How to Install a 4thgen Rear into your 3rdgen

Before you consider doing the swap, please read this! There are many pros to doing this swap. A couple of them are as follows: if the rear is from a Z28 it will have posi, disc brakes, and the gear will either be a 3.23 or 3.42! Its possible you might find the gear to be a 2.73, so check first. The cons to this, depending on how you see things, are as follows: your stock rims will stick out an extra 2” on each side do to the 4thgen rear being wider than your stock one and how confident you feel your car working ability is. It does not look bad, IMHO. It will give the car a mean stance to it. So actually there are no drawbacks!

AS ALWAYS NEVER work under a car that is NOT properly supported via a lift or jackstands!

Doing so may result in death or dismemberment or both. I am NOT responsible for any errors on your part. This is merely one mans experience!

Now on to the good stuff!

This is a very straight forward installation or a direct bolt in, which ever way you want to look at it. So with all that said, let’s get started.

When picking out the rear end, make sure it has the following things. Make sure it has the E-brake cables from the calipers, calipers, brake lines that are attached to the casing, the brake hoses on the calipers and one that goes from the casing toward the front of the car. Depending one what you want to do, you might want to get the E-brake cable brackets from the 4thgen. Its hard to explain what these things are. If you get under your car and look above the driveshaft, there will be some brackets with the cables going through them. I didnt do this but, recommended if you want this done right.

You will also need to get an adjustable proportioning valve, a double flaring tool, and a tubing cutter. You can find out how to do this by reading the article entitled “Installing a Wilwood Proportioning Valve” in Tech Central.

What you will need:

4thgen rear end (without it, whats the point?)

Good assortment of tools

4 Jack stands and a floor jack

Adjustable prop valve and proper installation tools for it

Brake fluid for bleeding the brakes, gear oil, and posi additive

You will need an extra set of hands or two. These rear ends are heavier than the stock one and a little awkward. Trust me on this! Get some help.

Before you begin the installation these are things that should be considered and are recommended. Drain and refill the differential with new oil and posi additive. Check axle seals, brake pads, and rotors. Replace them if they are under specs.

Depending on where you are doing this at, you might need other tools. Such as a breaker bar and a torque wrench. I did this at my shop, so I had access to an air gun and a lift. Ready? Good!

Installation Process

Start by blocking the front wheels with something such as blocks of wood or concrete; so the car wont go forward while you’re under there.

Jack up the rear of the car using the rear end and put 2 jack stands on the frame to support the car, use one of the lowest settings on the stands. Remove the rear wheels, undo the brake hose that connects to the line from the front of the car; brake fluid will drain so dont worry.

Remove the driveshaft by taking the bolts off the rear yolk, pushing forward, pull down, and then back so it will come out of the tranny, and lay it aside so its out of the way.

Loosen, but dont take out, the torque arm bolts, LCA bolts, bolts for the shocks, panhard rod bolt, and take the springs out.

Undo the stock E-brake cables from the harness above where the driveshaft was. Just pull the single cable back and the rear cable forward then unhook them. There are brackets on both sides that hold the cables so they don’t rub the driveshaft. Just bend/break the stock cables so they will come out of the brackets; you should see how they come out.

Now that everything is unhooked and/or loosened, jack up the rear end a little, and support it with jack stands on a medium/high setting.

Remove all the bolts/shocks from the rear so it is resting on the stands.

Let the torque arm rest on the ground and front of the rear will roll forward on the stands now, so watch out.

**Now comes the PITA part!**

You and your buddy will have to pick up the rear and get it out from under the car. You will have to get ahold of the rear somehow and kick the stands out of the way so you can lower and take the rear away. Then get the new rear and and set by the rear of the car. The goal here is to set the new rear on the jack and raise it up so that you can put stands under it so you can bolt it back up. You’ll have to use some inginutity here. It might take 3 people; one to use the jack and set the stands up, and 2 to keep the rear steady so it doesnt tip over. Be careful and take your time and you should be ok.

Once you get the rear situated right; begin by placing all the suspension parts on the rear, starting the bolts, and put the springs in. It doesnt matter where you start, just hook everything up.

Once that has been done, you can jack the rear back up and remove the stands from the rear and put them back on the frame of the car. Now for the brake cables……pry that slotted thing on the front part of the E-brake open so you can get the 4thgen cables in it. They new ones are bigger than the old ones. You should see what you have to do once you get to this point.

Now you have a couple choices here. Remember those brackets I told you about? Well you can either drill holes and mount the brackets in there necassary places to put the ebrake cables or you can do what I did. Simply hook up the cables as described above; there are two things on the rear that hold the brake cables from just flopping around. I just bent those things until the brake cables are tight and do not come close to the driveshaft. Simply put, keep bending those things until the cables are tight! If you look behind where you hooked the cables up at, there should be 2 little things in the underbody that you can hang something one. Push/pound/do what ever you have to do to get those cables in the slots. If you alter the rubber surrounding of the cable, its not biggy, since it wont rub the cables. Mounting the brackets is the right way to do it but, since I didnt have them I did it this way and it is working fine!

Once you have the cables fixed up, tighten all bolts to their required torque specs.

You are now done with the rear install! Yahoo!!!

Now you have another choice to make. You can just bleed the brakes from here using the stock stuff or install the prop valve. I didnt have the stuff to put the prop vavle on yet, so I used the stock stuff for about a week. However, this is not recommended since the rear brakes wont work very well if at all!

**If you have access to a lift, everything is the same except for moving rear ends. Using a lift, lower the car and sit the rear on stands, unbolt everything, raise the car up. The rear is now much easier to get to. Make the rear swap from old to new, lower the car back down, and put the bolts back in. Much easier but can be done either way.**

Now take her for a test drive and see if it was worth it, I know you wont be dissappointed. Happy driving!

If you have any questions about anything, feel free to email me.