Author Topic: How to tell? 1 or 2 pc rear main seal?  (Read 7181 times)

Offline MyOldScottsdale23

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How to tell? 1 or 2 pc rear main seal?
« on: January 15, 2012, 03:02:08 PM »
I have an 85 k-10 305. I have oil pan and pump off how do I tell if it has a 1 or 2 piece rear main seal?

Offline Blazin

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #1 on: January 15, 2012, 03:51:46 PM »
The dipstick is on the left side of the engine for a two piece, and the right side of the engine for a one piece seal.
The one piece goes on over the back of the crank shaft to replace it.
The two piece you need to remove the rear main bearing cap to replace it.
« Last Edit: January 15, 2012, 03:54:53 PM by Blazin »
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Offline MyOldScottsdale23

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #2 on: January 15, 2012, 09:19:09 PM »
Thanks, not the news I was wanting but thanks!

Offline Blazin

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #3 on: January 16, 2012, 06:46:36 AM »
Well I am assuming that the fact it was leaking was not news you wanted to hear either?
Wich do you have? Two piece you can change at the stage your at right now. One piece you would need to remove the transmission.
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Offline Lt.Del

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #4 on: January 16, 2012, 02:45:06 PM »
if you have the pan off, pull the rear main and look at the seal.  two halves = two piece.  A once piece is one complete circle without breaks. 
Blazin is correct about the oil dipstick.  My two piece has a driver's side dipstick.   Supposedly '86 started the one piece.  However, there have been signs that some late '85s had the '86 engine design in them.

Offline MyOldScottsdale23

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #5 on: January 28, 2012, 01:30:24 PM »
Yes my 85 has the one piece and boy do I wish it would have been leaking a cpl weeks ago when I dropped the trans and rebuilt it. My luck!

Offline Senck243

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How to tell? 1 or 2 pc rear main seal?
« Reply #6 on: June 30, 2012, 10:17:44 PM »
My 84 has the dipstick on the passenger side? That's a one piece correct ? 305 also
1984 k10 305, sm465, np208

Offline Blazin

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #7 on: July 01, 2012, 09:46:29 AM »
Passengers side is a one piece seal.
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Online zieg85

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #8 on: July 01, 2012, 02:44:33 PM »
Good to know, this thread ought to go in the tech section for future reference...
1984 C10 Custom Deluxe 4.1L 3 on the tree
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 4.56 
1985 C20 Scottsdale 7.4L 4 speed 3.21
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Offline Senck243

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How to tell? 1 or 2 pc rear main seal?
« Reply #9 on: November 30, 2012, 02:16:08 PM »
Is this a one piece or two piece ? Is it possible someone replaced the pan to a newer pan


Sent from heck
1984 k10 305, sm465, np208

Offline Senck243

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How to tell? 1 or 2 pc rear main seal?
« Reply #10 on: November 30, 2012, 04:08:09 PM »
After a bit of research I found out this is a two piece. Dipstick is on the passenger side 84 k10 305


Sent from heck
1984 k10 305, sm465, np208

Offline bake74

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #11 on: November 30, 2012, 06:56:28 PM »
      Have you replaced this yet ?  Now I am wondering if it is a 1 PC or a 2 PC ?
#1: The easiest and most obvious solution to any problem is 99% of the time correct.
#2: There is no such thing as impossible, it just takes longer.
  74 k10, 77k10    Tom

Offline Senck243

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How to tell? 1 or 2 pc rear main seal?
« Reply #12 on: November 30, 2012, 07:28:24 PM »
Not yet but saw on another forum that it is a two piece


Sent from heck
1984 k10 305, sm465, np208

Offline bake74

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #13 on: November 30, 2012, 07:33:38 PM »
     Make sure you reply when you know for sure, I will be watching.
#1: The easiest and most obvious solution to any problem is 99% of the time correct.
#2: There is no such thing as impossible, it just takes longer.
  74 k10, 77k10    Tom

Offline thirsty

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Re: How to tell? 1 or 2 pc rear main seal?
« Reply #14 on: December 01, 2012, 06:09:15 AM »
Measure the flange on the end of the crankshaft. A two piece is larger. I can get you a measurement of a two piece to compare it.

See in this picture. The flexplate in the middle is off a one piece and the flywheel on the right is off a two piece.
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