2008 Pacifica AWD
188,888 miles as of yesterday

I've been troubleshooting my pac for a while now, but can't seem to find the root of the issue... So here is what is going on:
when I accelerate from a start there is a shake which continues until about 20mph this shake is strong enough that if you were humming it would gives you vibrato.lol Between 20 to 55mph you feel nothing, the thing drives great. This is accelerating or just normal cruising. The fun starts at around 57 and goes until about 70 when this thing shakes like crazy whether accelerating or just idling along. Here is the weird thing: When you let off the gas at say 62 when its at its worse the vibration GOES AWAY. Then I apply gas, comes back, let off, goes away. The vibration is mostly felt in the seat and the steering wheel and it is a very fast vibration and your hand starts to go numb with it. lol
So being that this is a vibration while giving it some gas, I would assume its in the drive train somewhere..
What I've done so far:
(1) Replaced the ENTIRE front end. I mean everything except the steering knuckle. Entire strut housing, wheel bearing, cv axle, intermediary axle, inner and outer tie rod, sway bar bushings, links, control arms, etc.
(2) Rotated the tires... but I don't think its related since the tires would still shake whether or not the car is accelerating or not
(3) The rear driveshaft was replaced about 20000 miles ago, it still seems pretty good. The original was torn, but this one has not yet.
(4) Turned one brake since when i backed up it was squeaking
(5) Replaced the rear differential front bushing which has collapsed a little

I'm kind of out of ideas other than maybe motor mounts, but when I open the hood and rev the engine, nothing moves.

Thank you kindly for any ideas!
David

 

cradle bushings. Rack bushings

 

Funny you say that because I'm getting a bad clunking noise when I hit bumps when its really cold out in the morning. I've been wondering if its the cradle bushings. Have you heard of this before with the cradle bushing failing? Can you even get them anymore? Thank you for your reply. I really didn't think that they could cause a shake like that.
David

 

Rack in pinion is bolted to the frame so yeah would transfer right through to the tires.

part number should be 04880339AB

 

Thank you very much! Do you know the part number for the rack bushings? I have been trying to find them, but I haven't been able to get them. I ordered up the cradle bushings, I just hope they aren't a bitch to get out of the cradle, since there isn't a single video online that shows how to remove them.
Thank you very much!

 

https://www.factorychryslerparts.com/

 

So I replaced all 3 of the motor mounts after finding that the passenger mount was completely broken. The engine was kind of flopping within the mount since all of the rubber was busted on the passenger side mount. I also replaced all four of the cradle mounts.
Would you believe though that I still have the same damn launch shake and shake around 60mph? I assume now its probably a transmission thing... maybe its the torque converter not locking in right or something of the sort. I might just start to ignore it as best as I can...

 

I have a similar issue right now with my '07 Pacifica 3.8L FWD. It started as a shudder that would intermittently occur when accelerating at low speeds. Backing off the pedal and then getting back on it would give it a chance to "catch up" and fully engage the gear. I let it go for about 3 months with the same mindset you seem to be coming to. However, about 5 days ago, my wife was getting on the highway and the transmission went into "limp mode" (in case you're not familiar, this is a fail safe mode that keeps the transmission in 3rd gear to prevent damaging the transmission but still allowing you to get home or to a service shop). She was working for Grub Hub at the time, so she dropped off the order she had before returning home. She was able to back out of the parking spot she was in to make her delivery, but by the time she got home and parked, it will no longer go into reverse. It initially had a check engine light, code 0755 I believe. The description of the code was the output speed sensor was out of range from the input speed sensor. We did not experience any speedometer issues/twitches, so I opted to change the Solenoid pack and cleared the code. No change except there was no longer a check engine light or TCM code being thrown. I just got done changing the output speed sensor. No change, still no code. Tomorrow I will be changing the input speed sensor, but at this point, I don't expect this to solve the issue. Outside of possible internal tranny issues, the possibility that the transmission is stuck in limp mode for some reason, possibly the TCM itself. Moral of the story, get the shudder diagnosed by a reputable shop, unless you do your work yourself, then take the time now to figure out what the issue is before any escalation of the issue(s) occur.