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Transmission - Practice makes perfect?


theNomad
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So after pulling the transmission days before last year's vintage to redo all the seals and then install it the night before, I discovered it's leaking yet again!

I'm not naive enough to think I did a perfect job, but shoot, I sure thought I did. There's just not much to it!

 

It's a '74 4 speed. Initially I drove it around when I bought it and it 'seemed fine' but dripped a bit. After finally changing the trans and diff fluid I found out it was leaking from the input shaft in the bell housing. I pulled it, did the seals front and rear and rebuilt the shifter and slapped it in.

 

STILL LEAKING. I thought for sure it was a small error like speedo cable or something other than the seals I just put in. Checked them all. 

I got it up on in the air, ran it - no drips - dropped it in gear - drip drip drip! Crawled under while it was running to verify the leak location.

Yep, still coming out of the front clutch lever opening.

 

I filled it up with fluid as it was probably over a quart low after driving it just a couple hundred miles in the months prior so its a healthy leak. 

:facepalm:
I believe when I bought the car the leak was there but fluid was low enough not to drip. 

 

So here's the question: I have no real option but to pull it and redo all the seals once again. How should I be sure this is sealed the right way. Just do it all again and cross the fingers? Add some super black silicone to the edges of the seal? Use sealant on the flange cover paper gasket or make sure its bone dry? Any way to bench test it prior to install?

 

I'll still be at the vintage (but I'll bring a jack and some fluid!) 

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I went through the same thing.  I think my problem was I used rtv with the paper gasket which prevented the paper from doing its thing and expanding.   Second time I did it with no rtv and so far so good.  Only about 5000km on it though.  when I did it the second time I couldn't buy the gasket so I used some fel pro gasket paper and cut it myself.

 

Did the seal at the same time just in case, but I think it was the paper gasket

Edited by Zorac
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Check for wear by running your fingernail along the shaft where the seal bears against the input shaft.  If you feel a worn spot, groove or burr, you may be able to shim the new seal outward just a couple of mm so it bears against an unworn spot on the shaft.  I've saved crankshafts with grooves worn in 'em by a seal by doing just that.

 

mike

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Check for wear by running your fingernail along the shaft where the seal bears against the input shaft.  If you feel a worn spot, groove or burr, you may be able to shim the new seal outward just a couple of mm so it bears against an unworn spot on the shaft.  I've saved crankshafts with grooves worn in 'em by a seal by doing just that.
 
mike
Simple but genius. I will definitely use this trick In the future!

Sent from my SM-G930P using Tapatalk

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1 hour ago, Zorac said:

I went through the same thing.  I think my problem was I used rtv with the paper gasket which prevented the paper from doing its thing and expanding.   Second time I did it with no rtv and so far so good.  Only about 5000km on it though.  when I did it the second time I couldn't buy the gasket so I used some fel pro gasket paper and cut it myself.

 

Did the seal at the same time just in case, but I think it was the paper gasket

 That paper gasket was very thin. Do you think the felpro you bought was a little thicker? I'm all for OE but a slightly thicker gasket on an old pair of surfaces might be good.

I think if I recall I did put a thin smear on the paper gasket to hold it in place while I installed it, sounds like a bad move.

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1 hour ago, mike said:

Check for wear by running your fingernail along the shaft where the seal bears against the input shaft.  If you feel a worn spot, groove or burr, you may be able to shim the new seal outward just a couple of mm so it bears against an unworn spot on the shaft.  I've saved crankshafts with grooves worn in 'em by a seal by doing just that.

 

mike

I'll have to try every trick in the book once I pull it again. 

 

I'd like to bench test it in some way too, maybe fill and tilt it forward while spinning the input...

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Also check the large black plug just below the input shaft. It covers the front bearing on the countershaft. Fill the gearbox with oil, carefully clean the inside of the bell housing, put a 4x4 block under the back of the gearbox so the output shaft is a bit higher than the input shaft. With a 1/2” drill grab the end of the input shaft and spin it with the gearbox in 1st or 2nd gear and watch for leaks. 

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7 hours ago, theNomad said:

 That paper gasket was very thin. Do you think the felpro you bought was a little thicker? I'm all for OE but a slightly thicker gasket on an old pair of surfaces might be good.

I think if I recall I did put a thin smear on the paper gasket to hold it in place while I installed it, sounds like a bad move.

 

maybe a touch thicker?  the fel-pro part number is 3022 and the thickness is 1/64".  it was just what canadian tire had in stock when i was looking and close to the same thickness as the original.  for whatever reason, I couldn't order the original part.  tried ireland engineering, and fcpeuro.  probably could of got it from a dealer, but i wasn't waiting weeks for it to come from germany (had that happen with a differential seal which was dealer only).  ironically, because of the rtv, the old one came off in one piece and looked brand new, the rtv pretty much sealed and preserved it so i had a good template to cut from.

 

https://www.amazon.ca/Fel-Pro-3022-Gasket-Material/dp/B000CNKUFU

 

i was doing a very thin smear of rtv on both sides of the gasket, had both the front and rear paper gaskets leaking on the tranny as a result, had to replace them both.

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I replaced that sealing plug with new. Actually got two of them so I have a spare. If I see its leaking I'll try it one more time but pretty sure its not. The fluid is coming out the clutch lever square opening so I assume its from the input shaft, running down the right side onto the lip that diverts it out the square. I'll also check that all the freeze plugs are intact.

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OK, so it's on the bench once again. 

The input bearing all seems good but its cheap insurance to just redo it again. 

I see once again what I found the last time I took it apart. 


A freeze plug, THAT I'D REPLACED last time, came out again: Upper right side, third in line in the pic. 

So now I need to figure out why this is happening and how to prevent it in the future. 

I had bought a matching plug and tapped it into place the last time I sealed the tranny. 


Any expert advice? Slather black permatex on it when I get a new one installed? Spread the sides out a bit to see if it'll go in tighter?

 

I'll try that bench testing idea as well... Really don't want to do this again. Wasted $30 in Redline fluid too. Will be getting the cheap stuff from now on.

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Edited by theNomad
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