Recently on a WOT the transmission seemed to slip, car lost power and rpms shot up to rev limiter. I tried recreating the issue multiple times since with no slippage. Car also has been having issues where if you are cruising at say 55 and say give the car 60-70% open throttle the transmission downshifts into a lower gear hard. It slams into gear. Also in general some shifts have been harder.

Fluid is fresh, switches new. These transmission symptoms happen intermittently. So sometimes it gives issues and most other times it behaves perfectly normal. Any advise? Is the transmission on its way out?

 

What year and what mileage? Pre 07 had many more issues with transmissions.

My 99 TL would slip bad when giving power when accelerating from a rest around 2nd or 3rd gear. rpms would spike but no power.

 

Yup. Also driving conditions and prior maintenance??

Have you tried a reset?
Key off. Gas pedal to floor. Key to ON (not start, for 2-5 seconds.) Key off and remove. Release gas pedal. Listen for 2 clicks.

Do you have these problems in manual mode?

 

07 type S. 157k miles. But I think the tranny was previously replaced by previous owner as the vin number plate on the the transmission case does not match the cars vin.

 

Havent tried that reset but recently the battery was disconnected for a while and it still behaves the way it does so doubt a reset would do anything.

Dont really use manual but even in auto the issues are intermittent.

Maintenance is up to date switches fluids etc

 

OK, I'm NOT gonna say converter, then.

 

Can I ask why you don’t think it’s the converter?

 

because you have a 07-08 auto which was redesigned so its less likely its your converter than if you had a 04-06 model year

 

Does anyone know of a good transmission guy in nyc area that can diagnose my problem? Would a transmission scan tool help?

 

The 07-08 TL auto trans are robust but not 100% bullet proof, I always stay on top of my fluids and switches and all 3 of my TL has zero problem regarding shifting. It hard to tell you what wrong over the internet, you need a shop that give it a proper diagnostic. Worst case scenario is you need a new trans.

 

Were new switches OEM, or aftermarket? Aftermarket switches have been known to act funny.

 

oem