The Readers' Rigs page illustrates some of diesel pickup trucks and SUV's members of The Diesel Page own or drive. This month's photos and story come to us from Australian member Don Swanton.

A "SECRET CHEVY" Update
1990 Ford F250 Ambulance
6.5L Diesel & 4L80E auto.
December 2012

The "Secret Chevy" may be more than 20 years young, but it is still on the road after 5 years of tough going with me at the wheel. What modifications and repairs have been necessary during my 5 years and almost 100,000 km? What have I learned after 5 years?

I can confirm that Australia really is a land of sunshine and flooding rains. Oil production operations in the part of the Cooper Basin where I was working were shut in for about 18 months due to widespread flooding. Statistically it was proclaimed a 1 in 40 year flood.

First, fuel consumption and tire life.

During the past 5 years, I made about 10 field trips at 7000 km/trip, and round trips North/South and East /West across Australia. That adds up to about 20,000 kms of rough roads and tracks and about 80,000 kms of paved roads.

I have previously reported fuel consumption as 17 l/100km (14 mpg). It is actually 16 l/100 km (15 mpg). The error was that my electronic odo/speedo was set up with a GPS. Using road survey markers over several hundred kms, I found that my odo read 100 kms travelled when I had actually travelled 105 km. Similarly my travel speed was also 5% higher than indicated. I can confirm that tire pressure has a strong effect on fuel consumption. I now run 65 to 80 psi tire pressure on the paved roads. I have to reduce the tire pressure to less than 40 psi to improve the ride on rough roads. These operating conditions are within my tire load ratings and pressure ratings. I have not been game enough to run at 25 psi. I have been advised that you can do it, but you need to restrict your speed to less than 50 mph. Also your tires are more vulnerable to "staking" the sidewalls at low inflation pressures. On tires. I always carry two spares. One spare is fine, but prudence in remote areas suggests that you should get a new spare immediately after you mount your only spare tire. This is not always practical for me.

In my 100,000 kms, I have used 2 sets of tires, including 2 tires due to sidewall failures and 3 tires due to punctures. I had a "high tech" trial of a wider, lower profile tire in an attempt to fine tune my gear ratio, one tire failed after 3000 km. I thought the truck was sliding about a bit more than usual on the gravel road. By the time I stopped to inspect the tires, the failed tire was 3 donuts. Such is life. I had the rim straightened and put on a new tire after the trip was completed. I keep the second "high tech" tire as a spare in the garage.

Second, modifications to the vehicle.

The 4L80E transmission is bigger than the Ford C6 and there were minor clearance problems. The big item was that the GM transmission has a lot of wires and tubing around the transmission. I had a skid plate fabricated and installed to protect the transmission area. All the other underbody wiring was tucked into the frame. This was done just in time, as rocks and road debris were chewing off the insulation. As grass and other flammable debris can accumulate on top of the skid plate, I took advice on how to diagnose and extinguish the possible fire. So far no problems. In addition to a normal 1 kg extinguisher, I carry a second 2 kg extinguisher and a pair of welding gauntlets.

The next item was the torque convertor. Despite my instructions, the transmission vendor supplied the incorrect torque convertor. GM makes 4 different stall speed convertors for the 6.2, 6.5, 6.6 engines. You can identify them by the marks on the convertor. For a diesel you want the very low stall speed convertor. The correct convertor matches the shift points and the engine torque curve to get smooth shifts. The truck ran with the incorrect torque convertor, but the correct very low stall convertor was a significant improvement.

Next, on two occasions, I tore the locating tabs off the radiator. I thought it was from twisting the chassis on more adventurous tracks. My genius maintenance guy figured that it was because the road shocks were trying to throw the radiator up and down and the tabs were the only things holding the radiator down. Installing two hold downs over the top of the radiator solved the problems. The tubes were also re- rolled as the vibration was shaking them loose. On the first failure I used about 5 gal of water to get 500 km to the repair shop. On the second occasion I had the repairs done after the trip.

The basic engine has been bomb proof.

Accessories and drives have been a weak point. On one occasion the vacuum pump for the power brakes failed. It was about 2 AM and it was 600 kms to the repair shop, the last few kms through city traffic. Care and a strong left leg were necessary.

I've had two alternator failures. One was obvious and the one was an intermittent failure finally diagnosed and repaired by a clever electrician. Batteries die in the heat and from vibration. Dual batteries and dual alternators are lifesavers. I have replaced 4 batteries in 5 years. I experienced 1 serious electrical wiring failure which was resolved after a $700 towing bill. Again, a clever electrician solved the problems (old age and corrosion) and I continued on my way. When the headlight switch later disintegrating upon inspection, it was just other minor electrical problem. While I am on things electrical, my original halogen driving lights had to be retired. They were vulnerable to vibration and various bits failed once too often. I replaced the two 100W halogens with two 35W HID lights. Wow! These things really light up the night. Now I appreciate why all the long distance truckers use them. Highly recommended. Just be polite. They are dazzling. I didn't get pencil beams or anything. Just a wall of brilliant light that lights up everything 100M left and right and an easy mile in front. When you shut them down, the road surface goes from a natural grey to a dull orange. My concern with wandering camels has been severely reduced.

At one point, the bearings in the cabin heater fan failed. The entire dash had to be removed to replace the fan. Unfortunately it was reinstalled inadequately, and on the next field trip the dash padding was flexing up and down dramatically. More screws solved that problem. One cooling fan on the air conditioning condenser failed. It's amazing what some people have in their workshops. The windshield wiper motor also eventually seizing up.

I "lost" 2 emergency beacons off the roof. I thought that I had brushed them off under low hanging tree limbs, but when I investigated, I found that the crashing, banging, and shaking had broken the plastic bases and the lights shook off. I bolted new ones on more securely, and then actually brushed one off, but it made quite a loud smashing noise.

I broke one engine mount. No problems, I kept driving 2000 km until I got home and replaced it. I hear this is a common problem. I am now on the third set of accessory drive belts and have replaced a broken bolt that assisted in locating the power steering pump. The thermostat acted up and sometimes was reluctant to open. Replaced it and no further problems.

The fuel lines are a problem as the heat and age makes them brittle and they split and also fail at the standard clamps. Bio diesel is also suspected of attacking older style rubber fuel lines. Changing to screw type clamps helped. Although I am prepared to do emergency field repairs, I have been lucky. Two failures occurred on the hoist during routine maintenance and the third failed on the driveway of a friend's maintenance shop. I can almost forget the failure of a $1 piece of power steering hose. The plastic fuel tank floats in both main tanks failed. The diesel just dissolved them and their plastic lock nuts. In an effort to cure erratic level indications I replaced the rheostat wiring on the fuel level transmitters and the voltage regulator in the dash. No joy so far.

I encountered another problem when I was checking the accuracy of my fuel tank gauges. In my usual conservative fashion I was "running on empty" around the cit, when the engine faltered. I switched to the second tank. No problem, I figured, just like a petrol engine. When I did the same at 110 km/hr at midnight, 200 kms from anywhere, the fuel injection pump would not re-prime. Luckily, the next morning, I managed to get hold of a local mechanic, who used his sat phone to call the guys who did the diesel installation on my truck. They gave him the advice, he demonstrated it for me. 10 minutes all up. I now know how it's done and now have no fear about running out of fuel due to erratic fuel level readings. It cost me 10 hours lost time, $100 and a six pack. Since then I have demonstrated my cleverness / stupidity on 3 occasions.

About biodiesel - it's not diesel, it's more like perfume base. It just burns like diesel. I have problems filling my truck due to excessive foaming in the tank when I mix mineral and bio diesel. Annoying but not fatal. For everyone who is concerned about the durability of fuel injection system components and the need for lubricity additives, the US Air Force has determined that 2% biodiesel in your regular fuel does an exceptional job of providing additional lubricity to maximize the life of your equipment. Cheap too.

All my rough road travel beat up the front and rear suspension and the springs sagged. The springs, bushings and shocks were replaced and assisted, as appropriate. Koni adjustable shocks were used. Nolethene? bushes were used, except for the shock bushes. The stock set of shock bushings failed in the first trip. Nolethene? is the go. Unfortunately, I set up the truck to 4 x 4 specs. This raised the body about 2 to 3 inches, this changed the driveshaft angle and caused the transmission tailshaft bearing to beat out twice on one trip. A longer driveshaft solved that problem. 4L80 owners be advised.

Brakes were another problem. I had the rear brakes replaced soon after I bought the vehicle. I had to replace the entire front brake assemblies after 4 years driving. I drove away from a traffic light and they started pulling to one side. It got worse and when I found a safe spot I stopped. Wisps of smoke were coming off one front brake. Although the brake released when I backed up, I called for a tow as I was in busy city traffic and a lot of roads were closed because of flooding. Another 40 year flood? There could have been 20 years of accumulated wear, corrosion, and rubbish packed into the mechanism. My mechanic sourced a complete set of disks and calipers and I now have new front brakes. This was for a 20 year old American truck in Australia. Aussies are pretty resourceful. And the price was also reasonable.

After one trip using a tree branch as a "cruise control" I had a proper unit installed. Much improved. A Sony AM/FM/CD player with a USB port solved the music problem. One memory stick has 24 hrs of music. No more CD libraries for me. Unfortunately my dog learned how to operate the CD player and eventually broke a CD and loaded the broken piece. I had to tear the head unit down to remove the broken disc. Another skill mastered.

I've rearranged the "truck lounge" in the back. I bolted 2 modest sized tool boxes to the floor and shifted the bed/lounge to the top of the boxes on the port side of the van. This is the low side on crowned roads (RHD) and minimizes the problems of keeping things neat and tidy. Also seeing this is, or was, an ambulance and I work on isolated sites, I have added a bigger first aid kit suitable for a small workshop.

Despite all the problems that I have encountered, I still regard the vehicle as reliable transportation. It has never failed and left me stranded. It has travelled a lot of rough roads in difficult conditions. I carry considerable food and water, spares and tools. I can always call for help on the sat phone.

Don Swanton
Victoria Petroleum
Perth, Western Australia

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