Chrysler Repair: rattling noise and lurching: 1999 Breeze, transmission control unit, waranty

Question
Hi Roland,
I had a used transmission placed into my car after the first one kicked the bucket. I noticed immediatley it would lurch once i get it to 30 mph or out of first gear once i touch the brake. it seems to only do it when braking, also it sort of lurches when going up a steep mountain briefly also. Another concern is, about a month later, I now started getting a rattling noise upon start up of the ignition for about a brief second then it goes away until i shift it into drive and press the gas pedal. it goes away once i let off the gas but it starts up as i drive. What could be causing this? my mechanic told me to drive it until it gets worse because he couldn't hear it when i took it to him (but he also didn't drive the vehicle, he tried to hear it upon startup of the engine), or until it breaks down. The used transmission has a 100 day warranty my mechanic told me. Can you help me figure out what this is?

Answer
Hi Jamie,
What you describe is difficult to relate to a specific malfunction of an electronic transmission. Braking generally should not cause lurching of the transmission, nor would the transmission normally cause noises on starting the engine. I wonder rather whether it might have to do with one of the three engine mounts being worn out which causes the entire drive unit to move around too much in the engine compartment. That is particularly noticed when first starting, braking, accelerating. So take a look/listen with the hood open while a helper starts the engine: watch for any possibility of excessive motion of the drive unit.
You could also have any fault codes stored in the transmission control unit 'read out' using a plug-in code reader (the mechanic who put in the transmission should be willing to do that for free so that you can see if anything is wrong with now before the 'waranty' ends. Let me know of any such fault codes with numbers in the 0700's or 1700's as those are the ones speicifically related to the transmission. An Autozone parts store will also do such a readout for free, in most cases. There could well be evidence of impending serious trouble that it would be good to know of now.
Roland
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Roland