Rear Suspension and Differential

Several months ago, I decided to have the differential inspected as there was a tiny leak that, I assumed, was coming from the cover gasket. Besides, I was sure that after almost 40 years, the differential oil was ready to be replaced with a fresh and better quality lubricant.

But it never fails; you start doing one thing and end up with one of those situations where you think, "well since we're doing this we should also address..."

Yes, the "While I was there" syndrome.

For some of these types of repairs, I usually rely on mechanics. I don't have the tools, or a lift at home—and frankly—nor the energy to tackle major projects.

So I gladly paid to have all of this done. Of course, I do all the cleaning, painting and detailing of some of the parts, since I want them to look a certain way and I can save quite a bit of money by doing it myself.

My mechanic also lets me help and knows that I will want to detail other components while the car is up on the lift, so the arrangement works well.

In order to get to the differential, several components have to come off, including the spare wheel tub which I also restored at this time. (See Restoring the Spare Wheel Carrier article for more details on that project),

Note: this project was done (and photos were taken) while the old exhaust system still was on the car. After the suspension was addressed, I had a new true dual exhaust system installed. The last photo of this post shows the completed project and the new exhaust.

In order to remove the differential cover, the leaf spring has to come off, so there will plenty of pieces that will benefit from a good cleaning and detailing so everything looks fresh when reinstalled.

Here are the differential gears, which were inspected for wear, nicks, scoring, and breaks. None were found. We also inspected the differential case (or pumpkin, as some call it) for any damage or cracks. Again, everything was fine.

In hindsight, this was the perfect time to have removed the half-shafts for inspection and detailing, and replacing the side yoke seals. Alas, I did not have that done and, a few months later, one of the side yoke seals would start leaking.

Every time I look under the car those half-shafts look horrible compared to their surroundings, so one of these days I will remove them and I will repaint them.

And this is the differential cross member. It was in good shape overall, with just the expected surface rust and dirt accumulated over nearly 40 years.

And here's the differential cover ready for a good scrubbing and fresh cast paint.

I also cleaned and repainted the bottom shield/plate.

Cleaning and prepping the cross member for paint is a dirty job, and a well-ventilated area makes this process a little more bearable.

After the whole assembly was clean, I applied a thick coat of Loctite® Extend Rust Neutralizer with a throw-away 1" brush. Neutralizing rust is a good idea before refinishing this part.

Other products such as POR-15, are just as effective.

As the photo below shows, the liquid has a gray/blueish hue when applied to the metal, but once it dries it turns a very dark share of gray, almost black. At this point, you're ready for paint.

Instead of paint, I used Dupli-Color® Truck Bed Coating spray. I love the finish it leaves, which helps conceal small surface imperfections, plus how fast it dries. Of course, the best part is that the finish is very durable, which is ideal for a component like this one.

I also cleaned and painted the spring mount plate, and bought new Grade 8 nuts, bolts, and washers from the local ACE Hardware store.

But before reinstalling all these clean and refinished components, I took the time to clean the underside, as much as I could. And I also sprayed more Dupli-Color Truck Bed Coating after neutralizing as much rust as I could. All the detailing looked great and it was well worth the time and effort.

Not sure why I failed to brush some Extend Rust Neutralizer on the pumpkin and half-shafts. Every time I see these photos I realize that I wasted a perfect opportunity to make the whole area look a lot better.

You can also see that I had the exhaust removed in that area since it gave us a lot of extra room and all it took was a few bolts to drop the pipe and mufflers.

So here we have all components clean and ready for reassembly. The inside of the differential case was cleaned thoroughly and we also ordered a new gasket. The repainted cross member and differential cover were then reinstalled with new Grade 8 bolts and washers and looked fantastic.

But, while we were there... why in the world would we want to reuse the old leaf spring?

Leaf springs can be disassembled, cleaned, repainted and the plastic strips between the leaves, replaced with new pieces. But why go through all that trouble when, for a few more dollars, you can get a brand spanking new part?

So that's what I did. For about $150 I ordered a new 9-leaf spring from Eckler's Corvette. I did consider purchasing the single-leaf composite spring, but those cost substantially more (about $400), so I just went with the correct (and cheaper, although much heavier) part. Stupid choice, I know.

Anyway, as the photo below shows, the original spring was fatigued so using a new part was the smart thing to do. Besides, it looked a lot nicer than its old and rusty counterpart.

With the new spring in our hands, we were ready to start reassembling the differential. Everything was looking great.


OEM differential covers were notorious for doing this, but when this one broke it really felt like getting sucker-punched in the gut.

The solution? Order a new, heavy-duty replacement differential cover.

And since spending money goes hand-in-hand with classic Corvette ownership, I might as well get new adjustable rear strut rods while I had my credit card out of my wallet. But don't stop there... those original shocks look mighty tired, so...

The original strut rods did not want to come off without a fight. Which they lost.

And here they are installed. A much better look and easier to adjust. The new gas-filled shock absorbers were also installed, front and rear, and really improved the ride.

And here's the finished project, including a restored spare wheel carrier and true dual exhaust system with new mufflers.

Quite an improvement.

Thanks for following my restoration adventures which, sometimes, feel more like a series of unfortunate incidents!

Product Links... (#sponsored)

Loctite Extend Rust Neutralizer | Part No. 1381192 - 8 oz.
POR-15 Rust Preventive Coating Semi-Gloss Black | 1 qt.
Dupli-Color Truck Bed Coating Paint | 16.5 oz. 2-pack