Quad,
How does one fix the problem if that is the case?

 

Unfortunately, I don't have any magic fix... but Spillwaybob was wondering what might be causing the noise and what might be different between being in S vs regular mode - the torque converter lock-up in regular mode might be that difference.

If it does prove to be so, from the tests I suggested, then it is up to someone with more tranny knowledge than me to suggest a fix; although I am going to bet it will involve pulling the transmission, again unfortunately.

 

OK, yes the converter is unlocked in the S mode just as you suspected. The noise doesn't really bother me as I drive mostly in the S mode anyway but does this noise mean I have an impending failure lurking? If I keep the trans. in S, will I minimize the impending failure? Hello, Jaguar transmission tech.

 

In your case, I believe it would be worth checking and/or changing the transmission fluid. That is contrary from the recommended service, but it MIGHT just save your torque converter. The humming MIGHT very well be a slipping lockup. AND, I do not believe the lockuop is disabled in "S". What is the basis for that claim?

 

Ross, the issue is (as I beleive Spillway verified thru the testing I had suggested above) that, in S mode, the converter has not locked YET at the same speed at which he hears this noise when in regular mode (with converter locked)... in S, it will still lock, just at a higher road speed. This is the designed operation for S mode - it moves shift points (and I assume converter lock point) up a bit. Spillway's symptoms and subsequent test verified this, I believe.

So, the issue does not go away in the S mode, it just moves converter lock to a speed that doesn't generate the noise; it has probably just raised the frequency above some mechanical resonance... does this mean that it's no longer a problem? Probably not - the instability is still there, it just doesn't excite the resonance.

 

Steve,
I don't know if you have been following this thread but I have discovered that the humming noise at 52-55mph only occurs with the trans. in normal mode and disappears in the Sport (S) mode. The consensus is that the problem is with the lock-up in the torque converter. As one owner suggested, I'm going to try a trans. oil and filter change.
Bob
(See my post dated 04-10, 8:03PM)

 

I'm going to take your suggesstion and do a trans. oil and filter change, especially after I was quoted "about $900." by my local Jag dealer. But I have some questions about the procedure:
1. Is that allen head plug just above the pan flange at the right-rear corner of the trans. the fill & level plug?
2. What is the temperature of the oil to be when checking the final level?
3. The correct level at the specified temperature is oil just up to the bottom of the hole with engine running, right?
4. As long as the oil I use has the API classification of "LT71141" am I OK?
Hope you or someone else can answer these questions for me.
Thanks,
Bob

 

Bob:
1) yes
2)Some claim it is important. According to two manuals , less than 50deg C is right.
3)Yes
4)My opinion is YES, others differ.

 

Thanks a lot for answering my questions, I really appreciate it.
It will probably be next week before I can do this job and I will let you know the outcome.
Bob

 

I did this job and it wasn't too bad. After cleaning and replacing everything and filling the trans until overflow I ran it up to operating temp and went through all the gears and then filled it until it started running out of the fill hole again. I think all this sealed-for-life stuff is nonsense, and the part about needing specific Jag software and a computer is also a scare tactic. I got my fluid from Motorcars Ltd. It had all the right specs and of course they recommend it (Motorcars). Of course, time will tell, but I'm good now. Oh yeah, this won't get all the old fluid out, but I plan to do another just drain and refill in a couple of months. Just make sure you can get the fill plug out before you drain the pan !

 

"so im just going to wait to see if anybody finds an answer... "
The problem with that is that all of the suggestions, torque converter, jurid couplings, rear bearing, diff bearing, tires, center bearing, etc are valid and possible. So, if someone bothers to post the results of their noise, it might very well be a red herring as far as your noise.

 

For the new poster, this is very well an issue as there's not enough info yet to give you a simple diagnosis. But, you might try the same quick test - do you hear this rumble, at the same road speed, in both the S mode and in the Regular mode?

However, for the original poster this is why, instead of telling him a 'this is what happened to me' story, I suggested a test to narrow down the possibilities. From that test, assuming that he did do it as suggested, and that his results stated are correct, then it IS most likely related to torque converter lock/unlock; not tires, jurids, etc... Actual cause is not determined by this, just the conditions under which the symptoms occur and the general area where further analysis/inspection/testing is warranted.

With this information in hand, the possible inspection/troubleshooting requirements have now been reduced to the transmission (and perhaps flywheel?) - things related to the TC being locked. There should be no more 'red herrings' at this point. The rumble occurs when the TC is locked, it does not occur when the TC is unlocked, at the same road speed.

I would certainly repeat the test several times to verify that this truly is the case, but once it is verified, all other possible issues can be ignored until proven otherwise.

I have been very successful over my career in troubleshooting difficult, hard to find problems and have always tried to follow the 'divide and conquer' method - set a test scenario that has two possible outcomes - each test result typically divides the possible causes by a minimum of 2 - eventually the issue becomes obvious. It works 99% of the time by the 2nd or 3rd test.

Now the issue becomes - what's the next test? Unfortunately, I don't have that answer - but perhaps someone with more transmission experience/knowledge may. Fluid level check is certainly a valid step - but may not get you any further. Of course, if it IS low, and topping it off eliminates the symptoms, you have your answer by the 2nd test.

 

ls1monster-
The torque converter lockup scenario is specific to 52-54 mph, which is the speed that the tC locks up. Now, your problem Could be the TC, but your sysmptoms are very different, in that the torque converter is not doing anything different (like locking up) at the speeds you reported.
Now, as to others finding no solution, unfortunately many come looking for reasons and are going to take it to the dealer to sort out anyway, and my experience is that they seldom report back.
So, again, with your symptoms, I would look at rear wheel bearings, differential bearings, driveshaft bearing and go from there. Not much in the torque converter to set the fault you mentioned. You probably need to enlist help to hang their head out and listen for noise source.
Good Luck

 

Ross,
I completed the nasty job of changing the trans. oil and filter today.
I drove the car briefly and don't notice any change in the noise at 52mph. I couldn't find a drain plug on the convertor so the whole unit only has 6 qts. of new oil. Hopefully when the fresh oil has had a chance to get into the convertor, it will improve the lockup noise. If this happens down the line, I will report back and in the meantime I will monitor all posts to this thread and maybe someone will come up with a solution. Thanks again for your help.
Bob

 

spillway, any news on your noise after another month and a half of regular driving?

 

h20Boy, well, possibly something new. The hum is still there at 52-55mph in regular mode and disappears in the S mode, however, I think I might have heard the same noise at a higher speed (around 65 mph) in S mode. The noise was there briefly because I remember I was accelerating. I will try to verify this soon. If it is a lock up problem, then it would make sense that the noise would occur at a higher speed in S mode. Will get back to you as soon as I can verify this. Thanks for your interest
Spillwaybob

 

I'd go with main shaft U-joints..

Easy check is when cold..first start up, hold brake and put in reverse and then, while maintaining brake hold, in forward gear. Be sure you lock the doors prior to doing this otherwise that locking sound from them may drowned out the actual u-joint clunk noise.

The under acceleration is what drives me to think U-joints and the age of the car. Also the change in sports mode.

To be clear, is it a hum or slight vibration..or both?

Tom
2001 VDP