87 – 94 Jeep YJ Brake Master Cylinder Upgrade

This is for those of you who have an 87-94 Jeep Wrangler and want a little more brake power for hard wheeling. Don’t bother spending a lot of money on custom built or high performance master cylinders. All you really need is one for an 85 Ford E-350.

The master cylinder off of an E-350 is rated for 1 ton use. That means it will stop your YJ with ease. This is especially beneficial if you have over sized tires. A friend of mine in Louisiana did this upgrade to his 91. He says that he barely has to touch the brake pedal on the street, and when wheeling it is a breeze stopping on steep inclines. This upgrade is also beneficial if you tow a trailer with your jeep. It will give you more positive braking force when you have a heavier than normal load on your Jeep.

The only thing that you need to do for this upgrade is to bore the mounting holes on the new master cylinder. This can be done easily with a die grinder and a carbide burr, or simply find out the size of the mounting studs on the booster and drill the holes to appropriate size.

While we’re on the topic of YJ brake upgrades, another good one for your 87-94 is a 95 power brake booster. In 95 Jeep went to a dual diaphragm booster, the same as I mentioned for the XJ Cherokees in the “Jeep Cherokee Bendix 9 ABS Upgrade” article. The dual diaphragm booster with the 1 ton, E-350 master cylinder will make a world of difference in your braking abilities both on and off road.

Catastrophic Failures

Knowing a bunch of guys who work at garages or at dealerships has its perks. One of my favorites are the catastrophic equipment failure pictures they send me from time to time. I figured I would share them with our readers as well.

The first is a front differential out of a 2004 1500 series Dodge. Yes, what you are looking at is the completely nuked pinion bearing section. It’s a bit harder to see but the bottom of the differential case is also opened up as the result of some nice sized ring gear and carrier pieces.

Second is a grenaded transfer case. This is in a 2008 Dodge 4500 pickup. Apparently the guy pulls a trailer more often than not and one day BANG this happened to him… As you can probably tell from the picture the entire case split in half.


Jeep XJ, TJ, ZJ Upper Control Arm Upgrade

At the beginning of this year’s Tuff Truck season at Buck Motorsports Park, I threw together a 91 XJ Cherokee to compete with. It didn’t do too bad for the first couple races, aside from the motor being tired (175,000 miles). On the third race of the season, I was coming around the outside turn when I heard a pop and the wheel got really squirrely. Once I got back to the pits, I began inspecting the front end (tie rods, ball joints, etc.) but found nothing out of the ordinary. Upon further inspection I noticed that the front axle seemed to be rotated towards the back of the vehicle. My upper control arms were bent in a “U” form, forcing my outer knuckles to point to the sky and throwing my steering out of whack.

To remedy this problem, I removed another set of stock upper control arms from a donor XJ. Decided they needed to be reinforced if I was going to get any kind of longevity out of them. I went to Tractor Supply Co. and picked up a bar of 1”x1” square tubing. I cut the tubing to lengths and pressed them inside the stamped steel control arms. I then laid a bead of weld down both sides to fasten the tubing to the arms themselves.

Reinforced Control Arms

After running the rest of the season, the reinforced control arms are still straight and seem to be holding up fine. After running these in a tuff truck, knowing the abuse that consistent jumping and turning in 4 wheel low at wide open throttle puts on components, I would highly recommend this upgrade for anyone running an XJ, TJ, or ZJ with the same style control arms.

Jeep Cherokee Bendix 9 ABS Upgrade

If you have an ‘89 to ‘91 XJ Cherokee, you may have the problematic Bendix 9 Antilock Brake System. This ABS system was nationally recalled due to it being prone to failure. The Bendix system consists of a master cylinder, a motor/pump assembly, and 2 pressure accumulators. It is fairly simple to identify this system due to its lack of power brake booster that you would normally find behind the master cylinder on a normal power brake system.


Because the entire system is pressurized by an external pump, you must depressurize the system prior to removal. If this is not done, it can cause serious injury due to extreme pressure in the lines and accumulators. The system is easy to depressurize. Simply pump the brake pedal 25-40 times with the ignition switch in the off position.

Once the system is depressurized, you can proceed with the removal process. Start by disconnecting the brake lines from the master cylinder. Once the lines are free, remove the master cylinder from the firewall by the four bolts holding it in and disconnect the rod from the brake pedal. This can be difficult due to the position of the nuts under the dash, but a little patience goes a long way. Next, you must go back under the hood on the passenger side by the firewall. You will notice a black steel plate held on by several bolts. Under this plate resides the motor/pump assembly. Unplug and unbolt the assembly.

The accumulators are easily spotted as they look like mini air tanks. Remove the lines from the accumulators and pull them out as well. Once you have all the parts of the Bendix system removed, you are ready to re-install the “normal” power brake system.

You can use any brake booster and master cylinder combination for a Jeep Cherokee that you wish. My recommendation is to go with a booster from a ’95 or later because they are a dual diaphragm booster and give you a little better braking power. The booster bolts into the same 4 holes that you removed the Bendix master cylinder from. Then, the new master cylinder bolts onto the front of the booster like a normal setup.

You may need to do a little re-routing of brake lines to go from the master cylinder to the proportioning valve, but it’s pretty much the same setup. Two lines from the master cylinder go into the top of the prop valve, one line from the rear of the prop valve to the passenger side front caliper, lower front port on the prop valve to the front driver side caliper, and the lower rear port on the prop valve to the rear brakes.

There isn’t much information elsewhere that I have been able to turn up about this system aside from it being problematic. There really isn’t many pictures of the stuff floating around either. I did this conversion on my tuff truck by trial and error. I went through about 3 boosters and 5 master cylinders before I realized that all it took was a regular old Cherokee setup to swap right in.

If you have any questions or concerns on this conversion we encourage your to jump over the the Jeep Tech section of the forumHERE to discuss further.

Craig’s ’46 Willys

If you fully understand “the Jeep thing” you know it goes back quite a few years; In this case 1946.  This Willys, while obviously not a 100% OEM ’46, still has the old school character with some improvements to increase its trail performance.

The frame is from a Civilian model while the grill, head light hardware and fenders are GPW (Military).  The windshield is also from a civilian with the “Willys” scripts.  The tub is about 90% stainless steel with the concentration of original metal in the cowl and firewall.  Recently, Craig has installed a roll cage that will be getting a solid frame tie-in this winter.  The cage protects the occupants of the very comfortable bucket seats while providing support for a full soft top or bikini top.  For summer wheeling the Jeep also has a tonneau cover for keeping the mud off of any gear behind the seats.

Under the hood sits a fairly stock, freshly rebuilt L-134 4 cylinder engine.  I said fairly stock because this factory issued engine has a custom billet aluminum adapter for a two barrel Webber carb, which he machined himself. Power spins back through a T-90 transmission and splits at a Dana 18 transfer case.  Upfront there is a stock Dana 25 axle with a “Lincoln Locker”.  Craig reports the welded spider gears work wonders in woods but are taking a toll on the under sized differential.  His plan is to scout a later model Dana to replace it with.  Along with the front axle swap will also come a disk brake conversion.  Power crossover steering has already been installed as well as an after market steering wheel.

Under the rear of the Jeep sits a Dana 41 that is also subject to replacement.  Craig said his plan is to perform the front and rear swaps at the same time to make ring and pinion matching much easier and cost effective.  32×11.50 Super Swamper TSL SX’s stand on each corner of the Jeep wrapped around run of the mill black wagon wheels.

In case the specs above let the Jeep some place a little deeper or steeper than Craig may have planned there is an 8000lb Smittybuilt Winch ready to pull on the front bumper.  I recently witnessed it in action, not for self recovery, but to help a full sized late model Chevy out of the mud.  After wheeling Craig can air back up with an onboard compressor.

There is no doubt this Willy’s is still a strong war horse with plenty of fight left to come.  Craig has made it clear there are some awesome upgrades coming down the road for this Jeep.  Be sure to check back with 717 because this is one project you will want to follow!