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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: MyOldScottsdale23 on January 15, 2012, 03:02:08 PM

Title: How to tell? 1 or 2 pc rear main seal?
Post by: MyOldScottsdale23 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?
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: Blazin 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.
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: MyOldScottsdale23 on January 15, 2012, 09:19:09 PM
Thanks, not the news I was wanting but thanks!
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: Blazin 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.
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: Lt.Del 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.
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: MyOldScottsdale23 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!
Title: How to tell? 1 or 2 pc rear main seal?
Post by: Senck243 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
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: Blazin on July 01, 2012, 09:46:29 AM
Passengers side is a one piece seal.
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: zieg85 on July 01, 2012, 02:44:33 PM
Good to know, this thread ought to go in the tech section for future reference...
Title: How to tell? 1 or 2 pc rear main seal?
Post by: Senck243 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
Title: How to tell? 1 or 2 pc rear main seal?
Post by: Senck243 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
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: bake74 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 ?
Title: How to tell? 1 or 2 pc rear main seal?
Post by: Senck243 on November 30, 2012, 07:28:24 PM
Not yet but saw on another forum that it is a two piece


Sent from heck
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: bake74 on November 30, 2012, 07:33:38 PM
     Make sure you reply when you know for sure, I will be watching.
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: thirsty 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.
(http://www.suitorsgarage.com/projects/86chevy4x4/images/10180945.jpg)
Title: How to tell? 1 or 2 pc rear main seal?
Post by: Senck243 on December 02, 2012, 05:22:59 PM
It is definitely a two piece seal


Sent from heck
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: thirsty on December 02, 2012, 05:48:57 PM
How did you determine that it is a two piece for sure?
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: VileZambonie on December 02, 2012, 08:13:50 PM
There's some conflicting info here:

Small chevy 350 blocks will have a drivers side dipstick up to 1980. 1980 was when all of the small blocks went to passenger side dipstick. You will find one piece rear main seals were phased in in 1986. So it's true one piece rear main seal blocks will have a passenger side dipstick however so will two piece blocks so don't use that as a guide. You can tell by looking at the flexplate. If it's a counterweighted 350 it will be a one piece. The oil pans are different as well 55-79, 80-85, 86-99 and there are variances within those years too.
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: thirsty on December 02, 2012, 08:18:58 PM
There's some conflicting info here:
Was I right on the size of the flange on the crankshaft or is that conflicting also Vile?
Title: Re: How to tell? 1 or 2 pc rear main seal?
Post by: VileZambonie on December 02, 2012, 10:04:40 PM
The two piece has a counterweight on the end of the crankshaft, the one piece does not and is a perfect circle.

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