At pismo beach i was testing my truck on the RTI ramp. once my back left tire got in the air, it started spinning because i'm 2wd. so i pushed on the brake, but the tire just kept spinning. drum brake of course

I just had my brakes flushed recently

any idea?

 

Back drums are not properly adjusted. Do a search on the topic...

 

Were you giving it a lot of gas? If so, drum brakes are not known to overcome the torque of an engine. Ever seen someone hold the brakes down and floor it? Yeah, burnout time.

In other words, the front disc brakes hold but the rear drums dont.

 

nope, it was idling

at the shop yesterday i took off my tire but i couldnt get the drum off. i got it off partially, but it didnt want to come completely off. another mechanic said the drums have big grooves in them or something. even then though, we pushed on the brakes and couldnt move the tire, let go of the break, and we could move it

 

Sounds like an adjustment problem to me as well. Don't be afraid to taking a BFH to get the face off of the drum. Mine took a few good hits before it gave.