Stovebolt.com Forums The Shop Area The HiPo Shop Not happy with the front straight axle

IN my 1953 Chevy 3600 3\4 ton truck. I was at world of wheel car show in Chicago I found a company that builds front end suspensions to up grade from the dreaded straight axle. BUT they don't make one for the 8 lug wheel suspension of the 3/4 ton. They only make up to a 6 lug. So my only thought left was to find a truck rolling chassis with a similar wheel base as my truck. Anyone else done this to their 3/4 ton truck?

Thanks Elmo

What wheelbase is your 3600? They were available in multiple sizes.

Also, how handy are you? Doing a body swap is non-trivial if you are not fairly well versed in fabrication. I don't know offhand is anyone makes a kit for that. Ez-Chassis Swap might have something for you.

If the goal is improved brakes, take a look at this thread over in Big Bolts.

I have a 1979 AMC Pacer front suspension on my 1/2 ton with a stock engine. It has worked great for the past 13 years. BTW there is a kit to install it.

How is your existing front axle not satisfactory? Are the kingpin bushings up to snuff? Are all the steering joints tight or replaced? Is the steering box tight? Are the axle shims
(caster)there and setup properly? Fixing all these minor jobs is a whole lot easier and cheaper than a whole new setup!

Ed

Nothing to dread about a solid front axle when all components are in proper working order. This includes modern radial tires of the correct diameter and new shock absorbers.

Are you planning to auto-cross the truck? The solid axle is perfectly satisfactory for normal driving at all speeds that the truck is capable of achieving.

I was on my way to a car show last year. Going 55 down the road and ran over a medium size pot hole. The truck almost ended up in the other lane. If I were to hit that same pothole with my independent front suspension in my car, I'd be still in my lane.
So does that mean my front end is loose? I've replaced everything on that truck. Steering box was taken apart and rebuilt too.

Elmo

I've driven over 3000 miles in my 1950 1/2 ton in the last 18 months or so. Driving is equally split between highway and local roads. I've hit potholes at 50-55 as well and never had the truck act in a manner that caused me to lose control or make me consider the handling to be dangerous.

I would check the entire steering system with someone turning the wheel slowly while you observe each link in the system for delay/play/slop. How are the springs and shocks?

Certainly modern vehicles handle much better than 70 year old trucks but that doesn't mean that 70 year old vehicles are inherently unsafe or have loose, sloppy handling.

There is a front anti-sway bar available for AD trucks that is a bolt-on part (original equipment on panel trucks, I think). They are available from one or more of the restoration specialty suppliers. Perhaps that is something to consider installing. I have not installed one but probably will do so at some point.

The front shocks on my truck are Monroe OE Spectrum 33049 and the rears are Monroe Gas-Matic 5826. I have 16" rims and Firestone radials.

Anti-sway bars do their work while in a turn. Shouldn't have much effect at a pot hole.

The leaf springs have never been replaced. Think that has anything to do with the handling?

If the springs have never been replaced, what about the spring bushings and shackles? Those could be the source of your problem.

You said you "replaced everything". What does that include in your mind? Apparently not the springs.

Shocks? Drag link? King pins?

There is nothing inherantly wrong with solid axles, pretty much every big truck being made still uses them.

Weak springs will allow the axle to hop all over tarnation instead of resisting the hill or valley that the wheel goes over.

How many miles would you estimate your truck's suspension has on it?



Yes, a handling improvement of any kind would be welcome, I think.

How many miles would you estimate your truck's suspension has on it?

Probably 100 thousand miles

Elmo

I would bet the rear spring hanger pins and bushings are worn. A small amount of wear in these will make them act really stupid. Even with regular greasing, mine had lots of wear at 10k miles after replacement.

Personally, I would repair the existing suspension and steering systems before trying to re-engineer the truck.

I'm certainly not an expert on the handling characteristics of the AD series truck. I am, however, extremely familiar with the handling characteristics of antique vehicles in general. Unlike most people that own antique vehicles for weekend cruises or tooling around the neighborhood once a month, and who drive modern vehicles for the majority of the time on the road, I have never owned a modern vehicle.

All of the vehicles in my signature line are used as daily transportation, rush hour interstate travel, and vacation trips of over 1000miles (the 1995 F-150 is actually my mom's - I just maintain it.)

I will categorically state that the handling characteristics of vehicles of the era we're discussing are not anywhere close to being as bad as many people assume. The big cars of the '50s are not lumbering dinosaurs that wallow in turns and curves or have loose steering or anything like what is often described by those who have never driven them.

When properly repaired/restored and driven within their respective limits, these vehicles, including your AD 3/4 ton truck will perform extremely well and without scaring the daylights out of you every time you hit a pothole or sharp curve.

With modern shocks and radial tires, the performance is even better.

If you do decide to replace your springs and bushings, etc, I would do both front and rear to keep the truck level and prevent the front end from doing one thing while the rear end does something else on the same bump in the road.

That's really a function of failed shock absorbers. Weak (sagged) springs will just change the height of the suspension. They'll likely have the same amount of spring rate (springiness) although seized bushings can make them stiffer (unable to move like designed.)

Spring rates on front and rear were different as the came from the factory, so the front and rear will always to different things on the same bump. But changing from the factory spring rates on one axle would make the truck act differently. But again, shock absorbers control the bounce or hop.

Straight front axles are still used today (many 4x4 trucks), and they ride satisfactorily.

Elmo, my 54 did that a couple of times and I finally said enough. As I said above I replaced it with an AMC Pacer front end. It was not cheap then and it is not cheap now comparatively now.

Just to jump on Kevin, Ed and Otto's bandwagon ...

Replacing/upgrading your front end because you *want* to is one thing. And if that's the reason, more power to you and we'll help all we can.

Replacing/upgrading your front end because you think you *need* to is entirely another. And for all the reasons stated above. I'll just add that from pickups to tractor trailer trucks, I've put a fair amount of highway and back road miles in on straight axle trucks. The truck I drive for work most days has a straight axle (but with 11R22.5 tires, I don't mind the power steering ...;) ) and I hit plenty of pot holes around the Nation's Capitol ... I have no problem or hesitation to take my unrestored (but well maintained ) '49 1-Ton on the interstate -- and have, many times. It will cruise nicely all day at 65 MPH and sprint to 70 when needed. Straight axle, Huck brakes and bias ply tires. It has a little wander above 60, but its manageable. Potholes? Not too bad. At speeds above 60 MPH, I just try to hold the wheel straight and the truck will quickly resume course just fine after a few milliseconds of hinkyness.

Why is it able to do this? Have I put sway bars on it? Have I upgraded to an IFS? Do I have Power steering?? No to all of those. I am running the truck in its original configuration (suspension wise I did put a 261 and a 4.10 gear set in the truck) because *everything* is still within spec -- Springs, shackles, steering box, tie rod ends, pitman arm, front alignment, etc, etc. Just *one* of these things out of whack will cause issues at modern highway speeds.

Does my truck drive as well as a modern truck? No, of course not. But it drives fine. It's a different experience and requires a little more attention to what you are doing. Doable? yes. Enjoyable? Certainly.

The '65 GMC 1.5 ton I used to own was the real teller. It was a firetruck and it only had 8,000 miles on it when I bought it in 2007. Mechanically, it was still new. There was zero wear in the front end. You could drive that truck with one finger, even at slow speeds. At 65 MPH (um, I removed the governor and replaced the crappy Stromberg carburetor with a Holly 300), that truck handled like it was on rails!

So ... in my opinion, FWIW ... The factory straight axle/spring suspension/manual steering set up is perfectly adequate for today's highways as the boys have said above ... IF ... and this is a big if ... *everything* in the front end is within spec -- king pins, alignment, tie rod ends, pitman arm, drag link ends, steering box adjustment, springs, spring shackles, spring shackle pins, tires (age, tread, balance and pressure). The more *any* of those are off, the less enjoyable your driving experience will be.

Bottom line -- If you *want* to upgrade the front end, you go right ahead and we'll help you all the way. Just don't think you have to because the straight axle set up is "bad."

If you have a straight axle truck and it handles poorly, it just needs to be fixed, not heavily modified. Not at all against performance upgrades (Evan ... Heck, I'm a Group W Bench Stovebolter myself -- I put a 261 in my '49 ... and created a nuisance ... ) -- Just do them because you want to, not because you think you have to.

Respectfully,
John

You just need to take apart and inspect every single part of the suspension, front and rear, and replace what is worn and adjust what is not worn out.
Spring shackle pins and bushings.
Tierod ends. They need to be thoroughly cleaned and inspected. Make sure balls are round and not egg-shaped. Adjust them according to the Chevrolet Truck Shop Manual.
Draglink ends. Ditto, see tierods above.
Properly adjust the steering box with draglink separated from pitman arm.
New tires would help.

In my experience a sway bar will have a positive impact on straightline handline regarding bumps, potholes, etc...anything on the road that causes one wheel to go up or down while the other stays constant (not affected by said bump, hole, etc). The sway bar goes up/down on one side but not on the other. And that causes the bar to flex from the applied torque and that applied torque will pull or push on the other side in a likewise manner. In other words, hit a bump and it pushes one wheel upwards. The sway bar swings up and simultaneously pushes the other wheel up (admittedly not with 100% of the same force, but with not much of it lost). This causes the front end to momentarily assume a more equal posture as both wheels feel the same relative force. Hit a pothole and one wheel goes down but the transmitted force goes against the other wheel simultaneously. Since the force has nowhere to go it actually works to minimize the "drop" in the wheel hitting the pothole by limiting the amount of downward motion. At least this has been my observation.

... also make sure the caster shims are still installed and not turned around backwards.


By the way John M, I never thought I'd hear Arlo Guthrie quoted on this form.

52CARL, I plan on taking my truck in to have what you said, done.
Thank you all for your much needed advice.
Elmo

AA Fuel dragsters run over 330mph in a VERY straight line and they ALL have straight axles. A straight axle and suspension built to factory specs then 7 degree caster shims and p/s added will give a ride that you can let steer itself while you square dance in the bed. Correct shocks and polypropylene plastic between spring leaves can give a living room couch type ride.

Coilover: where do you get your poly to put between the leaves? A buddy here was looking for some a couple months ago and had a reaaly hard time. I don't think he ever found what he wanted.

Check Speedway for Poly.

The last I bought came from Cadillac Plastics in Addison Texas. I bought a roll and it has made spring inserts for 30 years.

I bought mine from Speedway, because they had edges to keep them contained within the leafs. Here is a [LINK] [speedwaymotors.com]

It will go straight real good Evan, but try to parallel park with those 7 degree shims.

As has been said up thread, there's nothing inherently wrong with straight axles. Big trucks use them and roll along at 80 MPH legally in some western states.

They ride rougher in part because the sprung/unsprung weight ratio is somewhat less favorable when one wheel goes over a bump and much less favorable when both wheels do. And as most of them have leaf springs, there is resistance within the spring pack adding to shock being transmitted into the frame. That's a door that swings both ways, enough resistance and there's no need for additional damping. I drove 50s/60s Kenworths and Peterbilts with no shocks anywhere. But the KW torsion-bar rears did have shocks as did the Pete air-leaf rears. Rear shocks on my 1-ton were an option mine didn't have. Loaded it was fine. Unloaded it bounced a lot. It now has rear shocks. My 50 Studebaker had the rear leaves encased in metal jackets with grease fittings. Greasing the springs made a noticeable difference.

Adding a rear swaybar will correct oversteer when loaded as will increased spring rate. Adding a front sway bar will correct understeer, likewise will increasing the spring rate. Adding caster will make the steering return to center quicker but make for heavier steering AND the rig will tend to follow ruts and such in the road. Radial tires will make it much harder to park unless you have power steering.

Changing the wheel offset to more outboard centerline changes the scrub radius and will also cause the rig to follow ruts. Changing the wheel offset also changes the effective spring rate, particularly on independent suspensions but to some degree on a straight axle in a turn or when one wheel hit a bump. Adding wider wheels to accommodate wider tires will change the offset by 1/2 the increase in wheel width.

I could have got a nice Mustang 2 front end for 1/3 of what I have in my straight axle. I'm not an expert so these are just my thoughts. When it comes to leaf springs verses coils that spring has no idea if it's straight or coiled. The magic is in the shocks. Everything tight with firm bushings and a sway bar and your golden. If you want to get more hardcore go with aluminum bushings and a pan hard bar. It was nice to see the wheel offset mentioned. My understanding is that if you extend the pivot point of the spindle it should be centered on the pad? To me an AD without a straight axle of some sort is like a hound without rabbits. I guess my point is that a straight axle does not restrict you on performance if you take into account all the new advances in parts and materials. Working with Pete and Jakes (thanks Jerry) and Superbell They made me a custom width 4" drop tube axle designed to leave the ground and safely return for up to a 5000 lb vehicle. I sent them a 53 axle to work off of instead of sending them dimensions. Everything is early Ford roadster stuff because it's readily available in chrome. It has roller bearing king pins and shock perches like a roadster. Jerry sent me raw spindles and I had a friend in the aerospace industry remove the Ford spindle pin and replace it with a Heidts pin so I could run the Wilwood brakes "you can't run on a straight axle". Then I sent them back to Pete and Jakes. Made some caliper brackets and done. Easy Peasy 4 years and thousands of dollars later. I have no regrets. She's pretty and all mine. I plan on taking her down the 1320 at 8.50 and 165 in a drag and drive. I plan on doing a little Autocrossing too. I agree 100% with John. If you want to great. Do you need to? probably not. Sorry I rambled on. Thank you for your time. Sorry I put so many pictures of my brakes up. It was a huge victory for me. Can't do it my a$$.