Looking to swap out the 2.73 for a 3.73
Thread Starter
Junior Member
Joined: Aug 2009
Posts: 2
Likes: 0
From: Bumpass, Va
Car: 1985 Camaro Sport
Engine: 355
Transmission: 5sp manual
Looking to swap out the 2.73 for a 3.73
What do I need in order to do this? I'm also planning on putting a posi unit in it as well
Supreme Member
iTrader: (1)
Joined: Sep 2010
Posts: 1,928
Likes: 1
From: Georgetown TX
Car: Base 91 'bird
Engine: 3.1 v6
Transmission: 4L60
Axle/Gears: 9-bolt 3.27 & PBR
Re: Looking to swap out the 2.73 for a 3.73
These are 9 bolt numbers so assuming that you'd need a series 3 carrier, ring and pinion gears and assorted rebuild components. Are you sure it's not a posi already? If it's a 9 bolt it likely needs to be rebuilt which can be done but it's expensive and/or time consuming. You may find it easier to find a 10 bolt and work with that or just buy a complete ready to go unit. All about time, money and your skill/knowledge level.
Senior Member

Joined: Dec 2009
Posts: 702
Likes: 4
From: Texas
Car: 1989 IROC LSX
Engine: Swapped LS6 Forged by LME
Transmission: 4L65E
Axle/Gears: 3.73
Re: Looking to swap out the 2.73 for a 3.73
Call Randy's Ring And Pinion 1-866-209-9261
They can tell you what you can and cant do.
They can tell you what you can and cant do.
Member
Joined: Feb 2006
Posts: 499
Likes: 0
From: Rock Hill, SC
Car: 91 GTA
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: stock
Re: Looking to swap out the 2.73 for a 3.73
These are 9 bolt numbers so assuming that you'd need a series 3 carrier, ring and pinion gears and assorted rebuild components. Are you sure it's not a posi already? If it's a 9 bolt it likely needs to be rebuilt which can be done but it's expensive and/or time consuming. You may find it easier to find a 10 bolt and work with that or just buy a complete ready to go unit. All about time, money and your skill/knowledge level.
Joined: Nov 2007
Posts: 845
Likes: 4
From: Salt Lake
Car: 1989 IROC & ROLL-Z
Engine: L98 Vortec FIRST TPI
Transmission: T56, Mech Speedo
Axle/Gears: G92 J65 3.27
Re: Looking to swap out the 2.73 for a 3.73
Supreme Member
iTrader: (1)
Joined: Sep 2010
Posts: 1,928
Likes: 1
From: Georgetown TX
Car: Base 91 'bird
Engine: 3.1 v6
Transmission: 4L60
Axle/Gears: 9-bolt 3.27 & PBR
Re: Looking to swap out the 2.73 for a 3.73
You're correct. I'm working on both and got them bass ackwards. Then even easier. Get a posi unit and the gears required and install them or have it done.
Re: Looking to swap out the 2.73 for a 3.73
The 2.73 fits a 2 series differential and the 3.73 fits a 3 series. You will need a 3 series limited slip differential, a good quality set of gears and a good quality installation kit.
The Eaton Posi, Yukon Dura Grip or Eaton Truetrac would be good choices. The Auburn or Eaton Governor Lock would not be good choices. The Power Trax Grip LS looks good, but I haven't tried one yet.
US Gear, Motive Performance or Yukon gears are good. The Yukon installation kit or Tom's Differentials installation kit are good ones. I don't know of any other kits that I can recommend because most of them are junk.
The Eaton Posi, Yukon Dura Grip or Eaton Truetrac would be good choices. The Auburn or Eaton Governor Lock would not be good choices. The Power Trax Grip LS looks good, but I haven't tried one yet.
US Gear, Motive Performance or Yukon gears are good. The Yukon installation kit or Tom's Differentials installation kit are good ones. I don't know of any other kits that I can recommend because most of them are junk.
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Thread Starter
Junior Member
Joined: Aug 2009
Posts: 2
Likes: 0
From: Bumpass, Va
Car: 1985 Camaro Sport
Engine: 355
Transmission: 5sp manual
Re: Looking to swap out the 2.73 for a 3.73
I believe what I have is a 10 bolt but I'll have to look at it when I get a chance. But I do appreciate all the input you guys have given me so far.
Supreme Member
iTrader: (1)
Joined: Sep 2010
Posts: 1,928
Likes: 1
From: Georgetown TX
Car: Base 91 'bird
Engine: 3.1 v6
Transmission: 4L60
Axle/Gears: 9-bolt 3.27 & PBR
Re: Looking to swap out the 2.73 for a 3.73
Also use the search feature and look at the stickies and FAQs. There are many threads on all aspects of rebuilding and upgrading the 10 bolt.
Supreme Member
Joined: Apr 2006
Posts: 4,482
Likes: 10
From: Northern, CA
Car: 1989 Iroc-Z Camaro
Engine: TBI,5.0
Transmission: Automatic 700R4
Axle/Gears: Eaton Posi,3.42,LPW Ultimate Cover
Re: Looking to swap out the 2.73 for a 3.73
I built a 10 Bolt =
This is a breakdown of my build. Some of these parts are necessary for the build and some can be changed to match your personal preference as in brand and style L.S.D./Locker.,etc.
It works for me because my launches are considered "soft" because of "lacking HP", automatic transmission and street tires.
This is a breakdown of my build. Some of these parts are necessary for the build and some can be changed to match your personal preference as in brand and style L.S.D./Locker.,etc.
- 3.42 ring and pinion =$ 200.00
- master bearing kit = $ 90.00
- axle bearings and seals = $ 30.00
- 28 spline Eaton posi. Unit = $ 500.00 ( highly recommended )
- 28 spline axles = $250.00
- installation/labor = $ 300.00
- and if you want ,a LPW Ultimate support cover = $ 160.00 ( also highly recommended )
- Thats $1,530.00 counting the cover.
- 3 year warranty on parts and labor
It works for me because my launches are considered "soft" because of "lacking HP", automatic transmission and street tires.
Last edited by Ron U.S.M.C.; Jan 9, 2015 at 03:26 AM.
Supreme Member
Joined: Sep 2011
Posts: 2,080
Likes: 34
From: Spring Hill, Fl.
Car: 87 iroc-z
Engine: 454
Transmission: th350
Axle/Gears: 3.73
Re: Looking to swap out the 2.73 for a 3.73
i swapped from 2.73 to 3.73 in my car. i just used the thick gear set for a 2-series carrier.
i gotta say though,...your wasting your time til you get a posi first. might be easier and cheaper to buy another rear with the gears you want and possibly better brakes?
i gotta say though,...your wasting your time til you get a posi first. might be easier and cheaper to buy another rear with the gears you want and possibly better brakes?
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