I recently purchased 1976 Cosworth Vega #2196, which has its original Saginaw 4-speed but with 4.10 posi gears swapped in by the PO for autox. I'm looking for a set of 3.73 gears to make it a little less frantic driving on the highway.
I'm getting a lot of drivetrain vibration that peaks between 50-70 mph (indicated, the speedo reads about 17% fast due to the 4.10 gearing). I have a lot of end play in the driver-side rear axle (not measured, but feels close to 1mm). The pass. side is a lot tighter. The input shaft also has some play. U-joints were pretty dry when I greased them while doing my first engine oil change, but not sloppy loose.
The tires that came with the car were 18 years old and have been replaced with new T/A Radials, machine balanced (my rural tire shop can't do road force balancing). Wheels appear to be straight and true as observed running at idle in 4th gear while on jack stands.
So before I start chasing things at random, does anyone have suggestions on what to look at first? Would the end play be suspect? I'll plan to fix that when I swap the gears, of course.
Oh, the car has dual Webers, and I have yet to sync them as it runs great as-is - I've been told they can set up some engine vibration if not in sync.
Since this is my second post here, for background, my first car (high school) was a '71 notchback that got a sleeved engine with tube headers and a GT cam - could chirp second gear all day long with the Opel 4-speed. In college, I swapped in a Buick 3.8l and automatic. My brothers had a pair of Kammbacks ('72, '73), and I had a '73 hatch for parts. Those are all long gone, of course.
Anyway, thanks for any suggestions before I dig into it.
es