Sienna shifting problem

I have a 99 Sienna LE approx 130K miles. I am bothered by some strange upshift behavior. From a cold start, the tranny makes one barely noticable upshift right away. Then it hangs before the next shift. In winter weather if might go 0.3 or more miles before upshifting. I am not jamming on the gas to force it, just waiting it out. In the warmer weather it still hangs but not as long. The fluid is clear and at the right level. Any thoughts please. Thanks. George

When was the transmission fluid last changed?
If it was more than 3 yrs/30k miles, then it is overdue for that service procedure.

However, if this transmission has not been serviced properly over the past 11 years, a trans fluid change at this point is unlikely to help it. What can you tell us about the service history of the transmission?

Not much. Bought it used in Jan 2007 with about 100K miles. Not sure when this shifting issue first came up. Also have P0420 light issues but my mechanic says these issues are unrelated. I have the had the CEL cleared by the mechanic and also by taking the battery off for a day or more at a time. Not sure if that would create drivability issues with the tranny or not. I have not had the tranny fluid changed in the 30K miles we have had it.

I think that you should take it to a local, independent transmission shop - i.e. not a corporate chain shop. Most have a basic diagnostic/evaluation they will do for something in the vicinity of $75 (give or take). If that turned up nothing that looks like disaster have them drop the pan and change the filter.

If you find a good local shop then I shouldn’t have to say this, but…don’t let anyone “flush” it unless the pan is first dropped and new filter put it.

If a diagnostic at a trans shop turns up any error codes, you can post them here for comment/feedback.

If the battery was disconnected for a while, this could cause some odd behavior for the next few times you drive it. The computer has to relearn or reprogram itself. If you’re lucky, this contributed to the odd shifting.

Change the transmission fluid and filter ASAP.

My 2000 Sienna, now with 105K miles, has done this since new. I used to be concerned about this too. I brought it to the attention of a dealer once and he told me that they are all programmed to do this for emissions purposes. If you Google search “Sienna delayed upshift,” or something like that, you’ll find lots of information on this topic. I found the following information on a Sienna forum:

“These transmissions have an upshift lockout that is controlled by coolant temperature. They are designed that way to warm up the engine faster and reduce emissions. By inhibiting the upshift the RPMs stay higher and the car warms up a tiny bit sooner.”

I would just make sure that the transmission fluid and filter are serviced on a regular basis and not worry too much about it otherwise. Seems as though this behavior is by design.