Working the Coker Tire Challenge Rally

Working the Coker Tire Challenge Rally

This weekend, Jennifer, Janice and I worked the Coker Tire Challenge Rally. I had helped earlier with the course layout so I knew where we would be going.

We met up with John and Rachel on Thursday afternoon. They had flown in from California to make final preparations on the route. We made a quick tour of the Coker Tire headquarters and got our badges and new T shirts. This time our goodie bag included a cool hat as well. We recycled our green shirts we wore at Great Race.

We met with John and reviewed how to operate the SEIKO clocks. It had been a couple of months since we had seen them but we remembered pretty quickly how to set them on the hour. We collected a check point sign for each Jeep and headed back to Cleveland after checking out a few of the familiar rally cars.

The next morning started early setting clocks in the dark at 7am. Jennifer’s partner was nowhere to be found. After a few calls we found he was confused on the start time and was running late. We made arrangements for an alternate place to meet Jennifer and left her at Coker to wait while the rest of the workers headed out to our positions.

We followed Rachel as she drove making a final check of the course measurements. This meant that she would not exceed 60 MPH even on the interstate. Our little caravan got some strange looks from passersby on the interstate. The outboard wheel unit for John’s rally computer always attracts attention.

We stopped in Kimbal and Jennifer made good progress on catching up. In fact, she was ahead of us before we got back on the road and we arranged for her to take a break and meet up along the route into Alabama. I dropped out of the caravan long enough to make sure every thing was OK with her and her partner and then we picked up the route.

We caught up well before check point one which was somewhere south of Stevenson. We all took some time to introduce our selves now that it was light. With the crew for checkpoint one in place, we moved on down the road.

Our caravan took us along the same route as the Crow Mountain Hillclimb where I will be working in a couple of weeks. We also passed the cool rock zoo along the way.

We dropped Jennifer and Jonathon at their control and moved on. Near Huntsville, we dropped off the other crew and then John, Rachel and I met for an early lunch. Due to the time zone difference, the Arby’s was just opening when we arrived.

Our checkpoint for the afternoon was a double. That meant cars would be passing us twice. The time around the loop was about six minutes so we had two cars passing us every minute for most of the time we were open.

We had a nice quiet place in a church yard on a lightly traveled road. However, we still had a few locals stop to see what was going on. Unfortunately one of the locals held up one of the contestants who was coming into our checkpoint as he was looking at us. They had to take a time delay.

After our checkpoint was over, we phoned in our results and headed up the route to find Jennifer who had moved to a different location for her afternoon assignment. We drove together to Corky’s farm to turn in our scores and eat some food grilled up by Sticky Finger’s catering.

We then headed out to the Walker Valley football game where Jennifer’s daughter was playing in the band. After the game, we headed home for some much needed rest.

We started early again the next day setting clocks at 7am. Jennifer had a new partner who arrived on time this day.

We headed north to Dunlap. We set up checkpoint one in the rain. Then we followed the route to check point two which was my assignment for the morning.

It was a nice hay field across from a house. The home owner came out and was excited to find that the Great Race was passing her house. She called her friends who stood in the yard taking pictures as the cars went by. “Now we know what the green dot is for!” we heard them say.

We were almost caught off guard when the first car passed us ten minutes early. But we had everything set up and clocked him in properly. The rest of the cars arrived in order and in their expected minutes. It was fun to watch the cars make their way through the winding farm road.

After we called in our scores we headed out to meet John and Rachel in Pikeville for our afternoon assignment. We realized we had a bit of time to kill, so we headed up to Sparta for lunch. We must have just missed John and Rachel there as we found they had stopped for lunch across the street from us. We met them in Pikeville at our expected rendezvous point and time.

We worked the last control of the day in a church yard near HWY 58 in Hamilton County. I think some of the contestants thought they had passed all the workers because several were very early to our checkpoint. They looked surprised to see us. Others got great scores at our checkpoint so they must have been paying attention.

We called in our scores as the cars were coming in. We met Jennifer back at Coker. Back at Coker there was a huge car show going on. Our fellow rally friend Tom Greig had come up from Atlanta to see the event. We walked around and admired the beautiful cars on display.

Then we visited T Bones bar for a snack and watched the crowd watch the UT football game on TV. After that, we headed back to Cleveland and hid the bed early knowing we had an even earlier start the next day.

Sunday we headed south at 6:20 am. We set out clocks in Trenton, Ga at 7:00am.

We dropped the first check point crew at a little church well before church time. Jennifer and Gary had a checkpoint on the brow of Lookout Mountain. They had a nice creek with a waterfall just behind them.

We were the last checkpoint of the day again. This meant we had to call in scores every few cars which adds to the challenge of recording their times correctly as they rally cars speed by. No one seemed surprised to see us this time and there appeared to be some really good scores on our leg. It was fun watching the old cars climb the hill to our checkpoint trying to maintain their assigned speed.

Back at Coker, Jennifer was doing multiple jobs for John as we collected equipment and scores. We finally got to sit down and eat just as Corky was announcing the results. The low scores continue to amaze me. I am not sure I could do as well with a computer much less with the limited vintage equipment they are allowed.

There were some very interesting cars running the rally. Harold Coker was running his Chrysler Airflow. Those cars are interesting in pictures but absolutely stunning when seen running on the road. There were several former race cars. The drivers of these seemed to enjoy pushing them to their limits as I sow several drifting them through corners. I bet Corky enjoys seeing them wear out their vintage tires as well.

The Coker Challenge is also open to modern cars and Street Rods. There was an interesting Willys Jeep in the event. It had a street rod independent front suspension and a Chevy V8. I don’t think it would do much off road but it was an interesting street machine.

It is always good to have a Jeep Cherokee when working checkpoints. It is easy to get off the road and opening the hatch makes for shade and light rain protection. Also there is plenty for room for check point sighs and other gear that we need to make working a checkpoint comfortable. Also, the on road manners of the Cherokee makes it easy to get from place to place quickly.

See our photo gallery

Thanks to Corky Coker and Hemmings Motor News for inviting us to a great event. I look forward to the next one. http://www.cokertirechallenge.com/

Resealing a Differential Cover

Resealing a Differential Cover

Ever since I put the 4.11 gears in Jenny’s Jeep her pink diff cover has had a slight leak. Not much, but enough to make a spot in her parking lot and leave a trail on the gas tank.

We tried tightening the bolts a little more. We tried waiting to see if it would seal its self like some new leaks do. But this one just kept dripping.

Rather than use the method I had learned years ago from Marcus at go.Jeep-xj.info, I had followed the instructions on the RTV tube. This method obviously did not work as well as the method I have used in the past that had never leaked.

We began by lifting the Jeep and preparing a clean catch pan for the diff oil. I was curious to take a look in side the differential anyway to see how the new gears looked.

The RTV had made an excellent seals on most of the cover as it was very hard to get off. The Blue Torch Fabworks cover had no flex like the stock cover so it all has to break loose at once. I had to use a chisel to pop it loose.

With the cover off, the unsealed spot was obvious. The RTV was separated between two bolts on the one side that leaked.

After scraping both surface clean, I applied a thin coat of RTV to the cover. I wiped down the differential housing carefully and made sure that the oil did not continue to drip out at the bottom. I let the RTV skin over for about five minutes before carefully setting the cover in place and starting two bolts so that it did not slide.

I checked the torque specs on the replacements bolts I had for the cover and set my torque wrench. I don’t normally use a torque wrench on the cover bolts but I wanted to make sure this one did not leak a second time. I toqued the bolts evenly in a crisscross pattern.

After letting the RTV set up a few minutes longer we refilled the housing with gear oil. We put some pipe dope on the plug and sealed it up. So far there are no leaks.

If it leaks again I will consider the Lube Locker gasket:

Lube Locker Chrysler 8.25 Differential Gasket

Replacing the Idle Air Controller on a Mazda MPV

Replacing the Idle Air Controller on a Mazda MPV

The idle speed on most modern fuel injected engines is controlled by an idle air control valve. This valve is controlled by the ECU and allows air to bypass the throttle body to maintain the idle speed.

The Idle Air controller on the Mazda MPV is located on the back of the intake manifold. It is held in place by two 10mm head bolts. Just remove the bolts and the old valve can be removed. It is easier to disconnect the wiring harness after the valve is off the manifold.

Install a new gasket and attach the wire to the replacement valve. Bolt the new valve down and you are done.

Start the engine and test the idle speed. The computer may take a moment to adjust to the new valve but the idle should smooth out and now be controlled ending embarrassing and dangerous stalls.

AW4 Troubleshooting

AW4 Troubleshooting
Diagnosis of faults in the Jeep AW4 transmission.

The automatic transmission used in the Jeep XJ Cherokee is nearly bullet proof. Seldom does it ever give trouble. Maybe that is why it is so hard to find good information on how to fix it when it occasionally does act up. The same transmission is used in 600hp turbo Supras so it can handle a lot of abuse.

To test if the trouble is electric or mechanical, pull the fuse to the TCU or disconnect the wiring harness. 1-2 will give first gear only, 3 will give third gear. D will give forth gear. The torque converter will not lock manually. You can drive the Jeep just fine this way until you figure out what is wrong.

If the transmission does not shift as described manually, then you have a serious problem and you need to get another transmission from the junkyard. Don’t buy a rebuilt one. If you have yours rebuilt make sure the shops knows how to handle the AW4. If you choose to rebuild it yourself, the FSM has lots of nice pictures.

Most of the time the trouble will be associated with the Transmission Control Unit or TCU. It is handy to have a spare for trouble shooting although the computer itself rarely goes bad.

A transmission control unit located under the passenger side panel under the glove box controls the AW4. The panel is one piece all the way across and there are more control boxes on the driver side so be careful when you remove it.

There are two controllers that I know about. The 1990 and earlier use a different one from the 1991 and up. Somewhere along the way they combined the TCU and the ECU but I don’t know what year that was. The 1991 and up unit has a green connector. It is not interchangeable with the earlier unit.

The TCU gets inputs from a speed sensor, the Throttle Position Sensor, the brake pedal, the battery and the ignition switch. Some models also have a power / comfort switch.

The only outputs control three solenoids. One controls the torque converter lockup and the other two select the four gears in a binary fashion.

First Gear S1 on S2 off
Second Gear S1 on S2 on
Third Gear S1 off S2 on
Forth Gear S1 off S2 off

As you can see, if the TCU has no power, you will get forth gear in D position. Also with the TCU off, 3 will give you third gear and 1-2 will give 1st gear. You can’t get 2nd manually.

The wires on the 1991 and up TCU are connected as follows:

C3 Speed Sensor Tan
C8 NSS 1-2 Light blue
C9 NSS D Green
C10 Brake switch Light Blue/ yellow
C11 Power switch Tan
C14 Torque Converter White
C15 Solenoid 2 Violet
C16 Solenoid 1 Blue
D7 Ground Black
D14 Battery Red
D16 Ignition Yellow
D1 TPS+ Gray
D3 TPS- Tan / orange

Note that the wire colors and traces may be different on different years. Check your FSM wiring diagrams for the right colors for your Jeep. The pin position is the same on all the TCUs however.

If the speed sensor signal is bad, the controller will force the transmission to stay in first gear. It will not shift at all. Unplugging the controller will give manual operation. This speed sensor is mounted in the side of the transmission under the transfer case shift linkage if you have 4wd. Don’t confuse it with the speedometer sensor in the transfer case.

The brake input is used to unlock the torque converter. The 1990 and earlier used +12 to lock and zero to unlock. The 1991 and up is the opposite.

The TPS voltage should read about .5 volts with the throttle closed and 4.5 volts with it open. It should transition smoothly between the two numbers. It seems to work fine even if the voltage is a little off.

The solenoids are located inside the transmission. They get power from the TCU. You can monitor the voltage to see if they are getting power at the right times. You can also add a power wire and switch to juice up solenoid 2 to get second gear when in the 1-2 position. This gives you control of 2nd gear which is hard to come by any other way.

You can check the solenoids by testing the resistance across the coils. Attach one side of your meter to the battery ground. Good grounds are hard to come by inside the Jeep. Connect the other side to each wire going to the solenoid. They should read around 15 ohms give or take a couple. They seem to read different warm than cold but will be in the teens if good.

The solenoids are expensive and require dropping the pan to change. Make sure you have eliminated other possibilities before swapping one.

Contrary to most wiring diagrams I have seen, the solenoids do not ground through the black wire. They ground to the transmission case. So if you are having trouble with a solenoid energizing, make sure it is properly grounded to the case and the case is properly grounded to the battery before swapping it out.

The speed sensor uses the black wire. If either the black wire or the white wire are damaged in the transmission wiring harness, the transmission may hang in first gear. The harness passes right behind the transfer case shift linkage and can be damaged by the linkage if it is moved around by a transfer case drop or something like that.

Normally, the transmission with switch to 2nd at 20 to 25 mph depending on the TPS signal. It gets its speed reference from the internal speed sensor so if you are in low range, the speed will be different.

In the 1-2 position, the torque converter can lock up in first or second gear. In 3 or D it will only lock in 3 or four. The normal sequence is to shift to second, and then third, then forth and then the torque converter will lock up giving an engine speed of about 2700 RPM at 55 MPH.

Armed with this information, you could be able to sort through nearly any fault in the AW4. The FSM is most unhelpful in that it calls for a DRBII scanner that seems to be unavailable at any price these days. Even if you had one the TCU only gives a few codes that are really not very helpful. You will probably still have to sort through each of the inputs and outputs to find out what is really wrong and get it working again.

Bad Ball Joints Again.

Bad Ball Joints Again.

After breaking a second axle U joint in just a few months time, I had to see what was wrong. While I still don’t really understand why, I know from experience that if the ball joints are loose, the U joints will break.

As I was putting the hub back in after changing the axle shaft, I saw the ball joint move. There should be zero up and down motion in the ball joints. They should only pivot. Mine was moving up and down almost a quarter of an inch. I knew this was trouble so I removed the axle shaft and replaced it with a 2wd stub shaft to wait until new ball joints arrived.

With the new ball joints in hand, I set about removing the old ones. They have only been in pace a couple of years or so. I followed the same procedure I have documented before in: Ball Joint Replacement.

When I went to separate the knuckle from the ball joints, the lower joint split and part came out with the knuckle and part stayed in the axle. I had found my problem. I am still not sure if it was a bad part or was not lubricated properly.

I pressed in the new ball joints using the same procedure described in: Ball Joint Replacement. To reduce stress on my press, I used a hammer to strike the end of the press between turns on the bolts. This trick allowed the press to easily push in the new joints without bending the press as I have done in the past.

The hammer taps help to keep the ball joint aligned as it presses in and relieves and sticking as it moves through the axle. Hammering also helps in the removal process as well.