Questions on rear shock design for 71

[Brad M.]

I do not have original rear shocks for my 71 and am trying to determine which is closest to original design among a couple options that I currently have.

I bought a set of the AC Delco current replacment version and painted them gray. The one thing that I am not too excited about on them is they say "made in Mexico" on them. They have stampings of "top", "73 661", "006441", and "warning do not heat or open". Clearly the stampings are quite a bit different than originals.

I recently purchased a set of unused GM Goodwrench rear shocks with stampings 4974648, 120-86-1, and bottom. These stampings are closer to the original stampings, but obviously do not have "pliacell", "Delco Products Dayton Ohio", and the part number is different, etc.

I noticed that the top cover part of the shock on the GM Goodwrench ones is shorter (about 4 3/8 inches) than on the current AC Delco replacement version (about 5 1/2 inches), such that if you pull the shock all the way out, you can see the chrome shaft on the GM Goodwrench version. Does anyone know how the original shocks were designed regarding this?
Based upon some pics that I have seen, my guess is that the originals are more consistent with the current replacement version than the GM Goodwrench version from 1986.

The GM Goodwrench version also has a horizontal indented line at top and bottom while the current AC Delco version does not. Did the originals have this indention?

One more question, the GM Goodwrench version stays in place where you move the shock to, while the current AC Delco version returns to an extended position when not under pressure. Which is better from a functionality standpoint, or does this make any difference?

[Rob M.]

Re: Questions on rear shock design for 71

Good question - I think many of us are trying to find reasonable shocks for road use and judging. I have posted a picture of original 1969 shocks that may answer some of your questions.

[Michael W.]

Re: Questions on rear shock design for 71

One more question, the GM Goodwrench version stays in place where you move the shock to, while the current AC Delco version returns to an extended position when not under pressure. Which is better from a functionality standpoint, or does this make any difference?

Shocks that are 'gas charged' will tend to extend themselves when not under load. The AC Delco shock is probably considered a low pressure shock while some of the aftermarket units (Bilsteins, Koni, etc.) are definitely a high pressure type. These latter units can affect the ride height of the car to a small degree by trying to extend themselves and lifting the car by a quarter inch or so.

As to which one is better, I think the internal valving and compression/rebound characteristics plays a bigger part in ride control than how much gas a shock has got.

Typically either of the shocks you have will work well with a stock type steel rear spring. An after market fibreglass rear spring might require more aggressive damping (not dampening!). Try them and see. Choose your favourite and dress it up best you can to look like an original for judging purposes.

[Brad M.]

Re: Questions on rear shock design for 71

Rob, can you measure the length of the top part of the shock? It looks from your pic that they may be the shorter design closer to the GM Goodwrench ones dated in 86.

[Rob M.]

Re: Questions on rear shock design for 71

Rob, can you measure the length of the top part of the shock? It looks from your pic that they may be the shorter design closer to the GM Goodwrench ones dated in 86.

I don't physically have these shocks - just the picture. You can try to scale the picture. If you assume that the main body length is the same as yours...

[Brad M.]

Re: Questions on rear shock design for 71

Thanks, I think the math does seem to work out that the sizing is consistent with the GM Goodwrench version. Plus the fact that you can see the chrome shaft in the pic, lends it to being more consistent with that version than the current delco ones. Interesting...

[Brad M.]

Re: Questions on rear shock design for 71

Of course one caveat to all this is that those in your pic are 69 shocks, and there is no guarantee that 71 shocks were designed exactly the same. I am think the original part numbers on 71 shocks may have different than for 69.

Anyway, it does seem that the GM Goodwrench ones are probably closer to originals, so I will probably use those.

[Joe L.]

Re: Questions on rear shock design for 71

Of course one caveat to all this is that those in your pic are 69 shocks, and there is no guarantee that 71 shocks were designed exactly the same. I am think the original part numbers on 71 shocks may have different than for 69.

Anyway, it does seem that the GM Goodwrench ones are probably closer to originals, so I will probably use those.

Brad-----


The 1969 shocks were exactly the same as the 1971. So, the 1969 shocks pictured would have a configuration identical or virtually identical to the ones originally used on your 1971.

The "Goodwrench" shocks you purchased were manufactured internally by Delco Chassis and were manufactured on the same basic tooling as original shocks. I have no record of the part number you mentioned for them but inasmuch as they were Goodwrench shocks, they were likely more of a "generic" shock that may have been used for some other applications. That might be why they vary with respect to the length of the rod shield.

The new shocks of current GM part number were not manufactured by any GM parts making operation or, even, any former GM parts making operation. They are manufactured by Monroe (Federal Mogul) or Garbriel (Arvin Meritor). They are manufactured on different tooling than the originals. However, I believe that these shocks are Corvette-only pieces, so that's why they might better conform to the original Corvette shock design specs than the perhaps more "generic" Goodwrench shocks.

[Michael G.]

Re: Questions on rear shock design for 71

Hey Guys,
In regards to the original shocks for the 71, does anyone know a source for replacement rubber bushings for these shocks and is it even possible to have them installed at the local machine shop? Seems to be life left in these units, but the rubber has seen better days. Thanks,
Mike

[Brad M.]

Re: Questions on rear shock design for 71

Thanks Joe, also regarding the part number, the boxes that these came in have the part number 12322206 for the rears, which is different than the number stamped on the shocks discussed previously, not sure if that is why you are not finding the number in the apparent extensive part number books you must have.

[Brad M.]

Re: Questions on rear shock design for 71

If you are referring to the lower bushings, I have seen them on the auction site before. No idea if you are referring to upper bushing.

[Brad M.]

Re: Questions on rear shock design for 71

Also, I located the pic of some original shocks that I had previously seen that were dated for 71. They do appear to have the longer rod shield design. (but the part number may be same as those previously posted as original 69 shocks)....

These were sold by someone on the auction site a while back and I downloaded the pics.

[Joe L.]

Re: Questions on rear shock design for 71

Hey Guys,
In regards to the original shocks for the 71, does anyone know a source for replacement rubber bushings for these shocks and is it even possible to have them installed at the local machine shop? Seems to be life left in these units, but the rubber has seen better days. Thanks,
Mike

Michael-----


If you're referring to the rear shock UPPER bushings, I know of no replacement being available. The same thing is true for the front shock lower bushings

For the rear shock lower bushings, it's easy to get them----GM #3735334.

[Joe L.]

Re: Questions on rear shock design for 71

Thanks Joe, also regarding the part number, the boxes that these came in have the part number 12322206 for the rears, which is different than the number stamped on the shocks discussed previously, not sure if that is why you are not finding the number in the apparent extensive part number books you must have.

Brad-----


The on-box, SERVICE part number for shocks is almost always different than the number actually stamped on the shock. This is because the shock on-box part number represents the contents of the box which includes the shock + hardware.

The GM #12322206 was never cataloged as a PRODUCTION-equivalent shock for a Corvette. So, it must be some sort of Delco replacement.

[Michael G.]

Re: Questions on rear shock design for 71

Thanks Guys,
Joe, I am having trouble establishing a good source for "GM Replacement" or "GM Restoration parts" other than EBAY or dealerships who would rather not be bothered with my requests. Is there a source you guys have found to be reliable and cooperative?
Mike