Rearend Gear Swap

Re-Ring The Rear Of Your '97-'01 Corvette

Andy Bolig Apr 1, 2001 0 Comment(s)

Step By Step

Remove the four bolts that hold the rear sway bar to the transaxle housing...

...and loosen the bolts that connect the rear section of the exhaust system. Mike will remove only the driver-side muffler right now and will wait until the transaxle is out to remove the passenger-side muffler.

Next, remove the exhaust from the manifolds and remove the intermediate pipe. Don’t forget to disconnect the oxygen sensors.

Remove the rear-brake calipers. Do not loosen any of the brake lines, or you’ll have to bleed the brakes when you’re done. Be sure to support the calipers so the weight isn’t hanging on the brake lines.

Now remove the screws that hold the tunnel cover in place. This is where a cordless drill or a pneumatic ratchet will be beneficial.

Remove the small cover on the bellhousing...

...and loosen the hub that holds the driveshaft in place.

Disconnect the emergency-brake cable, speed sensor, and upper ball joint so you can drop the transaxle cradle.

Put a jack or a support under the lower control arm ...

...and remove the upper shock bolts. This will allow the suspension to drop and remove the pressure from the spring. Do this on both sides.

Be sure to disconnect the lines and wires at the differential that will stay put while the cradle is lowered. Keep an eye out for any that you may have missed as you lower the cradle.

Use another jack to support the transaxle once the cradle is removed.

Loosen the transmission mount.

Mike pops the axleshafts out of the differential with a bar and lowers them with the cradle. With everything ready to be lowered, you can loosen the nuts that hold the cradle in place. The nuts must be loosened with handtools to prevent damage to the studs mounted in the body. Don’t use air or impact tools.

We used a transaxle lift to support and lower the cradle. Make sure you have some means of holding the cradle before you loosen the nuts.

With the cradle out of the way, you can disconnect the wires and cables to the transmission.

Before you lower and remove the transaxle, go to the front of the torque tube and pop out the plugs in the bottom of the tube.

The holes are threaded, and we put two screws into them snugly to hold the driveshaft in place once the tube was removed from the hub.

Next, disconnect the transmission-cooler lines.

Drain the differential before lowering the transaxle. It’s much easier now than with it lying on the floor.

With the cradle and axleshaft removed, you can easily remove the passenger-side muffler, too.

Use a jack to support the back of the engine and remove the bolts holding the front of the torque tube to the bellhousing. Lower the transaxle and torque tube slightly and then pull them back to remove the driveshaft from the hub. They should slide apart easily. A transmission jack will make this job much easier. Make sure the wiring harness that runs along the top of the torque tube is out of its brackets to prevent damage.

Remove the bolts holding the differential and transmission together.

Then pull the differential off of the output shaft.

Disconnect the transmission cooler lines.

Then go through the small access hole to remove the bolts that hold the torque converter.

Loosen the outer transmission bolts that hold the torque tube to the transmission; the torque tube will come right off.

Use the seal plate from the old differential or you’ll have a BIG leak. Note that the plate can go only one way. Take this time to check the shaft seal for wear, and also to switch any brackets to the new differential.

Make sure to remove and install the seal plate squarely, and that it seats totally.

Once all the necessary parts were switched over, Mike bolted the new differential (GM PN 12551769) to the transmission. Torque the differential bolts to 37 lb-ft.

On the other side of the transmission, we removed the original converter.

We filled the new Super Yank 3500 C/5 converter with fluid and installed it onto the input shaft. It must fit over the splines on the shaft fully and engage the front pump of the transmission properly. The Super Yank provides a superior launch without blowing the tires off the line, and yet retains good driveability.

With the new converter installed, we bolted the torque tube back on, put the bolts into the torque converter.

Then we torqued them to 47 lb-ft.

Putting the driveshaft back into the hub can be tricky. Put the driveshaft straight in, or it will give you trouble. They can be finicky, and this is a good reason to have a transmission jack.

Remove the small bolts that held the shaft but don’t tighten the hub at the front of the driveshaft.

Hook up all of the lines again, including the transmission cooler lines at the front of the torque tube and the shifter cable and wires.

Support the transaxle with a jack and remove the transmission jack.

Install the rear vibration damper...

...the transmission mount...

...and the passenger-side exhaust.

The cradle is next.

Tighten the nuts of the cradle to 81 lb-ft (again, using only handtools).

Remove the jack holding the transaxle and tighten down the transmission-mount nuts.

Insert the axleshafts into the differential and fasten the upper ball joint and shock mounts. Torque the upper ball joints to a minimum of 41 lb-ft. You’ll have to jack up on the lower control arm to get the bolts started in the upper shock mounts.

Connect the speed sensors and emergency cable again.

Remember these guys? Now you have to put them back in. This cover is actually a stiffening member for the car, so you have to put them all back in.

Next put in the intermediate exhaust pipe...

...and the driver-side muffler and tailpipe. Don’t forget to connect the oxygen sensors.

Finally, tighten the rear sway bar and install the rear brake calipers.

Because of the added slip of the converter, we installed a B&M Super Cooler to keep the fluid temperature down. This is used with the original cooler in the radiator, not instead of it.

We removed the top cover of the radiator so we could slip the fan assembly out of the hooks. This gave us more room to install the cooler.

The cooler kit comes with everything you need for installation. We put ours to the passenger side on the front of the radiator.

We ran the hoses to the lower cooler line. All of the fittings were in the kit.

Because of the gear difference, we ordered a recalibrated computer from Pro Auto Tech. The updated program also changes the percentage of allowed slip to compensate for the higher-stall converter and prevents an unwanted SES light.

We were done with the installation of parts, but we needed to fill the fluids.

The differential got GM Synthetic Axle Lubricant along with a bottle of limited-slip additive.

We topped off the transmission with Dexron-lll fluid.

Changing the rearend gears has always been one way to make major improvements in how a car launches from the line. The C5 Corvette obeys the same laws of physics other cars do; the only difference is the means by which changes are made. Many Corvette owners want a change of gear for quicker acceleration, but the computer system and the different-style transaxle of the C5 have kept many from making the change for fear of problems with these systems operating properly once everything is installed. We went to Norris Motorsports, where Mike Norris was installing a 3.42-ratio differential, typically found in manual-transmission cars, into an automatic-equipped 2000 with the 2.73 differential. Follow along as we install a new differential for more performance.

Once we had the fluids topped off, we had to do a computer relearn before the car would start. A computer relearn entails turning the key on for at least 11 minutes, and then turning the key off for at least 30 seconds. Do this three times in a row and then turn off the key for 30 seconds before trying to start the car. Start the car and run it until it reaches operating temperature to allow the driveshaft and hub to center, then stop the engine and go under and tighten the hub again. Once the hub is tight and the fluids are topped off, you can go out and feel the torque that you never knew your C5 had!

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