Th350 shaft seal leaking - The 1947 - Present Chevrolet & GMC Truck Message Board Network

DT1 · 10-13-2017, 10:00 AM

I've been chasing a transmission leak for a few days now and I'm pretty certain it's coming from the shift shaft seal. I replaced all the seals when I had the transmission out a few months ago, so this is sort of puzzling to me. I'm going to attempt to replace it again but this time the transmission will be in the truck. I have an Evercraft 7779250 seal removal tool but not the actual seal yet. Is there a specific seal that is better than most and is there something in particular that I need to do as to the removal/ replacement procedure?
Thanks

**VetteVet** · 10-13-2017, 11:45 AM

NAPA $2.00

Put a small amount of silicon sealer on the shaft when you install it.

https://www.youtube.com/watch?v=0c8OXpZyuBo

**tdangle** · 10-13-2017, 11:47 AM

I did the same thing recently. didn't have a seal removal tool, so I used a hooked tool and was able to pop it out. I had bought a seal kit from ebay and used the seal out of the kit. still leaked. I went to Napa, bought just the shift shaft seal and installed it. Hasn't leaked yet Much better quality as far as I could tell

Gromit · 10-13-2017, 09:31 PM

Might try some fine emery cloth on the shaft where it meets the seal - any imperfections in the metal will abrade the replacement seal. Obviously still have to replace the current seal but that might have been the issue and if so it will happen again with the new seal. I can't recall what grit I finished mine with but pretty sure at least 400 grit and probably 600 grit; there was quite a burr built up on the shaft - in fact I think one of the manuals says watch for that and don't force the shaft out through the case without deburring it.

10-13-2017, 10:00 AM	#1
DT1 Registered User Join Date: Oct 2009 Location: Gardnerville Nv No Mo Cali!! Posts: 869	Th350 shaft seal leaking I've been chasing a transmission leak for a few days now and I'm pretty certain it's coming from the shift shaft seal. I replaced all the seals when I had the transmission out a few months ago, so this is sort of puzzling to me. I'm going to attempt to replace it again but this time the transmission will be in the truck. I have an Evercraft 7779250 seal removal tool but not the actual seal yet. Is there a specific seal that is better than most and is there something in particular that I need to do as to the removal/ replacement procedure? Thanks

10-13-2017, 11:45 AM	#2
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,703	Re: Th350 shaft seal leaking NAPA $2.00 Put a small amount of silicon sealer on the shaft when you install it. https://www.youtube.com/watch?v=0c8OXpZyuBo __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

10-13-2017, 11:47 AM	#3
tdangle Senior Member Join Date: Mar 2005 Location: Jurupa Valley, Ca Posts: 1,209	Re: Th350 shaft seal leaking I did the same thing recently. didn't have a seal removal tool, so I used a hooked tool and was able to pop it out. I had bought a seal kit from ebay and used the seal out of the kit. still leaked. I went to Napa, bought just the shift shaft seal and installed it. Hasn't leaked yet Much better quality as far as I could tell __________________ Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC

10-13-2017, 09:31 PM	#4
Gromit Registered User Join Date: Jul 2015 Location: Central Coast, CA Posts: 498	Re: Th350 shaft seal leaking Might try some fine emery cloth on the shaft where it meets the seal - any imperfections in the metal will abrade the replacement seal. Obviously still have to replace the current seal but that might have been the issue and if so it will happen again with the new seal. I can't recall what grit I finished mine with but pretty sure at least 400 grit and probably 600 grit; there was quite a burr built up on the shaft - in fact I think one of the manuals says watch for that and don't force the shaft out through the case without deburring it.



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