Brake Tips For Trans-Am E Bodies
by Brad Schroeder
(Senior Product Engineer, Brake Parts Incorporated)

Over the years much information has been published in books, magazines, newsletters and on the internet concerning many topics of interest to Mopar restorers. One area that has not been very well documented, however, is brake system components. The purpose of this article is to clear up some misinformation, help owners to have their cars correct, and in some cases even save owners some time and money.
The power brake booster is p/n 3461118. Original boosters can be rebuilt. They are painted semi-gloss black and usually are seen with a daub of hemi orange paint above the installed master cylinder. One often seen item that is functional but is not concours correct is the booster check valve. Later replacement check valves have a raised right angle nipple, where on the original check valves did not have this nipple.

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Original style power booster check valve installed on a booster. Probably was installed on booster when painted, in which case it would be painted black.

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Later style replacement power booster check valve is installed on this car's booster.

Master cylinders owners have installed on their cars are often not correct. There are two basic master cylinder designs depending if the car has drum brakes or front disc. Drum brake master cylinders have equal size front and rear fluid reservoir chambers. Disc brake master cylinders have one fluid chamber that is much larger than the other. The reason for this is because the displacement of the disc brake caliper piston requires a much larger volume of brake fluid than the displacement of wheel cylinder pistons. T/A’s and AAR’s came standard with front disc brakes. However it is very common these days to spot drum brake master cylinders installed on these cars. This is a potentially dangerous mistake because it is possible to have too little brake fluid available for the calipers when using a drum brake master cylinder.

The original master cylinder installed on disc brake 1970 E- bodies (except hemi) was the p/n 2944453. It can be identified by a casting number 2229171 on the bottom. These assemblies are date coded with information stamped in the outlet side of the casting ( 0 100 would be the 100th day of 1970). Although there is not a kit available through the aftermarket specifically for this OE part, a Raybestos MK551 kit has the correct diameter internal seals and these seals can be used to replace worn out ones on the original pistons.

Master cylinders can also be professionally rebuilt at places like Brake and Equipment Warehouse in Minneapolis and White Post Restorations in Virginia. There are several aftermarket master cylinders that install and function correctly if an original part cannot be found. Raybestos and Napa part numbers 36283 and 36307 work fine but do not look exactly like the original. If your car has a drum brake master cylinder it should be replaced with a disc brake one! Disc brake master cylinders from that era were painted gloss black, even the filler cap. The gold anodized filler caps we see on so many restored Mopars look nice but are no more correct than chrome valve covers or headers.

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Chrysler part number 2944453 is the master cylinder used on all 1970 E bodies with disc brakes except for 426 hemi. The distinctive shape on the front of the casting is sometimes referred to as the "thermometer" front.

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The Chrysler part number 2944453 can be identified by the casting number 2229171.

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The datecode is stamped in the outlet side of the master cylinder casting in the second line. This example was made on the 173rd day of 1973.

Rotors are also available from the aftermarket. These can be purchased through local aftermarket auto parts stores like NAPA at a lower price without the shipping charges that the restoration parts businesses charge. (Raybestos p/n 7008, NAPA p/n 85530) Aftermarket rotors differ slightly from OE in that they are one piece instead of the original two piece design. On original rotors the flange where the wheel studs are installed was held in place by the installion of the mounting studs. Aftermarket rotors are machined out of a single casting but function correctly. The studs are included on the rotors but on the aftermarket versions they are all standard thread. The studs can be replaced with reverse thread ones on the driver’s side to be correct if desired.

Calipers are still readily available through the aftermarket. These are a single piston design for E bodies. Currently available calipers are rebuilt assemblies, not new, and therefore they are original OEM castings with new internals.

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Original (left) and aftermarket (right) rotors show the difference in mounting flange on original rotors.

Front brake hoses are also available from the local auto parts store. They are nearly identical to original with the exception of some information stenciled on the hose. Original front hoses also have a date code stamped in to one of their brass fittings. Though not available at local parts stores, excellent reproduction brake lines and parking brake cables are available through the restoration parts industry.

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Date codes stamped in end fittings on NOS front brake hoses.

There were two styles of parking brake cables used in 1970. One style had a flat steel outer cover. The other style had a spring coil winding. I believe the flat steel was used on all Trans am cars.

For the rear drum brakes, the original wheel cylinders have a casting number 3461776. Kits to rebuild original wheel cylinders or complete new aftermarket wheel cylinders are readily available through auto parts stores. Hardware kits are available through the aftermarket. New drums available at auto parts stores work well. When placed next to original drums minor differences can be seen in the castings. For cars with rallye wheels the outer surface of the drum behind the installed wheel was painted red. On cars that had the 15x7 steel wheels this area was not painted.

It should go without saying that the brake pads and shoes are still readily available. The only items that are not easy to find are the proportioning valve that is installed in the area below the master cylinder and I am not aware of anyone selling the rear brake hose.

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Portion of NOS parking brake cable showing flat steel covering.

I hope this information helps to keep your car stopping as quickly as it accelerates!

White Post Restorations
One Old Car Dr.
P.O. Drawer D
White Post, Virginia 22663 540-837-1140

Brake & Equipment Warehouse, Inc.
455 Harrison St. N.E.
Minneapolis, MN 55413 612-378-3141