Transmission pan gasket leaking - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chrismoore701 · 07-15-2017, 11:22 PM

Turbo 350 trans. Gasket had a small leak. Just finished a frame off and wanted everything perfect so I changed the gasket and put a new filter on. New gasket is rubber. Followed the proper torque sequence. Leaking more now thank before. Any thoughts? I hate to drop the pan again. I did not use any sealant or gasket material on the gasket

andyh1956 · 07-15-2017, 11:38 PM

Be Damn sure it's NOT the throttle pressure cable o-ring leaking. When fluid is new it's extremely difficult to see & it will run down & get on the pan flange.
You can buy some tracer dye & put in the oil & use a small UV light to see where it is leaking from.

Jake Wade · 07-16-2017, 08:31 AM

Shift shaft seal, dipstick tube seal, front pump, and as mentioned, throttle pressure cable o-ring are all places where it can be leaking and appear to be the pan gasket.

I prefer a cork gasket installed dry with bolt torque around 7 foot pounds.

TrailerTrash · 07-16-2017, 09:20 AM

I used a rubber gasket myself and had no luck at all it leaked right away.

mine also leaked from the shifter shaft that was an easy fix they make a tool to extract the old seal then you just pop the new one in.

S10Fan · 07-16-2017, 09:48 AM

Yes, for the shift shaft seal, please buy the tool, NAPA, less than 10 bucks, using a pick will scratch the shaft and it will never stop leaking.

I used a gasket from "Lube Locker", pricey but effective, along with a new heavy flange pan.

ron350 · 07-16-2017, 02:34 PM

S10FAN is this the correct Napa part # BK 7769250?

https://www.napaonline.com/en/p/BK_7769250

I don’t know if the Napa link will work here.

chrismoore701 · 07-16-2017, 03:00 PM

Already replaced the shift seal. I just replaced the pan gasket and now it's leaking. That's why I am sure it is the pan gasket

S10Fan · 07-18-2017, 06:42 AM

Quote:

Originally Posted by chrismoore701

Already replaced the shift seal. I just replaced the pan gasket and now it's leaking. That's why I am sure it is the pan gasket

If the torque convertor dust cover is still in place, remove it and make sure fluid isn't leaking from the front seal. Fluid from that seal will run down along the pan edges.

Transmission pan..... Make sure all surfaces are flat, someone along the way may have tightened the pan bolts to 6000 ft lbs and warped the flanges.

Gasket.... Buy a quality gasket, Fel-Pro, or Lube Locker (Summit, Jegs, etc)

chrismoore701 · 07-16-2017, 03:00 PM

Bought the tool. Nice little tool

07-15-2017, 11:22 PM	#1
chrismoore701 Registered User Join Date: Dec 2004 Location: Highland, IN Posts: 2,319	Transmission pan gasket leaking Turbo 350 trans. Gasket had a small leak. Just finished a frame off and wanted everything perfect so I changed the gasket and put a new filter on. New gasket is rubber. Followed the proper torque sequence. Leaking more now thank before. Any thoughts? I hate to drop the pan again. I did not use any sealant or gasket material on the gasket __________________ Chris _______________________________ 1979 Chevy Stepside SPORT 2018 Chevy Silverado, 39 years apart My build 2008-2016. http://m.imgur.com/a/bURrE

07-15-2017, 11:38 PM	#2
andyh1956 Registered User Join Date: Mar 2010 Location: thomastown mississippi Posts: 1,261	Re: Transmission pan gasket leaking Be Damn sure it's NOT the throttle pressure cable o-ring leaking. When fluid is new it's extremely difficult to see & it will run down & get on the pan flange. You can buy some tracer dye & put in the oil & use a small UV light to see where it is leaking from.

07-16-2017, 08:31 AM	#3
Jake Wade Registered User Join Date: Aug 2005 Location: Louisiana Posts: 711	Re: Transmission pan gasket leaking Shift shaft seal, dipstick tube seal, front pump, and as mentioned, throttle pressure cable o-ring are all places where it can be leaking and appear to be the pan gasket. I prefer a cork gasket installed dry with bolt torque around 7 foot pounds.

07-16-2017, 09:20 AM	#4
TrailerTrash Registered User Join Date: Jun 2015 Location: PA Posts: 441	Re: Transmission pan gasket leaking I used a rubber gasket myself and had no luck at all it leaked right away. mine also leaked from the shifter shaft that was an easy fix they make a tool to extract the old seal then you just pop the new one in. __________________ - When the Reaper makes his deal, trust in your steel - '77 C10 350/350 2/4 drop and a mild street engine

07-16-2017, 09:48 AM	#5
S10Fan Old Heap Driver Join Date: Mar 2008 Location: Newport News, Va Posts: 2,640	Re: Transmission pan gasket leaking Yes, for the shift shaft seal, please buy the tool, NAPA, less than 10 bucks, using a pick will scratch the shaft and it will never stop leaking. I used a gasket from "Lube Locker", pricey but effective, along with a new heavy flange pan. __________________ _____________________________ Bryan '99 Silverado 1500, 4.3, 5-speed, reg cab, short bed '50 Chevy 2DR Hard Top, 350/350, M2 Front End, 3:08 gear, cruiser. '40 F**d Sedan, all Chevy power, Heidt's front end, TCI rear, nice driver.

07-16-2017, 02:34 PM	#6
ron350 Registered User Join Date: Apr 2007 Location: Birmingham AL Posts: 251	Re: Transmission pan gasket leaking S10FAN is this the correct Napa part # BK 7769250? https://www.napaonline.com/en/p/BK_7769250 I don’t know if the Napa link will work here. __________________ Stock 75 C10 step side. 350 2 BBL, 350 trans. 150K miles.

07-16-2017, 03:00 PM	#7
chrismoore701 Registered User Join Date: Dec 2004 Location: Highland, IN Posts: 2,319	Re: Transmission pan gasket leaking Already replaced the shift seal. I just replaced the pan gasket and now it's leaking. That's why I am sure it is the pan gasket __________________ Chris _______________________________ 1979 Chevy Stepside SPORT 2018 Chevy Silverado, 39 years apart My build 2008-2016. http://m.imgur.com/a/bURrE



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