Long Overdue Progress! Making New Door Panels 12/8/24

[BBShark]

I was getting ready to put the car on the ground and looked under the front suspension. There were small chunks of plastic laying on the ground. The source was cushions that are sandwiched between the spring and the spring mount blocks. These have been installed for a week!

Here are the remains of the "cushions".



I found out these are a common problem with VBP dual mount spring. So much so that Van Steel is making reproductions. The problem is they are molded out of polypropylene. That is not what they should be made from. I used 80A polyurethane rubber in the back when I made my own mounts. I guess I'll do the same here.

 

[phantomjock]

YES!
Are you planning on making more than one set?
I could use a set for my front transverse spring as well.
They look just like the image you posted.

Let me know via PM.

Cheers - Jim

 

[BBShark]

I'm not sure what to do here. When I redid the rear spring mount, I realized that the spring shortens, mount to mount, when it bends in an arc. I was actually surprised how much. Fortunately (the rear mounts I made were pivoted on the neutral axis of the spring. VBP on left mine on right.



However the front is a different problem. The spring is pivoted offset from the netural axis by 1.2 inches. So if the spring bends 1/2" the mount blocks pivot and the difference is 1/8 of an inch (per side).



So that is probably why they use polypropylene cushions that allow the spring to slip. That is probably why my cushions crumbled when I had the car on the ground. The spring slipped through putting a shearing force on the cushions.

This is not a good idea. Even if the cushions didn't crumble, the spring would eventually walk it's way to one side or the other with normal driving.

A good idea to fix this is not obvious to me. Suggestions welcome!

 

[phantomjock]

That is a really good point. One of the major advantages to a transverse spring setup is the ARB action it can provide. But, if it slides each way - then the leverage would be changing -right? But it cant be sliding too much can it? But probably enough to sheer the mount cushions. Or, is heat and oxidation aka
Climate Change (ooooohhhh :banghead the problem?

Cheers - Jim

 

[BBShark]

Ah Ha!

I didn't know this but the C5 uses a dual mount transverse leaf spring. So what did GM do? They have some kind of compliant collar that is attached to the spring with a molded rib top and bottom. Then the collar is retained by a bracket that has a depression to capture the rib. I assume this depression is also in the crossmember.




So the change in length, caused by bending is minimized, and the centering (of the spring) is maintained. I may buy a junked spring to find out how GM did this.

One of the major advantages to a transverse spring setup is the ARB action it can provide

I was surprised out how well this spring does function as a sway bar. The rear spring, when supporting the cars weight, bends down in the center about 3/4 inch. Have heard this claim for years and was always skeptical.

 

[bobs77vet]

I have a C5 and have adjusted the ride height through the springs and swapped the shocks and sway bars for Z06 stuff, do you need some pictures of that part? i also have all the manuals let me know what you need. bob


isnt it bolted right to the frame? the holes on the end is how you adjust ride height

 

[BBShark]

I was looking at how the dual mount spring is mounted on a C5. It looks like a rubber collar that is bonded to the spring. So when the spring bends, the spring flattens and gets longer. The VBP spring has hard plastic pads that allow the spring to slide back and forth. That is what causes the pads to crumble.

I found this picture of a C5 spring. It looks like its rubber bonded onto the spring. See the crack where it is attached to the spring?

 

[bobs77vet]

hope this helps, a z06 spring is really stiff so i didnt use it but i did use the sway bar and shocks,

 

[bobs77vet]

maybe I am missing the issue. the distance in between the mounting points is static and doesnt change.....the when the spring goes up or down the angle of the wheel changes. the c3s did that with those strut arms also.

my pictures confirm the raised protusions are on both side of the mounting points

but the wheels/tires has to have an ARC where the A arms mount to the frames for bumps etc. so the spring follows the arc of the arm.

what am i missing?

and you would never want to do this but on my 37 ford we had those swivel extensions like on the ends of a leaf spring on the end of the transverse springs to compensate for the change in length

 

[BBShark]

Thanks for the pix. The problem is that the mounts (shown below), are fixed in position. But the spring, when it bends, changes length (between the mounts. For example, say it starts out flat and then bends 1/2 up in the center. That will pull those points in. This is made worse with the VBP spring because they are pivoted. This results in the spring pulling and pushing on the mounts as it bends.

It looks like GM fixed this by making compliant mounts that will allow the spring to pull/push and control that by the elasticity of the mounts. VBP was trying to do it by clamping onto the spring with hard plastic pads that allow the spring to slip in and out. That just causes them to crumble.

This is the C5 mount (closeup of your picture). Presumably rubber bonded onto the spring?

 

[bobs77vet]

got it, i dont have a set laying around but i do recall those "compliant mounts" were very durable and for all intents and purposes and part of the spring and not removeable.


i wonder if there is rebuild service you could send the springs you have to them for adding those types of mounts?

 

[BBShark]

I think I have this figured out. Looking at the C5 spring helped. The VBP dual mount spring is a good idea but pivoting them away from the centerline of the spring was a design flaw. A major design flaw. GM figured it out by making the cushions fixed in place (no pivot) and limited clamping force.

This is what I came up with. This is an aluminum yoke that has polyurethane rubber pads (green) on each side. Eliminates puling/pushing through the mounts when the spring bends.

 

[BBShark]

Made the new mount blocks finished and the cushions bonded to them. Copied the C5 scheme and eliminated the pivot. Also eliminated establishing compression of the cushions based o torque of the bolts. The compression now is established by the spacer height.

 

[BBShark]

Took a while but finally installed!

 

[bobs77vet]

very nice a 4 way clamp, out of curiosity could you clamp something to the springs on the inside of the clamps on both sides to stop it from moving?

 

[BBShark]

I thought about bonding a stop to the spring like you suggest, to keep it from moving. I probably should have done it but removing the offset pivot dramatically reduces change in length as it bends.

 

[BBShark]

So I finally had the car on the ground, ready to actually move it under it's own power and found my clutch won't release. Looks like I have to bleed the hydraulic cylinder again. In order to get under the car I had to raise the front to get to the hydraulic line. I did that and decided that's enough for one day.

Next day, go out to the garage and there is transmission fluid on the ground! I took a look and the is trans fluid on the yoke but nowhere else. I dried it off as best as I could an sprayed some chalk on it. Next day, I looked and fluid is leaking out of (what I thought) was a center when the yoke was machined. Now I'm thinking, does the yoke have a through hole in it? Some kind of vent?

The yoke I used is from a 70's Lincoln with a double cardan joint. Mark Wiliams sells these for $500. I wanted it because it's a take apart yoke. Here is the yoke I used:



Today I investigated and there is a 1/16 hole in this. So when I had the front raised the tail of the transmission was down and fluid wept out of this hole! I have a plan to fix this but this is another example of one step forward and three steps backwards.

A couple more days and I should be able to get back to the transmission.

 

[mfain]

So I finally had the car on the ground, ready to actually move it under it's own power and found my clutch won't release. Looks like I have to bleed the hydraulic cylinder again. In order to get under the car I had to raise the front to get to the hydraulic line. I did that and decided that's enough for one day.

Next day, go out to the garage and there is transmission fluid on the ground! I took a look and the is trans fluid on the yoke but nowhere else. I dried it off as best as I could an sprayed some chalk on it. Next day, I looked and fluid is leaking out of (what I thought) was a center when the yoke was machined. Now I'm thinking, does the yoke have a through hole in it? Some kind of vent?

The yoke I used is from a 70's Lincoln with a double cardan joint. Mark Wiliams sells these for $500. I wanted it because it's a take apart yoke. Here is the yoke I used:

View attachment 53261

Today I investigated and there is a 1/16 hole in this. So when I had the front raised the tail of the transmission was down and fluid wept out of this hole! I have a plan to fix this but this is another example of one step forward and three steps backwards.

A couple more days and I should be able to get back to the transmission.

I have the same issue with the yoke on my '91 Chevy 1-ton dually. If I leave it parked on an incline (nose uphill) for more than 3-4 days, the fluid drains from the torque converter into the trans and it leaks out of the hole in the yoke. I think the hole is to prevent air pressure build up between the inside of the yoke and the end of the tailshaft. I have a new-in-the-box, billet Mark Williams yoke made for a turbo 400 with the detachable end caps that I am not going to use. If you think it will fit and you might need it, I will drag it out and give you all the specs. I initially ordered it for my 6XD sequential, but it turns out that the transmission uses a slightly different spline shape (Jerico), so I had to order another one.

This is from the invoice: 39104 SLIP YOKE, RAPID RELEASE TURBO 400

 

[BBShark]

Thanks for the offer but the yoke I'm using is a Ford 31 spline. I thought when they center drilled it, the drill broke through because the casting was thin but it was purposely drilled through. And 1/16 hole makes me think it is a vent. The one I used was on the big 70's Lincolns and Thunderbirds and was a 2 piece shaft so maybe the vent kept it from pumping lubrication out of the splines.

Anyway, I can't get it off the transmission without removing the exhaust (for the 4th time). I will try this weekend to plug it with a 1/16 brass pin.

 

[BBShark]

In the last few days I was able to plug the hole in the yoke and reassemble and properly bleed my clutch.

Bleeding an Internal Hydraulic Throwout Bearing

I have had this car on jackstands for a loooong time. Yesterday I was finally ready to put it on the ground and drive it out of the garage. So, I started the car, pushed the clutch and tried to put it in reverse. Major grinding noise! I have a TKO trans with a Mcleod hydraulic throwout...

www.vettemod.com

So now I could actually put the car on the ground an move it under it's own power! But there is 6" of "wintery mix" on the ground. It's so stiff you can actually walk on the crust. Looks like I need a couple more days before I reach this milestone.