Packard Forum Index » V-8 (1955-56)

You know, I have never, ever heard of a 1955 or 1956 Cadillac owner wanting to convert their car to a three-on-the-tree, yet it seems like a panacea in the Packard world. I wonder why that is? Does it boil down to a damning indictment of the Twin Ultramatic? Or are there other facets to the story?

It's just that a great performing car is even better with a gearbox and overdrive.

My '56 "400" has a Twin Ultramafic that was refurbished three times and finally made to work..but it is still unreliable enough for me not to drive it far from home. The transmission leaks as usual in my experience.

I originally wanted to convert to the three speed overdrive but was talked out of it to keep the car original... Rare to find a three speed overdrive, lucky are those that have one.

In a previous post I said the engine stalled while driving, thinking it was fuel or ignition related, I later smelled the electrical burn..and then the windows became in operable. Next stop is a new wiring harness..as I think the problem was a ground that killed the firing of the engine.

The car is as bought except for paint and some interior.The original fabric was saved and only the leather had to be replaced. It has a new padded dash.
Engine work was done as needed ..

So how does one replace the wiring harness on this really big automobile?

Murphy

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Murphy,
I'm sorry I can't help you with your problem, but I wonder if you could help me with mine or direct me to someone. I have a 1955 Clipper Deluxe that I'm having trouble keeping rear trans seals in! I found a rebuilt trans from a friend but it's not quite the same. looking in the books I can come up with two numbers;450145 (cast iron) and 470060 (aluminum)
the one I just got is the 470060. do you know if they are interchangeable?? so far the only difference I can tell on the outside is the rear bolt that holds the rear flange on is 2" on the 470060 and 12" on the other????? I haven't started to R/R it yet because I have to do it off my back in the garage and don't want to start if it won't work.
Any help would be appreciated.
Thanks Randy

RSG, The complete units are interchangeable however there are some internal differences. The cast iron case was 55 and aluminum case was 56. There were some valving changes and some refinements in 56 units which increased reliability and changed the shift pattern somewhat from that of the 55. A significant change was the spines on input shaft are different so you will need the complete assy including the torque converter. Torque converters will not interchange between years without internal parts swaps. Depending on which model your new trans came out of there may also be some changes needed if your car has a different axle ratio. The speedometer drive gear is one item that may need to be swapped from your old unit. The senior cars have a larger output flange connecting to the driveshaft so that is another thing that could be different. If the new trans came from a push button equipped car it will be missing the lever for the shift linkage which will have to transfer over. Speaking of shift linkage, early 55 cars had a slightly different geometry on the lever and rod length was different. If your car is one of those then you may have to move the lever over even if the new one has a lever.

As a point of information 56 transmissions which were installed in hardtops had a different torque converter which was geared toward slightly increased performance than those used in sedans but they will still interchange.

So how does one replace the wiring harness on this really big automobile?

I had a friend who just had a new harness installed on a 56 Caribbean due to an underhood electrical fire. It's a very significant job, plan on 30 or more hours, one wire at a time.

What makes your Twin "unreliable"? I had mine rebuilt by a well-recognized rebuilder (and regular on this forum), nary a drop or drip and excellent performance in all respects.

Quote:

First and foremost there are several portions of the harness. If you are going to buy a new portion you will have to find where the problem lies and replace or repair the correct parts. The front harness covers the dash and engine. Body harness connects to the front portion under dash and goes to rear. Windows are a separate harness and so is push button shift if you have that option. The front harness does contain a couple of extra wires and some that are relocated for the push button shift so it is important to get the correct one. Other accessories have separate wires or even small harnesses which you do need to keep track of as they sometimes connect to the main.

Basically you disconnect everything in the engine compartment going to the main harness so you have the various tails free and clear and connected to nothing except each other at the trifurcation point at the firewall opening. There are numerous connections and directions the wires go so there is not really a step by step. Once things appear to be clear remove the grommet retainers and pull everything into the passenger compartment.

it is a project working under the dash and also a project to pull the dash out but I would seriously consider getting a helper and removing the dash to do all that confined work in the open. If your car has factory indash AC I don't think there is an option other than to remove. Once everything new is connected under the dash you then only have to feed the long tails in the loom thru the hole in the firewall as you and the helper lift the dash back. IMO, it is a piece of cake in the engine compt compared to working under the dash.

If you don't want to go to that extreme then the option is to spend hours on your back trying to see and reach places that are not going to co-operate. If you go the non removal way I suggest you remove the front seat and get padding as needed to get as comfortable as you can. It will be a long stretch of work. A couple of nice cool burning magnetic trouble lights you can stick out of the way on either side of the instrument cluster is a big help.

There is information on what is involved pulling the dash and a tiny bit on the main harness disconnect in this manual showing dealers how to install factory AC in the field. They did go to extremes in the manual and it is not necessary to remove everything they did just to remove the dash -- but it does show the attachment points and provide some guidance.https://www.packardinfo.com/xoops/html/downloads/55-56ACInstall.pdf

"A couple of nice cool burning magnetic trouble lights you can stick out of the way on either side of the instrument cluster is a big help."


Howard,
Can you expound upon this? What are you referring to, and what is their purpose? Thanks!

- Mark

Probably something like this to better illuminate when working under dash.

DOH! Of course. By "trouble light" I thought he was referring to some sort of diagnostic tool, and was wondering if "ringing out" the wires is required, etc.

Edit: Thanks Mal!