I'm considering an upgrade from 10" to 11" rear drum brakes on my 1970 Challenger U-code R/T SE. The car came with factory front disc brakes along with both A36 and B41 on the fender tag for the 3.55 Performance Package and 10" rear drums.

Is the proportioning valve on the firewall the same for 10" and 11"?

Would the distribution block on the housing be the same or different?

Would the brake lines themselves be different?

This car was rode hard, put up wet, then was abandoned before being picked up and sold at a Detroit police auction. I purchased it in late '93 from the auction winner.

The bodywork is nearly finished so i'm readying the rear end assembly for cleanup and rebuild before the reinstall on this car that will see use as a long distance cruiser. On inspection there is a '741' center section instead of the correct '489' unit along with outward protruding lumps on the outside of the housing which leaked axle grease when turned bottom side down so i don't know if that can be repaired. Although i have neither the skills nor the tools to accomplish the repairs i'd definitely go that route if possible. I'm in uncharted territory here so all opinions are welcome.

Thanks in advance, Russ



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distribution block/brake lines the same. the nub bolt that bolts thru the distribution block is the vent for the housing and not connected hydraulically to the brake system & why it leaked grease when the housing was turned upside down

Hard to tell but it kinda looks like the housing my have damage from the origanal chuk blowing up or maybe rust.
The one picture looks as if the grease is draining from the smooth rounded part of the
back of the housing.
If this is the case a simple weld could be the cure. Might be better off looking for a replacement since it has the wrong (weaker) chuk any way.
Just a thought.

I don't really consider 11 inch rear brakes an upgrade. The 10's are all you need on the rear as the rear only does maybe 30% of the braking anyway and they have enough grip to do the job. The 11's just bring more unsprung weight for no gain.
If you run drums all around the 11's are an upgrade on the front however.

Sheldon

I've done several 10" to 11" conversions and never noticed an improvement in braking. Wheel cylinder diameter might be the reason, the 11" brakes could have either the 7/8" or 15/16" wheel cylinder.

The main reason I changed was to make 3rd member changes easier; when removing axles, the bearing retainer passes beneath the 11" cross bar but tends to get hung up on the 10" cross bar.

Thanks folks, that's just what I was looking for

I've had a 440 Challenger R/T set up the same as my current project, i.e. A36, B41, auto ps, pdb and was very satisfied with that car's manners and drivability.

This rear will get replaced but i'll keep my tens out back.

Russ