WME

Try taking a gas charged Monroe and see how much force it takes to collapse it and then take a Bilstein and do the same.

Yes for the entire rear axle

Spring rate=lbs to deflect the spring 1". Adding an airbag can only add to the rate. KYB and Bilstein are DeCarbon style shocks and ADD to the initial stiffness. It takes about 60 pounds of pressure to move this style of shock. Time and miles will help smooth things a bit. The basic problem is the stock spring have a certain spring rate you have added more springs so the total rate goes up. P.S. Were the spring bushings replaced?

Yes 2" ID, not to sure about the clamps you posted. I went to a muffler shop. They have both stretcher and shrinker hydraulic powered. So the muffler fit perfectly. P.S. the stock is 2.5" inlet and outlet

Adding air bags won't make the ride any softer than just the spring. You would have to remove a spring leaf and then add the airbag. Adjusting the air pressure could keep the same ride height and a softer ride

You will need to remove the existing fuzzy. These folks have a bunch of different shapes. https://www.rubbertherightway.com/window-channels-sweepers-fuzzies-window-sweeps-fuzzies-9418-ctg.htm

A couple of things that MAY help. https://www.etrailer.com/RV-Vents-and-Fans/Lippert/LC389380.html https://www.etrailer.com/RV-Vents-and-Fans/Camco/CAM40595.html

I use a muffler that was for a Ford F250 pickup with a 460 cid and a single exhaust. On my little 4 banger no major back pressure and no noise. I use stock Toyota exhaust in to the muffler and I think it was 2.5" out all the way the behind the rear axle.

Do a little research Google "Clark Cortez RV". The passages seat did not rotate, but flipped over. The back of the seat became the bottom when flipped. My Class a has a rotating seat and it's PIA to rotate. You have to slide it back and forth on the rails as you turn it.

A compression check will tell you a lot too.

Does the new fridge work on the battery?

Very BASIC check on the temp sensor...http://schematicsdiagram.blogspot.com/2012/03/toyota-coolant-temperature-sensor.html do it on a cold engine Yes the exhaust heat could effect the sensor. An old trick is a 1/8" hole in the thermostat flange will let some water circulate and reduce the wild readings on an engine that is still warming up. Some stats have the hole from the factory

Segal's Law.. A man with 2 watches never knows what time it is. The block is the coolest part of the cooling system, the head is much hotter, the upper radiator hose is the hottest place in the cooling system.

Original Toyota sensor?

Toyota Red antifreeze and "normal" green antifreeze do not play well together. Do you know what was in your Toy? If it had green in it then never mind. If it had red you will need to flush the entire system, including the heater. Install 50% mix of antifreeze of your choice. A simple compression check will show up a blown head gasket about 90% of the time.

No air shocks, no overload coils on shock. The shock mounting bolts will fail. Choices 1. Overload 1/2 leaf spring 2. Add a leaf full length. Old Man Emu has them 3. Timbren booster 4. Zuk Mod or a variation of. 5. Air bags. Air bags can help level things at some camping spots

The problem with the foolie rear end isn't the bearings, it's the axle that fails. Worse is that they are no longer available so you just can't replace them as a preventive measure.

This is full on emergency redneck engineering. Get about 3" of bulk filler hose about the same diameter as the damaged hose. Slit it length ways and slip it over the damaged section and use a bunch of hose clamps to hold it tight and seal the leak. Linda's self fusing tape is also great for emergency radiator hose repair, wrap the split and hose clamp it. Remove the radiator cap and drive slowly

Its usually in the converter. Sometimes a blue cube, sometimes just a relay.

Ok first thing is no more mountains 🤡 Real starting point is NEW rotors and HD brake pads. Ceramic pads and new rotors run $150 and up at Rockauto. Your looking for a set for Toyota 1986 DRW pickup. IF you have the REAL 1 ton rear axle, if you have doolies then a normal 1/2 pickup Next is very important the "Engine,Transmission, Drive line section" of the forum has a LONG post titled "Load Sensing Proportional Valve"... This is a very important read. The factory pickup has a brake bias valve on the rear axle. It thinks your driving an empty pickup so, to stop rear wheel skids, it shifts most of the brake effort to the front. BUT you have a full MH so you need to fool the valve into thinking you have a fully loaded pickup so it shifts more brake to the rear wheels. With the weight of your house and dual rear wheels you can't shift to much brake effort to the rear. In fact if you read the post about the valve you will find owners who removed the valve completely.

Did they fail because they overheated, have a hydraulic failure or just wore out due to lack of maintenance??

Hey Bob, just in case you get bored with your 5th wheel Sunrader, here is something you could play with. https://bringatrailer.com/listing/1997-toyota-coaster-2/

Vent fan, top mount OR side mount...https://www.etrailer.com/RV-Vents-and-Fans/Ventline/VP-543SP.html

Sway bar, anti sway bar, anti roll bar, many names. It makes the rear more stable in cross winds AND gives your rig more sporty handling😂 Here is what one looks like...https://www.summitracing.com/parts/aco-k1-382-0u/make/toyota/year/1985

Propane is energy dense, 91,000 btu per gallon or 27 kWh per gallon. Solar isn't near as dense. SO maybe a bigger water tank, Get a 5 gallon tank insulate it and circulate your solar hot water through it. The tank would act as a preheated going in to your actual water heater. Then you could have 2 showers a day