How many miles on the vehicle? Has the transmission been serviced? What color is the transmission fluid and does it smell burned?
The "speedometer gear" the 'mechanic' was talking about is a gear inside the transmission that turns a cable that moves the speedometer. This is sealed the transmission body with an o-ring.
The shifting issue: Unplug the vacuum modulator and drive the vehicle. See if that clears up the problem. Try shifting manually. If either of these clear up the shifting problem, you have a bad modulator.
Your truck's transmission may be equipped with a vibration dampener. This dampener may have failed, causing the 'rattle'.
If the catalytic converter is equipped with a heat shield, these are notorious for causing rattles.
Hard start when cold sounds like a problem in the cold start circuit, like the engine is not getting the extra shot of fuel it needs when cold.
Going back to the rattling problem, I am going to presume that you have gone over everything with a socket, ratchet and wrench to ensure everything is tight, such as transmission cross members and driveshaft nuts and bolts.
Tuesday, June 7th, 2011 AT 7:34 PM