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 > General Truck Forums > Engine & Drivetrain

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 07-16-2018, 09:09 PM   #1
Sawlog
Registered User
 
Join Date: Jun 2017
Location: Central illinois
Posts: 143
Posi or not?

I have 3.08 rear gear in my 69 c10.
I want to go to 3.42. Do any of you not go to a posi rear end when you change gears?
If so, did you regret it?
Sawlog is offline   Reply With Quote
Old 07-16-2018, 09:13 PM   #2
mongocanfly
Post Whore

 
mongocanfly's Avatar
 
Join Date: May 2015
Location: Alabama
Posts: 14,557
Re: Posi or not?

I would ad the posi if it were mine.....but 3.42 is not much difference than 3.08....will depend a lot on your final trans gear and tire size...use a gear ratio calculator to determine your best options....http://www.csgnetwork.com/multirpmcalc.html
In your other post your talking about a ls/od trans swap.....a 3.73 or so will be much better with the od
__________________
Mongo...aka Greg

RIP Dad
RIP Jesse

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
2023 Chevy Z71..daily driver
mongocanfly is offline   Reply With Quote
Old 07-17-2018, 11:32 PM   #3
'68OrangeSunshine
Senior Member
 
'68OrangeSunshine's Avatar
 
Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 6,983
Re: Posi or not?

Posi is fun and handy offroad. If you are getting inside the pumpkin for any reason, you might as well add it.
Only reason not to add is expense. Or if you're building a truck for a retired schoolmarm.
__________________


Every 25 years I like to rebuild that 292, whether it needs it or not.
'68OrangeSunshine is online now   Reply With Quote
Old 07-19-2018, 07:31 PM   #4
Eddie H.
Registered User
 
Eddie H.'s Avatar
 
Join Date: Mar 2001
Location: Paradise TX USA
Posts: 1,200
Re: Posi or not?

It depends on what you want to do with the truck.
for most normal driving conditions, a posi is not needed.
If you want to burn rubber with both tires, then install a posi.
__________________
"Negative people always seem to have a problem for every solution"
Eddie H. is offline   Reply With Quote
Old 07-19-2018, 07:55 PM   #5
mattfranklin
Senior Member
 
mattfranklin's Avatar
 
Join Date: Dec 2011
Location: Moraga, CA
Posts: 797
Re: Posi or not?

The one negative with a posi is that if you are in snow or ice, and your right foot gets really into it, the back end can come around more quickly and get you sideways.

But if you're careful with your foot it will be ok and better at keeping you going rather than being stuck with one wheel drive.
__________________
(Very) Slow-Going Build Thread: Stock 1970 Short Step with Stock 1970 LT-1

http://67-72chevytrucks.com/vboard/s...d.php?t=567340
mattfranklin is offline   Reply With Quote
Old 07-20-2018, 11:36 AM   #6
weq92f
Registered User
 
Join Date: Oct 2016
Location: Dallas Texas
Posts: 2,845
Re: Posi or not?

Quote:
Originally Posted by mattfranklin View Post
The one negative with a posi is ... your right foot gets really into it, the back end can come around more quickly and get you sideways...
I consider that one of the benefits of running a posi!

-klb
__________________
67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi
07 335 sport turbo 6sp
94 Trans Am GT LT1 6sp posi -- sold after 22yrs
99 540 sport V8 6sp -- sold
73 240z L24 4sp -- given to friend
68 C10 step 350/350 3.73 open -- sold
weq92f is offline   Reply With Quote
Old 07-20-2018, 12:06 PM   #7
Grumpy old man
Senior Member
 
Grumpy old man's Avatar
 
Join Date: Dec 2013
Location: Gods country East,Tn
Posts: 8,545
Re: Posi or not?

"The one negative with a posi is that if you are in snow or ice, and your right foot gets really into it, the back end can come around more quickly and get you sideways."


Quote:
Originally Posted by weq92f View Post
I consider that one of the benefits of running a posi!

-klb
Is there any other reason for having a posi ?


Grumpy old man is offline   Reply With Quote
Old 07-20-2018, 12:11 PM   #8
truckster
Senior Member
 
truckster's Avatar
 
Join Date: Jan 2001
Location: Orem, Utah
Posts: 7,761
Re: Posi or not?

Quote:
Originally Posted by Grumpy old man View Post

Is there any other reason for having a posi ?


Yeah, it lets you wear out your rear tires more evenly.
__________________
I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson
truckster is online now   Reply With Quote
Old 07-20-2018, 06:48 PM   #9
Mike C
Registered User
 
Mike C's Avatar
 
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,709
Re: Posi or not?

3.42 are a 10% gear increase which really isn't enough to justify the expense IMO. 3.73 are a 21% change making it much more worthwhile, once again, IMO.

Not adding the limited slip would be a mistake (again, IMO!). I have a long bed 71 GMC that I used to drag my boat around the yard with and I added a posi and gears to it that were from my Jimmy's old 12 bolt. The added torque of the 4.11 really help and without the posi, it would get stuck in the yard sometimes!

Everything I own has a traction device of some kind except my '03 BMW. It's only a $4000 car and it costs $2500 to add the LSD! I'm way too cheap for that...
__________________
44 Willys MB
52 M38A1
64 Corvette Coupe
68 Camaro 'vert LT1 & TH700
69 Z/28 355 12.6's @110
69 Chevy Short Step 4 1/2"/7" drop
72 Jimmy 4WD 4spd 4" & 35's
02 GMC 2500HD 4x4 Duramax
Mike C is offline   Reply With Quote
Old 07-20-2018, 08:17 PM   #10
weq92f
Registered User
 
Join Date: Oct 2016
Location: Dallas Texas
Posts: 2,845
Re: Posi or not?

Quote:
Originally Posted by Mike C View Post
...Everything I own has a traction device of some kind except my '03 BMW. ...
Those BMWs are pretty stout. I have an '07 with an open diff. Whether it's the electronics ( even though they're disabled when experimenting in this way ) or mechanical, a near red line clutch dump in second from a stop will break both loose!

-klb
__________________
67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi
07 335 sport turbo 6sp
94 Trans Am GT LT1 6sp posi -- sold after 22yrs
99 540 sport V8 6sp -- sold
73 240z L24 4sp -- given to friend
68 C10 step 350/350 3.73 open -- sold
weq92f is offline   Reply With Quote
Old 07-21-2018, 07:55 PM   #11
Mike C
Registered User
 
Mike C's Avatar
 
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,709
Re: Posi or not?

LOL. That was true of the IRS in my 240z as well, but the car was way more fun to drive when I swapped a Precision Gear clutch type LSD in it. Wish the beemer one wasn't so stupid expensive...
__________________
44 Willys MB
52 M38A1
64 Corvette Coupe
68 Camaro 'vert LT1 & TH700
69 Z/28 355 12.6's @110
69 Chevy Short Step 4 1/2"/7" drop
72 Jimmy 4WD 4spd 4" & 35's
02 GMC 2500HD 4x4 Duramax
Mike C 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 09:02 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com