The factory limited slip differential on the Corvette... one of my many features that make that Corvette stand out over other sports car offerings. Even better yet, the differentials on these Corvettes are pretty robust and can handle the vast majority of users use cases and even hand some rather notable power gains.
While the differentials on these corvettes are quite robust, they do require some basic maintenance to keep happy. Most folks recommend changing the differnetial every 20k miles, or once a season if you are doing some sort of heavy usage like track or drifting. Changing the differential fluid on a C5 Corvette is quite probably the easiest task on the entire car, with us going so far as to say it's even easier than changing the oil on the motor.
Here's some easy information to follow on changing the differential fluid in your C5 Corvette
Parts List:
- Differential Fluid / Gear Oil
- GM Recommended
- Our preference for street: 2x Lucas Oil - 75w90 (contains limited slip additive)
- Our preference for track: 2x Heavy Duty / High Performance Lucas 80W90 Gear Oil (contains limited slip additive)
- Fluid Transfer Pump
- 10mm allen socket
- Oil Drain Pan (We recommend owning a big one to make life easier in general with draining fluids on vehicles)
C5 Differential Fluid Change Instructions
Step 1 - Get the car in the air
You're going to need to be able to access underneath the car, so getting it up in the air will be important. You also will want the car fairly level to assist in draining as much differential fluid out as possible. Pictured above is the Authors C5 Corvette on some rather old Quikjaks. Quikjaks are a pretty good product, though their customer service definitely reflects that they are the only game in town really for floor mounted lift alternatives.
Step 2 - Get your parts together.
You'll next want to get the few parts that you need together. Assemble the fluid transfer pump as well, being sure to pick the correct depth of tube going into the bottle to make sure you can get all of the fluid out.
Step 3 - Undo the FILL plug first.
So the importance of this step occurring first doesn't matter as much on the C5 corvette, but is a critical pattern to follow in general when draining fluids from a vehicle... ALWAYS undo the fill portion first. While essential for smooth draining, what is more important is that if you remove the drain but are then unable to open the fill... you'll have a disabled vehicle on your hands. So always undo the fill plug first!
Step 5 - Drain the Differential from the Plug on the Bottom
With the fill plug undone, next up you'll want to position your drain pan underneath the differential and undo the drain plug. It's important to note, that it is very likely you will get at least some oil on your hands, if not a mild amount on your forearm... so be sure that the transmission fluid has cooled, along with consider wearing gloves and keeping towels or rags in the immediate reachable vicinity to get anything you get on yourself off.
Crack open the 10mm plug and then undo it by hand. Allow the fluid to fully drain out of the differential. Don't be overly concerned if the fluid smells, differential fluid is always some of the smelliest fluids on a vehicle.
Once the fluid has fully drained out, close the drain plug. If you're the precise type, be aware that the torque value on both fill plugs is 26 ft/lbs.
Step 6 - Transfer the Gear Oil Into the Differential
With the drain plug sealed up and torqued, you'll next want to pump the gear oil that you have into the rear differential. You will be filling the differential until fluid pours back out of the fill opening, so place a paper towel accordingly to capture any oil that runs down the differential when it is full.
With the hand pump it's a moderately tedious task, but it's cheap and easy. You'll transfer the first bottle, nothing exciting to note there. What is worth noting is that as you begin to transfer the second bottle... it'll seem to drag on... and then you'll wonder if maybe you won't need 3 bottles... and then all of a sudden when you're about ready to give up, the fluid will begin to come out the fill hole and you're done!
Step 7 - Close it all back up!
Place the rear fill plug back in, torque to 26 ft/lbs, and congratulations, you've changed the differential fluid! Now go enjoy your corvette knowing that the differential is ready to go!
As you're in the vicinity, and the hand pump you just bought will also be needed for it... consider doing your transmission fluid at the same time!