Jeep Wrangler JK: How to Change Manual Transmission Fluid

Changing the transmission fluid on your Jeep JK is a quick and simple procedure you can do at home. This article explains how to do so.By Neftali Medina – December 2, 2015
Contributors: GPT Adventure Channel

This article applies to the Jeep Wrangler JK (2007-Present).

Are you experiencing any sluggish or hard shifting? It sounds like it’s about time to check and change your transmission fluid. Just like oil does for an engine, transmission fluid is responsible for keeping the inside of the gearbox lubricated. Overtime, the fluid’s consistency will begin to change, becoming too dirty and lacking additives to provide enough lubrication on the transmission’s internals. To avoid this issue, Jeep recommends the fluid be changed every 30,000 miles.

Materials Needed

  • 3 quarts of Mopar MS-9224 manual transmission fluid
  • 17mm wrench
  • Oil catch pan
  • Bottle pump
  • Cut H17 Allen key bit
  • Bench vise
  • Die grinder
  • Sawzall with steel blade

Step 1 – Make custom Allen key bit

The drain plug for your transmission is actually located an inch above the exhaust pipes. This makes loosening it a difficult task, unless you have a special tool for the job. The following instructions explain how to quickly make such a tool.

  • Take a 17mm Allen key bit and place it securely into a vice.
  • Measure approximately half an inch of the bit and cut the rest off using a sawzall.
  • Grind the edges of the bit (optional).

Figure 1. Cut the 17mm Allen key bit.

Step 2 – Place a drain pan under the transmission

Old transmission fluid is a terrible mess to clean up, so let’s make it a point to avoid any unnecessary spill-ups. Place a drain pain directly under the transmission and place a rag on top of the exhaust pipe.

Figure 2. Cover the top of the exhaust pipe.

Step 3 – Drain the transmission fluid

Loosen both the fill and drain bolts. The fill bolt is found on the passenger’s side of the transmission, and requires a 17mm Allen key bit to be removed. For the drain bolt, take your newly created 1/2 inch Allen key bit, insert it into the socket and use a 17mm wrench to loosen it. Once off, let the fluid drain into the oil pan.

Figure 3. Drain the transmission fluid.

Step 4 – Refill the transmission fluid

  • Install and tighten the drain bolt.
  • Take the bottle pump and place the line into the fill port.
  • Pump two quarts of transmission fluid into the casing.
  • Install and tighten the fill bolt.

Figure 4. Pump new fluid into the transmission.

Featured Video: How to Change Manual Transmission Fluid in Jeep JK

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Jeep Wrangler JK: Automatic Transmission Diagnostic Guide

There are too many issues that can cause your automatic transmission to fail. Fortunately, finding out the problem is not as hard as you may think. Here is how you can diagnose your automatic transmission.By Neftali Medina – December 1, 2015
Contributors: JK-Forum, Jeep Cherokee Club, Wayalife

This article applies to the Jeep Wrangler JK (2007-Present).

It’s a pretty rough feeling when you want to take the Jeep for a ride on the trail, only to find something wrong with its transmission. Like all Jeeps, it’s expected to be able to climb and tow its own body weight. Some common issues that occur include the transmission overheating, miss-shifting, or running in limp-mode. The good news is most of these problems are repairable under warranty, so the most difficult part requires diagnosing them, as explained below.

Material Needed

  • Your key

Step 1 – Check gear shifts

The gears may be sticking.

If there is a problem accelerating, pay attention to how it shifts. The gears may be getting stuck in-between shifts, causing the Jeep to run sluggish. This problem most commonly occurs on later models, and requires its computer to be re-flashed in order to be fixed. The following instructions work to check for any DTC codes on your Jeep JK.

  • Insert and turn your key into the “on” position, but do not crank the engine over.
  • Push the key into the ignition, then twist it back and fourth from “on” to “off” three times.
  • If done correctly, the dashboard will light up and the DTCs will be shown on the odometer.

The code you should keep an eye out for is DTC P0730. Due to the number of issues and complaints Jeep received, they released an update for an ECU flash in October of 2014 in order to combat this issue.

Figure 1. Jeep DTC.

Pro Tip

If the vehicle is under warranty, the dealership should still cover the repair costs. This is important because anything with transmission repair can easily cost into the thousands.

Step 2 – Check for limp-mode

The transmission may be stuck in limp-mode.

Limp-mode is set to go off when the transmission registers itself as being over-worked. Unfortunately, this causes it to not exceed 2nd gear, resulting in limited acceleration. The quick fix to this problem requires resetting the computer. However, this does not find out why the transmission went into limp-mode. Use the procedure listed above to find the problem and reset the computer.

Figure 2. Transmission error message.

Step 3 – Check the dashboard

The transmission may be running hot.

This problem has most commonly occurred on models built between 2007 to 2010. It occurs when the automatic transmission is placed under load, whether it be from towing or from climbing, resulting in the “Hot Oil” light turning on from inside the dashboard. Once the light turns on, the transmission has already been damaged and its life expectancy has shortened, so many JK owners have attempted to have Jeep fix the problem to no avail. Installing an aftermarket cooler does prevent the transmission from overheating, but may cause Jeep to void the warranty. However, call the Jeep service managers and voice your concern. They have turned over and installed the Mopar cooler on several vehicles, under warranty.

Figure 3. Transmission cooler.

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Jeep Wrangler JK: How to Install Transmission Cooler

An auxiliary trans fluid cooler helps keep the temps at down. Here’s how to install one in your Jeep Wrangler.By Mark Garrett – November 24, 2015

This article applies to the Jeep Wrangler JK (2007-present).

Your engine needs to be cooled to last and so does your automatic transmission. The factory runs the trans fluid through the radiator to cool it, but that does not always get the job done. You can perform a modification to your Jeep that will keep the transmission cool and make it last. An auxiliary transmission cooler is inexpensive and easy to install yourself. It will be one of the cheapest insurance policies you can get for your Jeep.

Materials Needed

  • Automatic transmission cooler kit
  • Two 3/8″ to 3/8″ barbed hose connectors
  • Towels
  • Vinyl gloves
  • 1/4″ drive ratchet and extensions
  • 5/16″ socket
  • Flat head screwdrivers
  • Phillips screwdriver
  • Funnel for transmission fluid
  • 1 quart of appropriate transmission fluid
  • Catch pan

If you have heard about a TSB (Technical Service Bulletin) about the HOT light for the transmission coming on, don’t get too excited. The TSB calls for installation of a factory designed trans cooler, but it is strictly for Wranglers sold internationally.

Step 1 – Remove grille

Remove the six plastic retaining screw/clips from the top of the grille. Figure 1 shows a plastic grille screw used prior to 2008. Screw it out as you pry the inside out. Then pull the clip out.

Figure 1. Grille screw clip.

Figure 2 shows the clip used in 2008s and newer. Slip a flat screwdriver in the tangs to pop the center up and then pry out.

Figure 2. Grille push clip.

There are a number of plastic clips that hold the grille on at the bottom. To unsnap them just grab the grille near the bottom and pull forward. They will unsnap and then the grille can be pulled out.

Figure 4. Bottom grille fasteners.

Before you remove the grille, remove the turn signal bulbs by holding the lock in and then twisting them counter-clockwise. Set the grille aside.

Figure 5. Turn signal bulb connector.

Pro Tip

You can buy a plastic fastener removal tool at your auto supply store.

Step 2 – Lay out trans cooler

There are a vast number of choices for trans coolers. The stacked plate design is what manufacturers use. Since B&M is a well-known brand, it’s the example we will use.

Figure 6. Cooler parts.

Some are more specific to your application with the factory designed version being the best fit. It is two to four times as much money but should fit perfectly.

Figure 7. Factory trans cooler kit.

Be sure all of the parts are there before you start.

Pro Tip

Invest in quality parts so you will not have issues later.

Step 3 – Attach mounts to cooler

Take the extra few minutes to mount the cooler correctly. Do it right the first time and you won’t have to do it over.

The metal straps that bolt to the cooler to mount it to your Jeep are the way to go. By attaching one to each corner, the cooler will mount solidly. You can try to use existing holes in the Jeep but may need to drill a couple in the bottom grille brace. Allow an inch or so between the cooler and the radiator. Mock everything up before bolting anything on.

Figure 8. Cooler with brackets bolted on.

Figure 9. Cooler mounted on Jeep.

When you are satisfied, tighten everything down.

Pro Tip

Be sure nothing rubs on the radiator, or any hoses rub sharp edges.

Step 4 – Attach cooler hoses

Attach the ends of the supplied hose to the cooler with a hose clamp. Tighten with a 5/16″ socket and ratchet. Run the hose under the bottom of the radiator or between the radiator and the grille support on the driver’s side.

Figure 10. Cooler hoses run to bottom.

Figure 11. Cooler hoses run to side.

Find the rubber hose part of the top cooler line as shown in Figure 12 and cut it. Some trans fluid will leak.

Figure 12. Trans cooler line (dark one) hose to cut.

Secure the hoses you ran from the cooler with wire ties so they are secure and away from harm. Cut the hose from the cooler so they have enough slack in them to hook up to the hose that was just cut per Figure 13. Attach the hose from the bottom of the cooler to the tube coming from the front of the Jeep (Number 1 in Figure 13). Attach the other hose from the cooler to the tube coming from the transmission (2 in Figure 13). Install clamps securely.

Figure 13. Hoses from cooler spliced into trans lines.

Pro Tip

Secure the rubber hoses well so they do not come loose or rub.

Step 5 – Check for leaks

Start your Jeep and let it get warm. Check for leaks at any point you spliced hose in. If there is a leak, snug the clamp up until it stops.

Step 6 – Add transmission fluid

Since some fluid was lost and the new cooler will need some, top off the transmission fluid.

Pro Tip

Check for leaks the following week in case anything pops up.

Step 7 – Replace grille

Replace the grille in the reverse that you took it off. Be sure to plug the turn signals back in.

Figure 14. Trans cooler installed.

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Jeep Wrangler JK: How to Replace Rear Axle Seals

Replacing the rear axle seal on your Jeep Wrangler is not an easy job, but hopefully this guide can make it a little easier on you.By Bassem Girgis – November 24, 2015

This article applies to the Jeep Wrangler JK (2007-Present).

A rear axle seal holds the axle fluid inside the rear axle of your Jeep Wrangler. Overtime, the seal could get worn and stop sealing properly. This job can be done at home; however, you must expect a little bit of work, as you have to remove many components to get to it. The symptom of a bad seal is oil leaks, so look around your axle and under your Jeep for any signs of fluid. You can also place a sheet of paper under the axle over night and check it in the morning to see if there was any leakage. Read on to learn how you can replace the rear axle seal on your Jeep Wrangler.

Figure 1. Axle seal.

Materials Needed

  • 5/16 wrench
  • 18mm socket
  • Cut-off wheel

Step 1 – Raise car

Loosen the lug nuts on the wheel you’ll be working on, raise the car, then secure it with jack stands. Remove the lug nuts and remove the wheel.

Figure 2. Raise and secure Jeep’s rear.

Step 2 – Remove caliper and rotor

Remove the four retainers holding the rotor to the axle. Then, remove the caliper by removing the two bolts holding it in place; you can use your 18mm socket for those. Secure the caliper in a safe place, but do not let it hang from its brake line. Remove the rotor by pulling straight out.

Figure 3. Remove rear brake.

Step 3 – Remove anti-lock brake sensor and e-brake cable

Remove the anti-lock brake sensor by pulling its red tab and disconnecting it. Then remove the emergency brake cable from the back by simply pulling it out.

Figure 4. Remove anti-lock sensor.

Figure 5. Disconnect emergency brake cable.

Step 4 – Remove axle

The axle retainer is held in place with four nuts. Remove the four nuts using your 18mm wrench, then pull the axle straight out. To remove the seal, you will have to remove the ring and bearing. To do that, use your cut-off wheel to cut through the ring, but don’t cut too much where you hurt the axle shaft. Then cut off the bearing the same way. As soon as the bearing breaks, pry it off and be careful not to touch the axle shaft. Once the ring and bearing is removed, the seal can slide off.

Figure 6. Cut the ring carefully until it breaks apart.

Step 5 – Install seal on axle shaft

Before you install the new seal on, clean the axle shaft thoroughly. Install the retainer and axle seal the same way you removed it. Install the axle seat all the way down, then install the bearing down the axle shaft. Finally, install the ring down the axle shaft.

Figure 7. Install seal, bearing, and then ring.

Step 6 – Re-install components

Installation is the reverse of removal. Install axle back in place, install the emergency brake cable, the anti-lock sensor, and finally the brakes in place. Tighten the caliper on top of the rotor, then install the wheel, lower the car, and finally tighten the lug nuts.

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Jeep Wrangler JK: How to Replace Front Axle U-Joints

The harder you off-road in your Jeep Wrangler, the faster you will need to replace your axle joints. Read on to learn how to do it.By Bassem Girgis – November 24, 2015
Contributors: JKagermeister

This article applies to the Jeep Wrangler JK (2007-Present).

The axle U-joints tend to wear and break because they are exposed to different weather conditions, along with working hard when you’re off-roading with your Jeep Wrangler. The axle U-joint connects your axle to your wheel, and it operates as a joint to keep your Jeep flexible when driving in various road conditions, which allows you to go over harder obstacles. Replacing the U-joint is not a hard process; however, you will need to remove various components to get to it, so if you’re not comfortable taking your Jeep apart, ask for professional help. Read on to learn how to replace the axle U-joints in the Jeep Wrangler.

Figure 1. Wrangler U-joint.

Materials Needed

  • Jack and jack stands
  • Tire iron
  • Socket set (21mm, 36mm, 13mm)
  • Allen wrench
  • New U-joint

Step 1 – Raise the car

Loosen the lug nuts on the wheel you will be working on, then raise the car using your jack. Secure the car with jack stands, then remove the wheel.

Figure 2. Raise the Jeep.

Step 2 – Remove brake caliper

Using your 21mm socket, remove the two bolts on the back of the caliper holding it in place, then remove the caliper. Hang it somewhere using a wire, but do not let it hang from the brake line.

Figure 3. Remove caliper’s bolts.

Figure 4. Hang brake caliper using wire hanger.

Step 3 – Remove axle shaft

Remove the axle nut using your 36mm socket, then remove the three bolts holding the bearing in place using your 13mm socket. Remove the axle shaft by pulling it out carefully.

Figure 5. Remove axle nut.

Figure 6. Remove bearing bolts.

Figure 7. Remove axle shaft.

  • Figure 8. Remove axle components.

Step 4 – Remove U-joints

Removing the U-joints from the axle shaft requires a machine. Take it to your closest auto shop and they could remove it for you and install the new ones for a decent price. You will need a machine to push the rod holding the U-joint to the axle shaft; if you can do it yourself with another tool at home, be careful not to damage the axle shaft.

Figure 9. Remove U-joints from axle shaft.

Step 5 – Install everything back on

Installation is the reverse of removal.

After you’ve installed the U-joint on the axle shaft, carefully install the axle shaft back in place, install the bearing, and tighten the axle nut. Install the brake caliper and tighten the two bolts on the back of it. Then finally, install the wheel, hand-tighten the lug nuts, lower the Jeep, and then tighten the lug nuts in a star fashion.

Related Discussion

Jeep Wrangler JK: How to Replace Clutch Slave Cylinder

The slave cylinder is mounted on the exterior of the transmission. The rod inside the cylinder moves with the clutch pedal to engage/disengage the clutch. A faulty slave cylinder can disengage the clutch inadequately, creating transmission grinds and damage.By Weston Chadwick – November 20, 2015
Contributors: smokeman, Stooge

This article applies to the Jeep Wrangler JK (2007-Present).

The slave cylinder moves the throw out bearing against the clutch pressure plate. This removes pressure from the clutch disc, keeping engine torque from traveling through the transmission. If the clutch disc was unable to depressurize, smooth shifting would not be possible. Brake fluid from the master cylinder reservoir travels through the hydraulic lines connected to the clutch master cylinder and slave cylinder. Brake fluid is not compressible, which allows the clutch pedals movement to act as a force against the rod in the slave cylinder.

Materials Needed

  • Floor jack
  • Jack stands (x2)
  • 3/8″ ratchet
  • 10mm-14mm sockets
  • Flat head screwdriver or pick
  • Rubber gloves
  • Safety glasses
  • Slave cylinder
  • DOT 3 brake fluid

Step 1 – Raise and support the front end

Engage your parking brake. Place your floor jack below one of the front jacking points and raise it until you can fit a jack stand beside it. Lower your Jeep’s weight onto the jack stand and repeat the process for the other side.

Figure 1. Jack up on the frame and put stands under the axle.

Step 2 – Remove mounting nuts from slave cylinder

The slave cylinder is located on the driver’s side of the transmission, near the front. Two mounting nuts hold it to the transmission.

Figure 2. A diagram of the slave cylinder.

Step 3 – Remove hydraulic line from slave cylinder

Use a pick or flat head screwdriver to move the metal clip to the unlocked position. Place your pick or screwdriver between the exposed portion of the clip and hydraulic line. Pull the metal clip away from the line until it clicks into the unlock position. Slide the hydraulic line out of the metal bracket. Remove the line from the slave cylinder with a pull/twist. There is a rubber O-ring at the bottom of this line. Make sure this O-ring is not damaged prior to install, otherwise the line will leak.

Figure 3. The hydraulic line bracket and clip.

Step 4 – Install new slave cylinder

Slide the slave cylinder onto the transmission studs, and then slide the hydraulic line bracket onto the top stud. Push the hydraulic line into the slave cylinder, making sure the rubber O-ring is installed. Begin tightening the mounting nuts, and then position the hydraulic line bracket upwards to connect the the line. Slide the line into the bracket and torque the mounting nuts to 17 ft/lbs.

Step 5 – Bleed slave cylinder

You will need a second person to bleed the slave cylinder. Fill the brake master cylinder fluid reservoir to the “max” level. You will see where it says min/max on the side. Use DOT 3 brake fluid. Remove the rubber dust cap from the bleed screw (see Figure 2). Turn the bleed screw half a turn while another person has the clutch pedal depressed. Make sure you’re wearing rubber gloves and safety glasses. Brake fluid will come out of the screw at a high velocity. Once the pressure is gone (a couple seconds), close the screw and have the other person pump the clutch pedal about ten times. Repeat the bleeding process several times to achieve a responsive clutch pedal.

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Jeep Wrangler JK: How to Replace Clutch Master Cylinder

The clutch master cylinder transfers hydraulic fluid pressure from the clutch pedal to the slave cylinder on the transmission. This system must remain absent from air and leaks. If a leak is present, the clutch pedal will quickly lose pressure and the clutch cannot be disengaged.By Weston Chadwick – November 13, 2015
Contributors: Mark Doiron, Stooge

This article applies to the Jeep Wrangler JK (2007-Present).

When you depress the clutch pedal, fluid from the brake fluid reservoir is forced into the hydraulic slave cylinder line. The clutch master cylinders piston creates a low pressure area where the fluid is drawn to. Fluid is not compressible, so the clutch pedals movement is transferred through the fluid. The slave cylinders piston then expands, disengaging the clutch inside the transmission.

Materials Needed

  • Clip removal tool
  • 10mm, 8mm, and 12mm sockets
  • 1/4″ or 3/8″ ratchet
  • Flat head screwdriver
  • Rubber cap
  • Rubber gloves
  • Safety glasses
  • DOT 3 brake fluid
  • Clutch master cylinder
  • Bungee cord
  • Needle nose pliers
  • Channel locks

Figure 1. The clutch master cylinder.

Step 1 – Remove part of driver’s side fender liner

Remove the two body plugs and 10mm bolt. Pry the body plugs out using a clip removal tool. Pull the liner back to expose the bottom side of the clutch master cylinder. You can wrap a bungee cord to the outside of the fender and inside the engine bay to keep the fender liner held back.

Figure 2. The inner fender liner.

Figure 3. The view once the fender liner is removed.

Step 2 – Remove wiring harness and ground wire from body

To create more room around the clutch master cylinder, these two components will need to be moved. This will also prevent you from loosening the brake booster. Pull against the wiring harness where the black clips slide over the firewall studs.

Figure 4. The wiring harness clips and ground wire.

Step 3 – Disconnect brake fluid reservoir line

This line will leak brake fluid once it’s disconnected. Plug the line with a bolt or rubber cap. Squeeze the clamps with needle nose pliers to move them.

Figure 5. The brake fluid reservoir to clutch master cylinder line.

Step 4 – Remove slave cylinder line from master cylinder

This line is installed very tightly into the clutch master cylinder. A metal clip locks the line to the master cylinder. Use a flat head screwdriver or pick to unlock the line by pulling against the exposed portion until it moves to the unlocked position. Pull/twist the line to remove it. There is a rubber O-ring seal on the line. Try not to lose it as you’re removing the line. It’s not a common part.

Figure 6. The clutch master cylinder to slave cylinder connection.

Figure 7. The slave cylinder line removed.

Step 5 – Disconnect clutch master cylinder from clutch pedal

The clutch master cylinder rod snaps onto the pedal using a stud. Locate the connection inside the vehicle and use a pry bar, screwdriver, or your hands to separate the two components.

Figure 8. The clutch pedal to master cylinder connection.

Figure 9. The connection stud.

This step can be done from inside or outside the cabin, depending on choice of work space. The master cylinder is keyed to the firewall. It must be rotated to line up the tabs on the cylinder with the slots on the firewall. Once it becomes unlocked from the firewall, disconnect the clutch pedal position sensor. Press down on the flexible tab while pulling the connector away from the master cylinder.

If your inside the cabin, rotate the cylinder counterclockwise and clockwise if your outside. Channel locks or similar pliers will give you a good gripping force for rotation.

Figure 10. Unlocking the clutch master cylinder from the firewall.

Figure 11. The clutch pedal position sensor connector.

Step 6 – Install new clutch master cylinder and bleed system

Install is the reverse of the removal steps. Reattach the master to the clutch lever. Reconnect the line feeding clutch fluid from the master to the slave cylinder. Reconnect the line to the brake fluid reservoir. Reattach the wiring harness and reinstall the fender liners.

Locate the slave cylinder. It’s located near the front of the transmission on the driver’s side. Make sure the brake fluid reservoir is filled to capacity with DOT 3 brake fluid. Remove the rubber dust cap from the bleed screw. Turn the bleed screw half a turn while another person has the clutch pedal depressed. Make sure your wearing rubber gloves and safety glasses. Brake fluid will come out of the screw at a high velocity. Once the pressure is gone (a couple seconds), close the screw and have the other person pump the clutch pedal about ten times. Repeat the bleeding process several times to achieve a responsive clutch pedal.

Figure 12. The slave cylinder.

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