Need help.
My 2002 Xk8 has been having a strange clacking sound as each gear shifts to the next.
Here's the strange part. It only happens when I drive it from a cold start.
I always let the car run for a few minutes in the morning to warm and I've always had a slight bit of this noise but it's getting worse.
I can rev the engine and there's nothing. When I put the car in drive and pull out, the rpm's rev, car drives out, and just before it shifts to the next gear, I hear a fast clacking sound. Then it does it when shifting to the next gear. Usually after the first full sequence of gears, it stops. And actually doesn't do it again that whole day, no matter how long the car sits. But the next morning, it does it again.
I can drive slowly and it still does it just before it shifts to the next gear. But only in the first few minutes from starting after sitting for at least 24 hours.
I've had the tensioners replaced but he didn't replace the chain. (We found factory metal tensioners were there already but the plastic ends had worn.)
I would assume this could only be a couple issues.
Timing chain?
Gear box?
Or maybe transmission.
Like I said, it only happens for the first few gear changes then it drives flawlessly the rest of the day. My mechanic can't figure it out so I'm praying someone here can give me some good advice on what to do. I'm open to replacing just about anything to stop this potentially chatostrophic situation!

 

In that moment of gear change the TCM should be releasing the torque converter lock up pressure. I cannot remember a specific post on such a problem and am certainly not an expert on torque converters but did have a TCM problem affecting torque converter lock-up. Solution was a JY TCM.

Just thinking with my fingers. Something else to think about and get other comments on.

 

Wouldn't this throw a code or limp mode?

 

My first thought would be a fluid level check. Unfortunately, I don't have a second thought.

 

Lol well, every fluid is new, full and maintained. I've had the trans fluid changed and it was deplorable. My mechanic is a former Jag mechanic so he's really good at my maintainence. I constantly check everything just in case.

This is a very specific issue that we can't pin down. It has to be one of three things.
Timing chain
Gear box
Transmission.
It only happens when shifting,
Sounds like a "chain" spinning until it reaches tension (hmmmmmm)
And only does it when first driven after sitting atleast 12 hours. Cool down.
I'd like to figure this out and fix before something bad happens.

 

Didn't in my case. The Jaguar dealer wanted to replace the TCM for about $2500 which ol' Tight Wad Tom was not about to do. Borrowed one of the AutoEnginuity's scan tools from H2Oboy and it displayed the lack of release.

Other things along this tree are the valve body/valves, electrical connections and the torque converter itself.

I don't mean to drive this discussion so far along the TCM/TC tree limb that it never returns since I have no idea what the problem is. Just following the clues you provided.

 

My mechanic and I are totally open to any options. He can hear it but can't reproduce it in the shop to test. So we're shooting blind!

 

Engine (timing chains etc) would be RPM specific and not be affected by shifting (much) but it sounds like the trans fluid is settling in the pan overnight and until the shift paths/valves are repressurized there is a lack of fluid. You said it was changed and all ok at proper level etc was this after you began hearing this?

 

I've done so much it's all becoming a blur now! lol As best I can remember, I heard the noise all along, but not as loud as now. Of course, top down things are louder so it's hard to tell.
If I remember, we did the trans fluid change because I was worried about the sound. It didn't really change it but the fluid was so black and thick I'm glad we did. Sealed for life! lol
Funny you mention RPM's. It does seem to only do it at the highest rpm before down shifting to next gear, then again at the same rpm in the next gear, just a little less, and then again when shifts to next gear, again a little less.
Usually after the first cycle through all the gears, it stops and never again until the next morning. I've noticed it doing it now if I stop at a light or sign, then take off again if I haven't driven very far after the first cycle of gears.
Mechanic says the timing chain looked very good when he replaced the tensioners and usually the primary tensioners don't cause the real problems.
I'm going to try to record it this morning and post a video of it. If I can figure out how! lol I'll also note the rpm's its hitting when it makes the noise.

 

What transmission fluid did you use on your drain/refill? Some strange shifting reported after new ATF but that could be associated with enhanced driver sensitivity after such work.

 

I'll have to check. He typically uses the best on the market with any fluid.
I remember somewhere I read that when the trans fluid is changed in our cars, it can need to be checked after a bit for the level. Since there's no dipstick, It's hard to tell. I think he measured what came out and put that much back in but I would think it may not be a totally accurate procedure.
Honestly, I'm going to have to check with him as this was last year and it did sit over the winter more than usual. Although I drove it every couple weeks.

 

My yr 2000 XK8 Coupe has exactly the same problem. It only started after a gearbox oil change (partial change & not flushed). The best way I can describe it is it sounds like during a gearchange a light chain becomes slack and tinkles on the casing. As the gear takes up it disappears. It only happens after a long period of sitting, and then only for the first few changes. After that the changes are smooth and slick.

The coincidence of oil change and the sound appearing is too strong to ignore. So it's something to do with either the fluid used (I believe the recommended fluid was used), it's level after running for a while, or something that gets disturbed during pan and filter removal.

It's going back into the same Indie for a look at the tensioners - I'll get them to look at the oil level.

 

Perfect description of the sound and the issue!
Mine does it between 2000 and 2500rpm. Just before shifting to the next gear. And as with yours, after a few minutes, drives like silk.
Tried to video it but just can't get it on sound.
I'll have mechanic check level too. I bet it's just low enough to be the issue.

 

One other possibility - oil foaming. During my apprenticeship (many years back), I used to programme hydraulic capstain lathes. When they were cold (after a weekend), the oil used to foam and the air bubbles flying through the valve blocks made a tinkling noise (on a propeller they call it cavitation).

 

Possible but happens every day. Only on first drive away.

 

Keep in mind on your 02 XKR I do not think there is a drain for the torque converter (I have the Mercedez trans so not sure of yours what models they stopped putting them in). So even a 'drain and fill' leaves half the old fluid in the system, this then gets mixed with the new. Another drain and proper leveling (up to temp) might be a path to discuss, then if it re-occurs go from there (you probably can use the same gasket but I'd put in another filter.)

 

Mines not an r, just an 8. I think he did flush out all the old but I'm going to find out tomorrow exactly what he did. I'd like to think it's as easy as proper level.

 

I hope so too Phil - hearing stuff tinkling about in a super complicated and expensive gearbox isn't the best thing that can happen in the morning!

 

This is probably a long-shot that has nothing to do with your problem but it turns out that I have heard that exact sound just once in the 6 years I have owned the car. It was immediately after I had a tire repair done to the right rear tire. The tire repair place jacked up the car only on the right rear to remove the tire, do the fix, and then replace it. As I was driving away I heard a sound like a chain not quite engaging on a bicycle for a few seconds and then it "engaged" and went away, never to return.

The only time I have heard something similar in other cars had something to do with the ABS system so that is what I figured it could be. In any event the sound never happened again.

Doug