If it doesn't do it in reverse, it leads me to believe it may have a broken motor mount. Have someone step on the brake while you look under the hood. Next, have them shift from park to reverse, then to drive. Look to see if the engine is lifting excessively on one side when it goes into drive. You might even have them apply the parking brake and carefully apply a little gas. If it has a broken mount, you will see the engine jump up noticeably when you hit drive.
If this doesn't show any problems, look at your u-joints and transmission mount next. Grab the drive shaft next to the joints. Try to move it from side to side, up and down. Look for excessive play in the joints. Make sure your trans. mount rubber isn't broken.
After all this, if nothing jumps out at you, go down to the auto parts store and buy a bottle of TransX, made by K&W Industries . I swear by this stuff. I worked in garages for 17 yrs and have seen it do wonders on transmissions that were slipping and shifting hard. Good Luck!
