Packard Forum Index » Modification Discussion

I know that Dodge vans from around '79 or so did, and I tried every which way to use one of those on the '56 Patrician that I had and could not find a way to make it work. The BEST way, IMHO, to eliminate the BTV is to use a '51-'56 manual brake setup, with a dual master cylinder under the floor, and a small diameter booster along for the ride. I will be doing something similar on my Speedster this summer, so people will get a better idea on what I'm talking about.

The TreadleVac in it's day was just fine because OEM kits were available. Who knows what materials are used in modern day kits????? This especialy true of the COmpensator Valve which makes the TV unit a peculiar design.

There is also issues with the fluid getting sucked into the vacuum unit.


ASIDE from the above issues with the Bendix TreadlVac there is a common misconception that a 'modern' DUAL or Tandem master cylinder is safer. Perhaps true but only to a marginal or negligable degree is the tandem safer.

THERE IS a DANGEROUS down side to the tandem master cylinder espeicaly at very low speeds. This danger element is really only evident at very low speeds of say 5 mph or less. It can be experienced on very slippery roads dur to ice, heavy snow, moss covered creek beds, descending steep hills, loose gravel and other such low speed negotiations of peril.

The problem is that the rear wheel cylinders do not recieve equal pressure as the front wheel cylinders and what happens is that the rear wheels will tend to continue driving the car forward while the front wheels loose traction due to slippery surface.

To eleminate the above problem, with a stick one can disengage the clutch. An automatic requires a fast shift to nuetral. The problem is that pushing in the clutch is somewhat natural reflex at very low braking speeds. Shifting to nuetral IS NOT a natural reaction.

I do not like the tradlevac due to various reports from reasonably technically astute people as well as my own experiences with the BTV. But, this has NOTHING to do with the fact that the BTV is single cylinder.

NONETHELESS, i do not like the modern dual master cylinders either. For 56 and 55's (don't know about earlier Packards) the best bet is to use the 96'ish Ford explorer power unit and brake pedal assembly with a ranger master cylinder. Mount it thru the left fresh air vent hole in the fire wall. U will need 2WO of the F pedal assemblies and stop lite switch to make one. Cost it out at about $150. Pedal position will be about 1 inch higher than stock packard pedal.

More research needs to be done to see if an earlier SINGLE F master cylinder will fit the 96'ish Explorer power unit,

Just one point of correction. One the '54s (I think 51-53 are the same also) the non-power master cylinder is mount on the frame rail forward of the firewall, right behind the steering box (not under the floor). The pedal arcs backwards under the floor, and then a bellcrank transfers the motion to a rod that pushes forward into the master cylinder. One of the master cylinder mounting bolts has a special elongated head that act as the lower pivot for the ultramatic transmission shift linkage.

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It IS safer because a dual line master cylinder will still give you two wheels with brakes if a line or hose fails. A single line master cylinder is useless if ANY line or hose fails. Name ONE vehicle made in the last 30 years that has a single line master cylinder. You can't, there are none.

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This is why they have proportioning valves on vehicles with front disc/rear drum brakes, so this exact scenario doesn't happen. When it comes to brakes DO NOT SCRIMP ON SAFETY!!!!


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Why would you need TWO Ford pedal assemblies???? I didn't, and it worked just fine, the pedal position was exactly where the stock location was in the end. And this modification will work on '51-'56 Packards, all models.

IIRC Eric, u cut the fresh air duct flange from the firewall to mount the Ford power unit. In that case only need one pedal assembly.

On mine i did not remove the flange thus not enuf pedal travel. To get enuf pedal travel cut foot pad and hinge point from one explorer pedal assembly and weld that truncated pedal arm to the back side of the pedal arm of the second pedal assembly and install it.

Yeah my post over at "unidentified engine noise" kind of changed so any other thoughts on brakes will be made over here.

don't get me wrong I don't absolutly hate the BTV, I enjoy the "feel" of the brakes that Packard mentions in them, however I don't feel safe using a single master cylinder unit that is extremely sensitive to malfunctions. And when does just doesn't work. Especialy after having brakes fail in a 4000+ lb car.

If it were brand new and the oe kits were availible or I was driving this car 53 years ago I would feel way better about using them.

But who knows who's opened it, when, and what they used to rebuild it. If it has even been rebuilt.

On another note what about making a floor plate to change the angle of the unit you replace the BTV with? Would that even give you enough travel to actuate them properly?

I was thinking that way you don't destroy the original but you could still pop the unit out the same way.

Why can't the master mount on the firewall like my chevy?

" A dual chamber master cylinder under the floor with a small diameter booster along for the ride"

How about a hydrovac unit similar to waht was used on medium duty juice brake trucks? My old IHC had a single chamber master on the firewall and a split system booster on the frame that was slaved to it.
MikeG

Problem is the steering column is directly in line with any reasonable place to put anything. Another setup requires a major change to something. Below the column and the leverage advantage is wrong for any modern unit, above the column and the pedal assy has to change because the pivot point is just above the column. Below the floor requires a complete pedal assy which may be possible with some of the street rod setups & might be the best option.

The fresh air vent area is the best location for anything that looks halfway proper and easily available, but then you have to give that up and change something there as well as new pedals.

The setup I'm thinking of used a small master that would probably mount to the floor like the original. The hydrovac doesn't really care where you put it, just a matter of pedal ratio as you say and finding an unobtrusive spot to mount it. Hmmmmmmmmmm
MikeG

There are several floor setups that might work. I had wondered on another thread some time ago if it would be possible to mount something under the floor yet have the pedal stem only coming thru. Arranged in such a fashion location wise that it would be able to be pressed by the existing suspended pedal. Would take some sort of captured roller on the end of stem because of the different arcs but the nice thing would be at first glance, with the boot attached everything would appear stock for those of the keep it original persuasion and the pedal would be lower than a standard brake setup.

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