I am trying to decide between chromo axle shafts, one set is 4140 and the other is 4340. Both cost the same, so the material is my deciding point. Oh and if your curious they are going in a toyota pickup.

The 4140 will break and the 4340 wont':D If you're comparing warns to mosers, I would say they are both good, BUT....the warns are better. Go with warn 4340. I doubt you will break them in a yota.:smokin:

AISI-SAE 41xx series is a Chromium-Molybdenum Steel

AISI-SAE 43XX series is a Nickle-Chromium-Molybdenum Steel

The 4340 is stronger than the 4140.

4140 that has been Hot Rolled, and Normalized has a tensil strength of 148,000 PSI, and a yeild of 95,000 PSI. 4340 that has been Hot Rolled, and Normalized has a tensil strength of 185,000 PSI, and a Yeild of 125,000.

I would get the 4340 shafts, if it was me.

Originally posted by Alaska Offroad
AISI-SAE 41xx series is a Chromium-Molybdenum Steel

AISI-SAE 43XX series is a Nickle-Chromium-Molybdenum Steel

The 4340 is stronger than the 4140.

4140 that has been Hot Rolled, and Normalized has a tensil strength of 148,000 PSI, and a yeild of 95,000 PSI. 4340 that has been Hot Rolled, and Normalized has a tensil strength of 185,000 PSI, and a Yeild of 125,000.

I would get the 4340 shafts, if it was me.

I wish more quote on quote "newbies" posted up info this good! Thanks man!

cm "can you dig it" k

Are you saying Moser Eng. uses 4140? Is so, they do not. Their axles are superior in strength because of their material, forging, heat treating, and Moser found cold splining process(by cold splining the shaft, you do not disrupt the original heat treating) Get Moser shafts if you have that option.

I'm not sure what Moser uses for axle shafts, but I think a lot of people will disagree that Mosers are stronger than warns.

Originally posted by CaptainFleXJ151
Are you saying Moser Eng. uses 4140? Is so, they do not. Their axles are superior in strength because of their material, forging, heat treating, and Moser found cold splining process(by cold splining the shaft, you do not disrupt the original heat treating) Get Moser shafts if you have that option.

Moser axles are not superior in strength period. I think that they heat treat the hole shaft and not just a section of it. They use something like 1541. I have heard more people break more mosers than warns. 4140 and 4340 is very close in strength went heat treated to the same rockwell but has silicon and nickel in it where the 4140 doesn't. What that does I don't really know maybe Goat1 can explain it to us. The reason Moser cuts his splines cold and after heat treat is because he can have one size axle for all. Then when you call up and say I need a shorter axle all he has to do is pull the blank off the shelf and cut it to length and spline it. Where the other manufacturers cut the axle to length then spline them and then they heat treat them. It is more economical and faster turn around to do it the way moser makes axles but that does not mean they are a better axle just cheaper and a better turn around time.

Originally posted by Donovan


Moser axles are not superior in strength period. I think that they heat treat the hole shaft and not just a section of it. They use something like 1541. I have heard more people break more mosers than warns. 4140 and 4340 is very close in strength went heat treated to the same rockwell but has silicon and nickel in it where the 4140 doesn't. What that does I don't really know maybe Goat1 can explain it to us. The reason Moser cuts his splines cold and after heat treat is because he can have one size axle for all. Then when you call up and say I need a shorter axle all he has to do is pull the blank off the shelf and cut it to length and spline it. Where the other manufacturers cut the axle to length then spline them and then they heat treat them. It is more economical and faster turn around to do it the way moser makes axles but that does not mean they are a better axle just cheaper and a better turn around time.

OK GOAT1 is the guru here but as far as I know 4340 doesn't have silicone in it . That is 300M that you are refering to. Also, 4340 CAN BE stronger because of the Nickel in it. It is because of this (Nickel) that 4340 can be heat treated to obtain a higher yeild strengths compared to 4140.

Originally posted by Goat Boy


OK GOAT1 is the guru here but as far as I know 4340 doesn't have silicone in it . That is 300M that you are refering to. Also, 4340 CAN BE stronger because of the Nickel in it. It is because of this (Nickel) that 4340 can be heat treated to obtain a higher yeild strengths compared to 4140.

I just looked and they both have silicon but 4340 has nickel and 300m has the same as 4340 but with vanadium in it.

Originally posted by Donovan


I just looked and they both have silicon but 4340 has nickel and 300m has the same as 4340 but with vanadium in it.

OK. I was off on the Vanadium. I don't want to get the book out. What is the %age of Si in each?

Moser uses a modified 1541. It's the same material used by spicer in the stock axle shafts. I asked the last time I was there if you are wondering how I know.

If you really want a strong shaft go with the 4340 and then dig up someone to roll the splines instead of cutting them. Rolled splines have a fatigue life twice that of a cut spline. In addition the compressive residual stress resulting from the rolling process will improve the load carrying capability of the shaft.

off the top of my head 4140 and 4340 both have .20 to .35 % Si.

Originally posted by CaptainFleXJ151
Are you saying Moser Eng. uses 4140? Is so, they do not. Their axles are superior in strength because of their material, forging, heat treating, and Moser found cold splining process(by cold splining the shaft, you do not disrupt the original heat treating) Get Moser shafts if you have that option.


Strong or not, when i recieve an axle and it is bent with fucked up splines and get no refund, they dont get my business anymore.

Originally posted by Goat Boy


OK. I was off on the Vanadium. I don't want to get the book out. What is the %age of Si in each?

4140 is 20/35% and 4340 is .15/.30%

Someone should start making 300M shafts to go with the CTMs. Jack, you listening?
Then we could have $6K SUPER D44s!

Great information on the 4130/4340 comparison.

What's up with induction hardening v.s. through hardening and which is better for wheeling? :smokin:

Originally posted by Donovan


4140 is 20/35% and 4340 is .15/.30%

You mean 4140 is .20/.35 right?

Originally posted by JR
Someone should start making 300M shafts to go with the CTMs. Jack, you listening?
Then we could have $6K SUPER D44s!

Great information on the 4130/4340 comparison.

What's up with induction hardening v.s. through hardening and which is better for wheeling? :smokin:

Induction is the way. Allows for a hard out side and a ductile in side. Kinda like a stale twinke.

actually I'm comparing the chromo axles offered by allpro to the axles that come in the full floater kit from front range offroad. Any one know where they get their shafts??

We've gone over this before but here it is again: the main difference chemically between 4140 and 4130 is that 4130 has up to 2% nickel and 4140 does not. 300m is technically 4340 modified with silicon and more vanadium. Now what these different alloys do for you is let you through harden and depending on the alloy, how hard you can Heat treat it. Basically with 4140 you should only go up to RC 40, 4340 up to 48, and 300M up to 55. You can take these alloys to a higher hardness but you will loose ductility and this is what I would recommend for as axle.
Now when shopping for axles, the material is not as important as how it is heat treated. From what I can tell, the warns are through hardened 4340 which is hard to beat, they are heat treated to about RC 54 which is a little too hard in my opinion, it makes them a little too brittle. The mosers are induction hardened 1541H, they are induction hardened because you can't through hardened 1541H. The biggest difference between the two is that you cannot induction harden both the shaft and the end yoke, so the end yokes are left soft on the mosers, this is the problem with the stock spicer axles. My problem with axles and most other people's is you break the end yokes that hold the u-joint, moser makes this area a little beefier but it's still not very strong, not as strong as hardened 4340 which is where the warns have the advantage. Now the superior's new front axles are supposed to be 4140 that is through hardened to RD 38 and the induction hardened on the shaft to RC 48 which in my mind is a better way.
Toymaniac: if you are talking about double splinned floater shafts, you need to find out if they are induction hardened or though harded and to what hardness. If they are both induction hardened, they are not to different, if they are through hardened, the 4340 can be better than the 4140, but it depends on how hard they are.

Goat1, thanks. I talked with allpro today and their shafts are made by superior axles, and are induction hardened, but they didn't have a hardness value.