Lowering diff or 6 link?
Thread Starter
Race Director
Joined: Dec 2000
Posts: 10,896
Likes: 2
From: CO
Lowering diff or 6 link?
My friend works at 3R racing here in colorado. they do alot of racing projects including vintage racing. He is currently working on a C2 and said that I could save alot of money and have my car handle just as well as a 6 link if I just lowered my diff. He said that it changes the suspension and it makes a HUGE difference. I know that it may affect ground clearance but what do you think of this? :confused:
Sounds like it could work by changing the geometry of the whole rear end. I know that a lack of true upper control arms results in a change of wheel angle when cornering. Would this help to reduce that effect?
Sounds like it could work by changing the geometry of the whole rear end. I know that a lack of true upper control arms results in a change of wheel angle when cornering. Would this help to reduce that effect?
Drifting
Joined: Jul 1999
Posts: 1,537
Likes: 41
From: Plano TX
Re: Lowering diff or 6 link? (flood)
I suspect they actually mean raising the diff, which lowers the body. Per the old GM guide it shows that there is a optimum geometry (angle) for the strut rod and drive shaft. If the the cars is just lowered buy using the spring, these angles are no longer optimum.
If the diff is rasied into the chassis with thinner bushings on the diff to frame cross memeber, this lowers the car, but allows for maintaing the correct angles.
Note that it also says to lower the strut rod attachement opint to the diff 1/2 and inch for proper strut rod to drive shaft geometry.
There is no need for a 6 link if the drive shaft does not move in and out too much from the diff. If it moves too much (worn diff center pin) the drive shaft will not maintain camber since it is the upper link.
Dave
If the diff is rasied into the chassis with thinner bushings on the diff to frame cross memeber, this lowers the car, but allows for maintaing the correct angles.
Note that it also says to lower the strut rod attachement opint to the diff 1/2 and inch for proper strut rod to drive shaft geometry.
There is no need for a 6 link if the drive shaft does not move in and out too much from the diff. If it moves too much (worn diff center pin) the drive shaft will not maintain camber since it is the upper link.
Dave
Thread Starter
Race Director
Joined: Dec 2000
Posts: 10,896
Likes: 2
From: CO
Re: Lowering diff or 6 link? (DaveL82)
Well it sounds like there is some merit to what he was saying. I will have to go down there and look at a few finished racers to see. I think he said something about making a spacer to drop the diff a little bit. But from what your saying you raise the diff.
Either way I will have to look and see what they did. The driver of the car claims that improves the handling close to what a 6 link will offer but it doesn't cost much at all. :cheers:
Either way I will have to look and see what they did. The driver of the car claims that improves the handling close to what a 6 link will offer but it doesn't cost much at all. :cheers:
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: Lowering diff or 6 link? (DaveL82)
The rear end is bolted to the top of the cross member so if you add a shim between the rearend and the crossmember you are moving the rear end up into the body more.
In the front of the rearend a thinner shim is required
Actually when you thing about it you could add a 1 inch shim between the rearend and the crossmember and a very thin shim in the front.
But what about drive shaft angle? The angles at the front of the drive shaft must perfectly match the rear end angle.
The motor/trany point down at say 2 degrees just for example. To cancel this angle the rear end must point up by 2 degrees. The 2 angles must cancel each other. They can not add together, example 2 degrees down at the transmission and 2 degrees down at the rear end. This would cause a problem of a driveshaft speeding up and slowing down every revolution.
You could easily raise the rearend in the car as long as you paid attention to pinion angle.
In the front of the rearend a thinner shim is required
Actually when you thing about it you could add a 1 inch shim between the rearend and the crossmember and a very thin shim in the front.
But what about drive shaft angle? The angles at the front of the drive shaft must perfectly match the rear end angle.
The motor/trany point down at say 2 degrees just for example. To cancel this angle the rear end must point up by 2 degrees. The 2 angles must cancel each other. They can not add together, example 2 degrees down at the transmission and 2 degrees down at the rear end. This would cause a problem of a driveshaft speeding up and slowing down every revolution.
You could easily raise the rearend in the car as long as you paid attention to pinion angle.
Instructor
Joined: May 2001
Posts: 228
Likes: 0
From: Santa Cruz CA
Re: Lowering diff or 6 link? (norvalwilhelm)
Corvette rear suspension has toe change through travel due to arc of the trailing arm and the arc of the half-shafts/strut rods. When car is lowered the rear wheels tend to toe-out under bump, if the diff is raised so that the half-shafts angle downward somewhat to the rear wheels (or the car is raised), then when in bump, the wheels toe-in. Toe-in at the rear is desirable, toe-out is very unstable.
I am contemplating my options, easiest to raise diff, but eliminating the t-arm and duplicating a C4 rear would be ultimately better. This topic has been on my mind a lot lately.
I am contemplating my options, easiest to raise diff, but eliminating the t-arm and duplicating a C4 rear would be ultimately better. This topic has been on my mind a lot lately.
Thread Starter
Race Director
Joined: Dec 2000
Posts: 10,896
Likes: 2
From: CO
Re: Lowering diff or 6 link? (68427)
This is all very interesting.
The reason that this method of changing the rear end placement is so interesting to me is that a professional race shop does this on their cars. I will take a digital camera and take some pics when I visit their shop and hopefully get some more info from the builders.
BTW these guys took first and second in C5's as sebring this year ! :cool:
The reason that this method of changing the rear end placement is so interesting to me is that a professional race shop does this on their cars. I will take a digital camera and take some pics when I visit their shop and hopefully get some more info from the builders.
BTW these guys took first and second in C5's as sebring this year ! :cool:
Melting Slicks
Joined: May 2002
Posts: 2,508
Likes: 0
From: Wisconsin
Re: Lowering diff or 6 link? (Chris O')
The Greenwood article mentions this and the optimum suspension heights.
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Burning Brakes
Joined: May 2000
Posts: 958
Likes: 0
From: Brisbane, Australia 1985 Coupe
Re: Lowering diff or 6 link? (Schmucker)
Sorry dude - it's at Terry Rudy's site http://www.corvettefaq.com/susp.asp
Vette Improvement Program - it's worth a read.
:cheers:
Vette Improvement Program - it's worth a read.
:cheers:
Drifting
Joined: Jul 1999
Posts: 1,537
Likes: 41
From: Plano TX
Re: Lowering diff or 6 link? (Chris O')
Why lowering/raising suspension there is one key measurement that the GM race book gives.
The outside strut rod pick up point must be 1 inch lower than the inside strut rod pick up point. They call this the D measurement. This is mentioned after they tell you to drop the inside strut down by 1/2 inch (Same as VBP smart strut kit). This should give optimum camber through suspension travel.
On the front they say the point were the tie rod inserts into the ball joint should be 1 to 1 1/2 inch lower than the center of the lower control arm shaft. This is called the Z height.
All measurements are with full fluids and drive in car.
I'm sure the race shop knows all these things! Let them do their thing.
Dave
The outside strut rod pick up point must be 1 inch lower than the inside strut rod pick up point. They call this the D measurement. This is mentioned after they tell you to drop the inside strut down by 1/2 inch (Same as VBP smart strut kit). This should give optimum camber through suspension travel.
On the front they say the point were the tie rod inserts into the ball joint should be 1 to 1 1/2 inch lower than the center of the lower control arm shaft. This is called the Z height.
All measurements are with full fluids and drive in car.
I'm sure the race shop knows all these things! Let them do their thing.
Dave
