C2 ride height and rear transverse spring rebuild/replace question.

[Mark F.]

Good day all. Planning my summer project and will work on the rear suspension and trying to fix the ride height of my 1966 L72 roadster with F41 suspension.

Current ride height appears to be low. For the rear car height, from the FAM page 4 B5 it says I should have about 9.05 inches of clearance (corrected for L72) for dimension "K". (K is the distance between ground and underside of sill molding measured 24" in front of rear tire center line.) and my actual dimension is 7.5

[Joe L.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

Good day all. Planning my summer project and will work on the rear suspension and trying to fix the ride height of my 1966 L72 roadster with F41 suspension.

Current ride height appears to be low. For the rear car height, from the FAM page 4 B5 it says I should have about 9.05 inches of clearance (corrected for L72) for dimension "K". (K is the distance between ground and underside of sill molding measured 24" in front of rear tire center line.) and my actual dimension is 7.5

Mark------


First, look at the spring with the car at normalized suspension (i.e. after a drive, short or otherwise). Note if the spring appears to be "flat" or with a very slight center-high arch. If it is as described, you don't have a spring problem and replacing or re-arching it, by itself, is not going to solve whatever ride height problem you actually may have. If there exists a center-low arch, then you probably need to replace the spring

I would suggest replacing the spring end cushions (2 on each side). That, by itself, may solve your problem. If these cushions are original, I can tell you, without question, that they need to be replaced.

[Mark F.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

Thanks Joe for the quick reply. Just went out and looked at the spring. It appears to be completely flat, level with the garage floor.

The previous owner but some what I believe are poly cushions on the ends of the spring/bolts and they will be replaced when I do the work, but they do not look that bad, so do not know if they are affecting the ride height.

I will attach some pictures. Hopefully these will come out correctly oriented. Thanks for your help. Mark

[Stephen L.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

Mark,
Before you start removing/replacing parts you should perform the ride height calculation shown in your AIM (In a 67 AIM it is page UPC 4 B5. Your "66 AIM should have a similiar page).
This measurement, DIMENSION "D", removes the influence of tire size etc. It is the difference between 2 points on the suspension, as it was delivered from the factory and is influenced by spring condition, rubber cushions, bolt length (trailing arm to spring) and strut adjustment........
It will give you a baseline to work from.

[Mark F.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

Thanks Stephen. I saw that page in my AIM. Not home now but if I remember correctly I need the weight on wheels to get the proper "D" measurements. I don't have a 4 post lift but I think I can find some ramps or blocks to set the rear wheels on while I take a measurement. Thanks. Mark

[Stephen L.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

If you need to, place the car on blocks at all 4 wheels to get an accurate measurement. I'd try to obtain the measurements with the car on the ground. If you jack it up for blocks the geometry could be different until you roll the car a few feet....... You should be able to reach the measurement points.

[Leif A.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

Thanks Stephen. I saw that page in my AIM. Not home now but if I remember correctly I need the weight on wheels to get the proper "D" measurements. I don't have a 4 post lift but I think I can find some ramps or blocks to set the rear wheels on while I take a measurement. Thanks. Mark

Mark,
You don't need either to take the "D" measurement. You can access the ends of the strut rods for measurement from the ground by laying on your back and sliding under the rear of the car with a tape measure. I just went out and tried just to be sure it was possible. My "D" measurement was 3.75" Measure from floor to center of outer strut rod bolt. Measure from floor to center of inner strut rod bolt. Subtract the outer measurement from the inner measurement and you have your "D" measurement.

[Mark E.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

A quick way to visually check rear ride height for C2/C3 is to look at the half shafts. They should be parallel to the ground.

Agree with Joe- if low, check bushings first.

[Edward J.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

Mark F., I would check all four corners sometimes a slight difference in front will affect the rear. Or vise versa. Also check you rear leaf spring bolt lengths, it appears the pic of one of the bolts shown look like a coarse thread? And the nut is not typical, Gm used a cotter pin to lock the nut.

[Patrick H.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

Just looking at your car in the pictures, which is difficult with the orientation, the ride height looks OK to me.

I'm curious as to why you thought it was not correct?

[Mark E.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

Just looking at your car in the pictures, which is difficult with the orientation, the ride height looks OK to me.

I'm curious as to why you thought it was not correct?

Agreed. The photos suggest the half shafts are actually pointed down just a bit, but may level out when adding driver and fuel.

How much fuel does the car have in these photos?

[Tim S.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

I am of the opinion the height looks good too. I also noticed the spring bolt and nut are not the OE pieces. What is the length of that bolt?

[Gary B.]

[Duke W.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

IIRC F-41 results in about a 1" ride height reduction, but I'm not sure this is called out in the AIM or CSM.

As Joe said, the number one cause of rear sag is compressed spring link bushings. GM may still offer them, same part number as called out in the AIM. Aftermarket types don't last long. I think Doc Rebuilt still sells them, and they are reported to last, and I assume his are GM parts that he resells.

Duke

[Gary B.]

Re: C2 ride height and rear transverse spring rebuild/replace question.

Duke,

The cushions are GM-discontinued. Can be found on eBay though.

Gary