Locking Differential

Well I really did something stupid today. I parked my coach on the grass to work on cleaning out the sewer valve assembly. It has been raining for the last month almost everyday, and guess what? The coach sank down in the soft ground about 4 inches.

I tried using the locking differential, but all that did was to dig 2 holes under the drive axle. As I tried rocking the coach back and forth by putting it in F and then in R, I dug a very nice rut in the soft ground. Coming to the realization that I was getting nowhere fast, I stopped and thought about the situation. I needed traction, and that is difficult to accomplish on slippery mud. So I waited 3 days and luckily no rain fell and the ground dried out.

I engaged the locking differential button, backed up a little, then drove forward and walked it right on out of the dried up bog!

Question: How does the locking differential work?:confused:

Well if you wanted to make us Prevost owners feel bad because we do not have one, you succeeded.

It is just like the name implies. Instead of the rear wheels turning independent of one another so you can make turns which causes the inner wheel to turn less then the outer wheel (not the inner wheel in a dual, but the inner wheel with respect to the turn radius) a differential is locked so the wheels on both sides of the coach turn the same direction and the same amount.

My guess is your differential is set up with a safety switch that automatically disengages it above a certain speed, and there are probably limitations on its use.

Tuga,

Please post some photos of this ordeal! I'm sure Karen was out there snapping away while you were in dispare. :) You know how guys are visual.

Jon,

When I was a kid I had a go cart with a B&S engine that had a chain that drove the left rear wheel. Later, I bought another go cart and it had what was called a "live" axle. Does the locking differential do the same thing as a "live" axle? Both wheels pulled equally?

When the locking differential is in the off position: making a left turn the right wheels will pull and the left wheels are just along for the ride? Why is that necessary?

Dale,

The ordeal is over, thank God. In south Louisiana it rains everyday in the summer, so I was really lucky to have 3 days with no rain for the ground to dry up.

Sorry we didn't take any pictures. Boy I was lucky to get that coach out:eek: Karen didn't tease me, she knew how upset I was. That will come a little later. Now I know how Kevin felt @ POG II.

Has anyone else gotten stuck in mud or am I the only dumba$$ to drive on soft, wet ground in a 50,000 pound vehicle?:(

Tuga, this site might help...http://auto.howstuffworks.com/differential.htm

As I use my bus more and feel lucky to belong to POG, I am put at ease that we all will make some mistake. I guess that's the school of hard knocks!
Kevin

Thanks Dale that is a great site.

To all, who WILL encounter these situations eventually.

Wood ash from a fire pit or fire place makes UNBELIEVABLE traction in slippery conditions. Just sprincle it heavily on the tires and forward from them and use as little throttle pressure as possible and most times you will walk out of most of these situations. It also helps to realize the situation as early on as possible for digging in doesn't help the odds.

Rule of thumb...... any time you experiance any wheel spin at all, stop immidiatly and assess and sprincle the wood ash if available.

I have been able to start from a dead stop on solid ice on a grade loaded using wood ash. I have been told it works in the mud as well.

Quote:

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Originally Posted by Joe Cannarozzi

To all, who WILL encounter these situations eventually.

Wood ash from a fire pit or fire place makes UNBELIEVABLE traction in slippery conditions. Just sprincle it heavily on the tires and forward from them and use as little throttle pressure as possible and most times you will walk out of most of these situations. It also helps to realize the situation as early on as possible for digging in doesn't help the odds.

Rule of thumb...... any time you experiance any wheel spin at all, stop immidiatly and assess and sprincle the wood ash if available.

I have been able to start from a dead stop on solid ice on a grade loaded using wood ash. I have been told it works in the mud as well.

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Joe, does it help if there is Some Red Hot Coals still burning in the ash when sprinkled below the tires? :D Just funnin with you, but sounds like very good information for the future. I guess I will have to dump my propane grill and put the Old Smokey back in the coach? :confused:

Gary S.

I used to pull double dump trailers in Mich. in the winter, 11 axles. When empty you have a 50000lb empty weight with litterally no weight on the drive tires, very bad. Carried 2 5gal pails at all times. Anytime your forced to stop on a grade your toast, used it many times.

Out of a bad situation comes some good: Thanks Joe, good post.;)

I am going to try to locate some wood ashes to bring to OSHKOSH. I understand that last year, MM did some landscaping on Dan the OSH dude's pasture. With my luck it will rain like the devil.:(

Hey, all you southern boys....Us northerners think "grits" are to be used in case you get stuck.

Lew

Hey Tuga, don't feel bad. A few years back I had a Monaco which I decided to drive onto a 5 acre property I have in Paso Robles, Calif. . Anyway, the Fire Dept. happened to open up a hydrant and the water drained down onto my make shift dirt road. I hit the wet spot going less than 5 miles an hour and sunk down to the axles in the front. It began craking all the fiberglass on the front end and to make matters worse I tried to back out and I broke off chunks of the front end. Anyway, within 3 hours of digging and pulling with a 4 wheel drive truck, we got it out thanks to my neighbors help. $14000.00 later, I had the Coach back. Now, I stay away from uncompacted areas. That goes for soft shoulders on Hwy's also.

Wood ash or sand grit works great on hard packed snow or slippery surfaces. Tuga BURIED his wheels and if you northern boys want to think of an analogy, imagine your bus body hung up on wet heavy snow while the wheels spin down through that stuff. You can provide traction till the bovines arrive but what Tuga needed, and got by waiting was a hard surface capable of supporting the coach drive tires.

Tuga, all the differential does is allows the wheels to travel at different speeds so when going around turns you are not scrubbing one set of wheels. The downside to a differential is that it will supply power to the set of tires that has the least traction. Newell did a great job providing the differential lock so you could get traction to both, equally and simultaneously.

In some trucks you can lock the wheels side to side (as you did) and also you can lock both sets of drive axles.

PRIOR to burying one's wheels...if you are on wet grass, the best strategy is to raise your tag (thereby putting all the weight on the drive axle) and s-l-o-w-l-y move forward.

Then one can get to Jon's top speed of 22.5 mph on the interstate without any trouble at all.

Contrary to public belief, there are times to go fast, times to go slow.

Thanks for the explanation Jon, I looked at the "How Stuff Works.com" website that Dale posted and it explains how a locking differential works with pictures. You are right about "burying the wheels", I could see that I wasn't going to get out of the mud until the mud dried completely. I was just lucky that it stopped raining.

If I would have had to have a tow truck PULL ME OUT, I don't know where the chains could have been attached to. Newell doesn't provide a welded ring or anything that I could see that could be used to latch onto. Would it be safe to attach the chain to the axle? On my 1987 Newell there were 2 receiver hitches in the front that could be used for towing, this one doesn't have anything like that (I wish it did).

Gary, I am sooo lucky not to have had any damage to my coach. Man, that must have been some ordeal.

Jeff, I tried raising my tag axle. It really doesn't come off of the ground like some coaches I have seen. It only dumps the air (pre set @ 25#) and it doesn't seem like it does much good. It was difficult to feel when the wheels were spinning. I was alone when I got stuck and by the time I walked outside to check it out, that baby was buried. So I just decided to wait. Boy I hope I never have to go through that again. :(

Tuga,

If you ever sense wheel spin when you are not on a hard surface (and the coach is not moving) the only safe thing to do is stop and shut it off until you know what you are dealing with.

Unlike a car where a little rocking may do the trick, a bus just has too much mass to even consider trying that unless you are confident you are not making matters worse.

If you are alone, and starting to bury it and want to get out without a tow, raise it up as high as it will go, try to get the wheels in question off the ground with a jack which needs to be adequately supported by boards, and try to place planks or boards under the wheel that is spinning. The key is to stop the thing from burying itself deeper.

Once at a PP rally in Colorado Springs we watched a guy spin his wheels in the soft mud until he got the coach chassis all the way down to the ground. The only way a tow truck could pull him back out was to secure itself some distance from the coach and at a slight angle to the coach. When the winch on the tow truck started pulling he was pulling the buried coach back and sideways simultaneously. He was literally plowing mud with the bottom of the bay doors. It hurt to watch that. Horsing a coach on a soft surface is guaranteed to create much bigger problems.

That's good advice Jon. Sunday morning after the ground dried up considerably, I did just what you suggested. I raised the body of the coach with the air bags to maximum height. I did this because there are 2 skid plates that are welded to the back frame and they were buried in the ground. I figured that they would hamper my efforts so I raised up the coach about 4 inches. It was just enough for them to clear.

Jacking up the coach like you suggested is a good idea. I carry about 8 or 9 oak blocks that are 6"x8"x18". They would have been perfect to use to jack it up with. I remember seeing a 20 ton bottle jack in one of your bays while we were in Santa Fe so I bought myself one a few months later and also bought the oak blocks. If this ever happens again, I'll be ready.

Thanks for the advice:D

Tuga,

Hope you and Karen had a great time in Destin.

I have had the fortune of getting my bus stuck twice. Both times at the same place (says something about my learning abilities) which is a campground at a ranch in the Texas Hill Country where we do some off roading. I didn't sink it to the axle, but got stuck because of slick mud and a lack of traction. The first time I used the winch on my Jeep to unstick it (I had to anchor the Jeep to another Jeep to keep it from just pulling the Jeep). The second time, I was able to pull the bus out with my Jeep which has lockers in the front and rear differentials. It would have made a great Jeep commerical. Prevost puts two nice rings under the front of the bus and two on the back of the bus for idiots like me. We were there this last weekend, and I thoroughly inspected the campground before driving the bus in given all the rain that we have seen in Texas. No problems this time.

Loc

Loc,

Thanks for sharing your story. Those tow rings in front & rear of your bus are a great idea. I wish that I had those on mine. :o I am going to see if I can have some rings welded to my chassis in case this happens again.

That would have made a great Jeep commerical. Maybe I should start towing a jeep!:D

Loc has raised an interesting question: Could you damage a transmission on a pickup truck by trying to pull a bus out of the mud if the bus is helping out by having the engine in Drive and rear wheels pulling?

Interesting question to which there could be more than one answer.

Often the difference between being stuck and moving is a slight amount of traction. When a coach gets buried by spinning the drive wheels deeper into mud it not only had to gain traction, but the drive wheels have to climb the sides of the hole they just dug.

On a flat slippery surface it often takes a little additional tow to start the coach moving again. In mud where you suffer not only the loss of traction, but must push or climb mud a lot more towing effort is required.

It sounds like Loc kept the Jeep stationary and the winch exerted the towing force. Some winches can exert many tons of pulling force.

If there is no winch, then the amount of force that can be applied is typically limited by the amount of traction the tow vehicle has. I doubt if a hard, steady application of power will ruin a transmission, torque converter or clutch unless it is applied continuously for an extended period of time. If I had to pull a bus with a four wheel drive I would definitely have someone driving the bus while the 4WD is simultaneously pulling. In a few seconds or less you will know if it is working. If it is not, but you continue the effort then something can get damaged, but my guess is you will lose traction on the 4WD before anything comes apart.

It is not impressive and takes time and effort, but in my opinion the most reliable way to get a stuck coach moving is to get traction under the drive wheel that is spinning by raising it and putting planking or some other means if supporting it under the wheels.

Tuga, in the rear you alread have an excellent tow point and that is the hitch. In the front you may have to add something, but the best thing to add is a little restraint to the driver.

Tuga,

I would agree with Jon that you would know if it was going to work before you destroyed anything.

The second time I got stuck I used the Jeep to pull the bus out. I have a 30 foot nylon webbed tow strap rated at 30K lbs of force that I hooked between the Jeep and Bus. I put the Jeep in 4WD Lo and locked both differentials. I had a friend drive the Jeep and I drove the bus. The great thing about the tow strap is that it provides a very smooth transition to the actual towing force - kinda like stretching a rubber band and then it snaps back into place. The bus was not badly stuck, just lost traction in soft mud but didnt sink. Just a little help was all that it took.

I have a 9,500 lb winch which with a snatch block can be doubled to 19,000 lbs. The first time, I just hooked the winch up to the back of the bus and had a friend work the winch while I drove the bus. I am certain that the winch probably would not have pulled the bus out without assitance from the bus.

On one other occasion, I have had to tow the bus for about 150 yards on pavement when the bus caught on fire and melted the chassis batteries (that's another story and everyone enjoys a good car-b-que). That time I used the same tow strap, put the Jeep in 4WD Lo and locked both differentials. I had no help from the bus as it would not run. While it was hard on the Jeep because it was an uphill climb, once I got the bus rolling it made it the 150 yards. The Jeep was straining, but it was a relatively short tow. I was more concerned that the Jeep would just spin the tires (35 inch off road tires) or break the strap than really hurt the Jeep. The Jeep is geared low (4.56 ratio) which probably made it possible.

This sounds like a Jeff Foxworthy joke. If you use your Jeep to tow your motorhome, you must be a redneck.

Loc

Tuga: Be sure to isolate and protect the on board computers when welding to the chassis. You can smoke em if you don't disconnect.

Loc: JDub says you are a redneck. I heard him.

Thanks for the advice Roger, but I am going to let Newell do the welding. I have an appointment to have my muffler changed next week on the way to OSH and I will have it done then.:D

Good redneck joke Loc.:)