Well the PO of my Tow rig had a nice set up that I'm adding too.
Hose emergency splice kit.
Bottle jack (block of wood as a base)
Some 14 gage wire
Stuff I'm adding:
Fuel pump. On a motor home you proably have two. A mechanical on the engine and a electric one at the tank since it's such a long distance. The Mechanical is about $14 at the parts store.
FI ECM (probably overkill but they are easy to swap on my truck)
Alternator ( I have a spare for my other truck. That should work in a pinch but a little under rated for the truck.)
Tire plug kit ($17 at parts store for small kit, $27 for the pro kit) Never know when your going to come around a corner and find a box of roofing nails dumped in the road.
electric compressor ($14 at Target)
Can of fix a flat.
Assortment of Nuts bolts and washers.
Couple wire coat hangers.
Spare vacuum line
The best two LONG plug wires from the last major tune up.
Tools: Spart parts are great but worthless without the tools. My travel box has the following.
Full set of Deep well 3/8 sockets.
Full set of 1/2 inch sockets
Ratchets, extensions, breaker bar.
Assorted screw drivers
Makita 7.2 volt angle drill with some common drill bits and a Uni Bit as well as screw driver tips.
Spare charged battery for Makita.
Assorted box end wrenches.
18 inch long pry bar.
Cheap VOM meter
Spark plug gapping tool
Sensor safe RTV
JB Weld (Awsome stuff. I have seen it seal a cracked water jacket in a engine block for 2 years.)
4 quarts of motor oil
2 Quarts of ATF
1 quart of gear oil
1 Gallon of anti freeze.
Pint of brake fluid
full can of brake cleaner
Spare oil filter
Line dry (fuel addative to get water out of the tank)
Octane boost (never know when you going to get a bad tank)
can of WD40 (this stuff is for drying out ignitions...worthless for all else)
small can of BP Blaster penetrating oil.
Stored in a pair of amo cans with good seals. One tall one short and long. The short and long can be used as a catch pan if I have to drain fluid for any reason.
I'm an above average shade tree. I rebuild my own automatic transmissions. The above I figure I can handle 90% of any break downs on the side of the road in under an hour. It's a little over kill but if it limits my time on the side of the road it's worth it.
Fact of the matter is most problems are lack of maintainace. Lots of stuff people don't relize has a service life much shorter then you would think.
Anti Freez is good for about 2 years. After that it becomes acidic and eats the cooling system from the inside out.
Brake fluid abosorbs moisture from the air. The older it is the lower the boiling point the faster they brakes will fade. It also becomes acidic and will eat the system from inside out. 2 years it should be changed.
both of these often get neglected in a RV that only gets used a few months a year.
Brakes...check the lines, calipers, wheel cylinder, linings before extended trips or every 10,000 miles (less on heavy vehicles).
Cooling system...look for any signs of leaks. Replace cap every 2 years, it's a wear item. There is a weap hole in the bottom the the water pump shaft housing. After running the engine for a few minutes to build pressure in the system (upper hose hard to squeeze) pat the bottom of the water pump with a white paper towel and see if it has any coolant leaking. Loosen the belts and check for any side to side play in the water pump. If it has either its on it's way out, replace. Water pumps usualy start giving little tell tail signs they are going LONG before they fail completly. That weep hole and shaft play is what they are.
While the belts are loose spin the alternator. some bearing noise is normal. It should spin free if it has some miles on it. brand new are a little stiff sometimes. If it growels when you spin it or is not smooth it's going bad.
It's funny but for all I have for long trips or my four wheeling trips I have NEVER (knock on wood) had to use my stuff on my vehicle. Now I have used it a LOT on other peoples vehicles that were broken down. I always find the same thing unless it's somthing catastrophic like snapped axle shafts.....Lack of maintance.
Another big one I see is bad alternators on vehicles that are otherwise maintained.....Main culprit is water getting in them when cleaning the engine. If you clean your engine regularly stay away from the alternator with engine cleaners or water. stay away from the electronics on the throttle bodies as well. Wipe that stuff clean with a rag.
Here is a write up I did for a web site I moderate. It's along the same lines but overkill here (I sure hope snapping axles is not a common thing on the road
Now I do a fair amount of back woods travel and primitive camping. Slow going stuff where you rarely get over 5mph for hours at a time and driving over terain most people would avoid walking. It's not unual for me to be 15 miles from the nearest paved road and No tow truck is going to get where I'm at. I have to fix it where it sits.