The truck shakes in the rear at 55 to 65 mph...Had repair work done after a collision behind the cab broke the driver's side rear leaf spring...The spring was replaced and had 4 wheel alignment done, new tires put on all around and 2 new rear wheels...Thanks!

for the rear the truck will have shocks and ;leaf springs ----front is shocks and coils

have a wheel alignment done on the rear
could be from failed suspension rubbers , broke spring ,broken center bolt if leaf spring

look under for damaged fuel lines /kinked===vacuum or evap lines and component damage

okay the transmission is probably fine ,,,but if you are having these problems like this have your trans axles checked out ..anytime you put the vehicle in a bind that creates hard shifting you are heading for expensive repairs ..Have the ball joints checked as well to see if all of this smooths the transmission out ..It could be something simple ..also remember that a faulty steering can cause this

You're wasting both time and money on a vehicle that is not worth the $$ you would have to spend to repair it - if you can at all. Junkyard, dude. Sorry. I replaced the leaf springs and hangers on a '03 Silverado several years ago - $1,000. I did it because I only paid $2,500 for the truck, which was otherwise OK.

Are the new springs that were fitted original factory or after market?
New springs will be less flexible than old ones until they settle into use. This will explain the increase in ride height. Old springs soften so the ride height drops a small amount. At higher speeds your getting more down force so the suspension will settle.
Remember she's a 20 year old truck, things start to sag as you get older.

> Does this vehicle have shock absorbers or leaf springs?
It would be either leaf or coil springs; shock absorbers serve to prevent that continued bouncing and these may be simply shot.
The crude way of checking shocks still works somewhat:
- Position yourself on each corner of the vehicle and through repeated pushing down and letting the corner come back up, get some momentum and then let go at the bottom of the cycle.
If the shocks (which may be located within coil springs- McPherson struts) are still effective, the vehicle should rise slightly once and then settle. If they are blown, there will be some continued 'overshoot.'
The leaked fluid can be checked for odor; brake fluid is pretty distinctive while lubricants will smell somewhat like oil or grease. This could be from a shock but most are now gas filled rather than with a type of hydraulic fluid.

check to see if a leaf spring sprung looseor broke a shackle

on a two wheel drive the shaft should only angle down if this a used truck I would say the rear
axel was hit on the side that the drive shaft angels away from and the alignment should be checked out.