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Thread: Hi just joined this club hoping I can get some help for my 57 Chevy Powerglide cast iron auto gearbox

  1. #1
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    Hi just joined this club hoping I can get some help for my 57 Chevy Powerglide cast iron auto gearbox

    Hi Fellow Trifive members. I am new to this site so I am Looking for some advice re my 57 283 Chevys cast iron Powerglide auto gearbox. Yes I know the P/Glide auto gearbox's burp out some fluid from the dipstick after a layup BUT even after only a week of not using the car I started up the engine with no blurping fluid leaks BUT after I turned off the engines ignition I could hear a dripping noise from underneath the passenger's side on the floor. On looking sure enough Trans oil was pouring out and the fluid was overflowing from the dipstick top. I recon a quart of fluid has come out. I have then started the engine up again and put it in drive to which it moved BUT more oil was still pouring out of the dipstick tube again. On talking to my garage the gearbox guy there said 'Rip out that old Power glide and fit a GM 3 speed auto box, but he also said that getting a garage to do the job was impossible as so many things need changing Regards Johnny

  2. #2
    Registered Member BamaNomad's Avatar
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    Welcome Trichevyboy! It seems you're in England? How long have you owned your Chevy?

    There's a FIX to the PG burping... maybe someone here has it handy, otherwise I'll take a look and see if I can find the details.

  3. #3
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    Hi its not the usual burping, thats an easy fix, I just drive the car more often. no burps then! This tranny fluid pours out of the dipstick on the turn of the ignition key and as the engine starts up. I have Owned 'Donna' since 2005 full service history from day one it came from Jacksonville FL it also came with £30 grands worth of invoices from Danchuck and other American spares shops in the USA. Its a 2 door mint, pillarless sports hardtop, with P/S I have been told a fluid line has broken inside the cast iron box which means its got to come out so I was thinking of changing the PG to a recon GM 3 speed box BUT the labour charge is massive over 2 grand plus the gearbox about a grand!

  4. #4
    Administrator 567chevys's Avatar
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    I posted this some time back , here it is again


    Hello All,

    I sell Transmission Adapter Plates and been selling many to a Guy back east that Has a Transmission Place
    I asked Him why These Transmission lose fluid, Here is what email me

    This is from a company that makes excellent upgrade parts and problem solutions for automatic transmissions.

    Here is a link to a technical discussion about the Cast Iron Powerglide leaking issue.

    https://www.sonnax.com/tech_resource...werglide-leaks



    Here is their explanation of the cause, and the proper fix for the pre-’58 Cast Iron Powerglide:

    Before 1958, the only vent for the transmission was the opening at the top of the fill tube. The dipstick did not have a positive seal, and was designed to allow air to enter and exit the transmission.

    The Hydra-matic™ transmission of that day had a similar dipstick, but it entered the transmission at the top of the case and vented the entire main case and extension housing cavity equally. Since all of the cavities of the Hydro-matic were well vented, leaks were not an issue. By comparison, on the C.I Powerglide, the dipstick tube enters the case at a lower level. This means that - when the fluid is at its proper level - this area is isolated from the rest of the main case cavity. When all of the area inside a transmission case is not vented equally, pockets of pressure are allowed to build up. The vented area of the main transmission case and the extension housing are connected by an orifice in the 11 O'clock position in the rear pump.

    This orifice was restricted by a small pin. Veteran C.I. Powerglide rebuilders learned the hard way that leaving the pin out of the orifice in the rear pump would cause the transmission to burp oil out of the dipstick. Before the vent was added to the main case in 1958, this burping action was the only way that a pressure build up could be exhausted from the main case. This pressure build-up also explains the numerous stubborn leaks.

    To retrofit a vent to the earlier transmissions, a 90° brass fitting was added to the extension housing. A length of fuel line hose with a plastic vent (from a 350 transmission) was attached to the fitting. The end of the hose with the vent was then attached near the top of the dipstick tube.

    Unfortunately, this root cause analysis was started more than 50 years too late for this problem, but hopefully it will help with the way we approach future ones.

    Hope this helps!

    Harrel Lamkin

    1955 2 DR Post
    1937 Chevy Coupe
    2019 Ford Super Duty F350
    2018 Ford Explorer
    1955 Chevy Nomad
    1935 Ford 2dr Slant back I have 4

  5. #5
    Registered Member busterwivell's Avatar
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    How interesting! I never knew that..............

  6. #6
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    Hi Harrel thanks for your reply BUT this is not the normal 'Burp' from the filler tube, but ALL of the Tranny fluid oil has pumped out from the filler tube as soon as I started the engine! I was told that the pump seal has split so the fluid is not returning to the TC or the gearbox so the only other place it can go is out of the box via the filler tube, Regards Johnny UK

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