Bad Vibration

[Coops]

after fitting gearbox last weekend the car has developed a bad vibration at anything over about 4k rpm, its bad enough to give me an ichy back at high revs as it vibrates right through the chassis and into the car/seat in which i'm sat.

if you depress the clutch pedal to disengage the gearbox it makes no difference, that includes if you hold it down before you turn engine on then continue to hold it down and rev it

it also makes no difference if the car is stationary or moving so its not outer drive train components, its definately engine or gearbox based

i have removed the aux belt and makes no difference so its not alternator or the water pump

i have disconnected the dogbone (solid) and it goes away, so its this thats transferring the vibration to the subframe/chassis. however i have run this dogbone for years with no issues, so the vibration is new

the gearbox is a renault 19 turbo diesel JC5. longer input shaft cause this maybe, catch flywheel?

any help/advice/diagnostics/prior experience of similar issues much appreciated

i'm stressed and want to go pod in a couple of weeks but its not looking good

cheers

Ben

[Purple]

Could be your main engine mounting (on driver side) is going? When that happened to me, I thought I had a gearbox failure from the noise location.

[cliopete]

Exhaust down pipe hitting steering rack possibly!!!!

[Allan]

check for play in your near side drive shaft, diff end....

just get your arm under and move it rotate while its on the ground, if it moves its probably a colapsed bearing on the tripod

[Coops]

the vibration is there when the car is sat still and you rev the engine, read the post people. its not going to be anything driveshaft/brake/wheel bearing related as they arent moving at all when the car is stationary

i have checked the exhuast,it catches on nothing and as said with the solid dogbone disconnected the vibration doesnt transfer to the chassis anymore, so its not any other part off the engine vibrating on the chassis, its an engine or gearbox issue, out of balance clutch? can it be knocked or damaged if gearbox isnt changed carefully?

i will check drivers side top engine mount as a possibility tonight

cheers for the input everyone

[Allan]

you running the 4th mount at the front ?

Also did you drop the subframe to do the box, maybe lose?

[cliokiz]

Yeah he did drop the frame.

When the input shaft is through the friction plate it'll fall into line anyway i would imagine so i don't think an unbalanced clutch would be to blame?

No expert on clutches though lol