[Chrysler300] Bad shaking in Power train? 300 G

["Michael D. OLear" <bookemdano50@xxxxxxx>]

Help! I got invited to the "Hot August Nights" in Reno this year as a result of "a vehicle of special interest". (They had me still 1500 down on the list after 4 years but finally read my write up on the one family 300 car and went down into the list, As the Lady at the office said, "How many 55 Chev's can we show?)
 
Now my problem. Under acceleration or in deceleration, mostly in second gear, (auto trans)  the car develops a heck of a shaking. (This just started and I never got an earlier warning of it). BUT!!!, it seemed to start right after putting on the parking brake. I have a steep driveway, pushed the brake on hard, pending blocking the wheels. Shortly thereafter, I put the car at the bottom of the slope between the street and the driveway, thus creating a "bridge" of the car with the front on the street and the rear up the steep driveway.
 
I backed up and heard this horrible sound, almost like the differential was disengaging and it seemed to be coming from the rear of the car.  I subsequently drove around the block and had no problem. I backed up the driveway with no further noise. A few days later I drove it to Reno, about 50 miles, put on the parking brake. After about 1 hour I again backed up to hear this horrible sound. Going forward the sound was gone, and again in backing, no sound. 
 
Driving back the 50 miles (always up hill to a greater and lesser degree) I felt what I believed to be the motor missing badly at times. Since I was climbing to 8000 elevation from 5000, I wrote it off to the fact the carbs were jetted for sea level, thus either  a carburetor problem and probably fouling of plugs. Annoying but seeming to clear.
 
The following morning (I live at 7000 feet and have to wait for the motor to warm) I drove about 7 miles, mostly downhill. It felt initially like the motor was missing with slight shaking a couple times, but on a steeper hill I downshifted to second and the car began to shake and again it felt like the rear end. With this I deducted it was not a missing problem, but some sort of drive train problem. Back to high gear, the shaking stopped. Driving around on flat ground, not pushing the 413, it again acted normal. Coming home up the steep hills my problem returned.
 
While not the greatest at diagnosis, I have driven for 50 years from the perfect machines to all the junkers I had and tried to keep running as a kid. My first guess was this hair brained idea of the parking brake that Chrysler put on a lot of their cars, since it seemed to coincide with my problem. But the sound was more a metallic crunching sound, but the crunching sound only occurred twice. The feel while driving feels more like a drive shaft trying to "find another place to live". 
 
I found the rear u-joints with no unusual play, while that center "thing" covered by the boot appeared to be ok. The boot was mostly gone, the grease around the 2 u-joint type fittings more like wax than grease and dirty. The joints themselves seemed ok, but boy I've never had dealings with such a thing before, so I really didn't know what to look for in some subtle problem. 
 
The brake was ok (but a pain to put back together)' The motor mounts are relative new, tightly attached. The transmission to frame spring (mounting the transmission to the frame) is weak, and allowed for what I believed to be excessive side sway. (I had hoped against hope that this was the problem.)  I shimmed it with 2 washers to get a tighter hold.
 
While I'm familiar with the twin axle, center rubber type bushings, this weird joint is not in my area of expertise. (If this was my old Chev, I would say this is the problem, but this joint does not seem, one, to be worn as to cause this problem, and two not as critical. It does tho have 80k miles on it, since I have put on 20k in the last 3 plus years.) But, this weired joint seems more to handle the up and down and forward and backward movement. And since it did occur AFTER I MADE A BRIDE OUT OF THE CAR, this bridge would have put both an up and down strain and a stretching pressure of the joint. But again, I can find no damage to it or metal in the old grease, and the sound I heard should have produced both.
 
HELP!! can the transmission or differential produce this shaking?, or has this weird joint outsmarted me?
 
I only have 2 weeks to get my "Black Beauty" purring again for Hot August Nights. 
 
Any help or suggestions would greatly be appreciated. I'm about to call auto repair places in Reno  for help. This car spends May thru Oct here in Tahoe, but I drive it back to Los Angeles to spend the Winter. Unfortunately for me, my trusted mechanic is in L.A. 
 
Michael Danny O'Lear, bookemdano50@xxxxxxx 
 
 

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