Straight axle - Is it safe?

specsintexas · Mar 21, 2011

I recently purchased a 1936 Chevy 2 door coupe. This car was built up in the 1960s. It has a very good running 283 SBC /350 Turbo combo with a Chevy 10 bolt rear end. The front straight axle came out of a 1957 Chevy pick-up truck and here is where I need some advice.
In order to make the wheels sit under the fenders correctly the front I-beam axle has been cut in half, narrowed about 6 inches, welded together and ****ressed front and back with 24 x 4 inch ½ inch fish plates which are also welded front and back of the axle. The welding job is superb and the axle looks OK nestled under the engine and between the two stock leaf springs mounted under the frame rails. In fact, if you did know the axle had been narrowed you probably wouldnt notice it unless you got under the vehicle.
I asked the previous owner how long he drove the car this way and he said he drove the car more than 8 years with that axle setup in the 70s. The brakes are stock 1957 Chevy truck drums. I am planning to put a disc brake kit on the car.
My question is this. Is this axle setup safe? Has anyone seen or done a similar axle set up. I am worried that the disc brakes will transmit too much energy to the axle and break the welds loose resulting in an accident.

dodored · Mar 21, 2011

When it comes to brakes and suspension I always aire on the conservative side. The upside is minimal and the downside is huge. Kind of like collecting nickels in front of a steam roller. Take the hit and buy the correct parts - Safety is a bargain!

R Frederick · Mar 21, 2011

Gosh, quit doing that!!! If it's a beam axle, it's most likey not a straight axle. It's a drop axle. Anyway, if you think it looks fishy - it's hard to tell if it was done right. Especially if you weren't there to see what they did. It would be a cheap investment to get yourself something nice and safe. BTW, don't get a speedway chromed I-beam.

"T'RANTULA" · Aug 7, 2011

Can you provide some pics? Ive taken a forged straight axle outta a van and chopped it, then STICK welded it back together and it is as strong as ever. As long as the welds look good and theres no perosity i would drive it any day.You can have the axle X-rayed to see if there are any cracks, but you said the guy drove it for 7 years so i would say its fine.

Buzznut · Aug 7, 2011

I'd want to see pics just out of curiosity, but they won't tell the story as to how much integrity the welds possess and how well it's been gusseted/****ressed. I would also bite the bullet and order a reproduction I-beam axle that is the correct width and drop. I'm sure other guys around here have more personal experience with which manufacturers parts are better than others, but as far as the current set-up goes, I would be wary as well.

48 Chubby · Aug 7, 2011

Stock I beam axles by Ford or Chevy are all forged. Me personally, I would much rather trust a properly welded stock type axle than an after market cast iron axle. I have also seen too many cheap tube axles crack and even break. If the welding was properly done then the fish plates were over kill.
Disc brakes won't apply any more stress on the axle than drums would, but they don't fade as badly when they get hot.
Four feet of 4"X1/2" steel reinforcement is heavy iron though. A replacement might ride and handle better due to the reduction of unsprung weight.
When shopping look for an axle that is forged not cast.

The one you have should last forever though.

Richard D · Aug 7, 2011

Have you tried refurbishing the truck brakes instead of swapping them out? May not need to go to all that expense.

Roger Walling · Aug 7, 2011

I am always amazed on how some people who do not know how to modify something are so quick to condem someones work.

Personally I think that the job is a little over kill and too heavy, but I would not say it is unsafe until examining it myself.

zman · Aug 7, 2011

pics would help, but if done properly I don't think it would be unsafe...

Verminator · Aug 7, 2011

My falcon's econo axle was narrowed 6 inches in 1968. welded and plated front and back. Raced from '68-75. then I rebuilt, restored, and have been punishing the car since 1995. 125+ mph and hard launches. NEVER an issue with the axle, checked regularly. New tube axles are bending all the time on the track.

I'd have it inspected, then wouldn't worry about it at all.

inline 292 · Aug 7, 2011

The reaction from the braking torque forces should only go as far as the spring mounts. Should have no effect on the axle mid-section.

dlotraf · Aug 7, 2011

It is probably stonger and better than anything new. I hear all these guys scared to weld an axle. Now mind you anything outside of the spring perches I wouldn't recomend, but in the center of the axle no problem. The center has the least stress put on it. Especially in a parallel leaf spring setup. There is almost no stress in that area. They have been narrowed for g***ers and altered wheelbase cars since they started running them. I would rather have that axle than any new axle. Most are from china, and it's all about money and profit margin, not quality anymore. I have two with narrowed axles, and have narrowed at least 15 or 20 back in the seventies for drag cars. Never saw one fail. And a couple of cars were wrecked and axles bent in the process, and the weld never failed.

Bib Overalls · Aug 7, 2011

You should be good to go. A lot of wheel standing, hard landing altereds ran narrowed beam axles. Done right, strength should not be an issue.

Ned Ludd · Aug 7, 2011

inline 292 said: ↑

The reaction from the braking torque forces should only go as far as the spring mounts. Should have no effect on the axle mid-section.
Click to expand...

Likewise shear forces and bending moments. The bending moment will be greatest between the spindle and the spring, least in the middle of the axle. If nothing else the axle was joined in the right place.

bobscogin · Aug 7, 2011

If done correctly, no problem. Run it.

Bob

Atwater Mike · Aug 7, 2011

dlotraf said: ↑

It is probably stonger and better than anything new. I hear all these guys scared to weld an axle. Now mind you anything outside of the spring perches I wouldn't recomend, but in the center of the axle no problem. The center has the least stress put on it. Especially in a parallel leaf spring setup. There is almost no stress in that area. They have been narrowed for g***ers and altered wheelbase cars since they started running them. I would rather have that axle than any new axle. Most are from china, and it's all about money and profit margin, not quality anymore. I have two with narrowed axles, and have narrowed at least 15 or 20 back in the seventies for drag cars. Never saw one fail. And a couple of cars were wrecked and axles bent in the process, and the weld never failed.
Click to expand...

Correct-Omundo!
The best welds are welds fused on the best steel. Forged axles (factory OEM axles) are the best steel, especially FoMoCo, which were made of Vanadium steel.
As for the center of the axle being the least prone to stress/failure, that is also correct.
A street rod company even split Ford dropped axles in the centers and pivoted them with a bracket, making a sort of 'Tjuana-Independant suspension'! No reports of failure, ever.

I used to make tube axles for drag cars...(and street cars to play 'G***er'!)
I used 2" O.D. Shelby tubing, (steam fitters quality) as I was wary of failure with too light a structure. (I had seen thin wall tube axles break just outboard of welds, mostly chromed tubes, but also unchromed Chrome Moly, .187" wall)
I figured the weight savings could be garnered with the omission of the front bumper, rather than thinwall tube and holes drilled in structural bracketry!

But I also installed '32-'36 Ford axles under '55-'57 Chevys. Even liberally drilled between wishbone bosses, always reliable.

Frosty21 · Aug 7, 2011

It would take an ungodly amount of force to brake fishplate welded around an axle with a stick welder.

lazee · Aug 7, 2011

In the near future i an going to narrow a chevy truck axle and i wont use fish plates,
However i will preform a stress test on it.

You can wrap a chain around the middle and have a friend with a 4 wheel drive drag ya down a well paved street with your brakes locked-- then look at it and see if it hurt it.
8 years is kinda like proof is in the pudding... "never drive a car your afraid of you will not have fun"
Wow! did ya realize that railroad tracks are but welded.

thirtytwo · Aug 7, 2011

kinda funny how some of you guys are afraid of somthing with plates on front and back for re-enforcing but yet see no problem with an old ford axle drilled full of holes?

50dodge4x4 · Aug 8, 2011

thirtytwo said: ↑

kinda funny how some of you guys are afraid of somthing with plates on front and back for re-enforcing but yet see no problem with an old ford axle drilled full of holes?
Click to expand...

I agree with this one.
Really, the two 1/2" fish plates without the axle are probably stronger then a drilled beam axle.

Kind of makes me wonder how you guys feel any independent suspension is safe, that whole deal is held on the car with a few bolts, most mounted in single shear. Gene

DocWatson · Aug 8, 2011

What gets me is how many supposed 'car guys' here on the H.A.M.B. of all places don't know the difference between a 'straight axle' an 'I' Beam and a dropped axle??

A straight axle is just that, straight across, no drop, no deviation just straight.

Doc.

Da Tinman · Aug 8, 2011

run it, if hasnt broke by now its not gonna.

Forged beams can be cut welded with no harmful effects.

48FordFanatic · Aug 8, 2011

inline 292 said: ↑

The reaction from the braking torque forces should only go as far as the spring mounts. Should have no effect on the axle mid-section.
Click to expand...

Wrong ! If you can imagine cutting the axle in half at its mid point, the braking force wants to rotate the axle in the (horizontal plane) about the point of connection to the spring. The reaction needed to resist this rotation is at the center of the axle. The reaction forces are not huge but they exsist and need to be considered. Just my 2 cents worth.

Ned Ludd · Aug 8, 2011

48FordFanatic said: ↑

Wrong ! If you can imagine cutting the axle in half at its mid point, the braking force wants to rotate the axle in the (horizontal plane) about the point of connection to the spring. The reaction needed to resist this rotation is at the center of the axle. The reaction forces are not huge but they exsist and need to be considered. Just my 2 cents worth.
Click to expand...

I'm not sure that's right. Yes, braking torque goes to both springs, albeit mostly to the spring on the side under consideration. Because resistance of that involves deflecting the spring into an S shape (***uming parallel leaf springs) some torsion goes through the axle to the spring on the other side. But, under most conditions something very similar will be happening at the other end of the axle which, due to the directions of rotation involved, will tend to cancel out the torque thus induced.

So, you'll get significant torque in the axle in a braking situation with the wheels on widely different surfaces, i.e. the cl***ic ABS demo situation. You'll get most torque in a spin about the front axle with both front wheels locked, so one wheel wants to roll forwards and the other back but can't due to the brakes. Neither of these is likely to cause failure of the axle, because the axle is quite elastic in torsion and will probably induce some sort of judder or hop before anything breaks.

"T'RANTULA" · Aug 8, 2011

thirtytwo said: ↑

kinda funny how some of you guys are afraid of somthing with plates on front and back for re-enforcing but yet see no problem with an old ford axle drilled full of holes?
Click to expand...

I agree too, I would trust a welded axle more than one full of holes and I have both styles !!!!

teddisnoke · Aug 9, 2011

Theres nothing like a good, hot arc, and a nice piece of forged steel:

http://public.fotki.com/bowtie0069/earlier-projects/funnycarfarmproject1/img3011.html

5.5 inches removed from the center of a Dodge A-100 straightaxle, using a custom-built jig, to keep the spring pads centered and aligned.

Dale

R. Seghi · Aug 9, 2011

I would just go buy the right size axle.

specsintexas · Aug 22, 2011

Just to let you know, I do not have pictures of the axle at this time but I may have some soon. I received 19 responses to this Request for Information about using a narrowed stock straight I-Beam axle joined with a diagonal **** weld and two 24 fish plates front and back. Three (3) responders were absolutely opposed to using this axle setup stating that they felt it was dangerous. Four (4) responders did not state an actual Yes or No but implied that they were not opposed to it on safety concerns. The remaining twelve (12) responders were more than OK with it. Three of the twelve affirmative responders actually ran shortened and welded up axles at the drags. Some of these folks actually did wheelies with them and some ran over the century mark (100 MPH).
Based upon the responses I got, my conclusion is the axle is more than OK and will be used as is. The feedback from the drag racers really tipped the scales on the plus side and provided me with a whole lot of confidence to go with the axle. I would like to thank you all for taking the time to respond.
Specs

brad chevy · Aug 22, 2011

Good decision, this was done back in the day on a routine basis and if it wasn"t safe the g***er popularity would not still be going strong today. I would trust your axle over any of the cheap China Speedy-Bill stuff sold today. Post some pics of your car when you get around to it.

Weasel · Aug 22, 2011

thirtytwo said: ↑

kinda funny how some of you guys are afraid of somthing with plates on front and back for re-enforcing but yet see no problem with an old ford axle drilled full of holes?
Click to expand...

Or an 'Hecho in China' drilled to within an inch of it's life piece and chromed to boot - and you can bet your bottom dollar they have not been embrittlement relieved, magnafluxed or x-rayed either....

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Straight axle - Is it safe?

specsintexas
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dodored
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Straight axle - Is it safe?

specsintexas Member from Buda, Texas (Austin Metro area)

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"T'RANTULA" Member from Ohio

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