How stiff are your doughnuts?

[GT40-Steven]

I was under the car this weekend since I have this purring sound from the transmission tunnel when taking off on a a tad bit then moderate throttle.
I used a crow bar to gently apply force to the prop shaft where the bearings are mounted and I could move the drive shaft about 10mm without applying to much force.
I also discovered some moron have been working on the car and not properly fastened the bearings to the chassis. I could at least do 2 full 360 deg turns on the nuts both at the from and rear bearing mounts. /Grrr
This got me suspecting that the purring came from the bearing mounts vibrating against the chassis. However the sound is still there so now I suspect the doughnut rubbers holding the bearings in the ring shaped mounts are worn out from the mounts moving around too much since they were not fastened properly. Thus the prop shaft flex to much during load.
I see no markings on the wall of the tunnel. Car got a proper rust protection update just a while ago from the prior owner so it should be easy spotted if it hit the tunnel walls. Does not look like the exhaust pipe can vibrate against the prop or the bottom of the chassis.

Anyway the rubber doughnuts feel like they flex a bit more then they should. Car 81k miles on the odo.
Do I need to replace the bearings totally to fix this? I guess this means removing the prop shaft assembly, dismantling the shaft and replace the bearings?

Do I dare to let this be like this even if the prop shaft can flex a bit? If so when is it time to really consider replacing the bearings?

[GT40-Steven]

50 looks and no idea what so ever? :thinking:

[bradc]

They shouldn't flex that much, imagine what will happen at 100kmh when the driveshaft is spinning really fast. How much movement is there now?

[Nick Mann]

I was under a VR4 or two today so I had a good look. It seems that if you look at the donuts from the rear of the car you can see a gap between the outer and the inner. On all the donuts I have pulled at you can make the inner touch the outer by pulling down on it. It is difficult (read 100kg bloke!) to keep the inner touching the outer without hanging off the prop shaft.

I have no idea if that info is useful or not, or even if that is acceptable play or not. I would guess the gap is approx 5-6mm, so is your 10mm of play up AND down? If just down, then I would imagine you are substantially deforming the stronger parts of the rubber, which can't be proving anything good. Having said that, I didn't use a crow bar on any customers prop shaft.

[GT40-Steven]

Thanks Nick! That confirm these bearings have to be replaced.
The force was applied to the side. I put the end of the crowbar to the tunnel wall and gently pushed on the prop shaft. The force applied can't be even near what you get hanging in it. More like 10 kg.

Oh and Bradc I don't notice anything at higher speeds.

Ho hum more expensive work. I guess these bearings are an arse to replace as well. Hope that workshop manual arrives soon.