Strange vibration

[giuliettaevo]

Hello,

My car has developed a strange vibration over the last period of time.

The car starts vibrating around 3k rpm in each gear. Driving in 5th gear at 2.5k it's fine,downshifting to 4th gives vibration at the same speed. Vibration is felt through the seat and drones in the car. Driveline, not wheels or steering.

Set up of the car;
- 2.4 5 cilinder commonrail jtd engine. 136 bhp with mods to about 180/190 bhp 400nm.Oem front pulley. Converted for rwd setup.
- Solid flywheel with pressure plate with double diaphragma for more pressure. Sprung plate from calibra turbo.
- R25/28 rwd gearbox.
- Custom propshaft with 2 cv joints. Balanced by reputable company.
- Bmw 188 diff.

It's my daily driver and i'm rather busy at the moment so i'm still driving around in it. As long as you stay in the right revrange it's ok to drive. If you pull past 3k revs it doesn't feel very good. It's making power but drones heavily inside the car at +3k revs. engine gives no fault codes.

Gearbox is a bit tired. Has quite a lot of play on the shaft to the propshaft. In neutral the box rattles quite hard due to the single mass flywheel. This also causes vibrations below 1.5k revs.

What could cause a vibration at certain revs? Engine, clutch or gearbox are my suspects. Could an injector cause this? Revving in neutral doesn't really give the vibrations.

Taking of the gearbox is a lot of work as the engine needs to come out. So any thought about other causes are more then welcome so i can investigate them..

[sierra1off]

I used a company called vibration free who can pinpoint the issue based on the frequency of the vibration and the revs it occurs at.
If its always over 3k whatever gear then its going to be the engine, flywheel or clutch .
Check engine mounts have not collapsed
Good luck

[giuliettaevo]

[Dez]

If it’s doing it directly related to engine rpm in different gears rather than road speed at different rpms, you need to be looking at engine related items- clutch, flywheel, crank damper, pulleys, belts etc. It could also possibly be something in the front half of the gearbox that is still spinning at input speed before it goes through the gearset- e.g. an input shaft bearing. Did you put a spigot bearing in the end of the crank when it was rwd converted? Could be that too.

[giuliettaevo]

Engine mounts are industrial style mounts. 55 shore full rubber mounts and in good condition.

[giuliettaevo]

Engine has a spigot bearing fitted. Only belt it has is for the alternator, no problem there. Crank damper in front pulley is allright.

Will test tomorrow if it vibrates while driving at +3k and then pressing the clutch.

[stealthstylz]

Is there an adapter plate between engine and gearbox?

[giuliettaevo]

Yep, 30mm aluminium adapterplate between engine and gearbox.

But the car has been used for quite some time and these vibrations are more from the last couple of weeks.

[stealthstylz]

Ah rules what I was thinking (slight misalignment) out then.

Mostb causes of vibrations that I see are:

Rubber in front crank pulley breaking up
Dual Mass Flywheel worn out
Propshaft wear (UJ's, rubber donuts, centre breathing carrier)

[giuliettaevo]

Sept 25, 2019 22:40:17 GMT stealthstylz said:

Most causes of vibrations that I see are:

Rubber in front crank pulley breaking up
Dual Mass Flywheel worn out
Propshaft wear (UJ's, rubber donuts, centre breathing carrier)

Front pulley looks fine. Solid flywheel. No rubber donut. No center bearing carrier due to 1 piece propshaft. Since the vibration comes at certain revs and not at a certain speed i'm certain the propshaft, diff and driveshafts are not the problem.

I guess i will have to bite the bullet and take it all out. I would have liked to have solved this issue without doing just that. I already have a newer 20v jtd engine waiting to go in but that will require a lot of work and it would be nice to be sure that the vibration issues would be solved before putting in even more power and torque..

[stealthstylz]

Another thought - could it be a dodgy injector? Been trying to think of what else causes vibrations, never seen it on a 5 pot JTD (never get them in TBF, only ones I see are the 2.0 in Insignia's only with spun mains) but on Transits and Mercedes when you get a injector fault it can start causing vibrations at certain rpm before they go bang altogether.

[slater]

Is it a misfire possibly?

[stealthstylz]

Sept 26, 2019 6:30:30 GMT slater said:

Is it a misfire possibly?

With the Transit's it can feel like a petrol misfire/pre detonation but it's not a misfire as such, the injectors leak into the cylinder when they're not meant to so you basically get pre detonation once the engine is hot enough to light it off, then a proper detonation at the correct time.