Gear Box Repair

Be prepared to spend big money on the repair. The 99 Acura TL and Accord using the same platform (U.S. version) were infamous for their problem with the 5-speed auto transmission. Honda admitted that there's a problem with the internals of the transmission. The transmission oil may overheat, which increases the pace of wear and tear of one or more clutch pack (especially the third one) and even gears. Now you are experiencing rough shifting and slipping; sooner or later your transmission will refuse to shift, not going above 60 km/h and then the tranny may just die.
Changing the transmission oil alone will not solve the problem, or even makes it die faster, if there's enough damage inside the transmission already. There's a tranmission oil filter inside the tranny, which filters out all the debris from those worn and torn internal component. If you didn't take out the filter and clean it or put in a new filter, and just flush the oil and put in new oil, you may actually washing off the debris that's collected and sitting on the filter, and now mixed with the new oil, flowing around the transmission. That will further increase the wear and tear.
My recommendation: Talk to the local authorized Honda/Acura dealer and see if they have a recall/extended warranty program on your car (providing your car's VIN). If they are willing to put in a new (even rebuilt) transmission for you for free or minimum service charge, do it. If they don't have such program, then you will have to bite the bullet and determine if it's worth it to spend some money taking out the filter from the transmission, clean the filter, put in new oil, and hope that will fix the problem. My guess-imation is that it's going to cost you around $2,000. Worst case scenario, you may have to put in a rebuilt transmission at your own cost. I don't even know how much that's going to cost you but for sure that's going to be a large % of the current used car value of your TL. Good luck.


2007-07-12 04:40:56 補充：
I remember you said you are going to put RE050 tires onto your car. That is not going to help, because now you are having more friction due to the stickier compound of the tire (even though not by much), and that will put more stress onto your transmission component.