Alfa Logo Ending backup "clutch chatter" Alfa Logo

For years my '67 Giulia Super has been periodically plagued with a severe jerking and shuddering when backing up, especially uphill. I asked gearhead friends with similar cars, dealers and the AROC tech lines. Other than "they all do that", the only suggestion was to reduce excess play in the drivetrain. So I replaced mounts and bushings and even swapped the rear axle... but the problem kept coming back and I never did have a clear idea what caused it.

Eventually, I came across an Alfa tech bulletin from 1965 for the Giulia 1300 series that suggested another fix...

Line drawing from Alfa bulletin showing bumper and adjustment of 'just contacting' to max preload of half a turn.

... and now I finally understand. When there is too much fore and aft play in the transmission bushing, the whole engine/trans unit can move enough under load to cause the mechanical clutch linkage to alternately grab and release (just like the old mechanical brakes would do when the chassis flexed under hard braking).

The real problem started when we couldn't get the proper 1600 bushing anymore and had to use the 1750/2000 bushing that was designed for the hydraulic clutch cars...

1600 Bushing Picture of early and late transmission mounts side by side. 1750/2000 Bushing

The actual Alfa part is, of course, NLA, but, it turns out that a GM hood bump stop from around the mid-80's (which cost almost nothing at my local junkyard) fits perfectly in the already existing hole in the rear of the steel cross member with a nut on each side, as in the drawings. I tack welded the inner nut to the cross member for ease of adjustment. Works like a charm.

(this article originally appeared in the Alfa Ricambi Performance Quarterly catalog/newsletter.)

And here's a comment from Steven Murphy (a racer in SA) about this problem:

  I remember having a clutch shudder problem when reversing in the beginning but when I changed it to hydraulic from the ancient cable actuating mechanism it went away. I also found that renewing the gearbox mounting bush and the engine mountings while still using the cable mechanism seemed to cure it to a very slight shudder. I had not renewed any of the rear suspension bushes before I changed to the hydraulic actuating mechanism so I don't know if they could have contributed to the shudder.

(And.. of course, switching to the hydraulic clutch system for which the new-style bushings were designed should completely eliminate the shudder..  but it isn't an option that everyone wants to pursue.  - Jack)

Here is more from Steven about Rear End Wobble...

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Talk to jack if you have comments
last modified Oct, 2002