Drinking the Koolaide... 😊

[Tybalt39]

Always a new issue....

I purchased replacement window trim pieces (the plastic window-surround that also retains the wall panels). Turns out this is intended to clip into aluminum pieces attached to the window frames. A PO removed all of that material (the windows are now held in-place by screws and large washers).

UPDATE:
Received the aluminum pieces from Applied. I may have to cut them up as there aren't enough to complete all windows. That's OK; I just need them as trim attachment, not window anchors.

Further update:
Apparently '73 coaches have a unique window trim and retaining rails. The aluminum rails I obtained were from a newer coach and didn't have the correct interlock for the plastic trim. I have one piece of short trim from this coach (found hidden behind an added piece of decorative wall panel) that I will cut into small sections to mount on various windows as needed just to hold the plastic trim in place over long spans. Live and learn....

 

[old_skool_luvr]

Previous owner had full-height opening cockpit windows installed - I strongly recommend if the community can get 25 orders together. Not much wind noise, comfortable at 65mph.

Being 6'2", those full height windows would be awesome to have!

Although....being someone who would rather drive with the window "down" (i do, even during the Winter, LOL!) i can just imagine the amount of turbulence those would cause while cruising at highway speeds. Definitely a bonus while just cruising around populated areas though.


Chris.

ps: thanks for the wheel/tire info as well. Not too often i run across someone who is into the finer details.

 

[old_skool_luvr]

Through-bumper hitches are nice! I'd be curious to see what the construction of the front one looks like. That'd be a first for me. I've got those on some offroad rigs so I can put a detachable 12k winch on there. Could come in handy if a GMC doesn't have an LSD...

These originally had hydraulic wipers that were plumbed in series with the power steering box. They're a strange animal. No delays, just speed control, and you can make them wipe super slowly so they look like an electric motor that's dying.

A point of clarification, power converters go from 120VAC to 12VDC, and power inverters go from 12VDC to 120VAC. These were originally equipped with big, loud, power converters endearingly referred to as buzz-boxes. The most common upgrade I've seen is switching to an Intellipower brand converter, often done between ten and twenty years ago. I've seen a lot of those in coaches, and haven't seen one that was problematic. I want to say they're typically 40A?

Interesting point on the LSD there. Is there a driveline company out there currently, that offers a LSD for the TH425 trans?

While i have a good amount of "reading knowledge" on these trucks, i have yet to dive into getting mine road worthy again (only brought it home a few days ago) but the first thing i noticed when i was looking the truck over (while discussing the purchasing deal) was that the wiper system was hydraulically operated via the power steering system. I'm guessing the system operates similar to hydraboost braking systems? Guess it'll help that i have two trucks with hydraboost brakes, LOL!


edit: you also wouldn't happen to be the owner of that gorgeous tan 6X6 that graces all of social media for the last few years?

 

[Rdenney]

The wipers aren't like Hydroboost, which uses an independent hydraulic pump used to power devices in parallel, as I understand it. (I may not understand that correctly.) The original wipers are mounted in series downstream from the power steering gearbox and run from the conventional Saginaw pump. The steering gearbox's return line powers the wiper.

The system includes an inline filter in the line from the gearbox to the wiper hydraulic motor--the filter screws into the motor and the hose screws into that. Those filters are often clogged, and that can play havoc with both the wipers and the power steering.

It's a standard upgrade to replace the hydraulic system with an electric wiper system originally designed by Ken Henderson and now (as I understand it) being sold by his son Alan.

GMC Motorhome Electric Wiper Motor Upgrade - GMC Motorhome Electric Wiper Upgrade

Rick "a worthwhile modification" Denney

 

[pvfjr]

Interesting point on the LSD there. Is there a driveline company out there currently, that offers a LSD for the TH425 trans?

Yes, there are two sources. Applied GMC sells them, and Jeff Ianatello (sp?) on the FB groups sells one. Jeff will tell you his is better. They're available with gearsets as well, so if you're considering lower gears, that's the time to elect an LSD.

I'm guessing the system operates similar to hydraboost braking systems?

Kind of. It's plumbed in series with the power steering gearbox, much like GM's hydroboost brakes. That's about the only similarity I can think of. They're interesting to operate. When you adjust the speed, you're not adjusting the delay. You're literally adjusting the speed. So the wipers can crawl across the windshield, but there's no intermittent delay. Quirky and amusing, but they work fine.

Hydroboost, which uses an independent hydraulic pump used to power devices in parallel,

That's not been my experience with hydroboost. All the rigs I've had with it (70s through 2000s 1-tons and a couple Astros) have had both the MC and the steering gear plumbed in series to the same power steering pump. It doesn't look like it's straightforward series arrangement since the MC has it's own return line, but the pressure lines were indeed in series.

 

[pvfjr]

edit: you also wouldn't happen to be the owner of that gorgeous tan 6X6 that graces all of social media for the last few years?

Haha, no, that one's not mine. My pockets aren't deep enough!

 

[old_skool_luvr]

They're interesting to operate. When you adjust the speed, you're not adjusting the delay. You're literally adjusting the speed. So the wipers can crawl across the windshield, but there's no intermittent delay. Quirky and amusing, but they work fine.

They sound like they operate just like the old vacuum wiper systems on transport trucks pre-80's.

 

[Tybalt39]

Question for the hive-mind...

Rear access hatches.
My generator door panel has become detached from the hinges. Shall I simply re-attach using existing hardware (repair the panel if needed and rivet to existing hinges) or use a piano hinge instead?

It doesn't show in any of the pictures of this coach, but some PO (after removing/losing the original twist-latches) was holding the hatch in place using a metal rod and plastic loops; one on the body and one on the hatch. I'm assuming this put some strain on the hinge attachment points. I have since installed an "original" SouthCo latch with no problems at all. I'm switching all of these latches to the "key" style.

UPDATE:

I have purchased OEM hinges from another owner in WA. Should arrive in a couple of days. Then, I just have to patch the holes in the SMC from those plastic clips.

 

[Tybalt39]

After months of waiting, the coach finally has new ball-joints (upper Moog and lower Applied/Moog) on the drivers side. Yes, the 3/8" hardened bolts were used. Paperwork indicates two ball-joints were replace a couple of years back; I'm hoping these were on the passenger side....

The coach is currently at an alignment shop that has experience with these vehicles (plus Kelvin D. imparted some wisdom). Of course, when taking the coach in, I lost rear brakes (on a downhill grade with a sharp turn at the bottom). Master cylinder "front" reservoir dry as a bone, rear "watery". So, they replaced four leaking brake cylinders too. I'm told the coach handled well at highway speeds for the test drive, but the rear brakes were "unbalanced", so off with the wheels again....

I'm really looking forward to driving at highway speeds without fighting the "drift". Just replacing the ball-joints made the vehicle track much better around town; the steering wheel needed little if any adjustment on straight roads.

 

[daver]

Find the issues as to why your battery is dying per Ken's suggestions. FYI, leaving a lead-acid battery in a low state of charge for an extended period of time (even a few weeks) is a death sentence to the battery. Your chassis battery might just be toast.

When you change your house battery(s) to LiFePO4 (lithium), add a DC-DC charger to control the charging from the engine alternator. Unless you are planning a monster size LFP battery capacity, don't complicate things with a second alternator.

I have some LiFePo4 55 Ahr cells and was thinking about using them for the home battery.
One concern I have is I could no longer jump the Chassis with the home battery because, assuming the batteries are more or less equally charged, the home battery would be way overstressed trying to put out 200 amps or so. My LiFePo4 cells only have a C value of 1, meaning they are only good for 55 amps output.
It's nice to have the self- jumping option after the coach has been sitting for a few months, plus, my Quadrajet has the the Leakey fuel bowl so it has to crank for 20 seconds to re-prime itself.
...still pondering the issue.

 

[RF_Burns]

I have some LiFePo4 55 Ahr cells and was thinking about using them for the home battery.
One concern I have is I could no longer jump the Chassis with the home battery because, assuming the batteries are more or less equally charged, the home battery would be way overstressed trying to put out 200 amps or so. My LiFePo4 cells only have a C value of 1, meaning they are only good for 55 amps output.
It's nice to have the self- jumping option after the coach has been sitting for a few months, plus, my Quadrajet has the the Leakey fuel bowl so it has to crank for 20 seconds to re-prime itself.
...still pondering the issue.

Install an electric fuel pump with a "Prime" button to pressure for a few seconds to fill the carb before cranking.
How many LiFePO4 batteries do you have to install? 4 or more in parallel should give you enough cranking amps. Also press the Boost button for a few minutes to give your chassis battery some charge. The higher voltage of the LFP batteries will give some charge to the lead acid chassis battery before cranking.

 

[Tybalt39]

Collected the coach from the shop. Drives straight at 55 with little correction needed.
OEM window trim installed.

Update!
(May 11 2024)

Applied fabric over padding. Yes, there are some unsightly "gathers". But, I'll have to redo these two panels sometime in the future as I now realize the bottom panel should come to the bottom of the window. The sofa will hide most of the gathers until then.

Now to paint the trim light gray.

 

[Tybalt39]

Back to the neutral safety switch....

I have no voltage at the reverse lights. I want to verify power at the neutral safety/reverse switch first. I assume the heavy purple wires are for starting. Can anyone ID the reverse light plug?


Update 19 Aug 2024:
Turns out everything is working; I just wasn't latching into the Reverse detent. My gear indicator slips.

 

[gerryg]

The light green goes to the back up lights. The dark green comes from the fuse box and should be +12 when the ignition is on.

 

[Bhart]

Greetings! I'm probably going to purchase a 1973 26' from a co-worker (test-drive and visual inspection happening Sunday). If all goes well, it's mine! I've been looking into these vehicles for a few years, but this is the first time I've had one close to me at a reasonable price in usable condition. Granted, even a "usable" GMC Motorhome will need much TLC and work to make it truly reliable and highway-safe, but I've set aside funds for immediate repairs.

If anyone knows the history, it's the blue "Mr. T on a Unicorn under a Rainbow" vehicle. I have another co-worker familiar with the Olds 455 engine (former hot-rodder), so I may have a local support "group" (the previous owner once-removed of this vehicle has two others; his wife told him to lose one...). My co-worker had it for only 6 months, planning to turn it into an Air BnB (never going to drive it). His plans changed.
View attachment 7980
I'm told it's already "dry" (no leaks), so once it is verified to be highway-safe, planned upgrades are:

• Astro/Safari steering column with wiper-delay, washer, and headlight dimmer on the "tree" (new wiper motor and electronic cruise control)
  • Update: Electric wiper-motor modification was already installed!
  • Update: New "Lumina" wiper arms and nozzles installed, both sold by Dorman, plus new reservoir/pump
• "NGMC" dashboard replacement
• Dakota Digital instrument cluster w/EVIC
• Vintage Air Gen IV HVAC with Dakota Digital temperature controls
• MicroLevel rear suspension controls/auto-leveling
• Android-based entertainment system in the dash, with heads-up navigation screen, etc.

Down the road, I intend to move to a lithium-based electrical system using a second alternator supplemented by solar panels (I've been using solar and lithium for my camping setup for some years; refrigerator, freezer, ice-maker, microwave oven, ceiling fans... in a tent...). Once that is accomplished:

• Lose the "roof-shakers" and install mini-split heat-pump
• Induction "hot plate" (700W is perfectly adequate for "medium" heat)
• Combination air-fryer/convection/microwave oven

In a perfect world, I'd love to get my hands on bumper covers and the "full" sliding front driver/passenger windows. Basically, this vehicle looks "futuristic" and I want to get the systems to match.

I would be interested in hearing personal experience with the quad-bag suspension system (I hear both positive and negative opinions) and thoughts on a rear-disc brake system. Since an instrument upgrade is planned, perhaps fuel-injection as well (tie the computers together)?

Probably re-paint and new art....

This has been a long-winded introduction, but... Hello from the Pacific Northwest!

When switching out the steering column, the lower shaft is GMC specific.

Charles Boyd probably the most experienced on swapping out the steering column.

Charles Boyd via Gmclist <gmclist@list.gmcnet.org>​	Thu, Dec 5, 2019, 5:50 PM
to gmclist, Charles

Sir, I have only done about 100 columns so I sure don't know it all and certainly haven't seen it all. The answer to your question is yes, maybe,
most of the time. The lower part of the column from the knuckle joint down is ~ 3" longer than a car column. Depending on what you want to do you
will need the lower inner shaft and external housing with gear shifter. If you are wanting to use the dimmer on the stalk stuff it is easier to use
the lower bearing housing with the guide hole for the dimmer switch from a donor column. If you do you will need to change the shifter detent from
the original housing to the new one. You will need to extend the dimmer rod to fit or find one the correct length out of a van? Or a particular
Mopar? If you want the flash to pass feature you will need dimmer switch out of a Jeep. If you want OEM switch for Electric wipers you need a switch
for a Lumina van. If you want cornering lights you need a turn signal switch out of a Caddy, if you want the telescopic feature you will need the
upper part of the Caddy column including steering wheel or modify a S-15 or ? If you are just repairing a worn column you can flip the nylon tilt
ball 180* and not move the index marks to get the nylon ball spring on virgin medal and take the play out. I usually replace the upper shaft with one
from donor column as they don't wear like the 12,000 lb motorhome does. All GMC Motorhomes I have seen have had play and the grove worn in it. If
you have particular questions ask and I'll try to answer.

http://www.gmcmhphotos.com/photos/s-10-steering-wheel-caddy-conversion/p47388-wear-pattern.html.

 

[Tybalt39]

The light green goes to the back up lights. The dark green comes from the fuse box and should be +12 when the ignition is on.

Thank you! Looks like the switch is functioning and needs no adjustment to go into reverse. Now to find where I lose connection from the switch back to the lights.... Looks like it's a lt-green wire all the way back.

 

[gerryg]

Thank you! Looks like the switch is functioning and needs no adjustment to go into reverse. Now to find where I lose connection from the switch back to the lights.... Looks like it's a lt-green wire all the way back.

There are 2 connectors where you can test connectivity. A 10-way connector where the dash meets the driver's side door card (okay not a door card but where a door card would be if there were a door) and a 6-way inside the coach in the wall at the driver's side rear near the tail light.

 

[Tybalt39]

There are 2 connectors where you can test connectivity. A 10-way connector where the dash meets the driver's side door card (okay not a door card but where a door card would be if there were a door) and a 6-way inside the coach in the wall at the driver's side rear near the tail light.

Thank you! A PO removed all OEM interior panels and attached cedar planking with construction adhesive to all aluminum frames. It has been fun restoring the walls....

I had planned to do the drivers side this summer and the rear later. Looks like I will be cutting into the wood on that side of the coach sooner than anticipated (assuming I don't find a break behind the drivers plastic panel).

 

[GMC Cruse]

Tybalt39: You need to download the wiring diagram for your coach:

Electrical - GMCMI

A list of downloadable files/links of GMC Motorhome Electrical. Including wire/circuit diagrams, cruise control (Rostra), lightbulb usage, living on 12 volt and the battery charger.

www.gmcmi.com

 

[cbirky]

Greetings! I'm probably going to purchase a 1973 26' from a co-worker (test-drive and visual inspection happening Sunday). If all goes well, it's mine! I've been looking into these vehicles for a few years, but this is the first time I've had one close to me at a reasonable price in usable condition. Granted, even a "usable" GMC Motorhome will need much TLC and work to make it truly reliable and highway-safe, but I've set aside funds for immediate repairs.

If anyone knows the history, it's the blue "Mr. T on a Unicorn under a Rainbow" vehicle. I have another co-worker familiar with the Olds 455 engine (former hot-rodder), so I may have a local support "group" (the previous owner once-removed of this vehicle has two others; his wife told him to lose one...). My co-worker had it for only 6 months, planning to turn it into an Air BnB (never going to drive it). His plans changed.
View attachment 7980
I'm told it's already "dry" (no leaks), so once it is verified to be highway-safe, planned upgrades are:

• Astro/Safari steering column with wiper-delay, washer, and headlight dimmer on the "tree" (new wiper motor and electronic cruise control)
  • Update: Electric wiper-motor modification was already installed!
  • Update: New "Lumina" wiper arms and nozzles installed, both sold by Dorman, plus new reservoir/pump
• "NGMC" dashboard replacement
• Dakota Digital instrument cluster w/EVIC
• Vintage Air Gen IV HVAC with Dakota Digital temperature controls
• MicroLevel rear suspension controls/auto-leveling
• Android-based entertainment system in the dash, with heads-up navigation screen, etc.

Down the road, I intend to move to a lithium-based electrical system using a second alternator supplemented by solar panels (I've been using solar and lithium for my camping setup for some years; refrigerator, freezer, ice-maker, microwave oven, ceiling fans... in a tent...). Once that is accomplished:

• Lose the "roof-shakers" and install mini-split heat-pump
• Induction "hot plate" (700W is perfectly adequate for "medium" heat)
• Combination air-fryer/convection/microwave oven

In a perfect world, I'd love to get my hands on bumper covers and the "full" sliding front driver/passenger windows. Basically, this vehicle looks "futuristic" and I want to get the systems to match.

I would be interested in hearing personal experience with the quad-bag suspension system (I hear both positive and negative opinions) and thoughts on a rear-disc brake system. Since an instrument upgrade is planned, perhaps fuel-injection as well (tie the computers together)?

Probably re-paint and new art....

This has been a long-winded introduction, but... Hello from the Pacific Northwest!

Just seeing this post now (I am onto on this forum very often). I am curious on some of the original planned upgrades as relates to the dash. your notes were;

• "NGMC" dashboard replacement
• Dakota Digital instrument cluster w/EVIC
• Vintage Air Gen IV HVAC with Dakota Digital temperature controls

if you can give any details on those items I would very much appreciate it. my dash is terrible (73 Painted Desert had beige on brown gauges with a blue back light. *completely* unreadable in anything but broad daylight) I was looking at the replacement from http://www.custominstrumentpanels.com/gmc.htm but I am not sure what you are referring to with the "NGMC" replacement. and my AC control doesnt work, so also curious there.

thanks!
Cameron