2005 TL with 55K. If I accelerate normally from a stop I experience a vibration going through 25 mph. If I instantly increase my speed it stops and operates normally. Thought it could be a wheel or tires issue, but just saw similar postings about transmission fluid or EGR valve, etc. Anybody with a similar problem, that they were able to solve, willing to give me a heads up on what I could have checked. Thanks.

 

This problems and fixes section is for the first generation TL (1996-1998) Ask in: https://acurazine.com/forums/forumdisplay.php?f=114
(The third generation (2004-2008) problems and fixes section) and I guarantee (don't quote me on that) you'll get more comprehensive responses from owners of the same generation TL. (Not that our own 1st generation members couldn't solve the problem; they're absolute geniuses.)

Hope you get your problem fixed.

 

Ok, after some searching in the 3rd gen section it seems like a lot of 3rd gen owners have problems with vibrations and rattles.

I suggest this link, if this isn't the thread and postings you were talking about in your post; people are having the same issues in this thread. They haven't solved the problems yet.
https://acurazine.com/forums/showthread.php?t=737571
Stuff like:
-change tranny fluid
-torque converter
-transmission sensors
-fuel pump/fuel management
-IAT sensor
-ECU reset
-New Tranny (o_O)
-try using unleaded race gasoline
-dirty EGR valve
Some stuff here you already thought up of.

 

moved to 3rd gen...

 

I have this problem since many miles ago but since I have the extended powertrain warranty I decided to bring my car in with under 15 miles left of the warranty. For me I get this shudder 90% of the time going up an incline and so my local dealer checked it out today and gave me a phone call telling me they ordered a new transmission! Wow do I feel sooo blessed! Its hard to duplicate especially on flat grond but thank God they drove the car around to really find the shudder. The problem sounded pretty technical, I think it had something to do with catching a gear to shift but I will report back with the full details after I get my car back.

 

Check for different amout of thread left on each tire. to use different diamter tires may damage your drivetrain or transmission. you should not use tires which are more than 25% of the thread worn than the others or at least in the front because TL's are FWD.

the full story:
I drive a 2007 TL 5-Aut and never had this problem until... I changed the stock 17" wheels/tires to a set of USED 18" A-Spec wheels/tires. But the guy who sold them to me had 2 sets (8 wheels and 8 tires) and let me choose the best 4 of each (remember they were used). After that I had the exact same problem "Acura fan" describes here, exactly at 25 mph. I went back to see if i could change a tire that had a bubble on one side and because the two front tires were different (all four were Michelin Pilot Sport 235/40ZR18 but there are sub-versions like N2, N3, N4 etc.) the FrontRight was difrerent version than FrontLeft tire. So I picked another tire of the same version than the good one, I think they were pairs before because both had the same thread remaining (almost new btw). After this, all the vibrations disapeared.

Hope this helps, if you have at least 2 tires of the same brand, model and thread remaining put them on the front.