C2-Excessive Rear Bounce-Worn Sombrero's in Cross Member?

[John L.]

This question has to do with a 66" big block. When driving the car over an uneven surface the rear of the car bounces excessively. 10+ years ago the total rear of the car was taken apart and rebuilt, trailing arms by Bairs, rear end done, new Eaton spring, new GM shocks, etc. Lately, I have been reading articles in the archives about replacing worn sombrero's in the cross member. The other night I took a look at mine and they are the orginal ones, each of which is worn and cracked. Could these these worn/cracked sombrero's be a cause of the excessive bounce problem? I realize its a big job replacing them and don't want to have this work done until I feel its the likely cause of the problem, thanks and appreciate your comments.

[Stephen L.]

Re: C2-Excessive Rear Bounce-Worn Sombrero's in Cross Member?

Before I'd attack the sombreros, I'd take a shock loose and see if its still "working".

[Edward J.]

Re: C2-Excessive Rear Bounce-Worn Sombrero's in Cross Member?

John I think that if the sombreros where gone the driveline angles would be off and you would see that they are molded to the metal sleeves and when they pull away from the sleeves you see it right away. Steve'd idea is a great first step. just remove the lower shock nuts and check the up and down motion should be some resistance.

[Michael W.]

Re: C2-Excessive Rear Bounce-Worn Sombrero's in Cross Member?

John-

The rear crossmember bushing would have to have failed completely to cause the condition you describe. This would be visible by lifting the car by the frame and seeing the crossmember drop which is not what you've described.

The shocks are the best place to start as mentioned by others.