Transmission

I have recently before i put my car on the road had my guts of my tranmission put in another casing because of a crack in mine. and ever sence they put it in my car now does 2 New FANTASIC things :bang: 1: pop out of first gear on a up hill slope,only way it will not pop out is if im still moving and put it in first, and 2: a bad viberation all through my car...like seriously at 120 KPH if i sat a girl on my shift she wouldnt last 10 seconds on there....i really need to know if something is put in the trans wrong will it make a viberation?
 
The driveshaft of the car is balanced to be installed a certain way. You can reinstall it 180 degrees out of normal position which causes vibrations. Other people have had issues with keeping the stock driveshaft and moving up to 3.73's and 4.10's. They'll have vibrations that they can't get rid of until they got an aluminum driveshaft. Not sure if it's an issue with the stock driveshaft's balance or not.
 
Firstremove the driveshaft and reinstall it a half turn from where it is now. I think you can only install it 2 ways but I'm not sure. On mine you can see the outline in the surface rust from where it was installed at the factory.
 
There should be a yellow paint mark on the D/S and axle flange. Match the two up and you will be lined up to factory specs.

With 3.55 or higher gears, the stock D/S balance may not be good enough to keep the vibrations down to an acceptible level. Balancing the driveshaft can fix that. A new FMS aluminum D/S is a good fix, but expensive - about $250 unless you can get an Ebay bargain.