My 1978 GMC motorhome

[Mike_H]

Which r&p and carrier does gm use in those transaxles? You'd think it was sourced from one of their live axle lines?

I'm not sure, but its crossed my mind. I have a couple guys locally I may try to get a final drive from and take some measurements. From what I've experienced in the GMC community, most people are happy to pay a few to figure this stuff out. Not a lot of critical thinking and an awful lot of followers. That is starting to change (thankfully). Some of the newer generation (like myself) to have found this platform are starting to question the old guard and they HATE it.

If I had a dollar for everyone of the old guard who has said some variation of, "You've done it now. You gutted it and you'll never get it finished, because no one ever does." I could actually PAY someone to restore it for me. Not like around here, where everyone is supportive of a good build. We might question methods and techniques, but very rarely do you hear, "Don't do it, you'll never finish." That is CONSTANT in the GMC community. Not very supportive.

From what I know about GM, they definitely cribed the carrier and Ring/Pinion from something. The question is was it something that there is aftermarket support for? Like an old 10 or 12 bolt? That would be cool.

 

[Rickyd]

I'm not sure, but its crossed my mind. I have a couple guys locally I may try to get a final drive from and take some measurements. From what I've experienced in the GMC community, most people are happy to pay a few to figure this stuff out. Not a lot of critical thinking and an awful lot of followers. That is starting to change (thankfully). Some of the newer generation (like myself) to have found this platform are starting to question the old guard and they HATE it.

If I had a dollar for everyone of the old guard who has said some variation of, "You've done it now. You gutted it and you'll never get it finished, because no one ever does." I could actually PAY someone to restore it for me. Not like around here, where everyone is supportive of a good build. We might question methods and techniques, but very rarely do you hear, "Don't do it, you'll never finish." That is CONSTANT in the GMC community. Not very supportive.

From what I know about GM, they definitely cribed the carrier and Ring/Pinion from something. The question is was it something that there is aftermarket support for? Like an old 10 or 12 bolt? That would be cool.

Th475? Similar or the same as the fwd cadillacs with 472 and 500's? I bet its something relatively stout.

I'd love to see a duramax in one. Even downrated like the van and kodiak versions to keep the transaxle alive that would be a great power/mpg combo

 

[Mike_H]

Th475? Similar or the same as the fwd cadillacs with 472 and 500's? I bet its something relatively stout.

I'd love to see a duramax in one. Even downrated like the van and kodiak versions to keep the transaxle alive that would be a great power/mpg combo

TH425, I believe, but yes, same as in the Caddy Eldo's.

A couple of people have tried the duramax...nobody has really pulled it off. there is a 6.5L AM General Diesel conversion kit going...$$$$$ though. A guy a few hours away has figured out a "kit" to put the 8.1L vortec in them and that is the way I'm leaning for mine...also an expensive ordeal. Most likely I'll just find a cheap, olds 455 to rebuild.

 

[Rickyd]

TH425, I believe, but yes, same as in the Caddy Eldo's.

A couple of people have tried the duramax...nobody has really pulled it off. there is a 6.5L AM General Diesel conversion kit going...$$$$$ though. A guy a few hours away has figured out a "kit" to put the 8.1L vortec in them and that is the way I'm leaning for mine...also an expensive ordeal. Most likely I'll just find a cheap, olds 455 to rebuild.

Something that would sit as much as a motorhome does would surely be better off with a carb or mechanical injection diesel. Thats a lot of junk to break on a modern diesel

 

[Farmergreg]

Something that would sit as much as a motorhome does would surely be better off with a carb or mechanical injection diesel. Thats a lot of junk to break on a modern diesel

Local hardware store owner sold his Olds car with a 455 in it, can't remember the model to a buddy of mine back around '81 or so. Catch was the hardware store also sold propane and the car was ran the majority of the time on propane.

The two things I remember about that car: Thee engine oil was spotlessly clean. And it could really burn off the tires!

 

[Mike_H]

Started really looking at the floors last couple days. I'm going to patch vs replace. There are about three bad spots that need fixing, and they are small. Its not worth tearing the whole thing up and setting the project back even longer.

This is the worst of it. I kind of expected this area to be bad, since this is where our biggest leak was and the sidewall was rotten too. Its dry (I've stopped the leak) but its very flaky. I'll pull this out and replace it. The steel pedastal in the foreground is the Driver's seat mount.

I also pulled one of the rear storage compartments today, so I can modify it to accept two 20Lb bottles of propane. I'm glad I did...This was really gone. This whole compartment will be rebuilt with 1/2" Exterior Plywood. The floors here are still OK.

I also started pulling the "extra" stuff off my roof so I can get some sealing and repair materials. The big thing to come down was the big storage box. I want to eliminate that. Going to be tough, as that is where I've been storing our chairs, my grills, the rug we put under the awning, etc. I'll have to come up with something to store them around the rear of the coach. I want the area for future solar panels though, and want to make sure I have a chance to seal up the roof while everything is exposed. The other thing coming down will be the fridge vent. That is a MUCH bigger hole to patch. I think I'm going to use some alumium flashing epoxied to the existing alumium and double it up with rivets...but I still need to do some research on that. Its a hole about 6" wide and probably 12-14" long.

 

[Mike_H]

I'm making a thing...

Trying to create an LED taillight that doesn't require a bunch of modifications to the coach or look like it was cludged in there (like some of the well known rebuilders do). These panels (my own design) fit under the factory lens and don't require any wiring or coach modification to fit. I designed an adapter housing and will pot them with epoxy. I will be offering them for sale in pretty soon (not that anyone here is a buyer). Its a bit of a distraction from my rebuild...but once I started down the path, I had to see it through.

 

[Mike_H]

Got the compartment rebuilt over the last couple days. I added a couple inches in height and now two 20lb propane tanks fit very nicely. I also found the old box had zero insulation in it. It was lined with galvanized sheet metal.

I replaced the back and side panels.

Haunted Menards for a while and found some 3/4” thick xps foam. I also found some bright white plastic sheeting in the FRP aisle. I grabbed that as an experiment.

The plastic is to brighten the interior of this compartment. I’m happy with how it turned out. Still needs some caulk in the corners.

 

[Mike_H]

Got most of my rotten flooring cut out today. Step one was just getting the garbage out. I have a couple of 4" squares, a 16 x 12 piece, I took 2" all the way around the shower area, and about a 72" x 12" piece that was under the kitchen to replace. That is just in the main living area I still need to get the wood out under the driver's seat. I used my multi tool for this and was pretty happy with how it worked. I was bummed that I had to pull my water heater to get the wood underneath it though. When I put the new tank in (after a bone headed mistake my first winter), I attached it like it should have been permanent. I got it off, but holy cow. I guess I know how I'm going to re-mount it again. I used a layer of butyl rubber, 1/4" aluminum rivets, then caulked the seams. That thing was sealed up tighter than Aunt Edna's pocketbook.

Step two is going to be routing a half lap joint into the plywood to create a flange for the replacement floor to be glued and screwed into the old floor. That, and using some construction adhesive on the aluminum structure underneath should give me a nice, solid floor again.

Once this is all done, I have a couple other areas to use some wood hardener on and then will put Kilz on the whole shooting match to try and keep any of the old stinky smells trapped in the wood...and hopefully prevent any more rot in the future.