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1940 Buick Series 70 manual transmission shift lever oil seals


larryo
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I have a 1940 Buick Series 70 manual transmission that is weeping oil from the both the shifter rod and selector rod shafts.  The shop manual diagram indicates that there is a "Transmission Case Seal" which seals the shift rod shaft and also a "Selector Lever Shaft Oil Seal" which seals the selector rod.  Does any one know where these seals are available and what is involved in their replacement. I have not done any disassembly yet.  I did located what I believe to be a replacement shift shaft seal (TSS-390) at Bob's Automobilia.....however I'm not sure, the item description is vague.   I cannot find a seal for the selector rod. 

Thank you for any help.  Larry

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Bobs seal is correct for one of the shifter shafts.

There is a second, vertical shaft that controls the transition from reverse and first to second and third (I dont remember what it is called). This shaft is a chronic leaker and there isnt a seal provided. However in rebuilding a '41 Buick Super, I used 2 "O" rings on that shaft, inside the transmission. The "O" rings are compressed some by the installation of the operating lever and the last I heard it isnt leaking.

 

Replacing that first seal may be problematic.

Since we were doing a complete trans rebuild, what we did was remove the shaft completely. To do that you have to knock out a "freeze plug" like plug on the opposite side of the trans. Once the shaft is out, seal replacement is easy. You'll have to deform that plug by using a ball pein hammer with the plug over a hole in something to reduce the diameter to reuse the plug and reinstallation - easier than it sounds.

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Thank you for your input.....sounds like I'll have to get a little innovative on the one seal....the "o"-rings sound like a good option.

My hope was to replace these seals without having to disassemble the tranny.  I know there are a variety of shaft seal extractors on the market for some of the later model GM transmissions.

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Larry, I started a response earlier today, but Don beat me to it.  The job Don is referring to is the rebuild of my '41 Super transmission.  As Don says, the Bob's part # you reference is the seal for the main shifter shaft, identified as the "transmission case seal" in the drawing from the shop manual, below.  For the "vertical" selector shaft that Don refers to, there is a seal shown in the shop manual drawing, as you can see.  However, we were unable to find one available anywhere, so Don came up with the O-ring improvisation, which as he says, is not leaking so far.  Good luck!

 

1998359346_shifter(2)_LI.thumb.jpg.01e0a5bf707f7ef3acb5bf26d1315f06.jpg

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There are seal pullers that involve a sort of sheet metal screw driven into the original seal to pull it out. That outer seal has a very narrou crossection and that type od puller may not work.  The inner seal will mean getting into the trans and, unfortunately, that is usually the major leaker

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Just to follow up, here's a pic of my transmission nine months and about a thousand miles after we did the job.  Mine was also leaking badly from both rod shafts.  As you can see, it's now dry.  However, I think you are going to have a tough time replacing the seals without disassembling the transmission.  Good luck, and keep us posted.

 

484177924_trans_2020(2).thumb.jpg.47070799d3ebfcbe413ab5a393166eb1.jpg

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