Help, 50mph shudder?!

I was driving home from work last night and once I got to 50mph on the highway my 03 taco started to shudder. I flipped the electronic transmission switch and it would go past 50 without a shudder, anyone got any ideas??? I'm taking it into a shop to have it looked at in the next couple days and it makes me nervous to drive it like that but it's my only transportation, looks like back roads for me till I figure it out haha

 

At 50 with ECT on Normal, it shifts into 4th. It sounds like your truck is not making as much power as it should, and when it shifts into 4th at such a low RPM/speed, it is realy struggling. I would try the basic performance enhancing maintenance:

-First, make sure you are using high quality gas
-Seafoam your engine
-Seafoam in your Gas tank (clean injectors)
-Check fuel filter
-Replace spark plugs if needed. Stock plugs are usually 30k miles
-Clean MAF

If this doesnt help, try a toyota dealer. It might be more $$$, but they usually offer the best help (in my experience at least).

 

Post what the dealer finds if you would. Could be helpful for all if it ever starts for us.

 

Is Seafoam just an injector cleaner? what would you use it on, specifically, aside from putting some in the gas tank?

 

bunches of seafoam mentioning threads here, but the easy way is http://www.seafoamsales.com/

 

Just learning about it myself:

http://www.tacomaworld.com/forum/1st-gen-tacomas/91570-carbon-engine-90k-checkup-question.html

I poured mine down the PCV Valve.

 

Not discounting any previous suggestions, but if it only happened that one time, I would experiment and make sure it doesn't happen every time you hover around the 50 mph mark (or any other specific speed) regardless of the other criteria.
It very well could be that you just lost a wheel weight or picked up some mud in one or more of the wheels, throwing the wheel/tire balance off.