Banging/vibration underneath - could it be propshaft/gearbox?

[gouldsborough7]

Hi all
Sorry to have totted up 4 enquiries in as many weeks, but I am gradually trying to resolve all kinds of unknowns with my 'new' Berlinetta (2 litre Cortina, 1992 vintage)

Driving on bumpy roads, especially those with a corrugated surface or lots of potholes, I experience a solid thumping noise around the gearbox area, accompanied by the gear-lever wobbling fairly violently.

At first, I thought it might be the exhaust pipe hitting the underside of the body, especially when the rear pipe starting fracturing away from the silencer. Long-story-short, I've fixed all of that, and the exhaust is now held in place (with fibre straps & clamps) in 3 places instead of the original 1.

As the banging is so solid, and in the centre of the car, I am now inclined to think either the gearbox or propshaft is dancing about in sympathy with the road defects.

Has anybody experienced this before? Could the gearbox/engine mountings be like marshmellow? Is this a Berlinetta quirk, with a tried/tested remedy? I would be obliged for any advice.

Cheers
Mike G

[Dane_Rescueman]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Hi,
I have had gearbox & engine mounts become bath sponges. I replaced the lot. The gearbox rubber becomes detached along it's edges with the metal surround. This is hidden by grime etc. There is not much clearance for the gearbox in the tunnel so any untoward movement can cause contact with the tunnel, or, the small 40mm square chassis member.

With the aid of a trolley jack, it takes no time at all to replace the mounts

[danny_nelson]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Okay the Berly had two sizes of tunnel. Early cars had the widest. The tunnel was narrowed to help with wider seats. The prop can hit, also the turning motion on the back axle can cause it to hit as well. The hand brake linkage can clash as well. and as Dane says the condition of the mounts is very important. You need to examine very closely and you can usually see where contact has happened. Good Luck you will get there with it all.

[Dane_Rescueman]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Ah, I forgot about the later mods. I have an older Berli with wide tunnel and baby seats!

[gouldsborough7]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Thanks guys for your ideas. Spongy mounts was sort of in the recesses of my brain.
Next question is what's the best source for new mounts - Ford or a.n.other?
Cheers
Mike G

[rob-53uk]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Hi Mike

Look inside your tunnel on the side with the handbrake mech.
If the gearbox is mounted in the middle of the tunnel this is what it will hit.The mount has a long hole for sideways movement Our Editor had the same thing(gearbox hitting tunnel)

[amalgamated users from prior forum]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Message originally posted by: Sue Roedel (MOC Editor)
And I also changed all the rubber bushes for nylon ones as I had Le Clonk at the back of the car which was the axle banging around on every bump. Yours sounds more gearbox than bushes but if you are getting Le Clonk then do the bushes next. Drove me potty for ages!

I also have Le Slapp which is the handbrake cable whallopping the underside of the car sometimes if I go over a bump at a particular speed/angle. All good fun when you have someone new in the car. The look of terror in their eyes is quite amusing!

Still waiting for my new wheels to arrive...

[amalgamated users from prior forum]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Message originally posted by: Anita
Slapp ! Our editor? Surely not!

[amalgamated users from prior forum]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Message originally posted by: Sue Roedel (MOC Editor)
Oh, Slapp Off Anita!

[CABRIOBOB]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Sue
Le slapp is caused by to much Le slack so keep it Le tight.

[gouldsborough7]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

I found the cause of Le Clonk, but had to resort to buying half an hour of hydraulic-hoist time at my local friendly garage. The back of the gearbox had only a tiny gap between it and other chassis-related metal. Also, the engine mountings were passed their Sell-by date. Got some serious mounts from Car Builder Solutions (get their brochure - they have lots of great bits & pieces) for only ?7 each.

I think the 'clonk' problem occurred whenever the car went over a series of bumps, which caused the engine to bounce up & down like on a trampoline. The rubber mounts were close to marsh-mellow in strength, and couldn't cope. The absence of a decent gap at the rear of the gearbox completed the scenario. Haven't got it all back together, and wont know for sure that it is cured until I do a test on local roads, but am fairly confident it will be OK. Will need to experiment with shims (washers), to obtain reliable gaps in the right places - wish I had a hoist or pit! Not quite the same with trolley-jacks and grovelling up-side-down on a trolley.

Cheers
Mike

[HairyDave]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Just a little reminder that thumping near the back could be the rear spring catching on the seatbelt mounting bolt. It was on mine in Guilisfield, only it hooked on the bolt! Giving me a lean. I cleared it and turned the bolts (both sides) around.

[stevejgreen]

Re: Banging/vibration underneath - could it be propshaft/gearbox?

Take some time to check your UJ’s. Unusual vibration puts them under shock loads for which they were not generally designed.