P38 vibration

tarphenry · Sep 17, 2017

After a 50 mile run @ 70mph on the motorway ,with no problems, we slowed and after about 2 miles on country roads again with no problems. I pulled away from a T junction and a slight vibration occurred . once moving it dissappeared and only re-occured when I attempted to increase speed. I am suspecting that it is the u/j on the fromt propshaft,but would appreciate the comments of others.Thanks in anticipation.

biketeacherdave · Sep 17, 2017

If you not done them in your owner ship swop them out quick before they let go

tarphenry · Sep 17, 2017

Thanks I will get a pair tomorrow and fit tues

johnnyb70 · Sep 17, 2017

Prop went on my van about a month ago. The exhaust always rattled against the leaf spring put on a new prop bingo rattle cured. Mine fell off and dragged along to a stop. Check em before changing as your problem could be many things. Check radius arm bushes and viscous coupling.
Jb

Grrrrrr · Sep 17, 2017

tarphenry said:
After a 50 mile run @ 70mph on the motorway ,with no problems, we slowed and after about 2 miles on country roads again with no problems. I pulled away from a T junction and a slight vibration occurred . once moving it dissappeared and only re-occured when I attempted to increase speed. I am suspecting that it is the u/j on the fromt propshaft,but would appreciate the comments of others.Thanks in anticipation.

Only does it under hard acceleration?

tarphenry · Sep 17, 2017

I dont accelrate hard ,but its when I put my foot down to pull away or increase speed

Grrrrrr · Sep 18, 2017

tarphenry said:
I dont accelrate hard ,but its when I put my foot down to pull away or increase speed

I am wondering about the flex plate. Never had one fail on me so unsure on the symptoms.

Guess question would be is it road speed related or engine speed related?

tarphenry · Sep 18, 2017

thanks ,I hope its not that. I would expect that to be engine speed related.

Mark Piercy · Sep 18, 2017

I get the same vibration around the 2200rpm mark, my engine mounts don't look so good!!

tarphenry · Sep 18, 2017

Thanks I will check them as well

tarphenry · Sep 18, 2017

Managed to remove most of the front prop (someone before me has made a right mess of the nuts) the final two on the gearbox end are just going round (Stripped thread I presume), so will have to cut the nuts off(painfull) new ones on order so will keep you informed

tarphenry · Sep 19, 2017

went for a short run today and the yibe has gone, so when the bits arrive (thur) i will tru and replace refurbed shaft.I must have knocked the exhaust yesterday cause now thats tapping on tickover.

johnnyb70 · Sep 20, 2017

Possible viscous coupling seized too.

johnnyb70 · Sep 20, 2017

"I pulled away from a t junction" suggests turning under load. disconnecting a prop will remove the vc from the drive train. Hope not a that's nla as far as I could see last time I looked.
Jb

tarphenry · Sep 20, 2017

Definitely not the viscous coupling,as i checked this when i jacked the vehicle up. thanks though

tarphenry · Sep 24, 2017

Further tests today reveal that it is definitely engine reated and is occurring at 2650 revs onwards .I will get to the bottom of this somehow. I have had it on Nanocom and no faults on engine or g/box, so its a physical problem.

Grrrrrr · Sep 24, 2017

tarphenry said:
Further tests today reveal that it is definitely engine reated and is occurring at 2650 revs onwards .I will get to the bottom of this somehow. I have had it on Nanocom and no faults on engine or g/box, so its a physical problem.

Does it do it in neutral?

tarphenry · Sep 25, 2017

yes it does, thinking either flex plate or engine mounting

Wazzajnr · Sep 25, 2017

Does the bottom crank pulley have a rubber damper on these?
Mate of mine has a BMW and has had an undiagnosed vibration for a while.
Yesterday, his bottom pulley fell off. Rubber centre torn out completely.
He's yet to find out if a new one fixes the vibration but might be worth a look.

myfirstl322 · Sep 25, 2017

Would worn crank thrust bearings cause this issue, I know these bearings are an issue in some (if not all?) BMW straight 6s.

P38 vibration

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