Grafting a C5 rear suspension on C3

Jim,

Just a thought. If you model the C5/C6 rear suspension geometry, you will see a very low roll center. To balance the suspension, you need to balance the front and rear roll stiffness, which requires an increasing stiff spring rate as the roll center lowers. Some of the C5/C6 suspensions have rear spring rates upwards of 700#/in. You may have to look at the C5/C6 rear monoleafs (or coil-overs) to get that kind of number. You could always raise the rear RC by adjusting the strut rods (or dog bone/a-arm) to change the IC, but that would probably be counter-productive and would eliminate one of the major benefits of the C5/C6 geometry.

As you have heard me say before, I am not fond of slip joint axle shafts because of the friction in the splines under high torque loads. The friction may cause slight binding that can cause unpredictable changes in suspension geometry during cornerning. If you use C5/C6 outer bearings, then it is possible to set up the flanges of Tom's heavy duty inner stub axles to accept a C5/C6 inner CV joint flange. Then you could use the later Corvette axle assemblies -- the CV joints allow for the axle length change during suspension travel, without the friction of splines. If axle length is a problem, it is not super expensive to have the shaft shortened or to have one of the driveline shops (like the Driveshaft Shop) build custom length axles.

I saw something else kind-of interesting the other day in Camaro Performers Magazine. The Driveshaft Shop (I'm starting to sound like a salesman - LOL) built an independant suspension 9-inch center section for a 2011 Camaro that uses a fabricated steel housing and late Corvette-style CV joints and axles. With that housing, you could weld the front and rear mounts anywhere you wanted them (the one for the Camaro actually uses a front mount that bolts to the 9-inch front pinion bearing retainer ring), and you could also weld pickup points for the upper and lower links directly to the housing. Then all you would have to do is fabricate provisions in a rear cross member to bolt the whole thing in.

Like your project -- keep us posted.

Cheers
 
Jim,

Just a thought. If you model the C5/C6 rear suspension geometry, you will see a very low roll center. To balance the suspension, you need to balance the front and rear roll stiffness, which requires an increasing stiff spring rate as the roll center lowers. Some of the C5/C6 suspensions have rear spring rates upwards of 700#/in. You may have to look at the C5/C6 rear monoleafs (or coil-overs) to get that kind of number. You could always raise the rear RC by adjusting the strut rods (or dog bone/a-arm) to change the IC, but that would probably be counter-productive and would eliminate one of the major benefits of the C5/C6 geometry.

As you have heard me say before, I am not fond of slip joint axle shafts because of the friction in the splines under high torque loads. The friction may cause slight binding that can cause unpredictable changes in suspension geometry during cornerning. If you use C5/C6 outer bearings, then it is possible to set up the flanges of Tom's heavy duty inner stub axles to accept a C5/C6 inner CV joint flange. Then you could use the later Corvette axle assemblies -- the CV joints allow for the axle length change during suspension travel, without the friction of splines. If axle length is a problem, it is not super expensive to have the shaft shortened or to have one of the driveline shops (like the Driveshaft Shop) build custom length axles.

I saw something else kind-of interesting the other day in Camaro Performers Magazine. The Driveshaft Shop (I'm starting to sound like a salesman - LOL) built an independant suspension 9-inch center section for a 2011 Camaro that uses a fabricated steel housing and late Corvette-style CV joints and axles. With that housing, you could weld the front and rear mounts anywhere you wanted them (the one for the Camaro actually uses a front mount that bolts to the 9-inch front pinion bearing retainer ring), and you could also weld pickup points for the upper and lower links directly to the housing. Then all you would have to do is fabricate provisions in a rear cross member to bolt the whole thing in.

Like your project -- keep us posted.

Cheers

that also sounds like the 2004-6 GTO suspension
 
C5/C6 Rear Suspension Revisited DIMENDIONS PLEASE

Rather than start a new thread - I thought I'd resurrect this old one - as it gets to the approach I am returning to, and the needed information. I have finally re-retired and am full time (except for those Honey-Dos that have been building up) working to get the car together.
I've been burning on both ends of the car and owe many pics - Airbox, Splitter, engine, motor plates, headers, Cage is done, working transmission install, and at the rear - the IRS.
My "version" turned out quite heavy and I am now reconsidering the C5/C6 approach - per my original postings here. As for due diligence; the following are a bit of a summary here on VetteMod of the most germane discussions and help offered to others:

69427 had questions about using C5/6 as conversion for Weight Reduction Efforts:
http://vettemod.com/forum/showthread.php?t=8083&highlight=C5+A-Arm+dimensions

Answers from BBShark, JeffP1167 provided pics of rear end

BBShark:
... C5 lower arm is 11" inside and 16.5" outside.

69427:
I measured 10 1/2 inside and 15" outside on a late C4 cradle sitting on the shelf. And I don't know if a C5 LCA would easily hook to a C4 knuckle.

BBShark:
Transverse length from the LCA bolts to the balljoint center is looks pretty much dead on 16". The ball joint is about 3.9" from the edge of the LCA bushing (inside where the 11" dimension is measured).

_________________________________________________________________________________

DaveL82 request for Ball Joint Tapers on C5 Spindles - answers from BBShark/mfain:
http://vettemod.com/forum/showthread.php?t=9081&highlight=C5/C6+COntrol+Arms
_________________________________________________________________________________
ardillo lambo's questions and answers from Boredom/BBShark
http://vettemod.com/forum/showthread.php?t=9164
_________________________________________________________________________________

Boredom builds own control Arms: (Nice pics - any follow-up?)
http://vettemod.com/forum/showthread.php?t=9081&highlight=C5/C6+COntrol+Arms&page=2
_________________________________________________________________________________

DavesL82 C4 version:
http://vettemod.com/forum/showthread.php?t=7128
_________________________________________________________________________________

Now - A picture is worth a 1000 words so here are two that I could use some help with.

I've colored the dimensions and arrows to hopefully help clarify these. Anybody have these measures "at hand?" Metric - or Imperial would be fine. The CAD drawing that are in the Downloads are nice, and well executed - but for basic planning purposes - maybe these will help a few folks looking to study and determine if this is the route they want to go.

First the Upright and UCA/LCA for the C5/C6 (and requested dimensions):

12695256a4f8b0e8f.jpg


Now, the Cradle:

12695256a4f8e830b.jpg

Any Help? And as Karsten said back on post #35:

MYBAD79 .... changing your mind half way into a project is expensive....

I'm much smarter (poorer- now!)

Thanks - and Cheers - Jim
 
Well - its been while, and I've had a chance to do some research and thinking on this effort. I'd better post some progress - or be accused of slacking -off!
So What is new?
I built a set of UCAs & LCAs - Upright and mounted to chassis with the Tabs shown in a previous posting - one of my teasers that TT made me post some more on..

Overall, they seemed effective, but HEAVY! I was willing to sacrifice that bit of weight gain - thinking good for balance - it is in the REAR - but after adding the Roll Cage and more bits - thought I'd better do something else. All the discussion about that last ounce makes me think we are all part of weight watchers!

I was fiddling about with a few ideas - and migrated back to the C5 Corvette bit. Earlier this month I "graduated" from my final tour of Active Duty - and said; "Screw It, I'll do it the way I should have from the start!" So I got a pair of C5 Uprights and started cleaning them up - no A-Arms - just the uprights.
They are just about polished - and I'll post the bling when they are "done," but spent some time on CAD today, and ordered a heap of bits from Coleman Racing to fab the IRS!
12695265be79347ef.jpg

My overall plan is to fab the ball joint holder for the upper using the cool "Spindle eye/Taper" Coleman Racing sells:
12695265bf8329794.jpg

I'll warn you now -- these were cheaper this morning when I placed the order - so watch the price of "precious metals!"

Another cool part they have is the Integral Ball Joint. It is a weld-able piece and ball joint in one. Saves about 1/2 pound per side:
12695265bf837f2b9.jpg

The plates I'll have fabricated by a "net buddy in Iowa - unless I find someone closer -- hint hint Ralphy! ;D

The overall approach is like this shamelessly swiped pic form somewhere on the 'net:
12695261b67ec07fd.jpg

While that may be a FRS - it is close enough to what I'm up to. Next - I'll need to source a pair of C5 Corvette CV half Shafts and have the Differential end modified to fit my TOM's C3 4.11 rear end!

AND - I'm planning on a Pushrod to Rockers Still for the Dampers. Those are installed and I gotta take those pics soon too.

So, Thanks to BBSHark (Great CAD Products); PAPPY for IRS encouragement; TT for the Forum; and all you guys for inputs, putting up with my "blather" and your help - I'll keep bearing down!
Cheers - Jim
 
the shock angle on that design is rather crappy, the more angle, the less efficient the shock is, especially on small suspension movement.
 
Jim,

A couple of things to think about. The upper ball joint is pressed into the upright, so if you replace it, you will have to machine the hole for a press fit for your new upper ball joint (or machine for a press in sleeve that will accept either a press in or screw in ball joint). The Coleman spindle eyes I ordered, while they had the right taper for the stock C6 upper ball joint, were too large in diameter for the stud. They may fit the ball joint stud that you ordered, but you still have the problem of getting the ball joint pressed into the upright. Also note that because of the KPI, the plates at the ends of your control arms will have to be "angled" so you don't bind the ball joint stud with full suspension travel. Did you look at the link I provided for you in the Ball Joint Taper thread -- it has some good discussion of some of these issues.

Pappy
 
TT - I'll keep that in mind - Getting the dampers to "do their thing" and not limuit them is important. Do you have a good ratio/angle to use with a pushrod setup? I'd like to use a pushrod and keep the shocks inboard - unlike that last pic I posted. Seems like with a rocker you can work the ratios to improve over the poor angles for some IRS setups.

Cheers - Jim
 
Jim,
The upper ball joint is pressed into the upright, so if you replace it, you will have to machine the hole for a press fit for your new upper ball joint (or machine for a press in sleeve that will accept either a press in or screw in ball joint).

DOOH - do you mean that not all Ball Joints have the same base?!! WTF!!! Well - Like you said..
The Coleman spindle eyes I ordered, while they had the right taper for the stock C6 upper ball joint, were too large in diameter for the stud.
Got that -- I think...(OBTW - I'm stuck on C5 uprights - sameo/sameo?)

At least that is why I plan on moving to all GM K-6141 - standardize a single shape and mate to that...
They may fit the ball joint stud that you ordered, but you still have the problem of getting the ball joint pressed into the upright. Also note that because of the KPI, the plates at the ends of your control arms will have to be "angled" so you don't bind the ball joint stud with full suspension travel.
I think I have that covered -- will fab and mock up to be sure -- its all $$$
I do have a mlocal machinist that will mill the upright for the upper ball joint to press fit.
Did you look at the link I provided for you in the Ball Joint Taper thread -- it has some good discussion of some of these issues.
INDEED! that is why I moved away from the "standard" C5/6 ball joints and am willing to build around the upright using other "bits," and do some VetteMod/Hot Rodding!

Cheers - Jim

Pappy[/QUOTE]
 
Rather than start a new thread - I thought I'd resurrect this old one - as it gets to the approach I am returning to, and the needed information. I have finally re-retired and am full time (except for those Honey-Dos that have been building up) working to get the car together.
I've been burning on both ends of the car and owe many pics - Airbox, Splitter, engine, motor plates, headers, Cage is done, working transmission install, and at the rear - the IRS.
My "version" turned out quite heavy and I am now reconsidering the C5/C6 approach - per my original postings here. As for due diligence; the following are a bit of a summary here on VetteMod of the most germane discussions and help offered to others:

69427 had questions about using C5/6 as conversion for Weight Reduction Efforts:
http://vettemod.com/forum/showthread.php?t=8083&highlight=C5+A-Arm+dimensions

Answers from BBShark, JeffP1167 provided pics of rear end

BBShark:
... C5 lower arm is 11" inside and 16.5" outside.

69427:
I measured 10 1/2 inside and 15" outside on a late C4 cradle sitting on the shelf. And I don't know if a C5 LCA would easily hook to a C4 knuckle.

BBShark:
Transverse length from the LCA bolts to the balljoint center is looks pretty much dead on 16". The ball joint is about 3.9" from the edge of the LCA bushing (inside where the 11" dimension is measured).

_________________________________________________________________________________

DaveL82 request for Ball Joint Tapers on C5 Spindles - answers from BBShark/mfain:
http://vettemod.com/forum/showthread.php?t=9081&highlight=C5/C6+COntrol+Arms
_________________________________________________________________________________
ardillo lambo's questions and answers from Boredom/BBShark
http://vettemod.com/forum/showthread.php?t=9164
_________________________________________________________________________________

Boredom builds own control Arms: (Nice pics - any follow-up?)
http://vettemod.com/forum/showthread.php?t=9081&highlight=C5/C6+COntrol+Arms&page=2
_________________________________________________________________________________

DavesL82 C4 version:
http://vettemod.com/forum/showthread.php?t=7128
_________________________________________________________________________________

Now - A picture is worth a 1000 words so here are two that I could use some help with.

I've colored the dimensions and arrows to hopefully help clarify these. Anybody have these measures "at hand?" Metric - or Imperial would be fine. The CAD drawing that are in the Downloads are nice, and well executed - but for basic planning purposes - maybe these will help a few folks looking to study and determine if this is the route they want to go.

First the Upright and UCA/LCA for the C5/C6 (and requested dimensions):

12695256a4f8b0e8f.jpg


Now, the Cradle:

12695256a4f8e830b.jpg

Any Help? And as Karsten said back on post #35:

MYBAD79 .... changing your mind half way into a project is expensive....

I'm much smarter (poorer- now!)

Thanks - and Cheers - Jim
thum_3030527d68f43a830.jpg

CAD model in solidworks for C5 Control arms

https://grabcad.com/library/corvette-c5-control-arms-1
 
dohacar -
Thanks for that! I've been on and off GrabCad and a few other CAD "depositories" but hadn't caught that one. Thanks!
Cheers - Jim
 
[
I've colored the dimensions and arrows to hopefully help clarify these. Anybody have these measures "at hand?" Metric - or Imperial would be fine. The CAD drawing that are in the Downloads are nice, and well executed - but for basic planning purposes - maybe these will help a few folks looking to study and determine if this is the route they want to go.

First the Upright and UCA/LCA for the C5/C6 (and requested dimensions):

12695256a4f8b0e8f.jpg


Now, the Cradle:

12695256a4f8e830b.jpg

Any Help? And as Karsten said back on post #35:

MYBAD79 .... changing your mind half way into a project is expensive....

I'm much smarter (poorer- now!)

Thanks - and Cheers - Jim[/QUOTE]

Jim,

I've got my 2011 C6 Z06 laser-leveled on stands, so I took some measurements for you. Since there is so much "stuff" in the way, I had to do it by dropping plumb lines. The measurements should be pretty good, but not in the .001 inch range.

IMG_2200_1.jpg

My cradle does not match the one in your picture exactly, but the front lateral measurement is 29 11/16 inch; the rear lateral is 28 1/4 inch; both longitudinal measurements are 15 15/16 inch; and the inside cradle is 20 inches. The inside of the cradle (below the inside cradle that you wanted measurements for and where the sway bar mounts are) is 17 3/8 inch. And the diagonal measurements for the cradle mounting bolts are 33 3/16 inch. It would be better to measure the control arms off the car. I did get enough measurements, at ride height, to begin refining the roll center and anti-squat values. My brother narrowed a cradle in the middle and used a 2010 Camaro third member with custom axle shafts in his C6 suspended 1950 Jaguar 120. It worked out pretty slick. Hope this helps.

P.S. This is the rear cradle. Did you want the front?

Pappy

Pappy
 

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Getting Back to the C5 - to - C3 IRS Project

Well, here is another "unabashed" question that shows my ignorance... :twitch:
"How can I adapt a C5 Hub to a Speicher 1350 U-Joint?"

Why you may ask? Well, I have these from my Giovanni setup, and want to keep my Tom's 4.11 rear end in the system.
126953caa2874c0c0.jpg


Seems like thre might be some way to do something like this on the Hub end:
126953caa220e80d2.jpg

I've been all over the web and can't find what is "going on inside" the boot in terms of connections, fastenings etc.
126953caa22144789.jpg
126953caa2212a97f.jpg

I suppose I could get a C5 CV setup and cut off the inboard end and have something grafted to mate with the Diff:
126953caa22163c7e.jpg

Any ideas?

TIA - Cheers -- Jim
 
A look inside - sort of...

Continuing to surf - Its raining and the garage floor is wet...

Found this image - but, "how does the end segment stay put?"126953cac6e4470eb.jpg Ok, I'll guess the Circlip is fastened on the shaft, so, I guess the "cup" (aka HOUSING) grabs the balls and tripod/race(so to speak) to keep everything in position.

That could mean the splined (hub) end could be flat on the inside? Might make for some opportunity to mount the base for a a U-Joint?

126953caca9f708f5.jpg

Jeep Cherokee version -
126953cad14b2f007.jpg
maybe a plan - are all hub splines the same - probably not...

Anybody have a picture of what is going on in there? Any other ideas?

Cheers - Jim
 
Last edited:
Or, as an alternative, I guess maybe keep the CV Hub intact and figure out some way to adapt the slip shaft to it, keeping the inboard U-Joint to Tom's Diff.

126953cacfcdd1c75.jpg

What say - sound "do-able?"
 
I don't think you want to mix unjoints with cv joints. U joints have a cyclic torque output unless at 0 degs. That's why ujoints are supposed to have similar angles at each end.

Tom's flange could probably bolt to an inner cv joint.
 
That is a idea I was toying with too. An advantage would be the inner CV joint with its compression ability, would eliminate the need for a slip joint.

I'll keep my eyes open for that opportunity too. It creates another mechanical complication to figure out.

The easiest seems the "Jeep" variant posted, but looking too use at track speeds.

Off road vehicles do the mix of CV and U-Joint - but much lower speeds I guess.

Thanks, and -
Cheers - Jim
 
I'll rephrase...

I don't think you want to mix unjoints with cv joints. U joints have a cyclic torque output unless at 0 degs. That's why ujoints are supposed to have similar angles at each end.

Tom's flange could probably bolt to an inner cv joint.

Had a bit of a look - and a lot of Off road activity like this - swapping CV for U-joint, and vice-verse.

Here is A few ideas I came across:
126953cba0ca7df46.jpg

Would certainly need the right spline count and some hardening, maybe custom built?

A drive flange would be ready made, maybe:

126953cba0cabf229.jpg


But, since my diff hasn't the flange stub axles - but set for 1350s on the inboard too - it made me realize - I may have misled with my original question. A more accurate one might have been:

"How to adapt a C5 Hub to a 1350 Speicer set up Half Shaft (and Differential)?" That sort of changes the viewpoint/perspective.

It is always important to ask the right question...:banghead:

I think this the best option:
126953caca9f708f5.jpg

and, as a paste-up

:126953cba0cb0af48.jpg

Using only the outer hub spline mount and housing (from the C5 half shaft), I'd keep all U-joints in my original half shaft setup (including the slip shaft) But no CVs.

Unless anyone knows the ID of that outer housing on a C5 axle - I may have to take a risk on eBay and just buy one. Anyone know those dimensions?
Time for a coffee and go stare at the rear end some more...:noworry:

Cheers - Jim
 
Looks like you have done way more homework on this than I have but, I seem to recall, you can pull the inner CV joint off the stub axle and buy a splined yoke for the u-joint. Presumably that is welded on to the axle stub.

A while back I had some axles shortened and balanced. This was at a driveline shop that primarily does trucks. However, the guy I talked to had lots of experience with car stuff. I was talking to him and he pretty much told me that anything was possible as far as adapting and converting. And all done with catalog items.

You might wan't to find a driveline shop close to you and show them what you are after.
 

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