I rebuilt my 12 bolt about 8 months ago. While I was at it I replaced the Axles with 4340 chromemoly axles before reading up on them. Well I have since done a little reading on them and from what I have read is was a bad idea.

Does any one run chromemoly on the street? had any trouble with them? I hear they don't like side loads.

I have not run them on the street, had them in a drag car years ago but I have trouble believing there is a problem

The only problem is paying more for axles than you need for the street.

Yukon, Moser, Strange, all sell Chromoly axle's. Must be O.K.

Works for me! :thumbsup:
I can't imagine why chrome moly axles would have any side load issues. http://www.chevelles.com/forums/images/smilies/confused.gif

race only axles are more "brittle" than a street or street/strip axle, not made for going around corners, or hitting potholes, which is hard on the axle flanges-talk to the axle manf., he will tell you if your ok or not

race only axles are more "brittle" than a street or street/strip axle, not made for going around corners, or hitting potholes, which is hard on the axle flanges-talk to the axle manf., he will tell you if your ok or not
Not all race cars go in a straight line.

Also not sure if I go along with the "more brittle" theory - maybe actually the opposite.
I know race ring and pinion are "softer" to handle the shock load of racing. Just my thoughts - I might be completely wrong on the axle thing.

Also not sure if I go along with the "more brittle" theory - maybe actually the opposite.
I know race ring and pinion are "softer" to handle the shock load of racing. Just my thoughts - I might be completely wrong on the axle thing.

Chromemoly is more brittle, Nascar does not allow chassis builders to use it in the cronstruction of a cup car, unless things have changed.

I took forcd ind advised and just call superior which is the maker of my axles. They said that street use is not a problem.

The tech guy said they have not had any problem with them in street apps. So I guess it is good to go. Thanks for the advise guys.

Chromemoly is more brittle, Nascar does not allow chassis builders to use it in the cronstruction of a cup car, unless things have changed.

Chrome-Moly is a generic term that refers to steel that has been alloyed with small amounts of Chromium and Molybdenum. 4130 which is commonly used for thin-wall tubing is completely different than 4340 which is commonly used for driveshafts and other thick-walled and solid components. 4130 does not take a deep heat-treat, whereas 4340 does.

You can't just throw-out Chrome-Moly and apply it to everything.

Chrome-Moly is a generic term that refers to steel that has been alloyed with small amounts of Chromium and Molybdenum. 4130 which is commonly used for thin-wall tubing is completely different than 4340 which is commonly used for driveshafts and other thick-walled and solid components. 4130 does not take a deep heat-treat, whereas 4340 does.

You can't just throw-out Chrome-Moly and apply it to everything.


Hmmm that I did not know. The axles are 4340

Chrome-Moly is a generic term that refers to steel that has been alloyed with small amounts of Chromium and Molybdenum. 4130 which is commonly used for thin-wall tubing is completely different than 4340 which is commonly used for driveshafts and other thick-walled and solid components. 4130 does not take a deep heat-treat, whereas 4340 does.

You can't just throw-out Chrome-Moly and apply it to everything.

Well, I guess I had may ass served up on a platter:o

They still don't use chrome whatever to build cup cars, crash test reults where not what they expected.

Now NHRA on the other hand lets builders use it, the chassis of a dragster, T/F and funny cars are designed to shear off and keep the driver in leaving the motor to go wherever it likes.

It is more difficult to weld chrome moly steel. Weld quality and repeatability may be why NASCAR does not allow it.

It is more difficult to weld chrome moly steel. Weld quality and repeatability may be why NASCAR does not allow it.

That could be but since the cars need to weigh over 3400 pounds, they still need to add weight using regular steel.

For chassis "Chrome Moly" being 4130 when purchased in tubing form is considerably stronger than mild steel which allows builders to use ultra thin tubing. I built several drag chasiss years ago with it and while acetelene welding is inferior to heliarc both work beutifully on the material. To the best of my understanding of the Nascar deal rule was drafted back when they where poor to keep cost down and while thats no longer the issue they use such thick materail that frame failures are not an issue.
I don't have a total understanding of the 4130 versus 4340 but if you buy tubing or plate its 4130, you buy a bar stock to machine into a part, its 4340. The axel however may be a forgeing? I had a set years ago made by Donovan and they where forged so he had a big flange on the end of a shaft and machned an axel from it, then heat treated it. Some custom axels have been made from bar stock but that is very small production huge waste. Some have been made from a bar stock pressed into a flange and welded on the outter end

For chassis "Chrome Moly" being 4130 when purchased in tubing form is considerably stronger than mild steel which allows builders to use ultra thin tubing. I built several drag chasiss years ago with it and while acetelene welding is inferior to heliarc both work beutifully on the material. To the best of my understanding of the Nascar deal rule was drafted back when they where poor to keep cost down and while thats no longer the issue they use such thick materail that frame failures are not an issue.
I don't have a total understanding of the 4130 versus 4340 but if you buy tubing or plate its 4130, you buy a bar stock to machine into a part, its 4340. The axel however may be a forgeing? I had a set years ago made by Donovan and they where forged so he had a big flange on the end of a shaft and machned an axel from it, then heat treated it. Some custom axels have been made from bar stock but that is very small production huge waste. Some have been made from a bar stock pressed into a flange and welded on the outter end

I did a little research on the chassis builders for cup cars and found that all use regular steel tubing in the construction. Now we all know that cost is not an issues with the teams now so we can only assume that the rule still applies.

I must admit I've never seen anyone try to weld chrome moly with a tourch:confused::confused::confused:

The guy who built my cars, Ken Keir Race cars, used a Tig welder and in the day when NHRA required the chassis be inspected by a SEMA certified welder, he did that as well.

I would suspect that the reason why they do not use 4130 tubing in the chassis is because of what happens to it when you weld on it. 4130 in thin sections (tube or sheet) has a unique combination of excellent tensile strength, toughness and response to mild heat treatment combined with good formability in the annealed condition and outstanding welding characteristics that make it a very good choice for fabrications. It must however be properly welded and stress relieved.

Many people weld 4130 with stainless rod, but the high nickel content in the filler rod means that the weld will not respond well to heat treatment. Even if you use the proper filler, but do not heat treat and stress relieve after welding; you are left with an expensive part with the same strength as mild steel and brittle weld areas! I suspect that this is the reason why Nascar has stayed away from 4130. Are inspections really going to catch any and all poor welds with 4130?

The other issue with 4130 that I already mentioned is that it does not take a deep heat-treat well. It also has a distaste for varying cross-sections. These characteristics make it a poor choice for machined or forged parts. It doesn't forge or machine well anyway.

I did a little research on the chassis builders for cup cars and found that all use regular steel tubing in the construction. Now we all know that cost is not an issues with the teams now so we can only assume that the rule still applies.

I must admit I've never seen anyone try to weld chrome moly with a tourch:confused::confused::confused:

The guy who built my cars, Ken Keir Race cars, used a Tig welder and in the day when NHRA required the chassis be inspected by a SEMA certified welder, he did that as well.

It welds nicly with a torch but that causes some deteriorization of the heat treat as the torch heats a large area around the weld. I beleive its still better than mild steel but certainly not the proper way. THe chassis I built where very lightly tacked with torch, then the chasiss & jig hauled to a real welder guy (not a lot of heliarc welders around in the mid 1960's)