Raising the differential?
Thread Starter
Pro
Joined: Aug 2006
Posts: 647
Likes: 12
From: Midwest
Raising the differential?
How many of you have raised your differentials? Did you follow the VIP papers method? I was thinking of doing this to my car as I do not have much half shaft angle. I have the rear apart installing a dual mount spring from VB and rebuilding the differential, so I am considering doing this at the same time. I am also installing the smart struts to lower the pivot point of the strut rods. I do not race my car but I do drive it hard and want it to handle as good as possible. Prior to this work I had a standard VB mono spring and long mounting bolts. Thanks for the input!
Drifting
Joined: Oct 2007
Posts: 1,458
Likes: 1
From: Collinsville MS
St. Jude Donor '08
are you sure you want to raise the diff? The ujoints work better with less angle on them. I'm not an expert on this but am doing pretty much the same as you right now, I have the rear all apart and have been doing some reading on how to align the rear end again and this was mentioned several times in the articles to try and keep as much angle out of the half shafts as you can. I would like to hear some opinions on this also just in case I am reading the wrong guy....
Tech Contributor
Joined: Jun 2004
Posts: 20,847
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Raising the differential housing causes a small amount of angle when the car is just sitting there (harmless), but this angle will disappear when cornering, and allow the outside (compressed) wheel to experience reduced toe-out, and hopefully produce zero or slight toe-in for reduced snap oversteer.
Racer
Joined: Apr 2005
Posts: 464
Likes: 0
From: Charleston South Carolina
Crank down on the rear spring bolts until the halfshafts are at just a slight angle down from the center. Then have someone watch you take off and record how much the car squats. Then adjust accordingly. If you don't like the ride height when your done then you might consider a stiffer rear spring. Mine has a slight angle at rest but when I launch, it comes down to a parallel position. I don't know what the angle is in the turns but I'm more concerned about launch angle. I have a 420# rear spring.
Melting Slicks
Joined: Jan 2006
Posts: 3,028
Likes: 2
From: North NJ
Crank down on the rear spring bolts until the halfshafts are at just a slight angle down from the center. Then have someone watch you take off and record how much the car squats. Then adjust accordingly. If you don't like the ride height when your done then you might consider a stiffer rear spring. Mine has a slight angle at rest but when I launch, it comes down to a parallel position. I don't know what the angle is in the turns but I'm more concerned about launch angle. I have a 420# rear spring.
Its a very tuff battle b/w proper half shaft angle and ride height wheel gap.I had my wheel gap down to an inch or so which looked great but my half shafts were angled UP which is a huge NO NO. I have the VBP dual mount spring and was using the longer 10" spring bolts to lower the ride height. So I switched to the stock 8" bolts and used a lot of the threads until my half shafts were slightly angled down from the center like mentioned. So with a full tank of gas and driver/passenger they still angle slightly down but on launch they go parallel.
The rear of the car will squat when launching unless you have a very stiff spring/shock combo so you need to setup your half shafts to be slightly angled down from the center diff to your TA's.
A stiffer spring won't help this aside from allowing you to set it up parallel and reduce squat. It won't help your wheel gap.
Now I have about 4-5" of wheel gap.
Eventually I'll look into this more and possibly go with 18's or 19" wheels or raise the diff like this thread states....so I'm listening.
By going with bigger wheels every inch bigger only occupies a half an inch of wheel gap.
What VIP article are you talking about?
Last edited by 68 NJConv 454; Dec 19, 2007 at 10:42 AM.
Melting Slicks
Joined: Dec 1999
Posts: 2,116
Likes: 156
From: Mid West
Cruise-In III Veteran
Here is the VIP article .... excellent read with lots of good advice.
http://www.corvettefaq.com/c3/vip.pdf
68 NJConv 454, your right about the ride height thing. Raising the differential just allows you to set the ride height and c.g. lower without upsetting the half shaft geometery. Here is how I approached raising the differential in my 76. Hope the figure makes since to you. It's just a quick sketch I thru together for a previous thread.
http://www.corvettefaq.com/c3/vip.pdf
68 NJConv 454, your right about the ride height thing. Raising the differential just allows you to set the ride height and c.g. lower without upsetting the half shaft geometery. Here is how I approached raising the differential in my 76. Hope the figure makes since to you. It's just a quick sketch I thru together for a previous thread.
Melting Slicks
Joined: Jan 2006
Posts: 3,028
Likes: 2
From: North NJ
Nice sketch.
Makes sense to me.
I've been reading alot about this modification today and I grasp it all until people go crazy throwing CG and rollcenter words around and then get into 5 & 6 links and toe-in, toe-out, over/under steer, caster, camber, flux capacitors then my eyes start to hurt.
I still have some learning to do before I cut up anything.
I may consider doing this mod but the most I can raise the diff if as much space as the differential tongue has b/w the top of the tongue and the frame mount. SO the thickness of the differenital tongue bushing. So maybe an inch and change. I don't know if that is worth the trouble since I'd like to change my wheel gap by 3 inches.
I am probably going to wait for this modification when I decide to go to bigger rims like 18's, 19's or 20's. I have the widness maxed out on both the front or back but the 17" is still a relatively small rim to todays standards. A 19" in the rear and 18" in front would look sweet.
We shall see.
Thanks for all the info guys.
Makes sense to me.
I've been reading alot about this modification today and I grasp it all until people go crazy throwing CG and rollcenter words around and then get into 5 & 6 links and toe-in, toe-out, over/under steer, caster, camber, flux capacitors then my eyes start to hurt.
I still have some learning to do before I cut up anything.
I may consider doing this mod but the most I can raise the diff if as much space as the differential tongue has b/w the top of the tongue and the frame mount. SO the thickness of the differenital tongue bushing. So maybe an inch and change. I don't know if that is worth the trouble since I'd like to change my wheel gap by 3 inches.
I am probably going to wait for this modification when I decide to go to bigger rims like 18's, 19's or 20's. I have the widness maxed out on both the front or back but the 17" is still a relatively small rim to todays standards. A 19" in the rear and 18" in front would look sweet.
We shall see.
Thanks for all the info guys.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Melting Slicks
Joined: Jan 2006
Posts: 3,028
Likes: 2
From: North NJ
