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05-20-2012, 03:21 PM | #1 |
Registered User
Join Date: Sep 2008
Location: Eagle River, Alaska
Posts: 84
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Return of the Transmission Leak
My 1972 K10 has a transmission leak. The pan had some kind of reddish-orange silicone bead around a rubber gasket that was leaking, but I removed that, scraped off the gunk, checked the pan for burrs/dents/distortion, and replaced the old gasket with a new cork gasket. Alternately torqued down the bolts supporting the pan, taking care not to over-torque, and refilled with ATF (MD3). Let the truck cool down, sitting overnight, and found that next morning it was leaking once again, with a significant pool on my garage floor. Checked the plug and it was dry, but found ATF all around the seal. Have been told to stay clear of rubber, not to use cork, and all kinds of different things but want to get the answer from people in the know so I am posting the question to you. Where am I going wrong here? What is the best gasket to use? Any guidance you might be able to provide would be greatly appreciated.
Thanks, AK
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AK72K10 ------------------------------- 1972 K10 350/350 LWB |
05-20-2012, 03:52 PM | #2 |
Registered User
Join Date: Jun 2010
Location: Upland Ca
Posts: 4,138
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Re: Return of the Transmission Leak
Could something else be leaking down making it look like the pan gasket? Fill tube seal, detent o-ring, cooler lines?
Often times these old pans are tweaked out must enough they won't seal. When I find one I can't seal with a standard cork gasket and 8-10 foot pounds of torque, I get a new GM pan or a cast aluminum pan and have had no more leaks.
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1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703 |
05-20-2012, 04:12 PM | #3 |
Overdrive club
Join Date: Sep 2007
Location: apache junction, arizona
Posts: 819
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Re: Return of the Transmission Leak
Also check the seal around the selector lever shaft!
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1971 c-10 1951 3100 chevy 1970 chevy c-30 Sold! |
05-20-2012, 05:15 PM | #4 |
Registered User
Join Date: Sep 2008
Location: Eagle River, Alaska
Posts: 84
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Re: Return of the Transmission Leak
@ Lee H - Cooler lines! I messed with them before, maybe they are not snug, I will check that tonight and work my way down from there.
@ brianthelion02 - I installed a Lokar shifter cable assembly, going to look at that seal around the selector shaft right after I check the cooler lines. Felt like I have been spinning my wheels, thanks again for giving me some traction here guys. AK
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AK72K10 ------------------------------- 1972 K10 350/350 LWB |
05-21-2012, 08:55 AM | #5 |
Registered User
Join Date: Dec 2004
Location: Arvada Colorado
Posts: 1,321
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Re: Return of the Transmission Leak
X2 on the selector shaft seal. I chased a trans leak on my CST for several months, only to finally discover that there was a big burr on the selector shaft that was cutting into the seal. It looked exactly like a pan gasket leak...
Took a dremel tool and smoothed it out...new seal...no more leak. The burr was most likely made by me when I changed the seal without the proper tool. I now own the tool...
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Larry 1949 Willys CJ2A, Kubota Turbo Diesel engine, Warn Overdrive, 11 inch brakes, 12volt, Warn M8000 Winch "Little Green" 1970 Rustoleum Roller Red C20 Custom Camper 454 TH400 "Big Red" 1971 K20 6.2 Turbo Diesel 4x4 4spd Ranger Overdrive "Pumpkin Wagon" 2005 VW Beetle Diesel 44+ MPG "Silver Bullet" |
05-21-2012, 03:44 PM | #6 |
Overdrive club
Join Date: Sep 2007
Location: apache junction, arizona
Posts: 819
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Re: Return of the Transmission Leak
Oh yes,that tricky little tool,lol! Most trans shops will do the job really cheaply. Sometimes that seal wont leak on a daily driver ,but let it sit a couple days and the torque converter drains back into the transmission case! All little leaks show up then!!
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1971 c-10 1951 3100 chevy 1970 chevy c-30 Sold! |
05-21-2012, 10:22 PM | #7 |
Senior Member
Join Date: Nov 2010
Location: Honolulu Hawaii
Posts: 308
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Re: Return of the Transmission Leak
+1
That's where my mystery leak was. It dripped down and onto the seal and made its way from to back along the gasket edge and dripped onto the floor toward the rear. I was assuming it was the seal since it was wet all along it but the shaft seal was the culprit all along. |
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