Drive train vibrations

[Ems]

There's a bad vibration in the drive train of the Manta.  I didn't have this problem before I removed the gearbox, clutch and flywheel.  I've fitted a new clutch, reconditioned gearbox, gear box rubber mounts, torque tube donut, torque tube rubber mounts and crank seal.

The vibration is there in every gear but feels worse in 4th and 5th.  From around 40mph in 5th the car vibrates badly and gets quite noisy.  

I ran the car through the gears with the prop disconnected and there was no vibration or noise, but probably should be expected as it wasn't under load.

I would welcome any suggestions.

Thank you.

[Jessopia74]

You check prop UJ’s ? Tight UJ could cause this 

[Jonathan Pounsett]

Have you changed any bushes or mountings that may have affected the drive angle? Have you had the prop apart? If so check the phasing. 

[cam.in.head]

make sure the rear of the prop is located correctly in the little end stops. it can sometimes be a little tight and end up sitting at an angle.ie not fully down. and the linking wire (if fitted) is not in the way either. 

you will see what i mean if you check. 

[Ems]

Thanks for the replies, the prop UJ's are hand tight and the rear bearing caps are sitting between the end stops.  The prop hasn't been dismantled.

The donut has been changed for a heavy duty one and the gearbox rubber mounts have been changed.  I'll have to see if I've got the old rubber mounts to compare the height.

 

[Metalbasher]

A few additional things to check:

1. the balance weights on the prop tube haven’t come off during handling (shouldn’t do since they’re resistance welded, but does happen)

2. The flywheel and clutch are correctly aligned centrally to the crank output

3. The new rubber doughnut isn’t too stiff, this will change the dynamic of the drivetrain frequency 

4. On my Sportshatch at least, there’s a big metal block strapped to the rear prop housing. This is there to modify the drivetrain frequency from new, does your car have this and is it refitted?

5. Try removing and refitting the prop 180 deg rotation. If the prop is out of balance to some degree, this may improve (or worsen) the vibration

[Metalbasher]

6. The centre bearing fitted inside the centre bearing rubber (doughnut) is seated correctly

[cam.in.head]

if the car will rev with no vibration in neutral that pretty much eliminates anything engine /clutchwise .

 i cant imagine you would have damaged the gearbox in any way so that should be ok.

so . we are talking gearbox back.   check new mounting is not making it sit wrong as you thought. its only a simple rubber block affair on 2 metal brakets after all.

otherwise the checklist above is a good idea.

do you have the facilities (or a garage that will use their lift) to run the car in gear to check prop for true running ?

 

[Ems]

Thank you for all your suggestions, the Manta's having it's MOT next week so I'll ask him to check.

I used an alignment tool for the clutch so hopefully that's ok, I think the C20XE flywheel can only bolt on one way.

I haven't got the big weight on the torque tube as I've got a steel one fitted.

The centre bearing was fitted the correct way, as I had to remove it once as it was out of alignment.

When I went through the gears with no prop attached there were no vibrations, but the gearbox wasn't under load.

Looks like I've still got plenty to do over the weekend!

 

[cam.in.head]

bit cold for playing out but im sure you will find the issue.

[H-400]

Had years ago the same issue. Drove the car on a car lift with forks under the rear axle. So someone could "drive" the car while I was standing under it. It was easy to find the problem, in my case it was a bearing of a half-shaft. 

[GTEPETE]

I once ran over a bin liner in the road, it wrapped around the prop and vibrated like hell!!!! so only takes a small weight to drop off the prop or something similar to make car vibrate...

[cam.in.head]

are you 100% sure the prop is located correctly ?

i know you said about the end stops but were you sure the retaining wire between the cups is not in the way/ twisted or broken.

(broken is not an issue as long as the wire remainder is not holding the cup slightly off at an angle )

[®evo03]

What about rear wheels, tried different one? Brakes? Drums or calipers.

Would you hear or feel it if car was on a ramp? 

Gearbox alignment ok? Torque tube ok ? 

[Ems]

I still haven't had the chance to check anything due to the weather.

When the car went for its MOT, I noticed the new oil seal at the front of the axle was leaking and oil had been coming out of the axle breather.

[cam.in.head]

that doesnt sound right, ?

the breather is right at the top ? you havnt overfilled it have you ?

[Ems]

I thought I'd update this thread.  I 've fitted a new propshaft which has cured the vibration.  I've also fitted a new oil seal and refilled the axle with the correct amount of oil, all is ok at the moment.

[Jessopia74]

5 hours ago, Ems said:

I thought I'd update this thread.  I 've fitted a new propshaft which has cured the vibration.  I've also fitted a new oil seal and refilled the axle with the correct amount of oil, all is ok at the moment.

Good stuff! Was anything obviously wrong on old prop? (UJ tight, loose etc)

[GTEPETE]

Was it easy to find another one? Was it a recon?

[Ems]

The old UJ's were loose. 

I had a new propshaft made for it.

[Jessopia74]

1 hour ago, Ems said:

The old UJ's were loose. 

I had a new propshaft made for it.

Made? What that cost 

[Ems]

57 minutes ago, Jessopia74 said:

Made? What that cost 

£252, they couldn't recondition the existing one due to the way they're manufactured by GM.

[cam.in.head]

blimey !

i must admit its unusual for the original props to wear but obviously anything is possible . glad its sorted now .

[Jessopia74]

5 minutes ago, Ems said:

£252, they couldn't recondition the existing one due to the way they're manufactured by GM.

Who was that with? The spiders are only peened into the yoke , seen vids of them been Redon. Wonder if they are not supposed to now?