Quick Background: The car is a 1971 442. Exactly 19 years ago, I had the original 455 motor rebuilt. I put the motor back in the car myself using the reproduction 2328 motor mounts shown on the right side of the picture in this LINK. I also re-used the original 455 frame mounts. Since then, I put ~25,000 easy miles on this motor with no issues.

The car gets driven every weekend. Yesterday, I started the car and put it into reverse. I felt & heard a loud clunk coming from under the hood as it shifted into reverse. I backed it up, then put it back in Park and left it running while I popped the hood. Everything appeared to be normal. I left the hood up and went back and put it into reverse again while peaking through the windshield. I noticed the motor jerked violently toward the driver side the instance I put it into reverse. Sure enough, the passenger side motor was not holding it. The bottom picture is from a video clip that I paused to capture the highest travel.

So now, I am wondering if it is possible to replace both mounts without pulling the motor. If so, I would like to hear all your tips and ideas and where to place the jack. Also, beside the fan shroud, what else needs to be disconnect before jacking the motor up? Also would I be damaging anything else in doing so? Do I have to loosen the transmission mount also? What else should I watch out for before I get into this.

Lastly, I heard that today's repro mounts are either too thick and/or have the frame hole in the wrong place. Does anyone have recent positive experience with a specific brand of the 2328 mounts to order? If so, which brand to use and which ones to stay away from.

Thanks in advance. P.S. To save others some time, here is a short cut to the Oldsmobile Motor Mount Application List




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Yes.
You'll still need to lift the motor with either from below with a floor jack or from above with a hoist.
Manifolds will need to come off first.

 

You should not have to remove the manifolds. Just place a wide piece of plywood across the bottom of the pan and use floor jack to raise the engine a little to remove the connecting bolt to the frame brackets, then remove the bolts to the mounts. I would recommend pulling the distributor so it does not get damaged from raising the engine.

 

Take the distributor cap off and move it forward so you don't break it. yea you know how I know this right? Also be careful of the fan to shroud clearance.
But is doable.

 

Good point about the distributor & cap.

 

Its odd that the passenger side mount let loose. Usually its the drivers side.

 

Apparently the OP has been drag racing in reverse...

 

This may be a good time to replace the transmission mount as well.

 

Certainly not a bad idea, but I can't say that I've seen a correlation between broken motor mounts and trans mount. Usually the trans mount deteriorates due to oil or trans fluid leaking on it.

 

Yes, I usually back up in a hurry
But Seriously, why is it more common for the driver side to go out first?
I also want to point put that the "clunk" was only noticeable from "PARK" to "Reverse", and from "Drive" to "Reverse". There was no "clunk" when I took it out of "Reverse" to "PARK" or "Drive". Any ideas why?

 

Engine torque under normal conditions (ie, driving forward) puts the driver's side mount in tension and the passenger side in compression. When backing up, it's the opposite. Since usually you spend a lot more time going forward, the driver's side mount nearly always fails first. Of course, it is also possible that your driver's side mount was replaced long ago but not the passenger side.

 

They were both replaced at the same time 19 years ago, when I put the motor back in the car.

 

19 years out of a set of motor mounts is spectacular.

 

Yes you can, transmission mounts are easy in my experience. I've done this, but when it was time to line the engine mount it was a pain. So I used a small jack from a toyota the one that's fold out. And jacked the moter sideways from inside the engine bay to line it all back in.
Don't let the car out think u.
Ronnie