Silicon on pump to case bolts?
Thread Starter
TECH Apprentice
Joined: Jan 2023
Posts: 340
Likes: 47
From: Corpus Christi, TX
Silicon on pump to case bolts? Seen a good amount of 2010 or newer 4l60's in the last few months and never usually see sealant on the pump to case bolts since they have orings that work well with clean surfaces. I should have taken photos of the sealant circles left behind after removing the pump but the local small dealership that has been bringing me transmissions lately is a bit impatient.
Do you think it was serviced recently or is that a GM factory deal even though they say in the service manual no sealant is needed right? thought I read that somewhere and wondering if I should folllow the example of precaution. Either way things are well with no come backs in the last year running privately out of my own place so I thank you guys for the help and wisdom we pledge here especially trans man he is just down to earth. Much love bro, stay strong out there techs.
Also Frank you are awesome, truly too much knowledge.
Do you think it was serviced recently or is that a GM factory deal even though they say in the service manual no sealant is needed right? thought I read that somewhere and wondering if I should folllow the example of precaution. Either way things are well with no come backs in the last year running privately out of my own place so I thank you guys for the help and wisdom we pledge here especially trans man he is just down to earth. Much love bro, stay strong out there techs.
Also Frank you are awesome, truly too much knowledge.
Last edited by Guy with a Chevy; Aug 6, 2025 at 07:30 PM.
LS1Tech Sponsor
Joined: Mar 2023
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From: BERWICK PA
WRONG person to ask. I am a hater of silicone and transmissions together. The orings should be plenty adequate .
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Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
Thread Starter
TECH Apprentice
Joined: Jan 2023
Posts: 340
Likes: 47
From: Corpus Christi, TX
After looking at the transmission a little more and getting the pan cleaned I can tell it was spray painted so it was most likely a rebuild and not something that the GM factory did. I have never added silicone to those o-rings, I have always just ensured that the surface is clean and that the o-rings are lubed lightly with trans oil and it works perfectly fine.
Somewhere in My memory I read something about even though the service manual says not to use sealant that GM would use it from time to time. Who knows if this is true
Had it been a full rebuild and not just an ISS replacement I would probably would have been more attentive. They wanted the sensor replaced so I ordered it and slapped it in there just like they asked. Clutch packs were checked for wear and pump was disassembled to ensure the unit was in good condition to return to service.
yes use ultra grey permatex RTV under the head and on the shank of the bolt. I wish the O ring were enough.
the paper gasket has a relief groove cut into it so tightening a bolt into a bolt hole filled with oil doesnt prevent the pump from torquing down and sealing. this unfortunately causes oil to wick up the shank and make a tiny leak. RTV has its place, just dont go crazy.
another place I use RTV is the back of new 4L80e internal harness plugs. They were never a very good design and the newest rostra ones are almost guaranteed to leak. fill the rear of the plug with grey permatex.
the paper gasket has a relief groove cut into it so tightening a bolt into a bolt hole filled with oil doesnt prevent the pump from torquing down and sealing. this unfortunately causes oil to wick up the shank and make a tiny leak. RTV has its place, just dont go crazy.
another place I use RTV is the back of new 4L80e internal harness plugs. They were never a very good design and the newest rostra ones are almost guaranteed to leak. fill the rear of the plug with grey permatex.
Staging Lane
Joined: Sep 2024
Posts: 58
Likes: 5
yes use ultra grey permatex RTV under the head and on the shank of the bolt. I wish the O ring were enough.
the paper gasket has a relief groove cut into it so tightening a bolt into a bolt hole filled with oil doesnt prevent the pump from torquing down and sealing. this unfortunately causes oil to wick up the shank and make a tiny leak. RTV has its place, just dont go crazy.
another place I use RTV is the back of new 4L80e internal harness plugs. They were never a very good design and the newest rostra ones are almost guaranteed to leak. fill the rear of the plug with grey permatex.
the paper gasket has a relief groove cut into it so tightening a bolt into a bolt hole filled with oil doesnt prevent the pump from torquing down and sealing. this unfortunately causes oil to wick up the shank and make a tiny leak. RTV has its place, just dont go crazy.
another place I use RTV is the back of new 4L80e internal harness plugs. They were never a very good design and the newest rostra ones are almost guaranteed to leak. fill the rear of the plug with grey permatex.
I have used it on a Subaru trans pan gasket though, it was the special Subaru stuff. Oh and the best RTV per the project farm guy is the Mopar brand.
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TECH Junkie
Joined: May 2012
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From: Poplarville, MS
I was at a transmission seminar back in the early 90s and Gil Younger of TransGo's brother was one of the speakers. He was saying to give ever builder in the shop two tubes of RTV, one for him to take home and one to actual use on the trans unit. Not worth not using RTV and have a comeback due to a leak.
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Brett Foote Staging Lane
Joined: Sep 2024
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Likes: 5
Many of the recalled leaking engines from various manufactures are due to RTV not lasting. The subaru is about the only thing I'd use it on, but never on metal to metal case halfs. Videos of so called experts applying RTV is also pretty funny, most all use way too much and of course in due time the excess inside the cases ends up in the strainer or filter. There is a certain brand car that had that issue and many ruined engines because of loss of oil pressure.
TECH Junkie
Joined: May 2012
Posts: 3,045
Likes: 713
From: Poplarville, MS
Many of the recalled leaking engines from various manufactures are due to RTV not lasting. The subaru is about the only thing I'd use it on, but never on metal to metal case halfs. Videos of so called experts applying RTV is also pretty funny, most all use way too much and of course in due time the excess inside the cases ends up in the strainer or filter. There is a certain brand car that had that issue and many ruined engines because of loss of oil pressure.
1) the factory does not use silicon.
2) theres a reason....transmission fluid will destroy it
3) I've built well over 100 4l60's and I do not use silicon ON ANYTHING with that trans... no leaks.
4) the orings are all thats needed
5) silicon under the pump bolt heads.... YUCK.
2) theres a reason....transmission fluid will destroy it
3) I've built well over 100 4l60's and I do not use silicon ON ANYTHING with that trans... no leaks.
4) the orings are all thats needed
5) silicon under the pump bolt heads.... YUCK.
Staging Lane
Joined: Sep 2024
Posts: 58
Likes: 5
Yes your correct. I still wouldn't use it. I mentioned the recall problems they have with it. The reason it is used at manufacturing is it is easy to automate it. They don't want to use something that takes more steps and careful attention.