Very little of what Dan "Utclmjmpr" wrote is accurate.
Yes, there is an almost cult like following. Of close to 13000 built, about 9000 are still in use.
But the front wheel bearings are not a problem as they are not overloaded, but GM took the cheap way to make the knuckles. We have a guy that fixes them and we do only know that his fix is good for more than 140K as that is the highest to date.
The one ton front end has a new an different set of problems. The one that bothers me most is that I can feel the camber problem in a hard corner.
The rear airsprings (airbags) are out of production and one supplier was bringing in parts made offshore, but there were issues. That is little consequence as there are multiple kits available to use current production parts.
They were all shipped with a 3.07 final drive (rear end) that came from the Toronado towing package. It was (is) wrong with the reduced speed limits. Others are available with greater ratios.
The front wheel spacers are not required if one takes the time to set the front end up the may the service manual directs. The problem was that most shops do not understand the different steering box.
The 455s only go about 180K before needing an overhaul. A 454 will not fit without major work because the it will only bolt to the 425 transmission with 2 of four bolts. Some of the later coaches were shipped with the 403 with no loss of performance.
Yes, the ride is very smooth. So smooth that when we used to have to "Push" travel and off duty driver could sleep in the back.
There are three good ways to get the engine out.
You can take it out the top, but the interior was at risk. You can borrow the hoist and gantry from many of the local chapters.
You can take it out the bottom and it is simple if you take it down with the transmission attached.
You can break the frame at it joint and pull the entire assembled drive line (ready to run) out the front. (I have had to do this to do an engine overhaul and a year later to repair crash damage.) With small effort, you can then test run the engine before re-installing.
The leaks in the rear suspension were largely a direct result of the cheap-assed plastic air fittings that GM used. If you replace them with real air fittings, the suspension will stay up for weeks.
The design and development actually started in 1970. While driveline is based on the Toronado, there are many important parts that were revised for the motorhome production and some were revised even more during the production run.
If you want one, you can acquire one at small cost, but beware. We have a saying: "A reliable and ready to travel GMC will cost you ~30k$us. That is all at once or as a kit." They unsaid thing is that sweat gets billed in at full shop rate.
There is still amazing support for the old girls. We have three companies that can supply most any part needed and about a dozen good shops to do work if you don't want to.
Want to look at a few, there are local rallies all the time and most have an open house on the schedule (usually a Sunday).
If you want to know more?
gmcers.org
Matt Colie -