A mechanic just put in a new transmission mount for me. He said it moved the transmission ~1/4" to a side when he rebolted the crossmember. Is this gonna be ok? I hate being away at school so I can't do it myself.

 

1/4" isn't anything to worry about. Actually you want a slight misalignment for the u-joints to work properly. Side to side movement isn't cause for concern, unless it's dramatic. It's up and down that you need to worry about. I've had cars in my shop that had terrible vibrations after installing an aftermarket trans mount that was only about 1/4" taller than stock. I swapped in a stock rubber mount and the vibrations went away. The problem is that this causes the u-joints to operate at different angles on different ends of the shaft, and this affects the critical speed that determines vibration characteristics.

 

Well the problems never end. I was also having issues with my throttle cable and today the housing broke completely in two. I kind of tied it off to give it some tension and I think it will work till I get a new one (on backorder since GM stopped making them). I took it for a drive and even at partial throttle the thing wouldn't shift till 4-5k. I adjusted the TV cable and I think THAT problem is fixed. But like TKO said in his post, I'm getting a vibration. It's at about 50mph when it's left in 3rd gear and I take my foot off the gas. Its smooth as glass everywhere else. Is this being caused by the mount?

 

potentially the mount, could also be tires or driveshaft.

Poly tranny mounts are basically this.

Try it, if its **** in your car don't use it.

to many different results to listen to one or another person.

ie, works fine in my car. Joe next door, gets vibs.


For your 50mph vid, check your tires, make sure pressure is equal on all 4 and that they are balanced properly and rotated. after that, could be driveshaft, which from reading above could be the mount.

 

Another area I've routinely found to be lacking is driveshaft balance. Technically you are supposed to get the shaft rebalanced every time you change the u-joints. I didn't use to put much stock in that, but recently I've started doing it on every vehicle I put u-joints in, and everyone has noticed that strange vibrations are gone, and the car seems a lot smoother. Even the factory balance isn't always dead on. Over time things wear, the shaft can get dented or rust, and this can all throw off the balance. I take mine to a local shop that does a lot of heavy truck stuff. Every shaft I've ever had them balance or make has been dead on. It's another $60 whenever I change the u-joints, but that isn't that often if you keep up with your maintenence. That $60 is money well spent when you're cruising down the highway at 80MPH in an American car that rides as smooth as a Mercedes.