6MT Tacoma won't shift under load

Lately, my 2010 Tacoma (base) has been acting really weird. It has become really difficult to put it in reverse or any gear when the truck is running. If I time the truck off, I can shift through the gears, and it is as smooth as butter. Has anyone gone through any something like this, and what was the fix? No leaks, Clutch doesn't seem worn, 132k miles, trans gear oil is good and somewhat new, the clutch pedal is within the adjustment, the master cylinder is not looking low,

 

Welcome aboard new member
Dot 3/4 brake fluid in clutch reservoir should be clear. If it's dark its past due for a change.

 

It sounds like you have worn syncro's in the transmission.

https://www.youtube.com/watch?v=nM4CuWlnJY0

https://www.youtube.com/watch?v=MXsRfbOiBhE

https://www.youtube.com/watch?v=l8wjrifuh44

 

Clutch problem. Try a thorough bleeding your hydraulics first.

 

I will definitely start with the cheapest route; a thorough bleeding. I pray that it is not the synchros.

 

Problem solved. I replaced the Clutch Master Cylinder. Since I had to bleed the slave cylinder, I just went ahead and flushed, bled, and fill the brakes; fluid is nice and clear now. Thank you all for giving some good advice .