The Stovebolt Site Forums The Shop Area The HiPo Shop How to lower my 1951 GMC 100

My husband wants to lower or 1951 GMC 100. We've never worked on an old classic truck before. He's not sure how these suspensions work. Is there anyone that has done this?

How much do you want to lower it and what other changes are you looking to make at the same time (power/disk brakes, power steering, overdrive transmission, etc)?

What is your long term use case for the truck (car shows, daily driver, occasional truck use, racing, etc)?

There are a lot of options and they all come with tradeoffs. With a bit more info on the bigger picture we can give you better advice.

The suspension in the 1951 GMC (or Chevy...same thing) was very basic. Until we get a better idea regarding the questions above, please let me add one specific caution: Over the past 60 years I've seen people lower these by removing leaves from the leaf springs. And I understand...it seems like a logical thought. Each spring has 8 leaves and it seems if you removed maybe 1/2 of them the truck would be lowered. And up to a point that is true. But (there's always a but)...In this style of suspension your front axle attaches only to those 2 leaf springs. Nothing else secures it. So if one of those leaf springs (which is old and has seen decades of use) breaks because it is now over-stressed because it has too few leaves, your axle could suddenly become disconnected and that would be a catastrophic problem.

It would be an occasional daily driver.
Not changing the brakes or steering.
I think he wants to lower it a couple inches.
He might v8 the truck, depending if the original motor starts and is in good condition.
We have to get a new starter for it. That could be tomorrow.

I think I saw in one of your posts that he's a mechanic. That's good...always something to work on with these. One thought on the V8...if he goes with a small block Chevy he may need to look for an exhaust manifold from a 265. The other type (those used on 283, 327, etc) will hit the steering box. The 265 manifold gives you just enough room to miss it.

He is looking at a small block 350.
He did notice he needs a different exhaust.
I'll let him know your suggestions.
I know a bit about some cars.
Dad didn't want his daughter stuck or suckered.
Thanks.

I think the SB350 will have the same situation (regarding the exhaust manifold). Occasionally you'll find on the big internet auction site just the driver's side exhaust manifold. Unless you wanted matching manifolds, the driver's side is all he'd need. As I recall the Y type (ram's horn) will put the exhaust output right smack in the way of the steering box but the 265 put the exhaust output in front of it. One thing I'll add is that the SBC350 might cause the front end to be a bit higher than it normally would be...those can weigh as little as 400~450 pounds but the GMC and Chevy inline sixes were notably heavier. Your dad had the right idea in my opinion!

Try dumping a couple of backhoe loader scoops of pea gravel from the local landscape company in the bed- - - - -it will lower the truck nicely, and smooth out the ride! LOL!
Jerry

This might shock some of the other members coming from me of all people, but at this point I would really recommend you get it running and drive it a while as-is before jumping into a lot of modifications.

Go through the brakes and steering to make sure they are in good condition, go through the first start tech tip to make sure you don't damage the engine trying to start it, and just put some miles on it.

Get a feel for how it performs with the stock parts and decide from there what you are willing to trade for changes.

If you do want to lower it immediately, you can get lowering springs for a reasonable cost. The downside is that they reduce your suspension travel and you will likely bottom out over bumps. Depending on how much driving you are doing and how much you want it to be lowered, that might be a trade you are willing to make.

🤣🤣🤣🤣🤣
You should have seen my dad's 99 Mazda b3000 with a load of rock in it!

Take a look at the pictures in this post. Mine has an AMC Pacer front suspension and a Chevy Nova rear end for cruising. Nowadays people use the Mustang 2 front suspension which is available aftermarket. I did raise the rear a little this year and changed the rear tire size a little.like this

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Don`t lower it. Drive it first. Embrace the nostalgia.

If you truly would like to lower the truck without having a really harsh ride or needing exotic parts look into a set of lowered springs. Lowered springs would drop the 1" to 3 " depending on the spring choice or application. There are a great many manufactures that have been providing lowered spring options for decades. Posie is a great company suppling lowered springs, their "Super Slider" springs offer a lowered stance with a softer ride. A quality set of springs combined with good shocks and perhaps "Anti-Sway Bars" will greatly improve the way your Truck rides and drives.

https://www.speedwaymotors.com/Search?query=super%20slide%20springs

Guitplayer. No, I have not. I drove it to KC 9 times and to the East Coast 3 times with no issues around 38000 miles total. The issue started after I changed the tires to a different tread pattern. I have isolated the problem and it has nothing to do with the way it was lowered.

If you are into the old truck experience and the lack of refinement compared to modern vehicles that comes with it, and just want it to sit a little closer to the ground, talk to Sid Drapal at Nostalgia Sid's Dropped Axles (www.droppedaxles.com). Sid drops the axle, freshens up kingpins, modifies the pitman arm, and can set you up with tubing and parts to convert to new style tie rod ends on the tie rod and drag link. New U-bolts and blocks for the rear. The install can be done in a day or two when you get your parts in. With a little more caster and proper toe setting, it drives nice and straight with no bump steer.

EchoBravoSierra speaks wisely.

Sorry I thought you had. Congrats!

+1 on NOT lowering it right away!

+1 on Sid providing you with a dropped axle, if you do decide to lower it- it is a way better way to go than doing a spring modification, if you intend on driving the truck a lot, because you will not lose any suspension travel/ride comfort.

I have a dropped axle from Sid in my 1950, and am very happy with the result- just understand that if you go for a drop greater than about 3-4 inches, you may have to move up to taller rims to keep the truck safe in the event of a tire blow-out. Another benefit to doing the drop, as mentioned above, is the option to upgrade to modern tie-rod ends at the same time.

I'm pretty sure Sid won't do one more than 4" for the Advance Design Chevys/New Design GMCs, because of the scrub line concerns.

What is done about tie rod to frame and oil pan clearance with a dropped axle?

I'm not sure if Sid tweaks the steering arms for that or if he just drills the holes for the new style tie rod ends. No clearance issues there to report on my truck.

I did have two issues:
1. The tie rod end used to point toward the inside of the wheel. With a 3" drop, it lines up with the fattest part of the inner sidewall. My truck has 15" wheels and had 235s all the way around. I had to put 215s on for clearance with the tie rod ends, and when I replaced my aging tires last year, I went with 205s because the 215 on the driver's side was still too close for comfort.
2. The lower shock mount in the back has a thick nut that used to point toward the inside of wheel, and you guessed it, points toward the fattest part of the sidewall with 3" blocks in the back. I got a normal thickness nut and cut the remaining stud off resulting in plenty of room.

Sid re-works the steering arms, and also drills them (and the pitman arm) for the modern rod ends. If the steering arms aren’t modified, the long tie rod will have interference issues with the leaf springs, and the pitman arm rod will not be level after stretching the axle. So, all 3 arms go to Sid with the axle.

In the pics below, the pitman arm rod end it sitting above the steering arm, and not inserted yet.

IHere are some pictures of my 51 . I picked up my axle from Sids at Hershey Swap Meet this fall. Mine is a four inch drop axle with Posie super slide springs. Dropped a total of 5 inches front and rear. The side by side picture is a before and after.

I'm running 205 / 70 up front and 235/65 rear. On 8 inch 80s stock steel wheels. Scrub line is 3 inches. 1 inch with just wheels with no tire on it. This would simulate avflat tire and then some. Sid was great to work with. I initially thought I need drop Blocks on the rear as well. But he told me I didn't need them with the Posie springs. Unless i wanted a tail dragger. He was absolutely correct. I removed my front axle , drag link and steering arms and took them to Hershey and swapped him my core for the new stuff. Installed in less than a day.

Sid even gave me the part numbers for the front and rear shocks needed. I'm running the stovebolt with stock brakes and steering. Only drove it a few miles up and down my local back road. Road and drove great.

I'm running 205 / 70 up front and 235/65 rear. On 8 inch 80s stock steel wheels. Scrub line is 3 inches. 1 inch with just wheels with no tire on it. This would simulate avflat tire and then some. Sid was great to work with. I initially thought I need drop Blocks on the rear as well. But he told me I didn't need them with the Posie springs. Unless i wanted a tail dragger. He was absolutely correct. I removed my front axle , drag link and steering arms and took them to Hershey and swapped him my core for the new stuff. Installed in less than a day. Axle is still below tie rod and pan. The one picture shows the difference in the arc of the spring. Those pictured are the rear.

That before and after picture even made the driver's door look better.

Nice truck! My husband likes the height.