55 GMC Series 1

Discussion in '1947-1954' started by MSmalley, Oct 23, 2019.

  1. MSmalley

    MSmalley Member

    Oct 9, 2019
    Katy, Texas
    Hello Everyone I am new to the post and new to restoring so looking forward to all the help. I have a 1955 GMC series 1 deluxe 5 window that is pretty much all original except it was converted to 12 volt before I purchased it in 1982. It is my first truck and I drove it couple of years in high school and parked it 1985 when I went into the service. Life took over and it stayed in the field until last month when I picked it up and trailered it down to Texas. I know shame on me, but hey it is spilled milk so I will have to just deal with it. It was running, but had a miss so will want to rebuild the motor, it is a numbers matching 248 connected to a hydramatic 100 trany and a torque tube rear end. The u joints made a lot of noise when I would let off the gas so I know that they need attention. I have lots of questions on the best way to get started etc, but I would like to know if it is worth rebuilding the torque tube and rear end. I would like to change the ring and pinion for drivability which I have seen in the post but haven't found any information on rebuilding the torque tube. The hydramatic was working fine when I was driving it but that was 34 years ago. I have no problem rebuilding the motor, but should I attempt the trany? Is it worth saving any of it or should I change out the trany and rear end for an open drive line? I know that I have written a book here sorry if that is not cool but wanted to get this started. I like doing a lot of research before I start a project so that I have a plan to follow. Thanks in advance for your help.

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  2. cmkruse

    cmkruse Member

    Feb 19, 2006
    guess it all comes down to if you want to keep it stock or do the upgrades. I opted to keep my chevy panel stock and now I wish I had at least changed the rear gear to the 3:55 for hi-way speeds. The only other changes I've made are to install a dual master cylinder instead of the single for safety and I upgraded to Bendix brakes for adjustment ease. The only other tip I can make is to make lots of notes on the tear down and take more than two pictures of everything you dismantle.
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  3. e015475

    e015475 Member

    Mar 13, 2014
    Show Low AZ
    You said "but had a miss so will want to rebuild the motor"

    Seems to me that you'd be a lot better off identifying the cause of the miss rather than just plunging into a rebuild. A compression test and leakdown will tell you what's going on inside the motor, If all is well, freshening up the ignition system with plugs, wires and points/condenser would be a good place to start. A carb kit and a good cleaning would be helpful too.

    As for the torque tube, I'd suggest that you look over on the stovebolt.com website for some help - seems to be a lot of folks interested in preserving originality there, plus there's a pretty extensive library of 'how to' articles.

    I'm no expert in automatic transmissions, but if it were mine, I'd drain the fluid out of it and replace it with fresh. I'd add some seal conditioner and see how well it seals up and shifts before I contemplated anything drastic like a rebuild.
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  4. Chiro

    Chiro Member

    Sep 3, 2006
    A New York Yankee living in Virginia
    ^^^What he said. However, A little insight into mine. 5.1 Chevy 1/2 ton. SM420 Muncie 4-speed. I converted the tranny to open driveline, replaced the rear with a '72 Nova rear (3.08:1 ratio for highway driving, 5 X 4 3/4" wheel stud spacing), installed Speedway front disc conversion (also 5 X 4 3/4" wheel stud spacing) and dual master under the floor with NO power booster. 235 engine from 1958. Blows a little smoke but not much. Runs well. Not crazy about a little missing going on but I'm going to replace the stock distributor with an HEI system soon so we'll see how that goes. Overall, excellent upgrades and drivability now.

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  5. 55.1stSuburban

    55.1stSuburban Member

    Aug 23, 2021
    nice truck, man :)

    did you end up keeping the hydramatic?
    A guy sells the part below..

    Attached Files:

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  6. vwnate1

    vwnate1 Member

    Jan 1, 2000
    I don't know how I missed this one before .

    Nice truck .

    Before opening up the engine you really should diagnose the miss, with a simple basic ignition upgrade you will be able to open the spark plug gaps to .040" or so and that should fix any miss caused by oil fouling .

    Pitting the correct tires on it will also make it easily cruise at 65 MPF, faster than that on the stock brakes and suspension is foolhardy, figure out if you want to upgrade the chassis before spending tie and effort when the Hydromatic tranny is hard to find and has very good reliability .

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