question about BIG GMC trucks

[drumyn61]

I'm about to buy this truck but I don't know a lot about big trucks. I have questions about brakes and the 270 engine's towing power, I want to use this as a car hauler for my race car.


Do these trucks have air brakes or drum brakes?
Can replacement parts be found easily?
Are original style truck brakes the best way to go with towing a car?
Is a 270 strong enough to tow or would it be better to go bigger.
I don't want to be stuck going top speed 65 worrying that things will start breaking if I push her.

[1project2many]

Neat idea.

Most of those trucks had hydraulic brakes. If you're only moving the race car then you probably have plenty of stopping power. Those old trucks were never meant to drive on an interstate and keep up with traffic. The 270 is a strong engine but GM would have used final drive gearing to multiply torque for pulling power which usually leads to reduced top speed.

What trans is in there? Are you planning to keep the tandem axles?

[mongocanfly]

That's a good looking truck..if i was planning on anything it would be to drop the cab on a later model chassis..better brakes..better towing..better everything....as for parts, the gmc is going to be harder to find parts for than a chevy would be..remember its 60 plus year old...not a lot of parts being made for those..and that may not be the original chassis..at least not all of it..the front looks original.I don't recall these trucks coming with a dual tandem setup

[drumyn61]

No, he said the tandem axle was added later on, but I think I like that look. It's a tough call. I wonder if the rear gears can be changed to make it a better highway driving truck?
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[svr]

Its possible it had air brakes it has what looks like an air horn on the roof, look under the hood for an air compressor and air brake cans on the axles. Lots of late model axles out there with air brakes both front rear with better gears to swap into it. Converting it to single rear axle would be my choice. Some states require a CDL to drive anything with air brakes, some things to think about.

[drumyn61]

Here are a few more pics:

[drumyn61]

a few more:

[mr48chev]

I don't think the 270 would find towing the race car much of a challenge but you might get real bored in the slow lane as that truck isn't going to be a freeway burner by any means.

I'd say it comes down to how far you are going to be towing on a regular basis. If the track you go to most of the time is within 20 miles I don't see it as an issue except you have to leave a bit earlier to be there when you want to. If the track (s) are a hundred or more miles away and you go every week it is going to be a bit different. You are going to still be running along about 50/55 mph max on the flat spots.

With that hoist the truck is an absolute beast but I'd guess that hoist and bed weigh as much as the truck it's self. Your wife could find more projects for that one than you might have time to tackle.

[mongocanfly]

Is that propane power? Interesting....Also I've never seen a dump bed cylinder setup like that one...also interesting...
What about the yellow truck in the background..

[joedoh]

part of what makes the 270 so capable of heavy loads is the torque multiplication of the rear gears. most of these big trucks had a two speed rear end and I think I see the handle for one on the floor of your truck. but neither will be a suitable highway gear, they are usually 8.10:1 and 6.10:1, and thats where the torque really gets multiplied. even with those big wheels that will still work out to a really tall ratio. if you try to lower the ratio for more top speed, you will lose all that torque that pulls the load. otherwise, you will need some type of overdrive and, I am just being brutally honest here, you will spend as much on an overdrive that can handle the torque as you would on an entire 20 year old dually chassis.

I dont know anyone except martinsr who advocates going highway speeds on a kingpin front suspension. I sure wouldnt. If you really want to make this a car hauler I am sure you can, but you might have to do like mr48 says and resign yourself to the slow lane, or you will probably spend more bringing this truck up to highway snuff than you would on an entire used late 70s/early 80s 454 rollback.

[svr]

A couple further observations, the wheels are what i call 10 hole motor wheels, they are split rim, i know of no replacements for that bolt pattern for newer style tubeless tires, a lot of tire shops wont even work on split rims anymore. No sign of an air compressor so it will have juice brakes with most likly a vacume booster. Brake parts will be a challenge on a rig that old.

[drumyn61]

Damn, I hate to go to a newer truck, but it looks like the writing is
on the wall.
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[1project2many]

I dont know anyone except martinsr who advocates going highway speeds on a kingpin front suspension. I sure wouldnt.

???

Kingpins are still in use today on many over the road trucks. Detroit, AXN, and Hendrickson all provide kinpin steer axles to the major truck companies. The problems that I've seen with the old GM trucks is that the steering components are not as resistant to flexing as the parts on today's trucks.

a lot of tire shops wont even work on split rims anymore.

That is a good point. There are a few around here but most people have more fear than interest.

[drumyn61]

Originally Posted by 1project2many

???

Kingpins are still in use today on many over the road trucks. Detroit, AXN, and Hendrickson all provide kinpin steer axles to the major truck companies. The problems that I've seen with the old GM trucks is that the steering components are not as resistant to flexing as the parts on today's trucks.



That is a good point. There are a few around here but most people have more fear than interest.

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[drumyn61]

It sucks because I really love vintage cars, and I just can't see my Willys coupe sitting on the back of some 80's aluminum bed car hauler.
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[Warrens69GMC]

Consider this F**D
https://losangeles.craigslist.org/an...156682786.html

[joedoh]

Originally Posted by 1project2many

???

Kingpins are still in use today on many over the road trucks. Detroit, AXN, and Hendrickson all provide kinpin steer axles to the major truck companies. The problems that I've seen with the old GM trucks is that the steering components are not as resistant to flexing as the parts on today's trucks.

sorry, I amend my comment to be about 50's kingpin front ends. they were never made to take steering/braking/suspension forces at what we call highway speeds today, the design speed was around 45mph.

[drumyn61]

I've seen this one for awhile but his price is insane.

[mongocanfly]

You don't necessarily have to go with a newer truck to be old and cool..check out 47 fasttoys build..find a 80s dually or cab chassis truck and do a cab swap....if the price is right...that truck in your picture would haul a bulldozer..kinda overkill for a racecar....
Believe me,, that 13k truck isn't that bad of a deal if you've ever built something like that..does the gasser come with it for that price?

Anyway..On the gmc truck it would be a nightmare trying to load and unload a race car off that high of a bed..especially if its a lowered car..

[1project2many]

It sucks because I really love vintage cars, and I just can't see my Willys coupe sitting on the back of some 80's aluminum bed car hauler.

I used to haul a '37 Chevy stock car on the back of a factory built '72 Chevy ramp truck. It was a perfect match as the car used to run in 67-73. Looked great. Trucks like that are still around and they're new enough to be usable.

Originally Posted by joedoh

sorry, I amend my comment to be about 50's kingpin front ends. they were never made to take steering/braking/suspension forces at what we call highway speeds today, the design speed was around 45mph.

Ahh.... That makes much more sense.

Anyway..On the gmc truck it would be a nightmare trying to load and unload a race car off that high of a bed..especially if its a lowered car..

It is very high to make a ramp truck. One of the coolest solutions I've seen was in Claremont NH where a local waste disposal company had a roundy-round car. They started with the bottom of a dumpster and added a workbench, generator, compressor, and toolbox as well as several cabinets of tools. There were hooks in the floor so the car could be chained. They would transport it on the back of a dumpster truck and at the track they'd lower the entire workshop + car into the pits. No one else there had as nice a setup to work in.

[drumyn61]

The entire reason I have been looking at dump trucks is because I was hoping to lift the bed slightly to give a better angle for loading and unloading.

I would be fine with a 72 ramp truck but I can't seem to find one anywhere!

My daily driver is a stock 60 and I drive the crap out of it, but I guess the bigger trucks need a little more finesse.

[_Ogre]

Originally Posted by drumyn61

I don't want to be stuck going top speed 65 worrying that things will start breaking if I push her.

unless it has a 2 speed rearend, 65mph would happen 1 time

[drumyn61]

Originally Posted by _Ogre

unless it has a 2 speed rearend, 65mph would happen 1 time

It has a 2 speed rear end.

I thought about the split rims but I figured since there are still a lot of farm trucks in use, there has to be a tire shop that still changes tires. Also, how often do tires need to be changed anyway.

[joedoh]

Originally Posted by _Ogre

unless it has a 2 speed rearend, 65mph would happen 1 time

even a two speed rear has 6.10 low ratio, and with 34" tall tires, 65mph will be around 4000 rpm.

[mongocanfly]

Good looking 60dd you got there..even with the dump bed raised at a reasonable loading angle you would need loooonng ramps to keep that loading angle..