The Jeep Guru – Page 81 – Jeep Performance Improvement Ideas

January 15, 2011January 15, 2011

Cat back Exhaust for Jeep Cherokee XJ

Cat Back Exhaust for Jeep Cherokee XJ

My old exhaust was crumbling apart. The tip had fallen off behind the holder and the muffler had a huge crack in the bottom. It rattled and rumbled.

I ordered the Dynomax system from Summit Racing through their Ebay store. It arrived in just a couple of days after I ordered. I had to laugh at the UPS man struggling with the huge box coming in my office door.

I began by lifting my Jeep and using a reciprocating saw to cut the muffler loose from the catalytic converter. There were a lot of old welds here so it was pretty messy. I cut the muffler to get room to work to clean it up.

The clamp at the rear hanger broke when I tried to unbolt it. I just twisted it out of the way. With both ends loose I was able to remove the muffler and tail pie as a unit from over the axle.

I used a variety of metal working tools to clean up the end of the cat. I cut off the bulk of the old pipes and weld beads with a torch. Then I used a 7 inch grinder to clean up the slag. I finished with my 4 ½ inch grinder fitted with a flap disk.

When I finished the reducer include in the kit slipped smoothly and snugly into place on the cat. There was a small hole in the pipe coming out of the cat so I elected to weld this joint closed rather than use the included clamp.

Next I slipped the muffler into place. I supported it on a stand while I fit up the tail pipe. It took some wiggling to get the tip to line up where I wanted it between the spring and the trailer hitch. When I finally got it in place I used a ratchet strap to hold it in position while I put a tack weld between the muffler and the tail pipe.

To get the rubber donut to connect properly with the hanger welded to the tail pipe, I removed the two bots that hold the hanger to the body. Then I slipped the donut over the hanger on the pipe and then I reattached the hanger using the bolts. This seemed easier than wrestling with the heavy rubber, which was cold and inflexible.

I then tightened the clamp on the rear hanger making sure the pipe was still positioned where I wanted it. I then installed the clamps at each end of the muffler. I rotated them so that the base of the clamp would face to the side. This gives maximum ground clearance and protects the ends of the bolts from damage.

Muffler clamped in palce - Jeep Cherokee

With all the clamps in place, I removed the support and gave it a good shake to make sure it was positioned where I wanted it. I then lowed the Jeep and started the engine. I raised it back up and checked for leaks. Finding none, I was ready for a test drive.

Cat back system complete - Jeep Cherokee

The Dynomax system has a nice throaty rumble without being loud. I am very happy to have my exhaust gasses exiting from behind the Jeep again instead of from underneath.

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January 13, 2011January 28, 2011

Rear Wheel Bearing Replacement

Rear Wheel Bearing Replacement – Jeep Cherokee Dana 35

Janice’s 1999 Jeep Cherokee has had a roar in the rear axel for a while now. I finally got around to checking on last week.

I ordered new bearings and seals from Crown Automotive. Since her rear differential is the Jeep Trac Loc, I had to have the friction modifier compound for the grease. I found that at Advance Auto.

I began by lifting the Jeep and removing the rear wheels and brake drums. These had never been off and still had the little clips from the assembly line on two of the lugs. I cut those off with dikes.

Next I let Janice remove the cover. Janice dropped it in the bucket of grease that made quite a mess.

Next I used a 1/4 inch 12 point box end wrench to remove the bolt from the cross pin. I had been concerned that pulling the axles on a Trac Loc diff would be more difficult but it was exactly the same as any other stock Jeep Carrier. I just removed the pin and slipped in the axle to release the C clip.

I removed the left side axle first as it seemed the noisiest. I had a little trouble getting the seal out because the brake shoes were in the way of getting a chisel in like I wanted to. But using a combination of the chisel, vise grips and a seal puller, I eventually popped it out.

I then used an axle bearing puller attachment on my slide hammer to pull the bearing. It takes quite an impact on the slide hammer to get the bearing to move. I have done this job on other Jeeps so I knew to hit it hard. The bearing came out smoothly once it stated to move.

The new bearing seems a very tight fit. I had trouble getting it to start straight in the axle tube. I did not have a bearing driver quite the right size and in trying different ones I somehow damaged the bearing. I noticed some of the rollers missing when I got it in place. So I had to use the slide hammer and pull the new damaged bearing.

I was more careful with the second bearing and got it in with no problem. I put a small amount of Permatex on the outside of the seal and drove it in place. I put a little gear oil on the seal to prelube it.

As I was wiping down the axle shaft to reinstall it, I noticed that there was checking in the bearing race on the shaft. Shaft will have to be replaced. I checked for spares but the only one I had was from a ZJ and the ABS tone ring was different. I replaced the original shaft temporarily.

I slipped it in place and reattached the C clip. I pulled the other shaft and noticed it had some wear as well. I will have to get two replacement shafts along with another bearing to complete the job. I reinstalled the other axle and C clip and coated the cover flange with Black RTV.

After letting the RTV set up for a minute or two, I reinstalled the cover and tightened the bolts in a crisscross manner. Janice refilled the diff with gear oil and the tube of friction modifier.

I later pulled the ZJ axles and looked at how to remove the tone rings. My bearing puller was not long enough to reach. I knew I could use my Dad’s press but I did not want to make the drive to his house.

I did some research on the internet and found a forum post that suggested that the rings would come off easily if heated. Since it was very cold out, I decided it would be a good time to try. The forum post had indicated that the tone ring was aluminum so I was being very careful not to crack it.

I put the axle shaft in the vise and began heating the ring with my acetylene torch. Soon I was able to pry the ring of the seat. I dropped it on the floor to cool. I noticed that it did not sound like aluminum.

I took a magnet to it and found it was indeed magnetic. That made sense to me since the tone ring is used to generate a magnetic field for the sensor to rear the wheel speed. It had to be steel. I was more aggressive with the heat on the second one and it slid off easily without any prying.

These shafts had no visible wear on the bearing races and look like they will make fine replacements. I just have to get more gear oil and another bearing and then find time to do the job again.

UPDATE: I have the spare axle shafts ready to go in but so far the old axles are running quietly. I will just let them run for a while.

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January 11, 2011January 12, 2011

Snow in Tennessee

The Blizzard of 2011-01-11

Snow in Tennessee

We thought we might get a little snow. Our snow always comes from the south. If it comes from the west it looses all its moisture crossing the plateau and by the time it backs up against the Appalachians, it is just cold or rain. The weather models called for three to five inches of snow and more south of us as the jet stream brought cold air south from Canada and moist air north from the Gulf of Mexico.

At midnight there was still no snow. There was a dusting early in the morning and Jennifer took a snapshot of the deck when it first turned white to preserve the memory is case that was all we got. I slept quietly in the down stairs room oblivious to the weather outside.

When I opened my eyes, I saw a big drift in the crotch of the tree visible from the window. I was surprised how the snow had collected there. Then I stepped to the window and looked at the ground. Everything was covered. There was a deep layer of powder covering the woods and yard.

I bundled up and took Smash outside. He loved romping in the deep powder. Getting snow at all in Southeast Tennessee is rare. Normally we get slush and it melts quickly so you have to get out early to see any of it.

So Smash and I headed for the creek. Only one unknown animal had crossed the path that morning. We left the first tracks in the snow. I stood and looked out at the ice on the fast flowing Cohulla Creek. The small branch that flows across my property was covered in a thin layer of ice. Smash wanted to go on his normal rounds in the woods but he decided to turn back and follow me.

Just as we were heading back to the house, Smash suggested one trail and I was returning on another, we heard noises from above. Jennifer and Caleb were making their way down to the creek. Janice had wisely elected to stay warm and thankfully make us pancakes.

I waited for them to make it down to the creek and we enjoyed the stillness of the forest draped in white. We hiked back up the hill to the house.

After some warm pancakes, I decided to get Scuffy out of the barn and go for a ride in the snow. I plowed through the snow easily and after a circle around the driveway, I decided to go see how the main road looked. There was a good eight to ten inches every where. There must have been some deeper drifts in the driveway because in some places you could see where the diff had drug in the center between the tracks of the Maxxis Buckshots.

Janice and Jennifer squeezed into the passenger racing bucket seat together and we drove out to the road. Scuffy climbed the hill easily but the engine was running really rough. Thinking back to the last time I got gas I realized it was on the way to Harlan for the fall crawl. So it could be that the low fuel light actually meant something this time. The big engine sputtered a few times but we made it to the road and back. It looked like only one of my neighbors had ventured out. Keith Valley road was still completely covered in snow.

Since Scuffy was running so poorly, I put him back in the barn before I got stranded. We then took Jennifer’s Jeep Princess out for a romp in the snow. Her Dick Cepek Crushers did well in the snow too.

Out at the main road I popped the transfer case into two wheel drive for a moment and spun a 180 to head back to the house. I put it back into 4wd just to be safe.

With Princess safely back on the porch, we decided to try the sled. The snow was too deep and fluffy for my steel runner style sled to go down. It kept getting buried in the snow. It looked like it would be an all day job to use the shovel and pack down a path for the sled. So Jennifer suggested that I use Princess to pack the snow.

I drove around the driveway and then pointed her Jeep up our sled run. It climbed easily to the top. I lost traction briefly near the crest but I just let the tires turn slowly until they got grip again so as not to spin out all our snow.

With two compressed paths down the hill we were soon able to work out a nice sled run. Smash enjoyed chasing us up and down the hill. He also provided entertainment between runs by grabbing a mouthful of snow and then laying on his back with his feet in the air and wiggling around like he was making a snow angle. He did this several times and I laughed so hard I hurt every time he did it.

Eventually we tired of trekking up and down the hill and packed it in. Janice made us some yummy Carroll Shelby Chili.

I decided to brave the roads and go get some gas for Scuffy. I expected the main roads to be clear with the crews having all day to work on them. We all loaded up in Princess. Caleb did not understand why he needed to get dressed. He was sure that PJ pants and no shirt was plenty for a trip to town. We waited while his mom encouraged him to at least take warmer clothes with him.

When I reached Keith Valley I was surprised to see it looked much the same as it did on my earlier venture. There was a tiny strip of pavement visible in the oncoming lane but the rest of the road was covered in snow and slush. The worst part about driving on it was that most people who had gone ahead of us had driven near the center of the road. There was still deep snow near the shoulder making it difficult to see where the road ended and the deep ditch began.

I had no trouble driving in the snow, but meeting oncoming traffic was difficult due to having to move over into the deeper stuff. And occasionally the people coming toward me wanted to use part of my lane as well even though they had more room than I did.

I was expecting Spring Place Road to be clear because it is a State Highway and they usually run plows and salt trucks even when there is no snow. Boy was I surprised. I had noticed Jennifer getting a bit nervous each time I met someone so I asked her how she felt about my continuing on in her Jeep to the gas station. She bravely encouraged me to go on.

I did a fun drift out onto the Sate Highway and then settled back into what looked like my lane. The road was completely covered in snow at that point. However just over the hill, ruts in each lane made it down to the pavement.

About halfway into town, we met a road grader plowing in the opposite direction. The inbound lane I was using was still pretty slick but easily passable in 4wd.

The gas station did not look like it had seen much activity during the day as there were just a few tracks in their parking lot. I filled my gas can with 93 octane while Jennifer refueled Princess. I would have just stolen fuel from one of my other Jeeps but none of them had the 93 octane that Scuffy’s racing engine requires.

I was fully expecting to catch the road grader as we headed back home. I was using two wheel drive as I drove along now in the dark. Then, suddenly, not far from where we had met the grader on our way into town, we hit snow covered road again. I was happy for the shift on the fly capability of the 231 transfer case as I moved the lever to 4H just as we hit the edge of the snow and ice. I guess the Grader operator had reached the end of his shift but I did not notice where he parked it.

We drove on snow and ice back to the turn on Keith Valley. We could see flashing brake lights near the turn. It looked like some one had a stalled truck and was being serviced in the middle of the road. I guess you have to work on it where it dies but thankfully he was just past our turn off.

The return trip was not so bad because I was able to easily drive on my side of the road. I did have a little trouble with oncoming traffic not wanting to stay on their side but I could easily slow down and let them slip past. Having two tires on wet pavement and two in snow and ice made for much firmer footing. However the lock right locker did make a few unexpected disengagements and sudden reengagements.

I later went out a poured the fuel into Scuffy and made sure it ran OK. Then we used Princess to tow the trash can out to the road just in case the trash truck decided to brave the weather.

This morning I made a few more sled runs before pointing Scuffy toward town. Keith Valley was slushier than the night before and easier to stay on my side of the road. There were still some drifts on the northbound lane.

I switched into 2wd at Spring Place Road. It still did not look plowed or salted but it was more slush than ice or snow. I am not used to driving Scuffy on pavement and with the still aired down Maxxis Buckshots, it was a bit wiggly but 45 MPH was no problem.

I saw a snow plow on HWY 64 and I accelerated up to 55 to match traffic. I got the hang of the wiggles caused by aired down tires and no sway bars.

In town I was surprised that at the busy intersection of 25th and Keith St, there was still a lot of snow. I stayed in 2wd but that caused a little dance in the rear as I accelerated from the stop light.

Westside drive leading toward my office looked like it had been plowed and salted. But Norman Chapel road and the Adkisson Drive in front of the Cleveland State Campus looked worse than Keith Valley. I put my Jeep back in 4wd to get over the speed humps.

As I pulled into the office I was met by the UPS truck. She was trying to back up to one of the bay doors but not doing too well. She eventually gave up and turned around. She had no trouble going forward. There was only a couple of cars in the office parking lot and it has been very quiet here so far today.

January 7, 2011January 7, 2011

How to troubleshoot a gas burner

Trouble shooting a gas burner

While there is a lot of mystery surrounding flame safety circuits, gas burners are actually quite easy to trouble shoot. They really only need three things to operate: a fuel supply, combustion air and an ignition source.

In a forced are furnace, the combustion fan will come on first to purge the chamber. After a predetermined time, the flame controller will open the gas valve and provide an ignition source. If the flame is not detected in a few seconds, the gas will shut off and a new cycle will be required to relight.

The gas will be controlled by an electric solenoid valve. It opens and closes with an audible click.

The first step in trouble shooting the system is to determine if the combustion fan is running. There is often a time delay before the fan begins to run after the system is energized. Check the time control relay if the fan will not start or does not start at the correct time.

Next there will be some kind of air proving mechanism. Often this is a simple as a paddle in the air steam connected to a switch. It may also be an air pressure switch. Make sure that the air proving signal is present before moving forward.

Once the controller is satisfied that there is sufficient air and the combustion chamber is purged, the gas valve will open and the ignition source will fire. You can usually tell if the gas valve is opening by listening for it to click or feeling for it to open.

The two most common types of ignition are the pilot light and the electronic ignition. The pilot light is a separate flame that runs all the time. The electronic ignition consists of a spark rod and a high voltage coil. The coil provides the voltage end to make a spark at the gap on the spark rod. A neon lamp can be held near the wire to ensure high voltage is present during the spark cycle.

If the controller does not sense a flame within a few seconds of opening the gas valve, it will close the valve again and purge the system.

If you are having trouble lighting the burner after the gas valve opens, verify the gas pressure and make sure the gas orifices are clean.

If the valve fails to open, suspect a problem with the gas control circuit. Often this is a printed circuit board. Filed repairs or modifications are not generally allowed to these boards for safety reasons. If the board is bad, you will have to replace it with an approved unit.

If the burner lights but goes out with in a few seconds, there may be a problem with the flame sensing mechanism. In many burners this is simply a rod that generates a voltage in the presence of a flame. If bad it will need to be cleaned or replaced. Some systems use an optical flame sensor. These need periodic cleaning and eventual replacement as the voltage from the flame eye decays with age.

If the flame is unstable check the gas source for proper pressure or contamination.

Understanding how a gas burner works can make trouble shooting relatively easy. However, it is often hard to access the components in an enclosed furnace. It may be possible to remove the burner form the duct work and bench test the unit. If you find that the air proving switch works o the bench but not with the unit installed, check for blockages in the duct work.

Never attempt to relight a burner that has not been properly purged. Never do anything that will shortcut or bypass the purge cycle. Using these steps you should be able to isolate the cause of a gas burner problem quickly and possible save an expensive service call.
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January 6, 2011January 6, 2011

A Process Improvement Story

A Process Improvement Story.

Back when I worked at Westvaco we had a need to change large heavy rollers called impression rollers. These impression rollers were changed about once a day and there were eight of them in a machine.

The process used for over 20 years was the one recommended by the printing press manufacturer. The process involved using a hand crank lifting table to raise and lower the rolls into place. Since the table lifted form directly under the roller, the paper web had to be cut in order to remove the roller. The web had to be taped back together afterwards. These tape splices were always difficult to get through the remainder of the printing press on start up.

We knew that on another brand of machine, they used a tray to catch the roller and the press had more travel in the impression roller mechanism so that the roller could be raised and lowered out of and into the tray. The tray was cantilevered so that it could slide between the roller and the web.

We decided to try to mimic the design of the other machine and provide a way to avoid cutting the paper. However, our machine was not capable of raising and lowering the rollers so we still had to have the capability of lifting the rollers.

We designed a hydraulic lifting table that was cantilevered from the operator end. The lifting bars rolled up and down on a post using roller bearings. The hydraulic cylinder was foot operated so that the operator could use his hands to align the roller into the bearing caps while he lifted it with his foot.

The lifting bars were narrow enough to slip between the web and the roller. We used webbing between the bars to support the roller so that it could be handled without damage.

The first prototype was very large and cumbersome as we were unsure of the strength needed to handle the rollers. Future versions were scaled down to make them more maneuverable and easier to handle.

These machines cost less than $2000 each to build. They were very simple to operate and completely reliable.

Down time on the machine cost about $1000 per hour so these machines paid for themselves almost every day they were used due to the time saved form not having to cut and splice the web.

I still have one of these machines in my shop and I use it for all sorts of lifting applications. It makes a great transmission jack. It is especially good for handling a heavy Jeep Transfer case transmission combination.