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2.73 replacement - what would you choose?

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Old Oct 23, 2008 | 06:11 PM
  #1  
Crouchman's Avatar
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From: Kettering, Ohio
Car: 1988 Iroc convertible
Engine: 305TPI
Transmission: T-5, swapped it in.
Axle/Gears: no clue, but I'll learn
2.73 replacement - what would you choose?

Hey all,
I've got a 2.73 rear end on my 88 IROC vert, did a tranny swap to T-5. 305, but I think the engine was rebuilt, runs pretty strong for a 305. Not taking it to the track, just want quick around town, etc. Advice? What would you put in? Wouldn't mind rear disc brakes. Something posi, I assume? Thanks!

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Old Oct 24, 2008 | 09:59 AM
  #2  
calebzman's Avatar
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From: Charleston, SC
Car: '85 TA
Engine: 350 turbo
Transmission: T56
Axle/Gears: 3.70 posi 9bolt
Re: 2.73 replacement - what would you choose?

You probably want to get a 3.42-3.73 9 or 10 bolt posi rear end. It will feel like another car.
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Old Oct 24, 2008 | 08:06 PM
  #3  
Crouchman's Avatar
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From: Kettering, Ohio
Car: 1988 Iroc convertible
Engine: 305TPI
Transmission: T-5, swapped it in.
Axle/Gears: no clue, but I'll learn
Re: 2.73 replacement - what would you choose?

thanks zman. I took it to the local IT shop to try to get a speedo gear...they said the 2.73 was for a 4 cylinder. Told them it was standard for the automatic. Recommended a 3.73. My issue is with the 700R4, I was taching at like 2200 at 75mph or so. Since the T-5 it's more like 3K+. I thought with the 3.73 it would really be up there. I'd like to be able to drive to Cleveland, couple hundred miles without it thaching at 4K. Seems like I've seen lots with the 3.42. If I knew what I know now, I think I would I'd have done a T-56. Not really a gearhead (noob, I guess) so I'm learning as I go. But it is SO MUCH FUN with the stick. Plus with the headers, Flowmaster, it sounds great. Just want it perfect.
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Old Oct 24, 2008 | 09:13 PM
  #4  
Saber's Avatar
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From: Tampa/New Hampshire
Car: 91 camaro RS, 87 T/A
Engine: 350 TBI, 305 TPI
Transmission: 700r4
Axle/Gears: 4th Gen 3.42/BW 3.45
Re: 2.73 replacement - what would you choose?

Get a set of 3.42"s or 3.45"s if you have a 9 bolt. Your better off swapping in a new rear end though, with disk brakes while your at it. Just go to your local JY and start popping diff covers off and counting ratios. I wouldnt go for 3.73"s though if your driving this thing daily, i think anything above 3.45" is overkill for a street car.
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Old Oct 25, 2008 | 08:13 AM
  #5  
gmgod's Avatar
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From: Springfield, MO
Car: 92 T/A VERT
Engine: LB9
Transmission: AUTO
Axle/Gears: 7.5 / 3.42's
Re: 2.73 replacement - what would you choose?

Originally Posted by Crouchman
My issue is with the 700R4, I was taching at like 2200 at 75mph or so.
Sounds like you've got 3.23's already...... I'd stick with them and get the right speedo gears for the t5.
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Old Oct 25, 2008 | 08:06 PM
  #6  
drknow90rs_ss@y's Avatar
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From: Wittman,Az
Car: 86 IROC-Z, '71 RS
Engine: 305 TPI/ 350
Transmission: 700R4/TH350
Re: 2.73 replacement - what would you choose?

Go to a jy and pick up a 10 bolt. most are 3:42 posi.
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Old Oct 25, 2008 | 09:09 PM
  #7  
Kevman's Avatar
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From: Windsor Ontario
Car: 1987 Firebird Formula
Engine: 2004 LQ4
Transmission: T-5 WC
Axle/Gears: 3.42
Re: 2.73 replacement - what would you choose?

I just put a 3.27 in my TA project car, better off dropping the whole thing and starting from scratch..
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Old Oct 27, 2008 | 05:02 PM
  #8  
Crouchman's Avatar
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From: Kettering, Ohio
Car: 1988 Iroc convertible
Engine: 305TPI
Transmission: T-5, swapped it in.
Axle/Gears: no clue, but I'll learn
Re: 2.73 replacement - what would you choose?

someone offered to sell me a 3.27, 9 bolt, 4 pinion posi Borg Warner with disc brake brackets. I've got a 2.73. Would I notice a decent difference with that? What he's offering sounds good...
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Old Nov 16, 2008 | 11:58 AM
  #9  
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From: Roy,UT USA
Re: 2.73 replacement - what would you choose?

In all honesty, I would stick with a 10 bolt rear. The 9 bolt rears are a bit stronger, but new replacement parts for them are virtually non-existent. You can get bearings, seals, etc., but there's no source for new posi carriers, and they're prone to burning out often. My suggestion would be a 10 bolt with either 3.23 or 3.42 gears. Either of those ratios work superb with the T5 on a street car, and they won't wind it up too high on the freeway. Btw, I was just up in your neck of the woods visiting my dad. He lives in Beavercreek.
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Old Nov 16, 2008 | 01:08 PM
  #10  
Crouchman's Avatar
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From: Kettering, Ohio
Car: 1988 Iroc convertible
Engine: 305TPI
Transmission: T-5, swapped it in.
Axle/Gears: no clue, but I'll learn
Re: 2.73 replacement - what would you choose?

No way! Hope the weather was better than it is right now. Cold & snow flurries, windy. Thanks for the input Pat. I think it will be a 10 bolt, I'll see what I can find 3.23 or 3.42.
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Old Nov 18, 2008 | 02:44 AM
  #11  
Pat Hall's Avatar
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From: Roy,UT USA
Re: 2.73 replacement - what would you choose?

Lol. As far as the weather went, I got there a few days after the hurricane winds and the massive power outage. Got there on a Sat., and we didn't get the power back on until the following Wed., so for those first 4 days we just sat around twittling our thumbs by candlelight! The good news on your end is that there's quite a few guys around there that part out 3rd gens, so you shouldn't have too much trouble tracking down a good 10 bolt. I would've gone on a parts shopping spree while I was there if it wasn't so expensive to ship anything large all the way back here! I did manage to smuggle a gallon jug of that great apple cider from Young's dairy in my suitcase though. Take care, Pat. P.S. Looked at the pics of your car in your vbgarage. Pretty sweet, lots of potential!

Last edited by Pat Hall; Nov 18, 2008 at 02:48 AM.
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Old Nov 18, 2008 | 10:10 AM
  #12  
RedHawkLB9's Avatar
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Joined: Sep 2008
Posts: 240
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Car: 89 Formy
Engine: carbed 355ci
Transmission: A4
Axle/Gears: 3.73 10 Bolt
Re: 2.73 replacement - what would you choose?

crouchman..how much did the t5 swap cost you?...i went from 2.73 to 3.73
in an auto car...but is is the best thing ive done so far
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