Part 3: The Wheels Are Coming Off

Disassembling the rear suspension and differential

Chris Petris Jan 28, 2005 0 Comment(s)

It's time to move ahead with Project Shark Attack. While we were runningaround on the Hot Rod Power Tour and the Bloomington Gold show, thecomponents we ordered in Part 2 of this series came pouring in.

Now we can remove some pieces and see if this '79 Corvette is what wethought it would be. The plan is to completely disassemble the rearsuspension and differential. Once all the pieces are cleaned andinspected, they'll be sent out for bead-blasting and powdercoating.

At the start of the project, we checked the underside and sprayed allthe fasteners with P-Blaster rust penetrant, allowing it to soak for along time. The penetrant helps the parts-removal process and sometimesthe flame wrench (torch) isn't necessary. As we disassembled the rearsuspension, the bolts came out easily and had minimum corrosion.

We discovered some interesting things during disassembly. Differentialgear oil was dribbling out from the inner right-side bolt hole of therear-spring retainer plate, which was probably caused by a bolt that wastoo long.

The driver-side axleshaft had a replacement U-joint, and we wondered whysomeone would replace only one. We removed the U-joint and found thereplacement was in worse shape than the originals with at least 124,000miles. It most likely was never greased.

The strut rod stud/shock mounts came out with minimal hammer blows. Thetrailing-arm pivot bolts could be pushed out easily. All the originalrubber suspension bushings were worn, cracked, and ready forreplacement, not surprising after 25 years.

The trailing arms were in fair shape and the spindle bearings sounded OKwhile rotating the spindle. There are a couple of options when it comesto the trailing arms. You can buy completely rebuilt assemblies, partialassemblies with bearing housing available, or rebuild your original one.We decided to rebuild the original trailing arms since we have thespecial tools required for the job. The tools are available fromCorvette Central, but are costly for one-time use.

Once all the subassemblies are removed, put the pieces on a sturdyworkbench. Remove the heavy road grime and greasy buildup beforecomponent disassembly. Use latex or vinyl gloves during disassembly, asdifferential fluid and grease can stay with you for days.

It's important to keep all parts until the job is done. Put the onesyou're replacing in one area to review after disassembly, which makes iteasier to order the additional parts not on the original list. Now thedisassembly of major components can begin, then an evaluation of theircondition after cleaning.

Now that the project is underway and there have been no major surprises,we can consider some upgrades. Replacing the transmission with afive-speed overdrive unit so a 3.70:1 ring-and-pinion can be installedin the differential should liven things up a bit. Until the ODtransmission is installed, the 3.70-ratio will be fun on Saturday nightcruises. The strut-rod assembly will be replaced with Vette Brakes &Products smart struts, which change the strut-rod angle for better rearcamber control. The steel spring will be replaced with a TRW fiberglassmono-spring for ride quality and durability. The U-joints will be BruteForce heavy-duty pieces from Advance Discount Auto Parts. We still don'tknow what brake calipers we'll use, but it isn't an issue until we workon the front suspension.

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When installing or removing the rear spring, it must be unloaded fromthe trailing arm. Use a C-clamp to prevent the high lift jack fromslipping. The same procedure can be done with a floor jack. Place thefloor jack lifting cup as close to the spring bolt as possible. Thecloser you get to the differential, the harder it is to unload thespring. The axleshafts can be safely removed after spring removal.

It can be difficult to remove the strut-rod stud/shock mount from itsserrated press fit in the spindle support without the special tool thatscrews on the stud. The tool is available from Corvette Central (PN582414) for $14.95 and should be in your toolbox. This can be a horriblejob if the strut-rod-bushing inner sleeve is corroded to the mount stud.We used a reciprocating saw to cut the mount stud between the ears ofthe spindle bearing support.

After removing the driveshaft, front differential mount, and the boltsthat retain the differential crossmember, a jack is placed under thedifferential while the crossmember rubber mounts are popped off theframe. These rubber mounts usually release easily, but sometimes ittakes a lot of force. If mounts are tough to release, give the bar aquick pull downward. A quick motion works better than applying extremepressure over a longer period.

Notice the extra washers and silicone on the spring-retainer-plate boltthat goes into the differential cover. The inside of the cover waswelded where the spring-retainer bolt went through. A bolt can easilypierce the minimal cast iron in the area. Welding cast iron can bedifficult and minor leakage after repair is common. The welded area willbe sandblasted and cleaned with alcohol before applying J-B Weld epoxy.

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