Question - A/T Transmission hesitates when shifting from 3-4th

[Giskarded]

I've got a 2001 4Runner with ~190K miles on it.
Everything looks good. I bought it used last month and had the timing belt and radiator changed out.

What I've noticed is that on a cold start, when accelerating on flat surfaces, the transmission shifts smoothly from 1-2 and 2-3, but when going from 3-4th, it revs up past the 2500 rpm before shifting to 4th.
After a couple of shifts from 3-4th on a short drive. It settles down and smoothly shifts from 3-4th at around 2100rpm.

Not quite sure what the issue could be.

 

[jsukey]

That's actually overdrive that it's shifting into. What does your transmission fluid look/smell like?

 

[Giskarded]

That's actually overdrive that it's shifting into. What does your transmission fluid look/smell like?

When I purchased it, the transmission fluid checked (using dipstick) was nice pink and translucent. Guessing they had changed it recently. I'll check back today and post an image.

Overdrive switch is off (I'm guess its off since I see no indicators that it's on).

 

[jsukey]

There won't be an indicater showing it to be on...just off. Hope they didn't wait till it was too late to change it. Transmission fluid is a detergent and if the previous owner waited until it was too late to change it, it very well could have done some damage to your transmission when the new fluid gets in there and starts unlodging old debris. Just trying to understand you, but if you have the overdrive off...there won't be any gear changes after 3rd gear. As I mentioned in my first post, our 4Runners only have a 3 speed transmission with an overdrive gear. Hope it's not slipping in 3rd...that may confirm what I said earlier.

 

[Giskarded]

There won't be an indicater showing it to be on...just off. Hope they didn't wait till it was too late to change it. Transmission fluid is a detergent and if the previous owner waited until it was too late to change it, it very well could have done some damage to your transmission when the new fluid gets in there and starts unlodging old debris. Just trying to understand you, but if you have the overdrive off...there won't be any gear changes after 3rd gear. As I mentioned in my first post, our 4Runners only have a 3 speed transmission with an overdrive gear. Hope it's not slipping in 3rd...that may confirm what I said earlier.

Sorry, I meant the OD Off indicator is off.

The vehicle shifts quickly from 1-2 and 2-3. But when going into the final gear, it hesitates and the revs go past 2500rpm (sometimes hitting nearly 2900) before it shifts into the final gear.
The issue goes away after a few minutes of driving and the shifts start happening at under 2500rpms.