Diff choice
Thread Starter
Instructor
Joined: Nov 2018
Posts: 152
Likes: 40
Diff choice
Hey guys I'm trying to figure out a diff setup. I want about a 3.9 rear gear, 4.1 would work too. 3.42 is just too low for my first gear ratio.
I need it to hold a lot of power.
Would you consider doing a zr1 or z06 case? Or just skip all of that and go to a 9" IRS setup? That's where I get a little concerned that this is going to end up being an expensive upgrade. IRS 9" suspension and spindles.... not going to end up cheap.
I have an auto 2.73 rear diff. Sometimes I think about just having it basically cut apart and modded to hell to take different guts. But at that point it's not too different in cost from a fabricated 9" housing.
I need it to hold a lot of power.
Would you consider doing a zr1 or z06 case? Or just skip all of that and go to a 9" IRS setup? That's where I get a little concerned that this is going to end up being an expensive upgrade. IRS 9" suspension and spindles.... not going to end up cheap.
I have an auto 2.73 rear diff. Sometimes I think about just having it basically cut apart and modded to hell to take different guts. But at that point it's not too different in cost from a fabricated 9" housing.
Le Mans Master
Joined: Apr 2013
Posts: 5,376
Likes: 1,118
Call RPM. Tell them what kind of power you want the diff to hold and what you intend to use it for and what other drivetrain mods you have.
Whatever it is, they can build something that will hold up, for a handsome price.
IMHO, if you’re at the point where you need a 9” IRS setup, then you’ll probably need one of their powerglide conversions or a high-end custom manual gearbox to go along with it.
Whatever it is, they can build something that will hold up, for a handsome price.
IMHO, if you’re at the point where you need a 9” IRS setup, then you’ll probably need one of their powerglide conversions or a high-end custom manual gearbox to go along with it.
Pro
Joined: Sep 2020
Posts: 537
Likes: 169
From: Ogden, Utah
Hey guys I'm trying to figure out a diff setup. I want about a 3.9 rear gear, 4.1 would work too. 3.42 is just too low for my first gear ratio.
I need it to hold a lot of power.
Would you consider doing a zr1 or z06 case? Or just skip all of that and go to a 9" IRS setup? That's where I get a little concerned that this is going to end up being an expensive upgrade. IRS 9" suspension and spindles.... not going to end up cheap.
I have an auto 2.73 rear diff. Sometimes I think about just having it basically cut apart and modded to hell to take different guts. But at that point it's not too different in cost from a fabricated 9" housing.
I need it to hold a lot of power.
Would you consider doing a zr1 or z06 case? Or just skip all of that and go to a 9" IRS setup? That's where I get a little concerned that this is going to end up being an expensive upgrade. IRS 9" suspension and spindles.... not going to end up cheap.
I have an auto 2.73 rear diff. Sometimes I think about just having it basically cut apart and modded to hell to take different guts. But at that point it's not too different in cost from a fabricated 9" housing.
Last edited by D-Dub2013; Mar 9, 2021 at 04:08 PM.
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2024 C6 of the Year Finalist - Modified
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Hey guys I'm trying to figure out a diff setup. I want about a 3.9 rear gear, 4.1 would work too. 3.42 is just too low for my first gear ratio.
I need it to hold a lot of power.
Would you consider doing a zr1 or z06 case? Or just skip all of that and go to a 9" IRS setup? That's where I get a little concerned that this is going to end up being an expensive upgrade. IRS 9" suspension and spindles.... not going to end up cheap.
I have an auto 2.73 rear diff. Sometimes I think about just having it basically cut apart and modded to hell to take different guts. But at that point it's not too different in cost from a fabricated 9" housing.
I need it to hold a lot of power.
Would you consider doing a zr1 or z06 case? Or just skip all of that and go to a 9" IRS setup? That's where I get a little concerned that this is going to end up being an expensive upgrade. IRS 9" suspension and spindles.... not going to end up cheap.
I have an auto 2.73 rear diff. Sometimes I think about just having it basically cut apart and modded to hell to take different guts. But at that point it's not too different in cost from a fabricated 9" housing.
Melting Slicks
Joined: Jul 2014
Posts: 2,136
Likes: 204
Since this is the FI section I'm going to assume you're running some form of FI. You need it to hold big power. Perhaps you can elaborate as to why you need such numerically high gears in a FI car making big power? 3.42 should be plenty of gear.
Thread Starter
Instructor
Joined: Nov 2018
Posts: 152
Likes: 40
Twin 78mm turbos on a 376 sleeved deal. Power will end up somewhere north of 1300, how much, no idea. 3.42 from a zr1 would be my go to, but as a starting line ratio it would be a dog at 5.26. With a 376 it will not be happy. Either have to blast boost out of the hole, or move down a gear, which is less ideal for a few reasons and will give me a bit too aggressive imho of a starting line ratio. Trans is a very custom deal.
Thread Starter
Instructor
Joined: Nov 2018
Posts: 152
Likes: 40
Do the cases ever break with autos? Or should I just go ahead and make a case from billet? I'm definitely going to do some trans brake dumps from 4k. Not sure how hard that's going to hit that rear gear compared to a stick car, but I'd like to be able to run radial class stuff.
Last edited by 4head; Mar 22, 2021 at 04:03 PM.
