Car is a 03 TL-S w/ 130k and a new transmission that was installed 20k miles ago at the dealer. I have observed pretty harsh downshifts occasionally at highway speed. When it happens, I will always be cruising around 55 mph and will be giving it about 3/4 throttle to pass someone. The transmission feels like it just slams into 3rd gear (I can feel it downshift 2 gears). There is no slippage and this only happens occasionally. No lights on the dash flash when this happens. Other then this, the tranny is very smooth the rest of the time. Do you think its the tranny or my motor mounts (which are original)?

 

have you ckd the motor mounts? if you didnt get a front with trans you are one of a very few!! mine was gone at 70 as were many others

could be the torque convertor coming in and out of lockup for slam but should be effortless
Ckd fluid level per book- 15 minute freeway drive- stop (take off ramp-park level and safely)- engine off-
ck fluid level is BETWEEN upper dots- not at either--in between them at that fluid temp

Level indicated changes with fluid temp

drop by the dealer and ask the service manager if the head tech can take a ride with you to see if its a real trans prob or not
With a rebuilt unit in there, they should be willing to do that and come up with some warranty if needed,,
but ck those motor mounts first--dont abuse the goodwill at dealer

 

3/4th throttle? how high RPMS? If you are close to flooring it, I would not be surprised transmission goes right from 5th to 3rd to gain the needed acceleration, the shift point could be hard somewhat at high rpms. I would stop doing what you doing, this type of driving damages our glass trannies.

 

^+1

 

I did not have the mount replaced with the trans, they never asked or told me that I needed one. Any good way in checking the mounts? I tried to make it do it again yesterday, but I couldn't. I talked to the service writer who I delt with when I had the trans replaced and he said that if I can't replicate the problem then they probably wouldn't be able to. I do have about 12k miles left on the warranty.

 

the tech would have said if it needed the mount with trans--thats when its often discovered but not every one is failed then

look from under the car -up at front and rear mounts for signs of small oil drip-
fluid filled mounts and vac boosted!
does front mount look compressed? in the diy are pics of old and new
the pass side fails after the front does - from taking extra load

the 2 person- hold brake and rev engine while watching engine movement
or prybar to part method of testing will find a bad mount

 

I looked at the front mount and it looks compressed. There is about a 2 finger gap from the top lip of the mount, to the top place that has the bolt on it. Does that mean its bad?

 

put the car in D5, hold your foot on the brake, and blip the throttle, and watch the engine for moment. alternate between D5 and R. engine should not move more than and inch or so. you can also put the car in Park, and rock the car back and forth to see engine mount moment. if the front mount is shot the engine will want to rise while in D5, or driving. excessive rocking of the motor back and forth will give you a jerky ride.