Originally posted by robtcorl In all the years and all the places I took my 4WD Chevy Suburban work trucks I only needed a tow once.
About a half mile from the hard road on a very muddy field road.
The tow truck got stuck and a larger tow truck had to pull us both out.
Having spent many years operating equipment and driving all manner of vehicles, I've been involved in towing or recovery operations on both sides, many times. One particular tow happened while I worked as a mechanic at the electric utility.
Friday afternoon the foreman called myself and another mechanic into the office. Seems they needed us to come in early Saturday and head out into the field to assist the tow company that usually towed all our vehicles with a recovery. Seems the tree trimming unit had a couple trucks out at a remote lake in the hills with mostly summer homes. The crew foreman directed the flagger to move the chipper dump (with chipper trailer) from the street onto the driveway of a customer. The driveway ran downhill towards the lake, and about 100 feet from the lakeshore turned 90° to the left, leveled off and ended at the side of the house. Because it leveled off there was a rock retaining wall about 5 feet high, and about 8 feet from the side of the house.
Now the trucks in the fleet almost all had air brakes.
Also, since it is not possible to find people in the utility industry who know how to drive trucks, most of the trucks had automatic transmissions, heavier duty versions of the kind in cars. One big difference is they do not have a park position. When you move the gear selector to what would be park in a car, the transmission is actually in reverse. Medium duty and big truck automatics (true automatics, not auto shit gearboxes) are identical to an automotive automatic transmission in every other way, although much more heavy duty. They are essentially a hydraulic pump that converts the rotational motion of the engine into forward or reverse motion.
Because if the weight involved, a simple park pawl like cars have would not be practical. Ergo, no park.
The airbrakes have a component called a spring brake, a spring inside the aircan that operates the brakes at each wheel on the drive axle(s) which holds the brakes in the applied position until air is supplied from a valve in the cab when the driver presses it in to release the brakes. Air is directed from the reservoir to a chamber in the aircans which overcomes the pressure of the springs, releasing the brakes.
So the transmission is always placed in neutral when parking, and the spring brakes applied by pulling out the knob on the dash which blocks the flow of air from the reservoir, allowing the springs to set the brakes. To drive the vehicle, one places a foot on the brake pedal, pushes in the knob to release the brakes, places the gear selector in reverse or drive, then moves their foot to the accelerator to get the rig moving.
And to park the truck, one brings it to a stop, places the gear selector in neutral, pulls the knob out to ally the breaks, and then shuts the engine off.
Well the crew foreman had a habit of using the flaggers to help out on jobs, and often would ask them to move the truck. Of course he never asked if they had ever been trained on how to operate one, or better yet, did they possess a CDL.
And this particular Friday afternoon, the young lady he asked to move the truck was happy to oblige, eager to be a team player, but until that day she had never operated anything larger than a 1/2 ton pickup. She managed to get the thing started, released the brake, placed it in gear, pulled it off of the road and onto the customer's driveway. She brought it to a stop, placed the gear selector all the way forward, failing to notice that it was reverse, not park, left the engine running, opened the door and hopped out.
As she hit the ground she noticed the truck and trailer rolling down the hill.
The transmission doesn't provide enough resistance to the forward motion of the vehicle while in reverse, when the engine is at idle.
So nothing was keeping 30,000lbs of truck and 3,000lbs of chipper trailer from rolling down the hill towards the lake.
The intrepid flagger, as eager to right the wrong she has just made as she was to help out, decides she should hop back into the truck and keep it from rolling down the hill into the lake. Unfortunately the door hit a large evergreen tree and nearly killed her as it slammed the door towards the closed position.
She then fell out as the door cleared the tree, nearly getting run over by the drive tires of the truck. The young lady survived and made a full recovery, suffering some broken ribs, minor spinal injuries (if there can be such a thing) and a broken arm.
The truck and trailer made out much better.
As it careened towards the lake, it drifted left a little bit, and just before the left turn in the driveway the left steer tire dropped into a dip on the inside of the bend. This made the front wheels rapidly rotate left, and the truck turned sharply and headed for the house. So then it looked as if the house was in peril. As the front wheels went over the top of the rock retaining wall, the weight of the front of the truck caused it to drop quite rapidly. The fuel tanks came to rest on top of the wall, and since the transmission was in reverse and the engine at idle, it stopped right there.
The front bumper was a few inches from the siding on the house.
So Saturday morning the other mechanic and I assembled at the shop, loaded a shop pickup with tools, jacks and such, and headed out to the lake to meet the tow truck driver.
This is the tow truck:
The tow truck was moved into position, in the driveway of the neighbor's house, to get a cleaner line towards the stuck truck. The boom was used first to pick up the chipper trailer so it could be connected to the shop pickup and pulled up to the road out of the way. Then both cables were let out and connected to the chipper dump, for safety.
The tow truck operator had us stop at the lumber yard and pick up some 8" x 12" beams. We cut them into 24" lengths, and stacked them 2 x 2 criss cross under the front axle of the chipper dump truck, in the space between the house and the rock wall. When we got close to the tires, we made a third stack under the axle, placed a jack under it and started jacking the truck up. As we made room for more timbers, we added them under the front tires, and as the need arose, we raised the jack support stack. Eventually we had the front of the truck high enough the fuel tanks were clear. We made a second stack on either side between the first stack and the retaining wall, and then used a 4"x12"x12' beam on either side to bridge from the cribbing to the driveway behind the retaining wall.
Since diesel engines have a fuel return to tank, and trucks with two tanks only have the fuel return to one tank, there is a line that connects them at the lower end, to equalize the fuel level between them. This was damaged when the tanks hit the retaining wall, so before moving the truck we had to crawl under it and make repairs.
When adequate air was built up I got in, released the brakes, placed it in reverse, and the tow truck operator used the cable to pull it back on to solid ground.
With the truck unstuck and ready for travel back to the shop, we had to pick up all those cut up beams and load them into the shop pickup. Gave us quite the workout. No one else wanted them so I tossed them into my pickup when we got back to the shop and used them for firewood. Kiln dried hemlock fir makes great firewood.