I have a '99 auto. I haven't been able to drive it for the last 2 1/2 months because of the weather. I backed it out of the garage the other day to start it, and noticed a leak of red fluid from the rear end on the garage floor. It looks like it is coming form the middle of the car. What could it be, the rear axle leaking or the tranny? If it is the tranny is it the pan gasket, or is it coming from the fill/drain plug?

 

All I can tell you for sure is that its transmission fluid. You'll have to slide underneath and take a looky-loo to find out where its coming from. Pan gasket, cooler lines, fill plug, rear seal at differential are some possibilities...

 

If its red its transmission fluid. The diff fluid is brown

If its laid idle for 3 months maybe the seal just dried out. A few heat cycles may fix it???

Here's the diagnostic procedure from the book

Fluid Leak Diagnosis
General Method

1. Verify that the leak is transmission fluid.
2. Thoroughly clean the suspected leak area.
3. Operate the vehicle for 24 km (15 mi), or until normal operating temperatures are reached.
4. Park the vehicle over clean paper or cardboard.
5. Shut OFF the engine.
6. Look for fluid spots on the paper.
7. Make the necessary repairs.

Powder Method

1. Thoroughly clean the suspected leak area with solvent.
2. Apply an aerosol type powder, such as foot powder, to the suspected leak area.
3. Operate the vehicle for 24 km (15 mi), or until normal operating temperatures are reached.
4. Shut OFF the engine.
5. Inspect the suspected leak area.
6. Trace the leak path through the powder in order to find the source of the leak.
7. Make the necessary repairs.

Dye and Black Light Method

A fluid dye and black light kit is available from various tool manufacturers.

1. Follow the manufacturer's instructions in order to determine the amount of dye to use.
2. Detect the leak with the black light.
3. Make the necessary repairs.

Find the Cause of the Leak

Pinpoint the leak and trace the leak back to the source. You must determine the cause of the leak in order to repair the leak properly. For example, if you replace a gasket, but the sealing flange is bent, the new gasket will not repair the leak. You must also repair the bent flange. Before you attempt to repair a leak, check for the following conditions, and make repairs as necessary:

* Gaskets Fluid level/pressure is too high
* Plugged vent or drain-back holes
* Improperly tightened fasteners
* Dirty or damaged threads
* Warped flanges or sealing surface
* Scratches, burrs, or other damage to the sealing surface
* Damaged or worn gasket
* Cracking or porosity of the component
* Improper sealant used, where applicable
* Incorrect gasket

* Seals Fluid level/pressure is too high
* Plugged vent or drain-back holes
* Damaged seal bore
* Damaged or worn seal
* Improper installation
* Cracks in component
* Manual or output shaft surface is scratched, nicked, or damaged
* Loose or worn bearing causing excess seal wear

Possible Points of Fluid Leaks

* Transmission Oil Pan Incorrectly tightened oil pan bolts
* Improperly installed or damaged oil pan gasket
* Damaged oil pan or mounting face
* Incorrect oil pan gasket

* Case Leak Damaged or missing fill tube seal
* Mislocated fill tube bracket
* Damaged vehicle speed sensor seal
* Damaged manual shaft seal
* Loose or damaged oil cooler connector fittings
* Worn or damaged propeller shaft oil seal
* Loose line pressure pipe plug
* Porous casting

* Leak at the Torque Converter End Converter leak in the weld area
* Converter seal lip cut. Check the converter hub for damage
* Converter seal bushing moved forward and damaged
* Converter seal garter spring missing from the seal
* Porous casting of the transmission case or the oil pump

* Leak at the Vent Pipe or the Fluid Fill Tube Overfilled system
* Water or coolant in the fluid. The fluid will appear milky
* Transmission case porous
* Incorrect fluid level indicator
* Plugged vent
* Drain-back holes plugged
* Mispositioned oil pump to case gasket, if equipped