HELP!! Clunk in transmission and limp mode activated when downshifting

Hi everyone, I have a 2012 Tacoma and recently experienced a puzzling situation I am hoping someone on here can help narrow down for me…

While towing a trailer on the highway I noticed some difficulties down shifting when pressing on the gas to accelerate. I have an automatic v6 and while going 70 on the highway sitting in 6th gear, if I press on the gas to speed up, the truck tries to shift into 5th. But following this the rear end clunks or shakes as if I hit a pot hole. Then my check engine light flashes and traction control comes on. Also the truck seems to go into some kind of limp mode where I lose throttle response and can barely go 45.

I was able to run the codes today and the only one that came up was C1405 (Open or Short in Front Speed Sensor Right). I am wondering how this all ties together, as I can’t make a connection between speed sensors and my transmission clunking and having trouble shifting. I do know I cracked the plug on that speed sensor so I wouldn’t be surprised if it got water in it. But I can’t justify how that is causing all this.

Hoping someone out there has had a similar problem before or anyone that has a good idea of what’s going on. I tow with my truck quite often and can’t until I get this resolved. Thanks everyone

***Edit
There is a p code I found on the scanner (p1604) (start ability malfunction). Any suggestions?

 

The check engine light flashing suggests a misfire, there should be P codes stored in the PCM.
You have a 5 speed transmission by the way.

 

@Dm93 thank you, I am not the brightest with transmissions and gearing. I just know 4th gear at 70mph my rpm’s are 3k, 5th gear rpm’s are 2.5k and then the rpm’s will drop to 2k so I assumed there was a 6th gear.
I will look into p codes. When the check engine light was flashing it did sound like it wasn’t running on all cylinders.
Thank you for the help. Much appreciated

 

I've heard of the 3rd genz going into like a "limp mode" & staying in 1 gear if the transmission gets overheated, but idk about all the clunking you're hearing/feeling... That's lame. Hope ya figure it out.

 

That's your torque converter going into lockup, ideally if your towing more than about half your tow rating you should be towing in 4th instead of 5th (overdrive).

I would expect there to be codes stored with the light flashing, it sure sounds like a misfire or torque converter shudder.

 

just came across this P code (P1604) any insight on this? Thanks

 

That's a pretty common code to see on Toyota's, it sets any tike the engine fails to start or stalls immediately after starting. No need to go chasing it.

Since you have a good scan tool you could monitor misfires when the problem is occuring and see if you have any.