| [GMCnet] Tid Bit. When making changes to your GMC. Does that change differ from proven automotive engineering practices. [message #332066] |
Mon, 14 May 2018 13:29  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
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We've had a GMC since 2003. Go to all the GMCMI events now. No mater were they are. Totally rebuilt 3 - 78 Royales. Two for us. One for a close friend. Now building another GMC to sell . In all this building. It's been very clear to me that GMC did a great job in engineering these coaches to high engineering standards, and the technology of the day. In changing anything. You need to evaluate if this new produce changing the original engineering parameters.
With our GMC's in the 40 to 45 years old range. We have lots of new products to install. Some products enhance the original GM designs. Mostly because of new technology that wasn't available, or known in the 70's. Electronic Fuel Injection ( EFI ) is a prime example. And our modern fuels are now formulated to be atomized by way of the pressures that EFI provides. We have EFI/computer, spark control systems in the Howell EFI package. I'm looking forward to the day when we can remove the camshaft from our engines. And have the valves controlled electronically. This will be a terrific enhancement in the way of better valve timing. Mileage, and torque. We now have an electronically controlled fan clutch to help stabilize our engine temps more closely. This is done by sensing engine temps. Not air temps from the radiator. Engine electric water pumps can't be far away. We're removing the failure prone tank selector switch in exchange for a two pump fuel delivery system. We have our original front wheel bearings now that will never have to be remove to get new grease put in them. Thus a true lifetime bearing now. We have some new air bags Due to the original bags not being produced. We have the Quad bag system that has some pros/cons ( Pros. Is a little more stable on the road. Can maintain ride height if a bag fails. Cons. Doesn't handle speed bumps as well. ) And maintains the original rear suspension design. Rear disc brakes to enhance braking. The original rear drum brakes did a good job. But you had to adjust them each year. Jim K at Applied came up with the 3:70 final drive. Fantastic improvement. This list is too long to continue.
Next are two ideas that don't fallow SAE ( Society of Automotive Engineers ) practices.
1 All wheels are made with what's called. Offset. This offset is to place the center of the tire in a very particular position over the Inter/outer wheel bearings. This position is in reference to the load carrying capacity of each of the inter/outer wheel bearings. Our rims have a lot of offset. This can be seen in comparing standard pickup rims to ours. Our lug nuts are out at the tire side wall. Pickup lug nuts are closer to being between the sidewalls. Most cars, and trucks don't have the front and rear tires travel in the same track. Our GMC's have the rear tires tracking wider then the front. There are spacers on the market that will space the front tires out to match the rear tire track. These spacers put excessive loads on the outer front wheel bearings. Pot holes/rough road surfaces acerbate this issue greatly. I would never ever install these on any GMC.
2 An SAE standard has stated for decades that upper/lower A frames should be parallel to each other for proper suspension geometry. With the 1 ton kit. The A frames are no longer parallel to each other. It's said that the 1 ton has a lifetime bearing. The lifetime is over when the bearing fails. Not the life of your GMC, or YOU. SORRY. We have lifetime bearings now that we can lube. And comply to SAE standards. Most original bearing have gone well over 100,000 miles over 40 some years before ever being serviced. From what I've been told. The GM 1 ton bearings are larger. This maybe true. But this 1 ton kit also has the spacer that's listed above. ( I believe the 1 ton spacer is even longer. ) GM never intended for the 1 ton bearing to be loaded in this over loaded condition all the time. ( As a note.) We just talked about overloading the rear tires/ bearings by running 3 tires with the Quad bag. At least the rear wheel bearing weren't being run with the bearings improperly loaded. I put a 1 ton unit in a friends GMC. Now wish that I wouldn't have done it. I know of many owners that have installed the 1 ton. Talk about the improved handling. But most of those GMC's were riding on worn out parts. Dave Lenzi IS the true expert on brakes/suspension components for GMC's. There is no debate on his knowledge. At the next GMCMI event. Ask Dave for a short version of his opinion of the 1 ton. I'm not saying. Don't install the 1 ton. I'm just saying that this is some info on it. It's your GMC. I'll personally go with SAE approved design applications.
GM did a lot of R/D in make our GMC's. We need to keep their design reasoning in mine. Items like electronic fuel injection WITH spark control. That is a technology that wasn't available back then. It's an excellent upgrade that should be at the top of every GMC owners list. I was slow to get mine on. Love it. My 2 cent on the topic. Bob Dunahugh
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