GMC Motorhome Technical Handouts

Technical Presentations | Papers

We would like to thank the individuals that volunteer their time and talents to assist everyone in keeping their GMC Motorhomes safe and sound on the road.

This ongoing list consists of tech sessions at conventions/rallies around the GMC Community, prepared papers and other technical information.

Granted, there’s nothing quite like attending a session in person. Do consider attending one today! Click here and check out the GMC Community Calendar.


DISCLAIMER | Technical information contributed by GMCMI members and the GMC Community is published as a service to the GMC Motorhome Community. Accuracy is not guaranteed. Independent verification is urged.


>> AIR CONDITIONING & HEAT STRIPS

Air Conditioning and Duracool – Updated
Emery Stora | 2009 Fall GMCMI Convention | Pueblo, Colorado
Updated at 2017 Vintage Motorhomes Celebration hosted by GMCMI | Shawnee, Oklahoma

Air Conditioning “Separating Hot from Cold”
Zay Brand | GMCWS Technical Article

GMCMH Heat/AC Dash Control and Vacuum Controls
John Watkins | 2018 Spring GMCMI Convention | Tucson, Arizona
The objective of the session is to provide a through understanding of the dash Heat/AC controls and how that knowledge can be used to help in troubleshooting.

Line Voltage Thermostat for Your Heat Strips
Kerry Pinkerton | 2015 Spring GMCMI Convention | Patterson, Louisiana
Do you run your heat strip and wake up hot or cold? This upgrade will be the best $20 you will ever spend on your coach.

Replace the Dash Air Compressor with a Modern One
Ken Henderson | Scheduled for 2011 Spring GMCMI Convention | Patterson, Louisiana
The objective of this seminar is to learn how to locate and install a modern Sanden-type dash air conditioning compressor as a replacement for the original A-6.

The Wonderful World of Type II HVAC Systems
Mark Wall | 2006 Fall GMCMI Convention | Berien Springs, Michigan


>> BACKUP CAMERA

Backup Cameras, Monitors and Integrated Systems
Byron Songer | 2012 Fall GMCMI Convention | Amana, Iowa
The session will cover the wide range of camera and monitor systems used as a safety supplement on many vehicles today. A review of costs, features and benefits as well as suggested sources for purchasing a system whether customized or off-the-shelf. Information regarding the integration of such a system with other video display uses such as GPS and entertainment systems.


>> BATHROOM

Bathroom Faucet Aerator
Christo Darsch | Article from the Summer issue of GMC Vintage RVing magazine

Do you have an original bathroom faucet with the pull knob for the shower on the front? They are notorious for having a terrible spray pattern, especially if the star-shaped insert inside the spigot falls out. I was nearly resigned to replacing the whole faucet when I found the perfect solution! Just get a Universal Faucet Adapter Neoperl TA-309 by NRG, available directly from nrgideas.com or from Amazon.

To install it, pull out the star-shaped insert (if you still have one) from the spigot. Install the faucet adapter into the spigot using the smallest rubber sleeve. Then lightly tighten the screw. Now, you can add any standard aerator and you’ll have a soft, splash-free spray pattern. What a difference!


>> BATTERIES

A Heart/Lung Transplant for Your GMC (Lithium Batteries)
Jerry Work | 2019 Fall GMCMI Convention | Mansfield, Ohio (via remote video conferencing)

Battery Systems, Living Large in your GMC
Jerry Work | 2009 Fall GMCMI Convention | Pueblo, Colorado

New Battery Connections
Andrew Cudlipp | Youtube Video


>> BRAKES

2, 4 or 6 Wheel Disc Brakes
Bill Harvey | GMCWS Technical Article

Bigger Brakes for the Manny Reaction Arm System
Al Branscomb | 2014 Fall GMCMI Convention | Chippewa Falls, Wisconsin

Choosing Brake Calipers for Your Reaction Arm Brake System
Al Branscomb | 2013 Fall GMCMI Convention | Branson, Missouri
The objective of this session is to discuss the merits of the brake torque reaction arm system as applied to the GMC motorhome and choosing the size and type of brake calipers to optimize the GMC braking capability whether moving or parked.

Drum Brakes – Replace
Andrew Cudlipp | Youtube Video

Hydro Boost Roundtable Handout
Bob Stone | 2017 Spring Vintage Motorhome Celebration | Shawnee, OK

Powermaster
Marvin Peck | deceased

Rear Brakes Modification
Chuck Aulgur | GMCWS Technical Article

Rear Brake Lines – Replace
Andrew Cudlipp | Youtube Video

Rear Drum and Disc Park Brake Upgrades
Al Branscomb | 2011 Spring GMCMI Convention | Patterson, LA
The objective of this seminar is to discuss drum and disc parkbrake problems and ways of maximizing effectiveness of both and discuss the operation and test results of the Kelsey Hayes parkbrake caliper and its application to the GMC Motorhome.

Rear Wheel Bearings – Repack or Replace
Andrew Cudlipp | Youtube Video


>> DASH

Custom Instrument Panels for the GMC
“Mac” MacNeal | GMCES Tech Document


>> ELECTRICAL

Alternative Power Charging Systems
Gary Worobec | GMCWS Technical Article

Boost Switch
Eugene Fisher | GMCWS Technical Article

GMC Charging System Checkout
Ken Burton | GMCWS Technical Article

GMC Motorhome House Electrical System:
Troubleshooting, Maintenance and Safety
Bob Hendrickson | GMCES Tech Document

GMC Motorhome Electrical System from the Top Down
Rick Denney | GMCES Tech Document

LED Replacement of Rear Tail Lights
Tom Whitton | GMCMI Technical Article

Living on 12 Volts
Henry Davis | GMCWS Technical Article

Grounding Your GMC
Ken Burton | 2011 Spring GMCMI Convention | Patterson, LA
The objective of this seminar is to give the GMC owner an understanding of the 3 major grounding systems in their GMC. We will cover the three major systems and also discuss other grounding issues with specific electrical and electronic accessories that are installed in the coach.


>> ENGINE & FUEL SYSTEM

Aluminum Radiator (New) Unboxing
Andrew Cudlipp | Youtube Video

Cadillac 500ci Engine Swap
Jim Wagner and Larry Weidner | 2004 Fall GMCWS Rally | Alburquerque, NM

Cooling Systems Basics
Steve Ferguson | GMCWS Technical VP

Cruise Control Upgrade
John Sharpe | GMCM Convention Presentation

Diesel GMC in a GMC
Marc Hogenboom | 2012 Spring GMCMI Convention | Shawnee, OK
The objective of this tech session is to explain what I did to install a diesel engine, what in my view the advantages of diesel are, and why I did it.

Drop-in Diesel Engine for GMC Motorhome
Manny Trovao | GMCWS Technical Article
Manny announced his plan to provide engine.

Engine Cooling Systems Basics
Steve Ferguson | GMCWS Technical Article

Engine Oil Flow Path for 455 and 403 GMC Engines
Rob Mueller and John Sharp | GMCWS Technical Article

Fan Shroud Modification
Billy Massey | GMCWS Technical Article

Fasteners and Gaskets – A Short Discussion
Matt Colie | 2018 Fall GMCMI Convention | Amana, IA

Fuel Delivery Updates
Bob Drewes | 2013 Spring GMCMI Convention | Dothan, AL
The objective of this session is to talk about fuel problems and items to improve the fuel system.

Fuel Injection for the GMC
Richard J. Waters | GMCES Tech Document

FiTech EFI is the Real Deal
Jerry Work | 2016 Fall GMCWS Rally | Coos Bay, OR

Gas Tank (Steel) How to Drop
Andrew Cudlipp | Youtube Video

Gas Tank (Steel) How to Install
Andrew Cudlipp | Youtube Video

Gas Tank (Steel) Repair with Silver Brazing Old School Style!
Andrew Cudlipp | Youtube Video

Gas Tank Venting & Problems With It
Paul Doane | 2017 Spring Vintage Motorhomes Celebration | Shawnee, OK

GMC Carburetor
Letter to Ralph Luby from Bob Drewes

Ignition System
Duane Simmons and Bob Lamey | 1998 Fall GMCMI Convention | Marion, NC

In Tank Fuel Pumps
Emery Stora | 2010 Fall GMCMI Convention | DuQuoin, IL

“Listen to Your GMC”
Gene Fisher | 2013 Spring GMCWS Rally

Loads, Speed, Motors & Differential Gearing
Chuck Botts, Jim Kanomata, and Granpa Billy | GMCWS Technical Article

Neutral Saftey Switch Issues
Gene Fisher | GMCWS Technical Article

Quadrajets Carburetors
Bob Drewes

Rebuilding and Tuning the Olds 455/403
Joe Mondello | GMCES Tech Document

Rebuilding that Motor
Larry Weidner | GMCES Tech Document

Rebuilding the Olds Engines
Jim Bounds | GMCES Tech Document

Spark Plug Application Guide
John Wright | GMC Great Lakers Tech Document

Starting an Engine That Has Been Sitting for an Extended Period – Check List
Larry Weidner | GMC Vintage RVing magazine – Issue 151 – Spring 2020

Starting Your GMC – Easy as 123
Gene Fisher | GMCWS Technical Article

Starter Wiring – Improved Cranking For Free
Gene Fisher | GMCWS Technical Article

TBI Initial Calibration
Bob Drewes | 2008 Fall GMCMI Convention | Harrington, DE

Ten Minute Combiner Install
Eugene Fisher | GMCWS Technical Article

Throttle Body Fuel Injection Upgrade
Ray Swarzendruber | GMCES Tech Document

Using an HHO System Improved My MPG by 43%
Chuck Botts | 2015 Spring GMCWS Rally | Updated 6-11-2015
Chuck’s experience installing the system and fielding the questions that people ask him about the installation prompted him to develop the presentation with lots of detail. There is a lot of detail in his presentation, because he feels that including any less will only prompt questions that cannot be answered without having been at the tech session in person.

Vapor Lock – Facts, Theories and Myths
Armand Minnie | 2015 Spring GMCWS Rally | Emerald Desert, CA

“What’s Up” with Electronic Fuel Injection?
Randy Van Winkle and Bob Drewes | 2011 Spring GMCMI Convention | Patterson, LA
The objective of this seminar is to provide an introduction into fuel injection for the GMC Motor Home. A discussion of some of the benefits of fuel injection along with simple explanations about how the computer controls the fuel and spark advance. Much of the session will actually show the computer controlling the engine and “learning” how to best meet requirements of the engine. Results of testing with lean cruise and how to get better mpg will be discussed. Tuning tips will be provided during the session.

What’s-Up-with-EFI?
George Beckman and Randy Van Winkle | 2014 Fall GMCWS Rally | Manteca, CA


>> EXTERIOR BODY

Briggs & Stratton Locks and Keys in the GMC Motorhome
Joe Ekl | 2013 Spring GMCMI Convention | Dothan, AL
The objective of the session is to explain the reasons the keys and locks no longer work on our GMC coaches, and how to decode your keys.

Caulking & Sealants
Gary Worobec | GMCWS Technical Article

Slowing Down Your ELECTRIC Windshield Wiper
Ken Henderson | 2017 Spring Vintage Motorhomes Celebration | Shawnee, OK

Entry Door Latch Tutorial
Ken Henderson | GMCMH Technical Paper

Painting My GMC
Armand Minnie | 2014 Fall GMCWS Rally

Principles of GMC Paint Design
Byron Songer | GMCES Tech Document

Refurbishing the GMC Windows
Armand Minnie | 2014 Fall GMCWS Rally

Repairing and Rebuilding Cockpit Windows
Kerry Pinkerton | 2014 Fall GMCMI Convention | Chippewa Falls, WI

Repainting the GMC Motorhome
Larry Bontrager | GMCES Tech Document

Windshield Replacment Clinic at GMCMI 2021 Fall Convention
Our GMCMI Windshield Replacement Clinic leader, Ken Burton, asked if there was anyone that would be willing to videotape an installation at the 2021 Fall GMCMI Convention in Chippewa Falls, Wisconsin. We are pleased that Doug Smith volunteered to accommodate Ken’s request by filming, editing, and supply the voiceover. A big thank you to Paul Hudak, Drew Hudak, and Paul Hudak from PDK Enterprises who have been working with Ken to make the clinic a great success!


>> FINAL DRIVE

Guide to Final Drive Ratios and Tire Size Information by Brand
Don Brown | GMCES Tech Document


>> FIRE

Fire Prevention
Rob Mueller | 2012 Spring GMCMI Convention | Shawnee, OK
The session will review the steps you can take to prevent fires in your GMC and what to do if it does catch fire.


>> FRONT SUSPENSION

Chevy 1-ton Front Hubs for the GMC
Bill Hubler | GMCWS Technical Article

Front Suspension Rebuild
Steve Ferguson

Getting Your GMC Under Control
Front Suspension Basics

How to Install a Modern, GMC Truck One Ton Front End on Your GMC
Karen Bradley


>> FURNISHINGS

Rebuilding the RV Refrigerator
Leon Herschberger | GMCES Tech Document


>> FRAME

A New Frame for the GMC Motorhome
Dale Ropp | 2017 Spring Vintage Motorhomes Celebration | Shawnee, OK
Photos illustrating the start to finish process.


>> HVAC

Horizontal Installation of the Atwood Furnace
Ray Swartzendruber | GMCES Tech Document

Operating and Troubleshooting the Suburban Dyna-Trail Furnace
John Nicholls | GMCES Tech Document

The Wonderful World of Type II HVAC Systems
Mark Wall | GMCES Tech Document


>> INTERIOR

Time for a Facelift? Modernizing the GMC Bathroom
Bill Kooistra | 2016 Fall GMCMI Convention | Mansfield, Ohio

Lined Drapes for the GMC
Geri Roemer | deceased

Rear Cabinet Project
Roy Alden | deceased


>> MAINTENANCE

Maintaining the GMC Motorhome
Fred Hudspeth | Ongoing at GMCMI Conventions since 2012 | Updated 11-7-17
An interactive exchange of owner experiences and recommendations on the maintenance and repair of the motorhome. Fred introduces topics from his Powerpoint program and facilitates discussion. This program is a continuation from convention-to-convention. Only a few of the topics are covered at each convention to allow full development of each topic. Further, no two convention audiences are ever alike.

GMC Maintenance & Friends Application
Byron Songer | GMCES Tech Document


>> MISCELLANEOUS

Coach Weighing
Alex Sirum | GMCES Tech Document

Dinosaur Boards
Chris Clark | GMCWS Technical Article

GMC 101
Ty Hardiman | 2019 Fall GMCMI Convention | Mansfield, Ohio

How to Make GMCMH Ramps
Dale Ropp | 2015 Spring GMCMI Convention | Patterson, Louisiana
Make it easier to work under your GMC Motorhome for under a $100.

Idiot’s Internet Guide
Gary Bovee | GMCWS Technical Article

Junk Yard Gems
Bob Cook and Chuck Garton | GMCWS Technical Article

Living Large in a GMC
Jerry Work | The Dovetail Joint website
How to add enough battery capacity to allow you to really enjoy your GMC without being plugged in to shore power.

Making Life Easier in My GMC  – Part 1
Kerry & Carolyn Pinkerton | 2014 Spring GMCMI Convention | Montgomery, Texas

Making Life Easier in My GMC – Part 2
Kerry & Carolyn Pinkerton | 2014 Fall GMCMI Convention | Chippewa Falls, Wisconsin

Making Life Easier in My GMC – Part 3
Kerry & Carolyn Pinkerton | 2015 Spring GMCMI Convention | Patterson, Louisiana

Making Life Easier in My GMC – Part 4
Kerry Pinkerton | 2015 Fall GMCMI Convention | Rapid City, South Dakota

Making Life Easier in My GMC – Part 5
Kerry & Carolyn Pinkerton | 2016 Fall GMCMI Convention | Mansfield, Ohio

Making Life Easier in My Vintage Motorhome – Part 6
Kerry & Carolyn Pinkerton | 2017 Spring Vintage Motorhomes Celebration | Shawnee, Oklahoma

Metal Shaping 101
Kerry Pinkerton | 2013 Spring GMCMI Convention | Dothan, Alabama
A presentation on the basics of shaping sheet metal. Description and demonstration on various techniques for stretching, shrinking, and smoothing metal, primarily using hand processes. Use of the wheeling machine (English Wheel) is described and demonstrated. More sophisticated machines such as power hammers, reciprocating machines, and planishing hammers are briefly described. This is an interactive format with questions and discussion encouraged.

My TZE Land Yacht
Dan Prigmore and Byron Songer | GMCES Tech Document

National Energy Strategy, Sifting Fact from Fiction
Jerry Work | 2009 Fall GMCMI Convention |Pueblo, Colorado

Preparing Yourself and Your Coach for Successful Long Distance Travel
Jerry & Sharon Work |  The Dovetail Joint website
Presented at 2012 Spring GMCWS Rally in Casa de Fruta, California

Restomoding the GMC Electronics
Richard Waters | 2015 Spring GMCMI Convention | Patterson, Louisiana

The GMC Unplugged
Carl Stouffer | 2013 Spring GMCWS Rally
A presentation on his work to adapt his GMC motorhome for dry camping.

The Forgotten Ammeter
Frank Folkmann | GMCES Tech Document

Short GMC History and Geneology
Jerry Work | The Dovetail Joint website

What Every GMC Qwner Should Know
Frank Condos | GMCWS Technical Article

Yes, You Can Reliably Take Your GMC on a Cross Country Adventure
Jerry & Sharon Work | The Dovetail Joint website
A guide to preparing yourself and your coach for long distance travel.

You Gotta Live in There Baby
Jerry & Sharon Work | The Dovetail Joint website
Tips on how to make your GMC as convenient and comfortable as home.


>> OIL

OYL, What’s in your Pan?
Frank Condos | 2009 Fall GMCMI Convention | Pueblo, CO

Low Oil Level Warning System
Nate Yacono (deceased) | 1988 Convention

What Can Your Oil Tell You
John Richardson | 2017 Spring Vintage Motorhomes Celebration | Shawnee, OK


>> ONAN GENERATOR

Onan Operators Manual and Parts Catalog “Power Drawer” NH Series

Onan Wiring Diagram Update
Ken Henderson | Updated 7/25/2017

Back in 2001, I got tired of trying to decipher the wiring diagram in the Onan manual.  So, I re-drew the diagram for my own use, leaving out the often-removed battery voltage regulator, replacing the ignition points with the Pertronix upgrade by Lawrence Gaskins, and adding a diode I consider important to relay K1.  Except for those changes, the circuits were supposed to be identical, simply displayed differently. By request, I published that “KH Onan Wiring” diagram and it has circulated widely in the GMC community since many agreed it was easier to read.

Recently another EE pointed out an error I’d made. When I began comparing my diagram with Onan’s original, I discovered several other deviations.  Fortunately, those would have been important only to someone REALLY digging into the circuits and evaluating their operation.  After correcting those errors, I published the diagram again, with a to-be-standard filename of “KH Onan Wiring yymmdd”. I finally arrived at “KH Onan Wiring 170725” and republished it at GMCMHPhotos.com under user “KenHenders”.  (Also available here by clicking title above.) Hopefully the diagram is now error-free. PLEASE let me know if you find that to be untrue.

Solid State Ignition for the Onan
Gary Bovee | GMCWS Technical Article

Onan 2004 Demo Pamphlet
Duane Simmons | 2004 Spring GMCMI Convention | Las Vegas, NV

Onan Carburetor Rebuild Kit Content and Instructions
(Source: GMCWS Technical Articles)

Onan Control Board Operation
Duane Simmons | 2001 Spring GMCWS Rally | Palm Desert, CA

Onan Electronic Ignition Upgrade
Chuck Aulgur | 1999 Fall GMCWS Rally | Albuquerque, NM

Onan Tips and Tricks
Gary Bovee | 2014 Fall GMCWS Rally

Feeding the Barbarian
How to run the Onan on either propane or gasoline at the flip of one DPDT toggle switch which can be mounted anywhere in the coach.
Jerry Work | 2016 Fall GMCWS Rally | Coos Bay, Oregon


>> REAR SUSPENSION

Airbag (original) Unboxing
Andrew Cudlipp | Youtube Video

Airbag – How to Replace
Andrew Cudlipp | Youtube Video

Air Suspension Systems
Duane Simmons | 1999 Fall GMCWS Rally | Albuquerque, NM

Electro Level II/Level Sensors
John Sharpe | 2016 GMCMI Summer Get-together | Branson, MO
John Sharpe | 2014 Spring GMCMI Convention | Montgomery, TX

GMC Air Suspension
Jeff Sirum | 2019 Spring GMCMI Convention | Tallahassee, FL

MicroLevel Intro Product Sheet
Keith Vasilakes | 2021 Spring GMC Vintage RVing magazine

Power Level System
Rick Denney | 2006 Fall GMCMI Convention | Berrien Springs, MI

Rear Suspension
Dale Ropp & Ken Henderson | 2014 Spring GMCMI Convention | Montgomery, TX

Shock Absorbers
Manny Trovao | 2008 GMCMI Convention | Santa Rosa, CA

Shock Absorbers Replacement | Video
Andrew Cudlipp | Youtube Video

Suggestions for Installing the QuadraBag System
Bill Brown | GMCES Tech Documents

SullyBilt Airbag Replacement
Todd Sullivan | 2012 Spring GMCMI Convention | Shawnee, OK
The objective of this tech session is to assist GMC motorhome owners to hear about the existence of a new factory like replacement option for the now obsolete original Firestone air spring rear suspension system. The session will consist of information on how the Sullybilt System works. Followed by a live change out of the stock system on a coach to demonstrate the ease of installation.

The Southland Air Bag System
Matt Frady | GMCES Tech Document

Wireless Air System
Gary Bovee | GMCWS Technical Article

Wireless Leveling System
John Shotwell | GMCES Tech Document

Air Bag Systems Comparison Spread Sheet
Mark Grueninger


>> STEERING

Getting Your GMC Under Control
Steve Ferguson | GMCWS Technical Article

GMC Motorhome Steering Box
Don Wirth | 2006 Fall GMCMI Convention | Berrien Springs, MI

Replacing the Upper Steering Column
annotated by John Sharpe | GMCES Tech Document

Saginaw Steering Boxes
Jim O’Clair (Hemmings Motor News) | GMCES Tech Document

Steering Column Upgrade and Repair
Richard Sowers | 2006 Fall GMCMI Convention | Berrien Springs, MI

Steering Inspection Guide
Rob Mueller | GMCWS Technical Article


>> TOWING

A GMC-specific Toad Brake System
Fred Veenschoten | GMCES Tech Document

Tow Bar Support
Diagram

GMC Towing Guide
Robert Mueller | GMCES Tech Document


>> TRAVEL

Do Alaska On Your Own – It is Easy!
Sharon Work | 2016 GMCWS Rally | Coos Bay, OR


>> WATER

Hot Water – Problem Solved
Armand Minnie | GMCES Tech Document

On-Demand Water Heater
Jack Christensen | 2015 Spring GMCWS Rally

Type1 Water Heater Replacement
1991 Letter to Ralph Luby from Selden P. McCabe, Jr. | McCabe deceased

Water Quality and Sanitizing Issues
Frank Folkmann | GMCES Tech Document


>> WHEELS | HUBS | TIRES

Align Your GMC in Nine Easy Steps Using the Jerry Work Designed Alignment Kit
Jerry Work | The Dovetail Joint website

Align it right!  
Jerry & Sharon Work | The Dovetail Joint website
Presented at 2012 Spring GMCWS Rally in Casa de Fruta, CA
You may be surprised to learn that your coach may never have had a proper alignment.  Learn why and what to do about it here.

Everything You Need to Know about Aligning Your GMC to Run Straight and True
Jerry Work | The Dovetail Joint website

Wheels – How to Repaint
Andrew Cudlipp | Youtube Video

Tire-pressure Monitoring Systems (TPMS) for Dummies
Richard Waters | 2013 Fall GMCMI Convention | Branson, MO
The objective of this session is to describe how TPMS can be a way to avoid catastrophic tire failures and expensive to repair damage, a description of the different types of  TPMS systems and how they work, plus an overview of currently available systems suitable for GMC motorhomes.

Tire Safety for GMCers
Byron Songer | GMCES Tech Document