (140K miles) was having similiar issues but we found metal shavings in the pan... Needed a full rebuild with valve body roughly a $5K rebuild.

On yours with the lower mileage I would say take it and have a complete transmission service done. Fresh filter, pan and fluid can make a world of difference also have them change the sleeve when they do this, if its not leaking now it will be soon. Also may be worth trying to reset the TCM/ECM pull the battery connections and touch the positive and negative battery cables together for about 10 seconds then reconnect and the car should start re-programming itself.

Last but not least if all else fails you can have the dealer do a re-flash of the TCM/ECU this also has been known to help, but mostly with lurch issues...

Good Luck and let us know what you end up finding out!

 

Thanks for the quick input CB!

Every now and then the computer seems "confused" too like sometimes the traction control is off when I start it (and I'm not in sport mode) but when I restart it it's back on and weird little glitchy things like that. Could that indicate that a simple reset of the TCM might clear this up? Same system? That would be great (and CHEAP!)

 

Ahhhh I see said the blind man when he picked up is hammer and saw... ;-)

Based on what you have described above it now sounds to me more like a good old weak battery issue. These cars are NOTORIOUS for bad batterys and when they start to go the first sign is exactly what you have described electrical gremlins galore!!

If you are not sure how old the battery is or when it was last changed I would opt to just pick up a new one, they run about $150 bucks and can be had at just about any part store (NAPA, PepBoys, Autozone) you could have it tested but the results are often not reliable.

A new battery has been known on the forum here to cure alot of what ails your cat!

 

That would be great. It certainly would be worth $150 to find out rather than the dreaded game chasing gremlins in my cat and racking up invoices...ugh...that's like...well...herding cats...OOOhhhhhh....I get it now!

I'm on my way to Auto Zone after work...

 

Merc 5 would be appropriate only if a complete flush & filter/pan change was completed. If not - then there might be trouble down the road (literally!) I would certainly invest in a full fluid, pan/filter change.

 

Is Merc 5 the identical ZF LifeGuard6 fluid? I suspect not but if it is then you'd be OK.

Well, if they filled it exactly right (which is a bit painful, and you DO need to do it).

 

Well go ahead and do the transmission service because it's needed. But you have the classic signs of a failing TQ clutch. Seems like the 2003 STR was more prone to that or maybe they just have more miles on them by now.

Have you read the TSB ??
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Maybe that's is needed. Is the issue the pressure being within specs? Will the two fluids (thus altered fluid density) cause the sensor to not be able to set a solid pressure switch/shift point consistently?

 

Not sure. I'll need to research it but I agree. I sense it isn't the same.

 

I haven't read the service bulletin yet. Is it on this forum somewhere? I'm still learning this forum so forgive if it's readily available. I just haven't seen it yet.

If it's the TQ clutch, that would throw an error code wouldn't it?

 

It should set a code but sometimes not. Here are two possible causes.
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Failed torque converter is also my first pick. My 03 STR presented with same symptoms that a trans. and TC rebuild remedied.

 

I had the same surging in my 03 S type R which turned out to be Torque Converter Lockup Clutch. On mine it threw up a Transmission fault but before that it was giving the same surging on steady drive at about 70mph.

 

Thanks! This is very useful. Sounds like installing the newest software might be the cheapest way to start to try to pin this down.

Where can I find these kinds of records?

 

From the input, it sounds like it's leaning towards the TC. When yours acted up, did it feel like a very subtle surging almost like it was shifting up and down about once per second? It's almost imperceptible unless you pay attention to the RPM and the "feel" of the ride.

 

That's exactly how mine acts, but only when cold.

 

Not sure what records you are talking about? But I got a complete service history printed out for my car from my local Jaguar dealer. It's very useful. I would see if you can round one up.
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I don't think it's only when it's cold for mine. Seems to happen all the time. Did you see clubairth1's post above? The paper on "Surge During Warm Up..." looks like your issue maybe.

 

I wish you the best luck in resolving your problem.
Regarding a TCM reset, you cannot achieve this by disconnecting the battery and shorting the leads together. You must reset the TCM with the dealer tool. Shorting the battery leads together will reset the ECM though.

Does this confusion behavior continue if you manually downshift into "5" while at speed?

When you say "Merc 5" is this a contraction for Mercon V? The only fluids that can be "added" to the ZF transmission with original fluid is more ZF LifeGuard6, Shell 1375.4, or Mercon SP. These are essentially the same oils.

And when the mechanic "added" the fluid, how did he accomplish this feat? There is no dipstick. The addition of fluid to the sealed-for-life transmission involves a relatively complex procedure, not a simple remove plug-add fluid-install plug.

The advice to replace the filter pan with fresh fluid is sound for the given miles your car has. I did this to my S Type at 66k miles.