Hard shift when accelerating hard to pass

When I give it the throttle full on to pass someone it shifts pretty hard. BANG into gear. Mostly notice it on the highway, but today going up a hill and gave 'er the foot and BANG into gear. Like it doesn't enjoy downshifting at all. WTF? Normal sane easy driving...zero issues. Ever.

History...
I have the tow package. 2 years and 20,000 miles ago my wife borrowed the truck, didn't see the large puddle of coolant in front of the truck in the driveway, and she took off on the highway. After a few miles it stuttered and wouldn't go anymore. She was in the middle of traffic when I arrived. I floored it to get it out of the intersection and then pulled over after 30...feet or so. Called a tow truck. Toyota mechanic says the transmission coolant hose right behind the radiator was "cut". All the fluid boiled out and she died. He replaced the hose and refilled it and it's been good to go for the last 20k or so. No issues.

2007 DCLB 4.0 118K miles. ALWAYS maintained as scheduled.

HELP?

 

Yup, sounds to me like you got a transmission problem.

In seriousness though I have no idea, has it done this since the incident a few years ago and is now getting worse or is it just now a problem rearing it's head?

Have you checked the fluid level using the proper technique? Does it do this only when you force it to automatically downshift by applying throttle or will it also do this if you manually downshift with the gear selector?

 

It’s done it a few random times since the incident a few years ago but just noticed it twice in the last two days. I have not tried manually downshifting but will. I have not checked the fluid level but will do that as well.

 

My first step would be to flush the tranny fluid and see if it improves any

 

Here OP if you haven't seen this thread
https://www.tacomaworld.com/threads/diy-full-flush-for-automatic-transmission.68462/

I've done this procedure it's not that daunting just a bit tedious. I use Valvoline maxlife ATF over the factory stuff, as do many others but whatever floats your boat as long as it's WS compatible.

That thread also details how to accurately check the fluid level, since our trucks do not have transmission dipsticks, which you should probably do first just to see where it is, and then again obviously after a drain/ refill or full flush or whatever you choose to do.

 

But if there's already hardware damage in there from the heat buildup from the incident I doubt any amount of new fluid through the system will fix that..

 

I double checked. That issue was 2 years and 20k ago. Not sure if it's related, but I'm going to flush and refill and see what happens. Thanks for the advice.

 

Resident transmission guru @gearcruncher swears by Lubegard. You may want to throw some in when you flush.

 

Nice! Thanks!