Rear end gears
Thread Starter
Junior Member
Joined: Mar 2017
Posts: 19
Likes: 0
Transmission: T5
Rear end gears
Hi all. looking for some advice on rear end gearing. I'm planning an LS3 / t56 swap in my 89 iroc and wasnt sure what would work best for rear end gearing. Was thinking 373 or 411. I would like to be able to drive on the highway at a reasonable RPM. Current rear with my T5 is a 308 posi. Any advice would be greatly appreciated.
Last edited by sonic1971; Jul 29, 2018 at 12:03 PM. Reason: title fix
Senior Member
iTrader: (4)
Joined: Jun 2014
Posts: 667
Likes: 16
From: Brainerd, MN
Car: '84 Trans Am
Engine: 357 SBC
Transmission: 700R4
Axle/Gears: 10 Bolt 3.73, Torsen Diff
Re: Rear end gears
You can go pretty steep with a double overdrive... I've heard\read of lots of people happy on the high way with both 3.73 and 4.11 in 6th gear.
Joined: May 2008
Posts: 867
Likes: 1
From: pawtucket RI
Car: 1986 iroc
Engine: alum. head 350 supercharged
Transmission: 6speed
Axle/Gears: ford 9in 3.90 35 spline moser axles
Re: Rear end gears
i have 3.90s now and cruise at 80 @1800 lol
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