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08-16-2020, 11:29 PM | #1 |
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Leaking SM -465
Hi Folks,
My first post for assistance. I have a newly acquired 72 C20 4x4 with a SM 465 transmission which is appears to be leaking from the front input shaft. The fluid on the ground smells/feels like gear oil and is not motor oil, so I can possibly rule out the rear main seal. I plan on putting dye in the transmission just to verify the location of the leak. What are the chances the seal will fix the issue or perhaps the front bearings are worn as well? Is there a diy way to check the play in the shaft? This thing is a beast, so I plan on borrowing a transmission jack. Thinking I’ll take the transfer case out as well & check the same. Heck, might as well put a clutch & throughout bearing in while I’m at it. Thanks everyone. |
08-16-2020, 11:44 PM | #2 |
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Re: Leaking SM -465
Nice k20 any pics ?
When apart you will have to check shaft seals as well for signs of wear grooves etc they may need replacement as well You may luck out find a missing bolt |
08-17-2020, 12:22 AM | #3 |
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Re: Leaking SM -465
In terms of checking for wear on the transmission shaft, would it be obvious by visual inspection or is there some other method to check for wear?
Here are a few more pics. I've started a gallery on this site, but not sure how to share the link. The engine has a slight miss, so I changed the plugs/wires and will be installing a pressure regulator - have 15 psi on an Edelbrock. Understand thats way too much. |
08-18-2020, 04:09 PM | #4 | |
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Re: Leaking SM -465
Quote:
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08-17-2020, 12:59 AM | #5 |
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Re: Leaking SM -465
Very nice looking truck
I have not had one of my Sm465 apart from experience though with looking at seals on something that spins look for wear marks and grooves that will cause leakage axles main seal area on a crank etc |
08-17-2020, 01:05 AM | #6 |
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Re: Leaking SM -465
Thanks gmc684x4. Hope to yank it out in a couple of weeks.
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08-17-2020, 01:26 AM | #7 |
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Re: Leaking SM -465
Here is what anouther fellow found his leak
And yes a worn front bearing will also allow it to leak as well by letting the shaft have more free play https://forum.ih8mud.com/threads/cal...ective.461937/ |
08-17-2020, 01:38 AM | #8 |
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Re: Leaking SM -465
anaheim gear 1-800-477-1103
This place came up a few thread reads across google |
08-17-2020, 09:30 AM | #9 |
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Re: Leaking SM -465
https://m.youtube.com/watch?v=0wMUZ-m4f6w
https://m.youtube.com/watch?v=IPy62F4-nD0 https://m.youtube.com/watch?v=04gMWHJL88M Nice looking K20. Those aren’t very easy to find in your part of the country. I grew up not to far away from Winchester. I used these three videos as a guide when I went thru my 465. If your going to tear it down far enough to work on the input shaft, buy the whole bearing/seal/synchro kit and freshen the whole thing up. Odds are your gears and shafts are fine so all you’ll need is bearings, seals, synchros, maybe the gear bushings, and possibly a third gear pop out repair if your having that issue. (I wasn’t) Remember in order to get the top cover off the transmission it has to be partially engaged in reverse. If it’s not partially in reverse you’ll never get it out without breaking the top cover or the reverse shift fork. It’s not hard to rebuild the 465 at all. You’ll need a good set of lock ring pliers(not the same as C-clip pliers) and a press though. This is my suggestion. If you’ve got one shaft or bearing that’s worn enough to leak the others probably aren’t far behind. Same goes with the 205 you’ve probably got for a transfer case. You’ll have it out any way so it’s a good time to go thru it as well. They are both very strong and very very easy to rebuild. The parts for my 465/205 combo weren’t even $250 total, including new nos gm gear bushings and paint.
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Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne: 5” lift, 35’s, front dana 60 blah blah blah… http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB: 4” lift 33”s… in a million pieces http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 35x12.5x20’s |
08-17-2020, 11:00 AM | #10 |
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Re: Leaking SM -465
Thanks 57taskforce. Great videos.
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08-17-2020, 11:10 AM | #11 |
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Re: Leaking SM -465
Anytime, glad I could help. It’s really a simple design one you jump into it.
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Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne: 5” lift, 35’s, front dana 60 blah blah blah… http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB: 4” lift 33”s… in a million pieces http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 35x12.5x20’s |
08-17-2020, 07:02 PM | #12 |
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Re: Leaking SM -465
Just for fun put some 205 sealer in that 465. I had a leak and it fixed it. 205 is supposed to swell existing old seals. Worth s try.
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08-18-2020, 07:36 AM | #13 |
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Re: Leaking SM -465
Thanks akart. It's worth a try.
I see lots of threads of people attempting to fix SM465 leaks without success and sometimes making things worse. Seems like there are lots of problems where the SM465 couples with the NP205. For what it's worth, I've never been a big RTV fan. I've always used gaskets and been careful to torque the bolts in a rotating fashion. I'll problally eat my words one day . |
08-18-2020, 05:08 PM | #14 |
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Re: Leaking SM -465
Sealer in a can is a short term temporary fix at best
Sm465 to np205 leaks are primarily due to not replacing the oring on the np205 input shaft and checking the surfaces for wear Any shaft seal surface that has worn surfaces needs replacement or be ready sleeved to restore the sealing surfaces The failure of restoring shaft seal surfaces and not replacing orings will make up a large smount of failing to reseal there transmission |
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