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Old 10-14-2018, 06:19 PM   #1
Jack15T
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Transmission to Transfer case leak?

Hi Folks, I am new to Auto transmissions. I have always had a manual. I recently purchased a 1971 K20 with a TH350. The transmission is losing fluid at a high rate but it doesn't appear to be leaking externally on to the ground or anywhere that is obvious. I refilled the transmission and decided to check the transfer case. When I pulled the fill plug, at least a pint of transmission type fluid came out of the transfer case. Is it possible for the auto trans to be pushing fluid into the transfer case? Thanks, Jack
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Old 10-14-2018, 07:03 PM   #2
57taskforce
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Re: Transmission to Transfer case leak?

The seal in the adaptor housing is leaking.
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Old 10-14-2018, 07:26 PM   #3
Jack15T
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Re: Transmission to Transfer case leak?

Thanks for the info.
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Old 10-15-2018, 11:53 AM   #4
cypressbog
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Re: Transmission to Transfer case leak?

Here's the adaptor you're using.

http://www.advanceadapters.com/produ...sions-6273963/
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Old 10-15-2018, 03:02 PM   #5
dozerbill72
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Re: Transmission to Transfer case leak?

Make sure to replace the O-ring on the input shaft of the transfercase as well. It seals the shaft to the drive coupler and is often overlooked, but will cause the issue.
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Old 10-15-2018, 07:15 PM   #6
Jack15T
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Re: Transmission to Transfer case leak?

Thanks for all your info guys. I will know more when I pull it out. Cheers, Jack
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Old 10-15-2018, 08:29 PM   #7
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Re: Transmission to Transfer case leak?

Couple things when you pull the adapter.

Install the seals so the open side faces the Trans and transfer.
And, you must use the OEM size gasket to maintain tolerances. You cannot just use gasket maker. You can goop gasket maker with the gasket if you like, I do not. But use that fat gasket!

Have fun, I just had to replace my adapter mating my 465 to my 205, it was cracked. I thought it was a gasket leak, I pulled and replaced the gasket, figured out the adapter was cracked, out came the transfer again the next weekend. Bummer!



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Old 10-16-2018, 08:29 AM   #8
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Re: Transmission to Transfer case leak?

Thans Jeff, Jack
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Old 10-16-2018, 02:37 PM   #9
cypressbog
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Re: Transmission to Transfer case leak?

Yep, I had a 71 4X4 that leaked bad. Ended up being the adaptor was cracked. This was in 2002 and the local GM dealer had a new one in stock for $350. Dealers no longer have them on the shelf, that's why I provided the link to where aftermarket adaptors are available.
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Old 10-16-2018, 03:23 PM   #10
jocko
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Re: Transmission to Transfer case leak?

Jeff mentions an excellent point - seal orientation is critical, and it's easy to screw it up if you just put it in the way you'd view a timing cover crank snout seal. Remember the goal is to keep fluid OUT of the adapter (it's dry in the middle) and IN the trans/t-case - but, you are installing the seal from the outside of the adapter, facing inward (not like a timing cover crank snout seal). So, when it comes to installing it - you'll need to press it in with the open side toward the outer faces of the adapter as Jeff said (that's the best description I've heard of the orientation Jeff - when folks say "with the lip out or in - it never helps me picture it, ha). Be careful to not damage the lip and ensure the spring stays inside the lip before you install the trans and t-case. Anyway, here's a ref pic also:
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Old 10-16-2018, 04:11 PM   #11
jeffahart
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Re: Transmission to Transfer case leak?

More good points from Jocko

A tidbit on install and how you don't catch a break with the automatic seals.
Two seals in automatic = be careful.
With the 465 to 205 adapter you only have one seal on the transfer case side. That means you can put the adapter on on transfer case and you don't have to worry about any seals getting damaged, easy money.

With yours, you have have to worry about the second seal when you mate transmission to transfer. If you don't line stuff up, and you fight to mate the splines on shaft and sleeve you can damage the seal... goto the end of the line and try again after the seal leaks!

Here's some tips on getting the mating to go smooth.
I make a cradle for the transfer and strap it to the jack. I know the center of balance on transfer, it makes it a one man job. You need to put headless studs in the transmission so you are guaranteed to hit the mark straight on. To make this easier jack the trans so the output shaft is parallel to the ground, set the transfer so the sleeve is parallel to the ground. Set a male spline on the output pointing straight down, put a female spline a the bottom of the sleeve pointing straight up. If you do this the two will mate so easily you will think you did something wrong, too easy! It's all about the setup!

Another tip. Keep the transfer strapped to the jack and clean the surfaces of the gaskets from under the truck. I carefully scrap with a razor blade and follow with a green pad. You will save yourself headache not trying to get the transfer out from under the truck. There is room under there, it's what I do.

Also, remove the hump. You can get to the front shaft CV bolts and the adapter bolts. It's worth the extra few minutes to get the access.

If you need pics on any of my rambling let me know, I won't babble on.

Have fun!


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Old 10-16-2018, 05:01 PM   #12
Jack15T
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Re: Transmission to Transfer case leak?

Thanks Guys, great info. I found this link to a DIY rebuild of the transfer case. I will probably go this route as it is leaking from everyplace possible. I am also going to replace the TH350 with a 700R4 since the Transmission isn't too healthy either. I would love to know how many miles are really on this truck. Maybe I'm better off not knowing. Anyway, thanks for the help. Cheers

http://www.wideopen4x4.com/NP205RebuildGuide.html
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Old 10-16-2018, 06:12 PM   #13
57taskforce
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Re: Transmission to Transfer case leak?

Looks like a good write up. They are really very simple once you get into it. I rebuilt my 205 last winter. Good Luck!
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'57 3100 350/700r4 35x12.5's
'72 K/20 Cheyenne 350/SM465 in pieces awaiting ly6 6.0 swap. http://67-72chevytrucks.com/vboard/s...d.php?t=662879
'98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6"RCD 315/75/16's
‘10 Camaro 2SS/RS l99 6l80e 52,000 miles Aqua Blue Metallic.
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Old 10-16-2018, 06:19 PM   #14
jocko
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Re: Transmission to Transfer case leak?

Quote:
Originally Posted by Jack15T View Post
Thanks Guys, great info. I found this link to a DIY rebuild of the transfer case. I will probably go this route as it is leaking from everyplace possible. I am also going to replace the TH350 with a 700R4 since the Transmission isn't too healthy either. I would love to know how many miles are really on this truck. Maybe I'm better off not knowing. Anyway, thanks for the help. Cheers

http://www.wideopen4x4.com/NP205RebuildGuide.html
That's a good one, but here's the BEST (my 2 cents ) (by member jbclassix): http://67-72chevytrucks.com/vboard/s...d.php?t=469726
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Old 10-16-2018, 07:27 PM   #15
57taskforce
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Re: Transmission to Transfer case leak?

Quote:
Originally Posted by jocko View Post
That's a good one, but here's the BEST (my 2 cents ) (by member jbclassix): http://67-72chevytrucks.com/vboard/s...d.php?t=469726
That’s the one I used when I did mine along with a 3 or 4 part series of videos on you tube.
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'57 3100 350/700r4 35x12.5's
'72 K/20 Cheyenne 350/SM465 in pieces awaiting ly6 6.0 swap. http://67-72chevytrucks.com/vboard/s...d.php?t=662879
'98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6"RCD 315/75/16's
‘10 Camaro 2SS/RS l99 6l80e 52,000 miles Aqua Blue Metallic.
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Old 10-18-2018, 12:34 PM   #16
Jack15T
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Re: Transmission to Transfer case leak?

Well, I have to agree with you guys. That was an exceptional write up. I will definitely be using it this winter when I get into this project. Thanks again. Cheers, Jack
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