The Stovebolt Site Forums The Shop Area General Truck Talk What to look for when buying an AD Chevy/GMC?

I’m looking at buying an Advance Design truck soon. I’d like something that runs and drives from the get go or is very close to it. The goal is simply to drive it and maintain it; no huge modifications or restoration is planned.

There is a particular ‘48 Chevy 3800 pickup that I have my eye on, and I’d like to learn a bit more about what to look for on it before I check it out in person.

So, what are things to watch out for on AD trucks? What are common rust spots? Unobtanium parts? Common mechanical problems?

Welcome to Stovebolt T.M.

There is a ton of info in the shop forums to cover the majority of your questions, but not really an all-in-one place thread to point you towards.

Here is a "Legacy Tech Tip" on Test Driving that is a good thing to read and consider as part of your searching/buying process.

One place I would suggest a very good place to read about AD trucks and the work put into them is found in the Project Journals forums. You can read through fellow Bolters projects and see what they worked on, including trials, tribulations and success stories to help educate yourself about AD trucks.

Others will be along to chime in and share their experience and knowledge too.

Just remember that you are looking at trucks that are 70 plus years old and regardless of how close (or far) from the orginal any individual truck may be they are not really comparable to modern trucks in terms of both operation and maintenance.

I am not an expert on model designations but a 3800 is going to be a pretty heavy duty version that is going to be a lot more truck like than the typical 3100 models that are a lot more common.

My truck is a 1950 3600 version and it has signifcant differences from the typical 3100 versions most people talk about.

Thanks. I read through that guide, and it's a good starting point. I should make up a prebuy inspection checklist for a walkaround and test drive.

I'm trying to keep in mind just how old of a truck it'll be, and I'm looking foreword to learning how to keep it alive and on the roads. When it comes to driving I'm expecting looking foreword to something that drives like an old work truck. I get bored out of my mind driving my 2005 Dodge Dakota, but my 1966 Jeep is a blast though it is slow and horridly uncomfortable relatively speaking.


From my understanding a 3100 is a 1/2 ton, a 3600 is a 3/4 ton, and a 3800 is a 1 ton. The 3800 has a bigger frame, crossmembers, brakes, leaf spring packs, front axle, gas tank, and deeper axle gears than the lower model trucks. Plus it has a 9-foot bed, which is how I can tell them apart at a glance. All of that information is from a 1948 Chevy truck brochure.

We have a 1949 3800 which is a 1-ton. See the link in my signature line.

BTW, this is your 4th post. You are past moderation so you can post away without needing the post approved.

Welcome to Stovebolt.

Owners of one ton’s are way cooler than the others.
Sounds like you are doing your research before you buy one and Welcome to the Bolt!

Don

Thanks for the welcomes.

It turns out the truck that I was looking at is actually a 3600 that’s mislabeled as a 3800. I’m a bit bummed about it, but I’ll probably end up looking at the truck anyways because it’s still cool.

On the bright side, I now know how to tell a 3100, 3600, and 3800 apart visually.

You may get a kick out of this Legacy Tech tip:

Spotting Guide for Advance Design trucks. Complete with huge poster type layout.

I’ve read through that a few times. It had been quite helpful.

According to the brochure the 3800s still have a hand-operated parking brake, whereas the truck I’m looking has a foot-operated parking brake. That’s what tipped me off that the truck might not be a 3800. The tech tip on bed sizes and stake pocket counts from that spotting guide plus some pictures from the internet helped me confirm.

One short note on the 3800's -- brake parts for the 1-ton Huck brakes are pretty much unobtanium, especially the drums. Shoes can be relined, but will be spendy. I haven't had to source suspension parts, but I suspect they may be the same. Sheet metal wise, the cabs and front clips are the same as 1/2-tons and the same things apply as far as usual rust areas (lower cab corners and lower cowls) Patch panels are available. Engines and trannies are not too bad (4-speed SM-420s have rebuild kits readily available.) Finding a driveable one would be great and money ahead. *Keeping* it driveable ... WAY easier with a 1/2-ton.

Check our Tech Tips for upgrades to keep the 3/4 and 1-ton AD trucks modern road friendly. Also, check in at the Tons o Fun (1-ton) forum for advice, too. A LOT of resident knowledge there.

Hope to have you join the 3/4 & 1-ton club! As Don said, we 1-ton (and most 3/4-ton) owners are generally better looking and more ruggedly he-man like!

Thanks for the info. I’ll be sure to look at the cab corners and lower cowl for rust.

I’ve read that the Eaton H052 and H072 axles are what come in 3600s and 3800s, respectively. I’ve also read that GM 14-bolt axle brakes bolt directly onto Eaton H052 and H072s, but I need to do some more research on it. I’d like to avoid an axle swap, but I’m not opposed to putting more modern drum brakes or even disks on the factory axle, at least if I can keep them hidden behind a solid steel wheel.

I’m realizing that top speed may eventually become a problem. I’m looking into the gearing swap as described in your gear swap article, but I’m also strongly considering adding an overdrive unit.
Novak, who I am familiar with for their Jeep parts, is going to be making a 2-speed, .76:1 ratio overdrive that bolts onto the back of many popular granny-geared 4 speeds, the SM420 included. My Jeep had a Warn overdrive on it and that convinced me that, when it comes to the drivability of old, low-power vehicles, it is better to have low axle gearing for acceleration and an overdrive than higher axle gearing by itsself. Plus having an overdrive unit adds another shifter which I will always be proponent of.
A 5-speed is not in consideration. I want to keep the truck as stock as I can while still making it somewhat drivable on modern roads, and a 5-speed pokes me just wrong when there are other options. Plus I swapped a SM420 into my Jeep and have fallen in love with them.

But the project creep is growing excessive and I digress…

After thinking I’d be looking at and potentially buying a 1-ton and being disappointed to learn it’s a 3/4-ton, my heart is settled on at least a 3/4 ton. Mostly for the longer bed; the shortbed look of a 3100 is not what I want.

As I mentioned I have a 3600. The original HO52 axle has a 4.56 ratio (some are actually a higher number) that I didn't really want so did a 14-bolt axle swap to get to a 4.10 ratio. I don't know if the 14-bolt brakes, etc. would work with the HO but I have my doubts.

The output of the transmission is an enclosed type drive shaft to a mid-ship bearing and an open drive shaft from there to the rear axle. I don't know if the overdrive that you mention can be adapted to the output of our type of transmission but maybe with some additional transmission changes to a more typical SM420 it may be possible. I am familiar with Novak and always liked their products although a bit pricy. However, I am not sure there is room for an overdrive unit at the back of the transmission without running into the frame cross member that supports the mid-ship bearing. The fornt portion of the drive shaft is fairly short.

I'm not trying to diswade you just trying to let you know what you may need to know as part of your decision process.

Thanks for the info. I don't know a single thing about torque-tube driveshafts, so I'll have to look into that part.

I do have a SM420 output yoke cover (I'm not sure if I''m using the correct terminology) and a "mechanics style" yoke from the SM420 I put in my Jeep. The transmission was a NOS, early-'80s-built unit made by ConDiesel for the M561 Goat but Novak's SM420 to D18 adapter fit without issue so I'd imagine and hope that I could slap a conventional (modern style) yoke onto the back of the SM420 that's in the truck.

As is obvious, I'm unfamiliar with the underside (or any side really) of these trucks. I'll probably just have to wait until I have a truck and see how much space and flexibility I have and how much custom fab work a swap would entail. I built a crossmember from scratch when I did a SM420 swap on my '66 Jeep and it hasn't broken yet so I'm not too worried about that sort of fabrication work, but every little mini-project added does play a factor in the overall difficulty of adding an overdrive.