OK. Just to recap:

All wheels replaced with genuine land rover replacements (I was told by one garage that one was buckled hence this action.
All tyres replaced with brand new ones (done once to scorpion ST's and once to Grabber AT2's)
All 4 UJ's replaced on probs
Both Prob replaced with brand new Hardy Spicer onces.
Steering damper replaced
All shocks replaced with Koni Adjustables.
All air springs replaced
Air compressor and valve block replaced (not really relevant but thought that I'd mention it anyway)
Rear wheel bearings replaced
Gearbox replaced a while back for a reconditioned one.
Diff oil replaced, seemed in pretty good nik.
Full engine rebuild by RPI engineering (this cost more than the car was worth, a small fortune in fact, which shows you how much I want to fix the problem as the car is very dear to me)
Replaced flex plate
Viscous coupling tested and confirmed as working
All suspension bushes replaced
Ball joints etc checked and confirmed OK

Props off one at a time - checked.
Chassis alignment / impact damage - no crash assumed.
Shocks - Koni's fitted after issue started so not shocks.
Front and rear mass dampers - checked.
Gearbox mounts - checked.
Engine bearers - checked.
Braks discs / pads - checked.
Torque converter drive split plate

Nothing felt through the steering so must be coming up through the chassis, possibly from the rear wheels or maybe the gearbox.

What does the cabin sit on? Are there rubber mounts between it and the chassis or does it just bolt straight on?

Is it better if you drop the tyre pressure to 30psi all round?
 
Grrrrrr said:
OK. Just to recap:

All wheels replaced with genuine land rover replacements (I was told by one garage that one was buckled hence this action.
All tyres replaced with brand new ones (done once to scorpion ST's and once to Grabber AT2's)
All 4 UJ's replaced on probs
Both Prob replaced with brand new Hardy Spicer onces.
Steering damper replaced
All shocks replaced with Koni Adjustables.
All air springs replaced
Air compressor and valve block replaced (not really relevant but thought that I'd mention it anyway)
Rear wheel bearings replaced
Gearbox replaced a while back for a reconditioned one.
Diff oil replaced, seemed in pretty good nik.
Full engine rebuild by RPI engineering (this cost more than the car was worth, a small fortune in fact, which shows you how much I want to fix the problem as the car is very dear to me)
Replaced flex plate
Viscous coupling tested and confirmed as working
All suspension bushes replaced
Ball joints etc checked and confirmed OK

Props off one at a time - checked.
Chassis alignment / impact damage - no crash assumed.
Shocks - Koni's fitted after issue started so not shocks.
Front and rear mass dampers - checked.
Gearbox mounts - checked.
Engine bearers - checked.
Braks discs / pads - checked.
Torque converter drive split plate

Nothing felt through the steering so must be coming up through the chassis, possibly from the rear wheels or maybe the gearbox.

What does the cabin sit on? Are there rubber mounts between it and the chassis or does it just bolt straight on?

Is it better if you drop the tyre pressure to 30psi all round?
Click to expand...

Main crankshaft pulley.:)
 
tomcat59alan said:
Main crankshaft pulley.:)
Click to expand...

You're thinking it is loose or missing a bolt? Maybe the damper breaking down? Presumably that would mean the vibration would be worse standing still but higher revs?

Although, would they not have done that on the engine rebuild? What did they do on the engine rebuild exactly?
 
Does the engine rev cleanly in neutral, the vibration only happens when your actually moving?
Have you tried shifting it into low range and seeing if it still does it?
 
In the OP he says at 50MPH.. i wouldnt want to be in low ratio at 50 !

One thing also to consider how old are the tyres.. does the car get driven much ? Tyres can develop flat spots when not driven much.. perhaps if there is another friendly P38 owner on the forum in your area a test to swap over the wheels may be interesting ??



As an aside my P38 gets some vibration at about 60mph and the passenger seat vibrates... However this only happens on certain roads. on one dual carriage way near me, the A331, it happens northbound but not south bound. the M3 is fine as is the M25, depending on which section. The M1 is fine for the P38 as well. The A31 south is like offroading in places.. i've nearly lost a filling in the merc with some of the ruts !

i'm running my tyres at 28 squared with even tread wear. (pirelli scorpions) Tyres are all balanced, tracking is spot on.. airbags are anotts, which are allegedly slightly stiffer than the dunlop ones..

I can only assume that it is potentially a dynamic vibration transmitted by road surface. The boxster suffers from, for me, a bad wheel shake on the A31 towards Guildford, is fine everywhere else, but not away from Guildford, the P38 also but not so much!

Basically our roads are crap. i've driven on better ones in Africa !! Make sure the tyres havn't flat spotted or you have tread delamination.. also are you running standard wheels ? I have the sport wheels (19's) on mine and they do need a spigot ring or you get damn awful vibration at 50 MPH
 
Ok, if you put it into low range the engine/gearbox will still be doing the same speed, the transfer box onwards to the axles will be going slower. this would see if its engine /gearbox speed related or actual road speed thats causing it, revving the engine in neutral would be to see if it was engine related.
The only things he hasnt mentioned are the transfer box and the transmission drum brake, could be thats imbalanced
 
Possibly a silly question to our learned posters - what would happen if the vehicle was supported on four heavy duty axle stands? Bung it in drive and with an assistant watch for what wobbles around at inception speed and increases with rpm.

Well, it was just a thought.....
 
Fergie46 said:
Possibly a silly question to our learned posters - what would happen if the vehicle was supported on four heavy duty axle stands? Bung it in drive and with an assistant watch for what wobbles around at inception speed and increases with rpm.

Well, it was just a thought.....
Click to expand...

Chain it down!!:):)
 
I have 2001 P38 4.5 V8 and i have this vibration issue at around 60mph, to be honest since i first owned the car there was a little bit of a shake, but now it really does shakes the car like crazy. Slowing down from 60mph is really bad too. If you accelerate through the 60mph area it sort of gets better at 70mph, any higher speed and its back. I have changed and or checked tyres, wheels steering damper, ball joints but its still there. Has anyone figured this out yet, seems to be a common problem.
 
ANDREW REEVES said:
I have 2001 P38 4.5 V8 and i have this vibration issue at around 60mph, to be honest since i first owned the car there was a little bit of a shake, but now it really does shakes the car like crazy. Slowing down from 60mph is really bad too. If you accelerate through the 60mph area it sort of gets better at 70mph, any higher speed and its back. I have changed and or checked tyres, wheels steering damper, ball joints but its still there. Has anyone figured this out yet, seems to be a common problem.
Click to expand...

It's a common problem if it has L322 wheels fitted without slip rings.
 
Hi had this problem with my SAAB 900 started around 50 and was still there at 85 to 90 above that say 120+ its gone or I could not feel it
the car had warped brake discs but this was only felt when braking changed the discs same problem
the tyres where in good nick 2.5 mm of tread but changed them anyway now no problem
can only think the old ones were distorted or weak around the tread area they were pirellis so should be good quality
 
Spigot rings are a real basic. I drove with one missing once( changed wheels around) it was undrivable. May I suggest a break down on all suspension bushes changed. Radius arm bushes often cause these issues. Also ball joints. Often neglected but cause havoc.
 
Have you ever changed the torque converter..Could the handbrake cable be transmitting noise into the cabbin ..
 
20170616_164100.jpg


I have a 2000 4.6 P38. Vibration at 70mph was a pain. Tried all the normal replacements. And had the tyres balanced to 0 (which I still do). One day an Aston Martin went by at colossal speed I said "wow" but my wife said "yes but he doesn't have our 70mph wobble!"
Eventually including the wobble the car was getting skittish and tramlining. As it was summer and a long continental trip was a couple of months off I decided to replace the top and bottom ball joints. Not an easy job. I also replaced both front brake discs and callipers. And put on a new set of tyres.
Before I took them off the ball joints looked ok apart from a slight split in one rubber. But when they came out they turned out to be in a very bad state.
Result, on our continental trip no 70mph wobble and she drives like a new one. Job was well worth doing.
 
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