Transmission mount

I was stopped on a hill the other day and had to step on the gas to get up the steep slope. When I did this I heard a roar (for the first time) coming from under my Blazer. It only happens when I accelerate hard from a complete stop. It sounds like a grinding/rubbing, and it only lasts a second. I looked at my motor mounts and they don't seem to my budging. Does this sound like a bad tranny mount/rubber bushing? And if it is how easy are they to replace?

I would inspect the transmission mount first and also grab the driveshaft and check for play, if there is play in the driveshaft that can be u-joints.

I would sooner suspect a failed motor mount.  Have a friend watch the motor as you hold the brake while in drive and give it some throttle.  If the motor torques over enough to allow the fan to hit the shroud, there's your problem.

Yeah there is no play on the motor ( thought it was hitting the fan at first but that isn't the case) and I went from reverese and forwards back to reverse and no problems. So I think the u-joints are eliminated too. Thanks for the help. I am going to go check it out now.

what did you find?

and yes, changing the tranny mount is easy. Unbolt it, jack it up, pull hte cross brace and swap out the mount. You may not have to pull the cross brace, although thats only 4 bolts.

By the way, I wanted to follow up and say that it was the tranny mount and it was as simple as jacking the tranny up, unbolting the mount, then swapping and reinstalling. The bolts for the mount are a little tedious to remove though, because of the limited room.