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How to Install or Replace Transmission Oil Pan on Jeep A904 A999 Auto Transmission

Updated on July 7, 2014

This is for the following makes and models.

  • Jeep CJ (1980-1986) w/ A904 or A999 Automatic Transmission.
  • Jeep Wrangler (YJ) (1987-1991) w/ A999 Automatic Transmission.
  • Jeep Cherokee (XJ) (1984-1986) w/ A904 or A999 Automatic Transmission.
  • Jeep SJ & J-10 (1984-1990) w/ A999 Automatic Transmission.

Change the dirty pan, gasket, oil, or filter out on your Jeep auto transmission...

If your pan is dirty then you may not get very far. Chances are most people don't even worry about the transmission oil pan. If they can't see it or feel that is is broken then it probably isn't.

But since the transmission is the second vital piece in your drive train you should really take care of it. No engine or no tranny then NO GO! So if you need to change the following out then read this guide.

  • Changing the stock transmission oil pan.
  • Replacing the stock transmission oil pan with a deep style pan.
  • Replacing the gasket due to a leaking pan.
  • Replacing the filter in the transmission pan.
  • Changing just the fluid out.

At the very least you should drain or power flush the fluid out at least every 50K miles on your Jeep. Even more if you are a heavy off-roader, tow a lot, or are just plain hard on the transmission. The filter should also be changed at the same time.

What a pan, filter, gasket, and drain plug looks like.


Some things you will need before you get started...

These are some things you should have on hand before you get started.

  1. Jack and Jack Stands
  2. Oil Pan to capture used oil.
  3. Hand tools.
  4. Rags or Towels.
  5. ATF fluid at least 4 quarts and more if you have a deep pan.

You also want to make sure that before you do any work that you have all the parts needed for the install and they are in good condition, with no tears, cracks, or damage.

Jeep Wrangler YJ


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So now on to the install...

So grab all the stuff you have for the install and make sure it is handy as you start the install. Read the instructions thoroughly so you are familiar with the entire process.

  1. This job requires that the car is completely cool as working around hot parts can cause burns.
  2. If you cannot get under the vehicle easily and safely you may need to put it on jack stands. You will not have to remove the wheels or anything.
  3. Hopefully your pan will have a drain plug and you can simply drain all the oil into the drain pan. If it does then do this now. Then remove pan as outlined below.
  4. If you do not have a drain plug then you have to loosen all of the bolts at least 3-4 good turns. The pan should release from the bottom of the transmission. If not then take a flat object like a knife and work around the pan until it unseats. Make sure you have something below to capture oil as this can be messy. Once that is done, remove all of the bolts completely EXCEPT for 2 on the same side.
  5. This should allow the pan to tip down to one side and drain the oil. Make sure you are holding it so it does not put extra strain on the bolts. Once you drain as much oil as you can then remove the last two bolts and the pan.
  6. Drain the excess oil still in the pan into the oil drain pan and wipe out and clean the pan if you are going to reuse it.
  7. Next take a rag and clean the mating surface of the pan to the transmission removing all of the old gasket, sealant, and other gunk. If there are parts you can't remove with a rag use a razor but be careful you do not score the metal.
  8. You should be able to see the filter attached to the transmission with three screws.Remove those screws and the filter and toss the filter away. Take the new filter and if you have new washers and screws put those through the filter the same way you removed it and if you have a new pickup sensor attach that to the screws (O Ring side up) and lightly tighten the NEW filter to the transmission. Torque the screws to the proper specifications and DO NOT over tighten (around 35 in. lbs). Look at the old filter for re-assembly comparisons.
  9. Now re-attach the new GASKET onto either a new pan or the old pan (make sure all the mating surfaces are clean) aligning the holes that the bolts go through and attach the pan to the transmission and put in each bolt through the pan and hand tighten all of them. Then equally torque all the bolts making sure that the gasket seats properly and does not tear.
  10. Reinstall the drain plug if applicable, remove the jack stands and lower the Jeep onto the ground.

GchanMako Starter Jeep Cherokee XJ
GchanMako Starter Jeep Cherokee XJ | Source

Filler Up!

Now once the vehicle is even and on the ground we need to fill the transmission up with ATF fluid before we do anything else. DO NOT run the motor without fluid in the transmission.

  1. Put ATF fluid through a funnel into the dipstick tube that measure the transmission fluid. Refer to your owners manual if you are unsure. Fill it with enough fluid that it registers on the dipstick.
  2. Let it sit for about 10-15 minutes so it can drain down the tube. Then recheck the dipstick for the fluid level and add fluid as needed.
  3. Now you can START the motor and place the vehicle in neutral. Do this until the vehicle has warmed up to its normal temperature.
  4. Go ahead and put the transmission through all the gears 3-4 times stopping for 20 seconds in each gear.and then place the transmission in neutral once again.
  5. Making sure that chocks are installed behind the wheels, check the fluid again and add as needed to get it to the factory approved level.
  6. Make sure there are no leaks under the vehicle at the pan or drain plug. If there is, turn the vehicle off and recheck your installation.
  7. Test drive the vehicle to make sure everything is working properly. Remember to check all bolts and re-tighten after 50-100 miles.

So now you are done and you should have a better and smoother working transmission. And you are ready to take on the open road, off-road trail, or towing those toys again!


Jeeps are FUN FUN FUN!

So you have upgraded or maintained your Jeep automatic transmission. So you should be running smooth and be able to tackle those trails again.

Jeeps are fun vehicles to own. And in the Jeep spirit you should know a few things about why they are fun and what to do when you encounter others with your same Jeep passion.


If you see another Jeep that is fixed up or has some upgrades on it, you should wave. Now there is a customary Jeep wave but for now you should always just acknowledge another Jeeper with a nice wave. I just raise my hand signalling them and saying HEY I see you.


Everyone should take the Jeep out on the trail at least once. But don't worry there are a lot of trails you can take that are very easy and wont damage your Jeep.As you get bolder and more experienced you can take nor more difficult trails. But remember the golden rule, NEVER take a Jeep out that you are not willing to wreck.

So there are a couple of things to remember, but most of all if you can take the top off, then do so, but above all else...HAVE FUN!


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