Well, after two days of driving it and checking it, the guys at AAMCO could not find any problem. So I went for a drive with the shop manager. I could not reproduce the problem either! So, either the kitty healed herself, or it is an intermittent problem. Aaarrgghh! Nice to have the Jag back, anyway. And nice to see that the local AAMCO folks are honest, too. They could have sold me a re-manufactured tranny, and a bill of goods to go with it!

 

I am still getting the vibration. The manager at AAMCO convinced me that the transmission was not slipping, as I had thought. But it still vibrates on acceleration between 40-45 mph.

 

I had a a GM car once with an almost identical complaint. It started out with a strong hesitation when accelerating from a full stop, progressed to a major "shudder" when accelerating at speed with anything but the lightest touch of the gas pedal, and eventually deteriorated to the car lurching and the engine dying when stopping, unless I was quick enough to slip it out of gear at the stops. Getting going again became almost impossible, I had to rev it up and throw it into gear.

The problem ended up being something not yet mentioned here: The lock-up torque converter system. There was an electrically controlled valve that would not release the pressure to the lock-up circuit when stopped, and would not fully engage it at speeds.

The fix was replacing the valve, but because it had been causing the the TC to slip so much (it started shuddering a LOT before I managed the repair) I replaced the TC also.

Although this was a known problem for that particular tranny, I was told that even a small glop of crud floating around in the system could mimic the condition in any vehical with a lock-up torque converter.

My vote is going for this as the problem: Either a failed Torque Converter, of the associated control valving.

If it is indeed the valve, maybe the fix could be as simple as removing the left front tire and plastic fender liner, tipping a few things around to get at the valving cover and replacing the switch!

(The GM switch was only $40, so you know the Jaguar switch shouldn't be much more than $400!)

Please keep us posted on how it goes, and best of luck.

 

Since I got it back from AAMCO, I have replaced a very slightly bent wheel, had all the wheels balanced, rotated and aligned, and I greased the driveshaft carrier bearing. Still have the vibration. I have been wondering if it could be the torque converter or the transfer case. But the torque converter is between the engine and transmission, I believe, so it should behave differently at different RPM's, I would think. So I tried shifting manually, first into 4th gear then 3rd, and accelerating through the 40-45 mph range. The vibration was the same in both cases. I think that eliminates the torque converter. I have also noticed that the vibration does not seem to be there for the first 3-5 minutes that I am driving, which seems like something is heating up. I think I read somewhere that the viscous coupling in the torque converter locks when it heats up, so that could still be the problem. I am thinking of taking it to the dealer next week for a diagnosis.

 

Bruce in ND - The big difference that I see from what you have described is that my kitten has no hesitation when accelerating from a stop. When I first got the car, last Fall, it did have some hesitation. But after I changed the transmission fluid, it no longer does that. There is no hesitation - it leaps forward, well, like a cat! The only symptom is that it has a vibration that has a frequency of about one cycle per wheel revolution. It only happens when accelerating; it starts somewhere between 35-40 mph, is strongest between 40-45 mph, and is gone by 50 mph. It does not happen on deceleration or constant speed. It also does not happen during the first five minutes or so from when I start the car and begin driving. And, if I manually shift to 4th or 3rd, the vibration is the same, even though the engine speed (RPM) is quite different. I feel the vibration mainly through the steering wheel.

Since this is apparently not a transmission problem, I am now writing about it on another thread entitled "Drive Train Vibration?"

 

Have you considered finding a quality salvage yard and purchasing a used transmission?

Putting out so much $ for a new or rebuilt transmission is so difficult when you really didn't pay that much for the car. This car should have many more miles in it.

 

Bamaman - I don't see any reason to buy a used transmission now that AAMCO has told me that they don't think there is anything wrong with the transmission. If I find out differently, I would still not want a used one, since these cars are known to have transmission problems. And since the car only has 35,000 miles on it, the engine should be good for many more miles. But thanks for your input.

 

I have a question, I have sort of the same problem or at least not a problem as of yet. I have no problem from a stop, my cat takes right off, when I give it gas I have a slight flutter. Then the flutter stops, and the RPM's are steady, and she increase in speed and to me it doesn't feel like the trans. But here's another thing I noticed, that when I'm going 45 to 65 MPH I get the flutter again, when I hold a speed no flutter unless I'm going up a slight hill. I was thinking maybe a fuel problem, or a need to change the filter. It hasn't been changed since I've owned the car and I've put 14000 on it in a little over a year. Anybody have any thoughts?