The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 01-27-2020, 06:31 PM   #1
truckin 79
Registered User
 
Join Date: Jun 2014
Location: Lvld CO
Posts: 300
Changing rear end fluid posi or not

Did a 79 1/2 ever come with a posi rear end? I need to change gasket and fluid but did not know if I needed to add special posi fluid. I have a big oil sludge hanging under rear end and so I think it is leaking gear oil and needs changed.
thanks
__________________
79 Chevy 2wd BIG10 350 TH400
truckin 79 is offline   Reply With Quote
Old 01-27-2020, 07:45 PM   #2
Matt Man
Senior Member
 
Matt Man's Avatar
 
Join Date: Oct 2009
Location: Western, Idaho
Posts: 1,379
Re: Changing rear end fluid posi or not

Could have came with a g80 which required the additive. Once you have the cover off you will know if it has one or not.
__________________
86 c30 crew cab dually 454/400 4/6 drop SOLD 1-8-11
1981 chevy K10 shorty 350/350C 12bolt, 10bolt, NP208
4" lift 35's
4.10's Detroit locker/Truetrac
Vintage Air
67 GMC Stepside Straight six/3 on the tree "The Peach"

K10 build http://67-72chevytrucks.com/vboard/s...d.php?t=671934

The Peach build http://67-72chevytrucks.com/vboard/s...d.php?t=733903



Matt Man is offline   Reply With Quote
Old 01-27-2020, 10:30 PM   #3
mongocanfly
Post Whore
 
Join Date: May 2015
Location: Alabama
Posts: 10,535
Re: Changing rear end fluid posi or not

Does it still have the spid in the glove box?...
__________________
Mongo...aka Greg

1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598
Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334
Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563
2013 GMC Z71..daily driver
mongocanfly is offline   Reply With Quote
Old 01-28-2020, 07:59 AM   #4
cadillac_al
Registered User
 
Join Date: Oct 2013
Location: Maine
Posts: 1,869
Re: Changing rear end fluid posi or not

I always used Carquest gear oil that works in either one.
__________________
76 Chevy K20
76 GMC K15
77 Chevy C10
cadillac_al is offline   Reply With Quote
Old 01-29-2020, 11:02 AM   #5
CSHADES
Registered User
 
CSHADES's Avatar
 
Join Date: Nov 2015
Location: portage wi
Posts: 400
Re: Changing rear end fluid posi or not

We started using the Ford posi additive to anything with posi traction.
CSHADES is offline   Reply With Quote
Old 01-29-2020, 12:27 PM   #6
truckin 79
Registered User
 
Join Date: Jun 2014
Location: Lvld CO
Posts: 300
Re: Changing rear end fluid posi or not

I do not have spid had to change glove box doors as hinge was gone. I just assumed most later trucks with be a one legger and no posi. I heard that if you go with Synthetic a person does not need to posi additive. Is this true?
__________________
79 Chevy 2wd BIG10 350 TH400
truckin 79 is offline   Reply With Quote
Old 01-29-2020, 01:30 PM   #7
Matt Man
Senior Member
 
Matt Man's Avatar
 
Join Date: Oct 2009
Location: Western, Idaho
Posts: 1,379
Re: Changing rear end fluid posi or not

Quote:
Originally Posted by truckin 79 View Post
I do not have spid had to change glove box doors as hinge was gone. I just assumed most later trucks with be a one legger and no posi. I heard that if you go with Synthetic a person does not need to posi additive. Is this true?
No synthetic fluid does not replace the posi additive.

This is a open rear end:


This is a g80 rear end:


The g80 in the half ton axles (12 bolt, 10 bolt) are not very good I would be surprised that it would still be in there. My 81 came with one but when I got the truck it was not there, just had a open diff.
__________________
86 c30 crew cab dually 454/400 4/6 drop SOLD 1-8-11
1981 chevy K10 shorty 350/350C 12bolt, 10bolt, NP208
4" lift 35's
4.10's Detroit locker/Truetrac
Vintage Air
67 GMC Stepside Straight six/3 on the tree "The Peach"

K10 build http://67-72chevytrucks.com/vboard/s...d.php?t=671934

The Peach build http://67-72chevytrucks.com/vboard/s...d.php?t=733903




Last edited by Matt Man; 01-29-2020 at 07:49 PM.
Matt Man is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 05:39 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Copyright 1997-2013 67-72chevytrucks.com