Question on upper rear

tramminc · Veteran Member

Question on upper rear

cdnpont · Canadian Poncho Superstar!

10 1/16 OC. 1967 Impala upper arm.

But you have a Catalina right? It's not going to be the same if even similar. It has two arms off the center section just like a Chevelle right?

Not sure if you could even get an answer here, but you never know.

tramminc · Veteran Member

Yes a 1968 Catalina, Bonneville should be the same.

seventy2plus2 · Canadian Poncho Superstar!

Don't assume Bonneville will be the same, it has a longer wheelbase.

dcneric · Poncho Master!

Isn't the idea of having adjustable upper rear diff arms to be able to set or change the pinion angle?

If that is the case, measure the angle of the trans output and set the pinion to the same angle for a neutral setting. They should run parallel. For straight line racing the diff pinion leans 5 degrees down from neutral angle.

Hope this makes sense. As the true c-to-c from the factory isn't needed.

cdnpont · Canadian Poncho Superstar!

Sometimes I think the intention of buying them adjustable is besides the point. Most guys probably like the look, bushing options and the cool gear factor of them. They probably just adjust and bolt them right in. If she runs smooth and true with no vibration, then they'll call it good, with the option to adjust to correct if something that isn't right, or further mods are made. And that would have been me with mine, but with now adding a new driveshaft and bigger yokes, I'll take a measure and see just where those angles sit.

It's nice to know the stock length to start. Adjust the length center to center, tighten up the jam nuts on bench and simply install them as a baseline.

Perhaps a USA Pontiac forum would be helpful? PY forums?

North · Guru

are you referring to the upper control arms on the diff? I have 69 Catalina and a Bonneville I could measure for you. The 69 has 122" and 125" wheelbase versus the 121" and 124" for 65-68 American cars. I know that the Catalina and Bonneville have the same control arms upper and lower, they adjust the wheelbase by changing the frame mounting points.

seventy2plus2 · Canadian Poncho Superstar!

Yes, he's referring to the rear upper control arms (frame to diff).

I was looking for this thread a while ago when davepl was disassembling the 70 Catalina. I figured Dave could have easily measured the rear upper control arms as he'd cut away the fenders.