1990 LeSabre Motor and Transmission Mounts
 

Lately I've been noticing more engine vibration and noise than I have in the past. Nothing excessive mind you, but I notice it. It's been a slow increase in noise over the past several years, so this is nothing that has suddenly appeared. The car runs phenomenally well, idles smooth and gets terrific fuel economy, so I do not attribute the vibration to any kind of performance issue. My car has 122K on the clock, and at 30 years old I have to believe that the engine and transmission mounts have outlived their service life with flying colors.

My questions for the group are:

1) Is there a particular brand of engine and transmission mount that is preferred? I'm planning on going with hydraulic mounts as opposed to the solid rubber mounts.

2) Are there differences between 1st design, 2nd design, and in one mounts case 3rd design mounts that I should be aware of that affects mounting and fitment? My car is an earlier 1990 that came off the line in 09/89.

Thanks in advance!

To add, the noise is noticed only during acceleration. It evaporates when cruising at speed. Also, the struts and tires are relatively new, and I did and alignment a couple of years ago (roughly 7K miles ago when I replaced the struts) and the car tracks and brakes perfectly straight with no drifting or pulling whatsoever...so suspension, tire and alignment issues are eliminated as a source of the noise. Additionally, I just recently proactively rebooted the CV driveshafts on both sides, and the CV joints are in A1 condition.

Have you inspected the motor mounts? I'd hate for someone to tell you the best mounts ever . . . if they are not the issue.

Yes, visually when I replaced my oil pan gasket. I didn't see anything that looked out of sorts. Then I tried the stationary test with the hood up, foot on the brake, and giving it gas in both drive and reverse. I do see some rocking movement, but the engine isn't rocking severely. I don't believe the any of the mounts are broken, I just believe they are worn and not performing like they should. Again, I know these do have a lifespan like everything else, and after 122K and 30 years I have to believe they are due to be replaced.

"30 years" would be more of an issue than 122,000 miles.

That having been said, I'm curious what vibration and noise you're experiencing, and in what conditions.

Intermittent clunk from park to reverse or from neutral into drive. Slight vibration accompanied by engine noise during acceleration, most notable when accelerating up hills. Calms down when the road flattens.

I just gave the mileage for reference as it would likely have been a question that was asked.. The age of the mounts is where my concerns and suspicions of mount failure lands. Age and oil takes a toll on rubber mounts.

What RPM does it idle at?

700 @ 195º in closed loop. Again, I have no performance issues.

I'm beginning to sense no one has any recommendations on the best motor / transmission mounts. I can round up a set of NOS mounts on ebay, and I normally like to stick with GM parts when possible, but in this case I don't want to chance it by rolling the dice and installing 30+ year old rubber mounts in the car. Rubber degrades with time...even sitting on the shelf.

I've not heard anything good about aftermarket mounts in the A-bodies, which may be similar to yours (depending on which rev your car has). GM made ones are no longer available for these either, and I wouldn't pay a premium for NOS parts that are going to be hard from age. That's the problem with old cars from a defunct manufacturer.
I just changed the mounts in both of our Buick Century's. The one in front of you feet is captive under the mounting bracket and rack and pinion.

https://cimg5.ibsrv.net/gimg/www.gmf...56d8f9b876.jpg
New mount in place, '92 Century


https://cimg6.ibsrv.net/gimg/www.gmf...d040047cf6.jpg
New mount in place, power train raised and engine cradle lowered.
https://cimg7.ibsrv.net/gimg/www.gmf...522c41a94f.jpg
Failed mount
I was suspicious the mounts were failed on the '92. The were both completely apart when the weight was off the power train. I did not expect them to be failed on the '96, but only the front one was partially intact. Neither moved much or excessively when shifting R to D.

CorvairGeek - Thanks for the reply with pics. Although not identical, I can see where GM's H and A FWD platforms are similar, and can be prone to experience the same issues. What made you suspicious that you had bad mounts on the 92?