TH350 external seals/gaskets - The 1947 - Present Chevrolet & GMC Truck Message Board Network

that_ry_guy · 06-19-2015, 08:56 AM

Good morning. Looking for a little help from the transmission gurus out there. I am cleaning up my TH350 to go back into my project. It was working well a year ago so I think the internal components are fine. Obviously there is a problem with some. Oil leakage (spent yesterday scraping crud, decreasing today). Hard to pinpoint the exact location. My question is which seal/gaskets should I change to cover all my bases? Was thinking input and output shafts, shift selector, oil pan. Anything else you would replace?

Thanks for the advice!

MARKDTN · 06-19-2015, 10:11 AM

I would replace the speedometer driven gear "bullet". They wear over time and leak.

Bigdav160 · 06-19-2015, 10:13 AM

Kick down cable and dipstick seals

rcazwillis · 06-19-2015, 10:17 AM

If it were me in that position, I would replace pan gasket, tail shaft housing gasket, tail shaft slip yoke seal, modulator o-ring, dipstick o-ring, and speedometer o-ring. I think you can do all of these without much disassembly. New filter too. Probably get a good gasket kit and use the pieces needed.

67 chevelle · 06-19-2015, 03:02 PM

looks like most of that came from the engine

06-19-2015, 08:56 AM	#1
that_ry_guy Registered User Join Date: Apr 2014 Location: North Vancouver, BC Posts: 15	TH350 external seals/gaskets Good morning. Looking for a little help from the transmission gurus out there. I am cleaning up my TH350 to go back into my project. It was working well a year ago so I think the internal components are fine. Obviously there is a problem with some. Oil leakage (spent yesterday scraping crud, decreasing today). Hard to pinpoint the exact location. My question is which seal/gaskets should I change to cover all my bases? Was thinking input and output shafts, shift selector, oil pan. Anything else you would replace? Thanks for the advice! Attached Images

06-19-2015, 10:11 AM	#2
MARKDTN Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 2,134	Re: TH350 external seals/gaskets I would replace the speedometer driven gear "bullet". They wear over time and leak. __________________ '83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project

06-19-2015, 10:13 AM	#3
Bigdav160 Registered User Join Date: Apr 2011 Location: Klein Texas Posts: 3,852	Re: TH350 external seals/gaskets Kick down cable and dipstick seals __________________ My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe

06-19-2015, 10:17 AM	#4
rcazwillis Registered User Join Date: Aug 2013 Location: Fort Worth, TX Posts: 309	Re: TH350 external seals/gaskets If it were me in that position, I would replace pan gasket, tail shaft housing gasket, tail shaft slip yoke seal, modulator o-ring, dipstick o-ring, and speedometer o-ring. I think you can do all of these without much disassembly. New filter too. Probably get a good gasket kit and use the pieces needed.

06-19-2015, 03:02 PM	#5
67 chevelle Registered User Join Date: May 2013 Location: WEST PALM FLORIDA Posts: 1,174	Re: TH350 external seals/gaskets looks like most of that came from the engine __________________ 68 Long Fleet , ly6 , turbo 350 , 3-5 drop , original paint , front discs 67 Small window , 7 foot bed , tweaked 6.0 LSX 2004R Medium Olive 58 Apache fleet , 235 , offy intake , dual exhaust , 4 on the floor , red/white 69 Long Fleet , Custom , 6.0, 4l60 , AC , Medium Olive



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