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Because a leaky butt really drops you down on the cool meter.
Okay, let me quit it! Here's the scenario. You pull your baby out of the garage and notice that something has leaked out of the rear of the car. The odd thing is that the leak is not dead center of the rear, itís more to the left (or right if you're really having a bad day). What you are probably experiencing is the failure of the output shaft seal (normally the driver's side in the C5). I say probably because doing a little "wide open throttle" (or WOT as it is known here) can also cause you to wake up to a wet spot. In the case of WOT, this is a normal occurrence, as the differential has a exhaust outlet in which differential fluid will leak out of in order to relieve case pressure.
If you're more of a cruiser, then you probably just have a leaking output shaft seal. You have 2 ways of identifying the source of the leak.
The professional way if the leaking source is not obvious is to add some Black Light Oil Dye to the differential and then check the area with a black light after some normal driving. The fluid will glow either a bright yellow or bright green. This allows you to identify the leak without doing unnecessary and costly repairs. If you want the GM dye, one place you can order it from the GM Special Parts website
(this site only works with Internet Explorer). The part number is J-28431, which can be used in engine, transmission, and rear axle oils, as well as power steering fluids. (Note: part number J-29545 is only for use in engine coolants)
The second way if the leak is obvious enough, is to do a visual inspection. Look at the picture below.
You can clearly see how the leak is confined to about a 180 degree area of the seal. The differential side covers have been known to leak due to a design flaw although in this situation, this is not the case (just be aware of that possibility). We know that this is not the case here as oil does not leak in a upward
Now that we have identified the leaking source, let's get that baby fixed!
The first thing you should do is get some replacement differential fluid. Now would be a good time to replace that old, stinky stuff. The service manual calls for SAE 75W-90 Synthetic Gear Lubricant or equivalent. The manual also states to add 4 ounces of Limited-Slip Differential Lubricant Additive. Today, you can buy this gear oil already mixed. Mobile one and Red Line are two brands that I found with the limited-slip additive already built in.
NOTE! After replacing the differential gear oil, do not go WOT for a minimum of 300 miles. Doing so may result in scoring of the ring and pinion gears leading to differential noise!!!
Some of the tools that were not in my "shade tree" collection that you may have to get, or that will make the job easier are:
Torque Wrenches - the nuts and bolts in this repair have specific torque settings. Since your life is depending on the tightness of these nuts and bolts, it would be smart to spend a few dollars and make sure that you torque them to the GM specifications. I have attached a PDF document to the bottom of this post that contain those settings.
A 21mm wrench for the lower arm ball joint nut, a short set of Hex sockets (notice the sizes in the picture - that 10mm is for the differential drain and fill plugs), and a 33mm deep-socket for the axle bolt. If you don't screw up your parking brake assembly and do not have to separate the stabilizer from the upper and lower control arms, then you will not need the 21mm wrench.
Ask me how I know...
A drift punch or something equivalent.
Last of all, you'll need the replacement seal.
Notice the grease that is inside the interior lining of the seal. Do not wipe that off!
Here's something you should consider. The differential has 2 output shaft seals. The right seal is not known for leaking but you never know. I bought 2 seals for a couple of reasons. One, because the differential has two of these seals. Two, the seals were dirt cheap; they were something like $12 each. Lastly, knowing how much of a shade tree mechanic I am, I wanted to have an ace in the hole just in case I screwed up one of those seals. Well guess what happened. I screwed up one of the seals when installing it. This is something you may want to consider if your mechanic skills are anything like mine.
My method of doing this repair differs from Cajun Dude's in that I actually removed the drive shaft. The reason I did so was because of the limited amount of space that I had to work in while trying to seat the seal. Look at this picture:
Even after I removed the drive shaft, it was still somewhat awkward to get up in there and figure out how to swing my hammer to seat the seal. One thing that Cajun Dude said that was right on target was tap, tap, taparoo... :yesnod:
As some of you may know, I bought the J-46405 tool that the TSB concerning this repair
calls for. I have mixed emotions about its effectiveness when doing the repair the way I did. If I had taken the entire differential out of the car, the tool would have been a must have for me. However, using it in this situation was helpful, but what probably would have worked best was if this tool had a 3-foot shaft. That way, I could have stood back from the wheel well and whacked away on that seal. I did use it to do the install so I guess it ended up paying for itself.
Okay, let's get started! I'm going to keep this as close to the manual as possible. Note: One thing that I did when removing nuts and bolts was to put them back where they originally went so that they would not get lost, and so that I would know where they went when it was time to reassemble everything. Good rule to follow for a shade tree mechanic!
Shift the transmission into PARK (A/T) or NEUTRAL (M/T).
Work the parking brake a whole bunch of times and then apply it. This will loosen the shoes up from the rotors. If you don't do this, your rotors may be a PITA to get off. They may also rip the parking brake shoes!.
Raise and suitably support the vehicle.
Remove the tire and wheel assembly.
Insert a drift or punch into the brake rotor cooling fins and against the brake caliper to prevent the wheel hub and bearing from turning.
Loosen (do not remove
) the spindle nut retaining the rear wheel drive shaft to the hub.
Remove the drift or punch.
Release the parking brake.
Using a 15mm socket, remove the caliper bolts. You'll need to hold the caliper pin still using a 5/8" wrench. Be careful not to stress the brake line going to the caliper.
At this point, use your jack to support the lower control arm.
Remove the 2 bolts at the top of the shock absorber.
Remove the 2 bolts that hold the upper control arm to the frame.
Separate the outer tie rod end from the knuckle and reposition the tie rod toward the rear of the vehicle.
Here's the way I removed mine before I got smart enough to go buy some Hex sockets:
Disconnect the wheel speed sensor electrical connector.