What year MH models are too old to consider buying?

It all depends on what type motorhome you are considering. Older gas-powered motorhomes had carburators rather than fuel injection, the 4L80 transmission in early Chevrolet chassis was worthless--later coaches used Allison transmissions. Chassis were made heavier-duty etc.
High-line diesel pushers like ours and similar units will probably go forever if cared for.
Carburators and 3-speed transmissions kept mileage low--4- and 5-speed transmissions with lock-up and fuel injection improved mileage in the early 90's. My dad's '89 Pace Arrow got 6.5 MPG on the same roads our '91 Pace Arrow got 8 MPG. Don't look for much improvement in the mileage of newer gas motorhomes. With DPs, bigger engines and emission controls have adversely impacted mileage in newer DPs. Weight with slides of course had a big impact. Late versions of our coach probably get around 2 MPG less than our coach, but they are heavier and have more HP.
Until you get more specific on what you are looking at, it is hard to give generalities.
Good luck!

Anything older than about 1991 will have a carburetor instead of fuel injection. Carburetor's work fine, they do drink a little more fuel than injected models. Expect about 6mpg on carbureted, maybe 8mpg on injected.

The suspension is the same on newer as it was on the older coaches. Chevy P30 chassis are weak while the fords are a little stronger.

Older coaches seem to be built better, but you also get no slides which is a desirable option. I love my slide, and now that i've had one I would not be without one. Just a few things to kick around.

I have a buddy with a 1987 motorhome that has a carburetor. That is to old. By 1990, most have fuel injection.

By the way I bought my 1997 Bounder when it was new, so that is NOT old - I keep telling myself it is just paid off, and not old . . .

I have a 30E floorplan. I did not want to go larger than about 30' because the engines of the time where not powerful enough to take a 20,000 RV up a hill and tow a car at a reasonable speed. Now they are, because they have changed to a larger capacity 5 and 6 speed transmission. My E4OD transmission is pretty much maxed out as far as being able to live with the load it is expected to carry for 100,000 miles. Normally the transmissions are expected to last well over 150,000 miles in a pickup, but their typical load is moving a 8,000 pound pickup in city traffic, with some hills, and sometimes spending time towing in the 15,000 - 18,000 GCVW range. Motorhomes do spend most of their time moving around 15,000 (my empty weight) to 21,000 GCVW (my weight while towing my Ford Edge. So I am not expecting as long of a transmission life. I do have a digital transmission gauge, so I can slow down when it gets over 215F, and will install a second cooler if it had ever run over 220 on the mountains or 200 on flat areas.

Problems that you might run into are leaking roofs, stains on the roof (from leaks) or perhaps some leaking plumbing. If they did not winterize the RV properly, then several hidden pipes might have cracked at some point. Check for water leaks near the water heater. The pump should turn on, pressurize the system, then stay off for about 5 minutes minimum before cycling back on.

Good luck with your search.

Fred.

If you're looking for gas, try to stay above 1999. If it's a Ford make sure that the engine is the 362HP V10. Ford had all the issues resolved by that time. You could have some ride/suspension issues with the F53 chassis, but the folks here can help with the least expensive fixes.

If it's a Workhorse chassis, they had some serious brake issues that should have been fixed in a recall. The WH also had a recall on a clip on the fuel system that must be taken care of. The issue with a Workhorse chassis is that the engine and chassis are no longer in production. Consequently parts could be an issue at some point in the future. I had a 2005 WH and dearly loved it.

Good luck on your search.

Thanks so much, everyone! This is wonderful info! Very valuable to guide me in my search!

A friend of mine bought a 1976 Winnebago, 17,000 miles and it still looks near new inside.

My 1986 Winnabago Elandan with 454, 3 speed trans and carb gets between 8.5 and 9 MPG and with the money we saved buying it We can buy enough gas to drive it for about 50 years.The question you have to ask yourself with an older motorhome is "how much of the upkeep and small repairs can you do yourself?". It will take a while to work out all the bugs and update it the way you want it. If you have to take it in and pay the ubsurd prices the dealers charge then something newer will end up cheaper. But if you can do it yourself you can make it exactly the way you want it at a huge savings.

The biggest problem with older motor homes are the rubber items. Rubber bushings can harden and fall apart. Rubber belts and hoses can crack and fail. Rubber seals on shocks, brakes, and wheel bearings, along with engine components can harden and start to leak.
Basically the older the coach the more often minor/major things will fail and need to be replaced.
Just because a coach looks great on the inside does not mean that the mechanical components are in good shape.
I have restored a lot of different vehicles and the worst ones to deal with were the low mileage vehicles that sat unused for long periods of time. I would much rather have a higher mileage unit that was used regularly and properly maintained.

There is NOTHING wrong with a carbureted engine. From 1991 to 1995 GM was throttle body. While this helped cold starts and altitude, it does NOTHING for performance and is less efficient than a carburetor, because it does not atomize the fuel as well. Intake manifold designs were still limited by the wet intake, so no advantage there. Ford fuel injection of the same time period was absolute junk. It was not even a closed loop system. Back when my engine had a carb, in cold weather my motorhome got better mileage than my brother's 1995 TBI pickup truck. There is no real advantage to fuel injection until they went to the high pressure port injection.

It was also in the 1996/97 years that GM came out with the fast burn heads. The combination of better head design, and port injection brought about significant improvements in HP and mileage.

As far as the trans is concerned, the 4L85e is one very tough trans. It is the same design as the old TH400 and shares many internal parts. The only limitation is that it uses a variable slip torque converter. Great design, but requires changing the fluid more often. 15K miles, max. I had a dealer worn me about that with a car I had of the same design. While there were many out there replacing transmissions in the low 100k mile range, I had 180K on mine when I sold it and never had a problem. I drive my vehicles hard, and even towed with it. You just have to change the fluid more often.

Personally, the 2 biggest issues you face with age are rust and long term stress to the shell which potentially causes leaks. Everything else can be fixed. Personally, if I were looking at the 90s coaches, I would be looking for a DP and specifically a Foretravel. Very well built from that time period. You will also find the DPs of that era got better fuel mileage than the modern diesels, due to smog requirements.

There is no "good" answer here. It depends. Depends on the particular MH in question, your skill with repairs, budget, and what you want. No one can tell you what to buy. MH's change over the years like anything else. There is no set timeframe when any particular MH will start having parts fail. Really depends on the MH and how it was cared for and maintained. I can look at 2 69 Camaros. one will be a heap of junk and one might be totally restored and updated.