Noisy Prop-shaft Advice

[swedishandgerman]

I regularly read about people struggling to eliminate noisy prop-shafts

Much advice gets given out about centre bearings and rubber doughnuts. That is pertinent as neither last forever. However, if your engine and gearbox mounts have had it, you may never eliminate the noise and if you do, but the mounts have sagged, you're going to wreck your new bearing and rubber silencer

The mounts on these cars don't last well. They're rubber and get hot, under a lot of load and get covered in oil and mank. At best they go hard and engine damping is reduced. At worst they delaminate allowing the engine to break free

Usually they sag so the engine and gearbox drop lower. In a P1800 that can allow the prop to band against the prop housing. This sag makes the prop at a wonky angle as explained in the Youtube movie attached here

Those engine mounts aren't too expensive and a nice rewarding little DIY job

https://www.youtube.com/watch?v=gmV4qwLfOMY

[ExCee70]

Was there not an option to use a heavier duty Land Rover mount?

Sure I saw it mentioned recently, will have a search.

Timely posting as I have just replaced the gearbox mounting rubber and had a new prop made but not considered the condition of the engine mounts. Makes sense to check/replace them too.

[Derek UK]

Fitting heavy duty mounts maybe worthwhile for competition use. Land Rover ones are cheap but anything stiffer than standard will only transmit more noise and vibration through the car. In this scenario that's what you are trying to minimise. Selecting rubber that both supported and gave good isolation was perhaps less sophisticated back then, but Volvo did their best. I'm sure that the stiffness of the 2 engine mounts and the gearbox mount were selected to compliment each other. Replacing the gearbox one with a stiffer one, perhaps a 164 one, may lift the box a bit but will in effect make it a hard mount compared to the engine ones. It may cure you clearance problems but at the expense of more vibration. Whether or not the rubber density of the current mounts is the same compared to the originals is another matter!

[amazon69]

Derek makes pertinent points, as ever.
I swapped my engine mounts for Land Rover ones to try to save a few bob.
That didn't go well because they were so harsh that the whole car became a vibrating fiasco.
I don't recommend them.

[Pigeon]

Engine mounts off a 740 will fit if you cut the locating peg off.

[Derek UK]

740 mounts are a few quid more than Amazon ones so wouldn't be my first choice. They might be stiffer too.

[Pigeon]

More expensive? How bizarre... But also, more available. I got a set from a scrappie, in excellent condition, in a case of Urgent Need (one of the originals came apart on the road and I had to prop the engine in place with bits of wood out of the ditch to get home). Worked a treat - can't really say how they compared to the originals for compliance, given how soggy the dud ones had got, but I certainly didn't notice any increase in harshness.