Rear Axle Leak

The only things I can think of at the moment, is either brake fluid or rear end fluid.

Leaking oil at the rear wheels can be one of two things, Easy fix is brake fluid, this would be the rear brake wheel cylinder leaking. Check your brake fluid tank under the hood for low fluid. If that is ok. Your leak may be your rear axle shaft seal. You need to remove the tire/wheel ether way. Jack up the car to pull the wheel, take your lugs loose while the tire is still on the ground, it is easy to take them loose this way. Take the EM: brake off, and jack up this side of the car. Your car could have disk or drums as both are offered on some Dodges. Once the tire is off you will see if you have disk or drums brakes. If drums you will need to pull the drum off at access the brake cylinder to see if that is leaking or not. If drums you have to back off the brake shoes by the adjusting wheel thru a small access window in the back plate. If you have disk brakes the caliper is right there and will be easy to see if it is leaking. If you have determined it is the rear axle seal leaking, this may be best done by a shop, due to needing a few special tools to remove the axle and then reinstall a seal. You will need a slide hammer. If drum brakes you will have to remove the brake backing plate, this means shoes and all hardware, please take pictures and get as good focus as you can to see how everything goes back together. Once down to the axle mounting, remove the 4 bolts and attach the slide hammer and pop out the axle, catch any fluid that will leak out, once out you can determine which type of seal set up you have as some have press fit collars that may have to be cut off. . Hope this helps FixYa up.

Leaking oil at the rear wheels can be one of two things, Easy fix is brake fluid, this would be the rear brake wheel cylinder leaking. Check your brake fluid tank under the hood for low fluid. If that is ok. Your leak may be your rear axle shaft seal. You need to remove the tire/wheel ether way. Jack up the car to pull the wheel, take your lugs loose while the tire is still on the ground, it is easy to take them loose this way. Take the EM: brake off, and jack up this side of the car. Your car could have disk or drums as both are offered on the 2003 Town car. Once the tire is off you will see if you have disk or drums brakes. If drums you will need to pull the drum off at access the brake cylinder to see if that is leaking or not. If drums you have to back off the brake shoes by the adjusting wheel thru a small access window in the back plate. If you have disk brakes the caliper is right there and will be easy to see if it is leaking. If you have determined it is the rear axle seal leaking, this may be best done by a shop, due to needing a few special tools to remove the axle and then reinstall a seal. You will need a slide hammer. If drum brakes you will have to remove the brake backing plate, this means shoes and all hardware, please take pictures and get as good focus as you can to see how everything goes back together. Once down to the axle mounting, remove the 4 bolts and attach the slide hammer and pop out the axle, catch any fluid that will leak out. Hope this helps FixYa up.

Where is the leak? Toward the middle or at the right or left sides near the rear wheels?

as long as it doesn't get on the brakes you're ok

If what you see leaking is very oily and does not evaporate, likely it is an axle seal. If there are no leaks in the brake system, that's the only thing back there that can leak. If the axle bearing is going away, it can damage the seal so make sure you look for small shiny metal flakes behind the seal when you replace it or you will be doing the job again very soon. Can't remember...that IS rear wheel drive right?

JACK up the truck and block other rear wheel both back and take hand brake off ,,remove rear wheel/brake drum/handbrake cable from rear brake/remove metal brake hose/remove rearbacking plate with all parts fitted to it ie brakeshous 4or5 bolts holding the rear axle in to housing and when all parts off then put on a IMPACK PULLER and remove complete backing plate with axle assy and take to the engineering shop to get it pressed off and a new bearing and seal assy pressed back on .
Then refit in reverse of removal and bleed the brakes and top up the rear axle of oil (EP90) apply h/brake take out blocks and lower jack and test drive .. BUT MAKE SURE THE BRAKES ARE 100%

You should be ok replacing the outer seal but check for bearing play or fautly outer wheel bearing before you disassemble. If to much lateral movement in axle shaft it will take out your new seal rather quickley.

Axle Shaft Removal

1. Raise and support the vehicle. For additional information, refer to Section 100-02 .

1. Remove the wheel and tire assembly. For additional information, refer to Section 204-04 .

1. Remove the differential housing cover (4033).
   1. Loosen the bolts and drain the lubricant from the rear axle housing (4010).
   1. Remove the bolts.
   1. Remove the differential housing cover.

Remove the rear brake disc (2C026). For additional information, refer to Section 206-04 .

1. CAUTION: Turning the differential case (4204) or an axle shaft (4234) with the differential pinion shaft (4211) removed will cause the differential pinion gears (4215) to fall out of the assembly and damage the components.
   Remove the differential pinion shaft.
   1. Remove the differential pinion shaft lock bolt.
   1. Remove the differential pinion shaft.
2. CAUTION: Do not damage the rubber O-ring in the U-washer groove.
3. Remove the U-washer (4N237).
4. Push the axle shaft inboard.
5. Remove the U-washer.

Reinstall the differential pinion shaft.

1. Install the differential pinion shaft.
2. Install the differential pinion shaft lock bolt finger-tight.
3. CAUTION: Do not damage the wheel bearing oil seal (1177).
   Remove the axle shaft.

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Seal Removal

1. Remove the axle shaft (4334). For additional information, refer to Axle Shaft in this section.

1. CAUTION: Never remove the wheel bearing oil seal (1177) by itself. Always remove the rear wheel bearing (1225) and the inner wheel bearing oil seal at the same time.
   NOTE: If the wheel bearing oil seal is leaking, the axle housing vent may be plugged with foreign material.
   Using the special tools, remove the rear wheel bearing and wheel bearing oil seal together.

Installation

1. Lubricate the new rear wheel bearing.
   • For 4.0L SOHC and 4.0L EI with limited slip rear axles and 5.0L vehicles, use SAE 75W-140 High Performance Rear Axle Lubricant F1TZ-19580-B or equivalent meeting Ford specification WSL-M2C192-A.
   • For 4.0L SOHC and 4.0L EI with conventional rear axles, use SAE 80W-90 Premium Rear Axle Lubricant XY-80W90-QL or equivalent meeting Ford specification WSP-M2C197-A.

1. Using the special tools, install the rear wheel bearing.

1. Lubricate the lip of the new wheel bearing oil seal.
   • Use Premium Long-Life Grease XG-1-C or equivalent meeting Ford specification ESA-M1C75-B.

1. Using the special tools, install the wheel bearing oil seal.

1. Install the axle shaft. For additional information, refer to Axle Shaft in this section.

You are correct, it's not brake fluid. Check the level in your rear axle, it sounds like you have bad seals in the axles allowing the rear differential gear oil to leak inside the brake drums.
This is a heavy weight oil, 80 or 90 weight. This leakage will ruin your brake pads, and if enough leaks out, your rear differential will blow. The seals aren't expensive, but it's a lot of labor to pull everything apart to get at the seals, plus new rear brakes. My Ford ( and I'm sure your GMC) require removal of the rear axles to change the seals. Good Luck! countrycurt0