Odd clunk on the 75

Started by Treecher, August 11, 2023, 05:22:55 PM

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As seems to be the case with some Alfas, you fix one thing and something else goes wrong. I've just changed the clutch slave cylinder - not for the faint-hearted and now I have an odd knocking sound/sensation.

Sometimes, when you start the car up there is a knock from underneath somewhere. Then, when going over a slightly bumpy road, the thumps/knocks can be felt through the floor. It's not horrendous but a definite noise. I had something similar before and it turned out to be the exhaust hitting somewhere underneath. A few adjustments and it went away.

I'm wondering if the same thing is happening again but I have the exhaust a vigorous wiggle around and it seems to be OK unless it's an up/down issue.

I was told it could be a bush on top of the bellhousing or an engine mount. Need to investigate further....

Any ideas!?


Gearbox mounts perhaps.   Front and / or rear.
Current Alfa:
1975 Alfetta GT 2.0 Race car
1979 Alfetta GTV (Resto)
1972 105 2000 GTV (Resto)
1987 Alfa 75 2.5

Past Alfas:
1982 Alfetta Sportiva (briefly in my possession. Restored and sold)
1989 Alfa 75 2.5
1982 Alfetta Sedan 2.0
1976 Alfetta GT


My car use to have an odd, intermittent clunk/knock. It wouldn't always happen in the same scenario, but it turned out to be a dead rear engine mount.
The back of the engine would move down just enough so the sump would occasionally knock against the steering rack.
The Daily: Jumped Up Taxi (BF F6 Typhoon). Oh the torque! ;)
The Slightly More Imediate Project: Supercharged Toyota MR2.
The Long Standing Conundrum: 1990 75 V6 (Potenziata)............. What to do, what to do???


The clutch cover could be hitting the bump stop above it fixed to the underside of the transmission tunnel if the gearbox mounts are damaged or loose.

Do not rule out the up/down exhaust mount possibility.
Transaxle Alfas Haul More Arse.


Check the bolts holding the longitudinal braces under the car are tight. There are six bolts (3 per side). I have seen them loose on a few cars. Causes clunking noises on less than smooth roads.
Luke Clayton



Sounds like a De-Dion bush.
Have it all checked by a suiltable Alfa mechanic
Special tools to replace it properly.
I have the tool and done heaps of them.