Rear Suspension '70

[Juliet P.]

I'm in the process of rebuilding my rear suspension, pulling the T-arms for complete rebuilding (at Tony's Corvette). I would think that I should replace U-joints while I'm at it, but what else should be done? Are the U-joints still available from GM and are they like the originals? How do I tell if my rear spring is OK? It did still have some arch when the car was not jacked up. As long as it doesn't fall apart when I remove it, is it still OK? Also I have some sort of an ooze from the Rear. What's the likely source? Here's a picture. It was clean (well somewhat cleaner ) about 8k miles ago. Brake calipers etc were new 11k miles ago. Thanks. ~Juliet

[Juliet P.]

Photo Online

Here's another pic of the rear ooze. Thanks, ~Juliet

[John C. Woods]

Re: Photo Online

Juliet: I'm not sure what type of restoration you are trying to do with your car, so it's somewhat difficult to answer your questions. On the one hand, you can replace the strut rod bushings, spring cushions and perhaps the lower shock bushings (if you have original shocks with the two-sided lower bushings) and leave the rear spring work at that. If you are doing a full-bore restoration, then you'd want to repaint the spring and perhaps replace the liners, plus all sorts of other cosmetic work. The retainers on the end of the spring should not be painted. They can be easily replaced as well but don't forget to peen over the retainer like your originals are installed. You may just find that with the new cushions/bushings, your car sits just fine as-is without attempting to match the original spring arch.

Your universal joints probably have the work "Spicer" on the end caps with no fitting for adding grease. I don't know where you might obtain NOS replacements. If you find a source, I'd like some too! You can obtain new universal joints without the grease fittings from various parts suppliers by asking for their "heavy duty" replacements. I've found that they will almost always pass for judging purposes. I'd say the trade off between having new universal joints that come very close to matching those now on your car favors replacing them. Don't forget the new end-cap retainers.

With respect to your rear end, they all usually lose some fluid with continued use. Unless it is giving some form of trouble or you plan to remove it for an overhaul for other reasons, I'd clean it, keep it serviced and leave it at that. Once you clean it up really well, you'll want to keep something on it to keep it from rusting more. I use a CRC product called SP-350, that is available from chemical/electrical supply houses. I've found that it lasts longer on the car than some of the products used for similar purposes such as Pre-Lube, etc. In other words, if it were my car I would most likely not remove the rear end just to clean it or to stop a weeping-type leak, if that's all that is wrong with it.

I hope this helps. Good luck on your project!

[Juliet P.]

Wow! Great post!

John, Thanks for all the info. I'm trying to restore the car to Top Flight Standards without it becoming a full body off restoration. That said, I do DRIVE the car (5k mi a year) and though I'd like it to LOOK like a trailer queen there's no way I can resist driving it! Plus, my '70 is my backup car when my '87 daily driver is being worked on.

Cosmetically I plan on doing everything I can 'while it's apart.' That includes the rear spring, so thanks for the tips on the refinishing it. I also need to replace the shocks with GM ones as the current shocks are not originals unfortunately. I have the part numbers from the archives which Joe Lucia posted for shocks. I do plan on replacing the U joints because I have some play in the rear end right now. Much (if not all) I'm guessing is due to the right rear wheel bearing, but not much has been done to the suspension of this car so I'd suspect with 55k miles the U-joints are original which might be part of the problem too. Thanks for the Heavy Duty U-joint info.

I'm undecided as to just cleaning up vs. dropping the rear diff. It does look like from the slower ooze on the driver side that it's coming from the gasket between the front pumpkin and back cover. So while I'm at it I might just as well take that out have it checked over / restored / rebuilt at Tony's and then I can de-rust my driveshaft too. I did clean it up nicely last year (first time it was cleaned in it's life I think!) - the gunk was so thick at that time I was amazed when I found the red tag - It was not visible before. I'll check the fluid level and see how low it is in 5k miles I've driven since last cleanup. I suppose that will be the deciding factor.

Speaking of rust - is the CRC product one of those oil based products which just coats the part and needs to be reapplied regularly? I'm wondering if it might not be better (since I do drive the beast!) to put a matt finish clear on the 'natural' parts. Would that hold up better and how much of a deduction would be involved for a light clear coat? Thanks, ~Juliet

http://www.1970corvetteregistry.org

[John C. Woods]

Re: Wow! Great post!

Juliet: Every restorer must make their own decisions with respect to what finishes they elect to apply to various parts, including components which originally had no paint or plating finish. Some very experienced restorers with high scoring Duntov cars paint each natural cast part with "as cast" paint, knowing full well that some judges will make originality point deductions for it. Others use a mixture of "as cast" paint, "stainless steel" paint and so forth in a further attempt to match the painted finish they use to the original finish of the component. Their logic is that they don't like the looks of rusted parts on their restored car and they are more than willing to take a point hit or two here and there in order for the car to appear the way they want it to. Components that frequently receive this treatment are those which are not easy to get to once the restoration project has been completed. Examples include: the rear carrier, the rear hubs and front springs. Some restorers will paint these parts but leave other components which afford easier access in their natural finish state.

The challenge with clear coatings on these parts is that there is a balance between how much is needed to seal the air from the part and keep it from rusting and how much can be used before the coating becomes obvious to someone who is judging the car. Paint is paint, regardless of the color and natural components cannot "grow" paint on them. If the clear coat paint is obvious, then it is subject to the same deductions that "as cast" coatings might receive. I am not sure how well the clear coating you mentioned will stand up to heat and other abuse before it begins to discolor and otherwise deteriorate?

I have been told that the CRC product (SP-350) I mentioned in my prior post was designed as a shelf preservative for newly machined parts. It is a light oil with something like a pariffin included in the mixture. It's available by the case in 12 oz spray cans or in a 5 gal. bucket. Spray it on and wipe it down, then come back after a day and the excess will be puddled on the bottom side of the components. Wipe that excess off and it's good for a fair period of time. Unlike paint coatings, it wears off, washes off and otherwise needs to be refreshed. Also, this treatment shows up any rust that is underneath.

Choices, choices, choices...

[Wayne C.]

Can't get to your photo

When I click on your url, I get this message:

"Forbidden

You don't have permission to access /c3/juliet/reardiffbefore2.jpg on this server."

[Joe L.]

Re: Can't get to your photo

Wayne and Juliet-----

I get the same message.

[John H.]

Pops Right Up For Me... *NM*

[Joe L.]

Re: Rear Suspension '70

Juliet-----

The half shaft (and driveshaft, for that matter) u-joints should DEFINITELY be replaced. I can virtually guarantee that when you remove the trunnion caps you're going to find that at least one trunnion of each u-joint will be brinnelled. That means that the u-joint is scrap metal. In fact, for the half-shaft joints, you may find that when you remove the trunnion caps that you will "pour" the needle bearings out in the form of powdered iron oxide (rust particles).

Half shaft and driveshaft u-joints are still available from GM. However, their configuration is TOTALLY different from the originals. They have a round center section and are made from forged powder metal. I believe that they are manufactured by Spicer, though, as were many original GM u-joints. The original half-shaft joints used on your car were likely not of Spicer manufacture. These were GM #3889696 and I think that most, if not all, of these were of GM internal manufacture. They were discontinued years ago and replaced by GM #374246 which was a u-joint of Spicer manufacture and was used in PRODUCTION on mid-70s+ C3 half-shafts. GM #374246 were also discontinued several years ago and replaced by GM #26049843 which is the u-joint I described above. Then, very recently, the latter part was discontinued and replaced by GM #12471503. I don't know what the configuration of this u-joint is but I expect that it's similar to the 26049843. The GM #12471503 currently GM lists for $92.18/each.

I recommend replacing with Spicer brand u-joints. Spicer has two styles. The first is the lubed-for-life which have no grease fittings, like ALL original half-shaft u-joints used for 63-82 Corvettes. However, the configuration of these joints may have changed and may be just like the units supplied through GM. Spicer's other line have grease fittings. However, when last I purchased a set of these, they were still otherwise configured like the originals.

Like I say, Spicer brand is the brand that I favor. Neapco is a good second choice. I would use no others. Many others, including those with popular American brand names, are cheap "foreign"-sourced units. Often, these will have fewer and larger roller bearings and will have a SHORT service life.

[Juliet P.]

Re: Rear Suspension '70

Thanks everyone. I now have the right rear T-arm completely out of the car and the difficult bolt out of the left rear T-arm. I'll finish up the rest of the left side in the next few days. I'm pooped!!! I'll need to go to the office tomorrow to rest up.

I don't know what's up with my web account and why that forbidden page is showing. It did that for me once and then when I reloaded it, the picture came up fine. Maybe Corvette Forum (where I have my free homepages) is having some technical difficulties or something. I haven't logged in over there yet tonight to see if anyone else is having problems.

Thanks for the U-joint information Joe. Spicer it is. FWIW while I was under the car (E-brake cables) I did notice the SPICER stamped in the end of the front U-joint on the drive shaft as John suggested. The rear ones I haven't inspected closely enough (or removed enough goop) to see yet.

I'm sure I'll have a zillion other questions as I continue to work through this. Thanks for the help everyone. ~Juliet

http://www.1970corvetteregistry.org

[Bill W.]

Re: Wow! Great post!

I cant get to it either . Bill

[Juliet P.]

Re: Wow! Great post!

Thanks John. I'll wait till after I see the blasted half shafts to decide. Who knows, I may NEED to cover them up with some paint. You're right - decisions, decisions, decisions. I just need to make sure that none of them make me afrait to drive it - even through a puddle! That was NOT part of the original plan. ~Juliet

[Mike Sasser]

Re: Rear Suspension, leak

Juliet, I had a leak on my 79 and discovered that it was leaking at the fill plug even though it was tight. I put some sealing tape around the plug and it never leaked another drop

[George C.]

Re: Can't get to your photo

Can't get to photo's