My 99 LS400 has only 49k miles and runs and drives great. But it is still a 20 year old car and I am worried about the condition of all the 20 year old rubber parts. Time can be as harmful for rubber parts as miles... I have had the timing belt and tires replaced but wonder about the suspension bushings, engine and transmission mounts. I had a local mechanic look at the front end bushings and he claimed they look fine but I am not sure how or how thoroughly he inspected them. My question is: What are the symptoms of bad bushings and engine/transmission mounts? How do you know when they need replacement? And, if I were to prioritize the replacement of these parts due to budgetary reasons, what would you recommend replacing first?

 

Mechanic says it's good, it drives good. So drive it. When bushings start wearing out you'll notice the clunks and noises.

 

I definitely would not touch anything until the problem finds you first. Keep an eye out for tire wear, bad handling, klunky noises, etc.

But in general, from my own experience owning and fixing many old cars, the whole rubber thing is overblown in my opinion. Seems to me like a tactic to get low prices on good old low mileage cars.

 

if the car sees extreme temperature swings then yes the rubber will more likely be brittle but if the car drives fine then I wouldn't worry too much.
do pay attention to clunk sounds, feathering tires, car straying or other abnormal behavior to indicate bad suspension bits.

 

The main rubber you have to worry about as the car ages are all the vacuum and coolant lines. They get brittle as the rubber dries out and ages.

Suspension rubber won't cause your wheel to fall off if\when it breaks. It'll just start making noise and giving vibrations\shakes as it deteriorates.

 

I own two LS400 and DIY as a rule. Sound like you are ok. Reasonably if it feels good and tight it is ok.
A few things seem typical that I have experienced. Slight clunking when going over rough spots at slow speed. Control arm strut bar bushings are bad.
They can look quite ok but are not if they do the clunking. Can be a bit of a hassle if the bolts are seized as mine were. Buy OEM stuff. I paid 35$ each.
A bit worne bushing can also give wheel alignment a bit off. I wore down rear tires by half fast due to 3 times too much toe in in rear.
Easy fix. Adjusted to spec.

 

I appreciate all the advice and freely admit I am probably being neurotic about this. In my defense, I have been driving company cars for almost 30 years and turned them in at 60k miles, with the company paying for all maintenance. This is the first older car I have owned in years and my first ever Lexus. I have to say, I am amazed at how sturdily the Lexus is constructed compared to the Tauruses, Luminas and Impalas I have driving for three decades. My wife's 2016 Jetta already has more door dings than my LS.