Metallurgical engineers--4340 chrome moly or 8620 material for intermediate/output...

[nvrstuk]

Changing my drivetrain some and looking to determine what material is strongest for a 32 spline shaft in my KluneV that will be the input for the NP205.

Charts show the 4340 to have many times the yield and tensile strength over 8620 yet sites show it as shaft material of choice.

Thanks

 

[pcf_mark]

As I understand 8620 is used for input shafts in high horsepower applications because it has a higher yield point. It takes more force to deflect but it has the same ultimate strength as 4340. Repeated deflection is what causes the part to fail. By making the part stiffer it does not deflect and should last many shock cycles.

 

[nvrstuk]

Thanks!



I've read 1/2 dozen not really conflicting reports but...

makeitfrom.com

 

[TAC71]

Brian , transmission shafts I have had made have always been heat treated 8620. I have heard of another material called 300m that is supposed to be stronger but have no knowledge or experience with it.

 

[bronconut73]

BC uses 300M on their replacement Dana20 out put shaft. Same exact size as stock so no mods but much stronger because of the 300M.
300M is supposed to be uber tough. Been reading about it for years but have never laid my own eyes on it.

 

[ntsqd]

Many years ago I suggested that Chuck look at 300M for the output shaft based on my experiences with it in off-road racing. It is THE alloy to use for making the half-shafts used in Class 1, 1/2-1600, 5, 5 Open, 10, & 12 cars because it handles reversing torsion better than just about anything else. As far as heritage goes, 300M is modification in actual alloy composition from 4340M, which in turn is a slightly modified version of 4340.

Equally important as the alloy used is the design of the shaft. If at all possible it should have adjacent OD's that are smaller than the minor diameter of the spline and large to very large radii at every "inside" corner where the diameter changes.

Anyone other than Brian and I'd suggest that one of the HSLA's commonly used in power transmission shafts might work. I know it won't for him, so I'll just not go there.

 

[nvrstuk]

lol


I appreciate the input. I am updating (yup-again Gary!) my drivetrain. Some might think I'm going backwards but that's ok...

I have been running a KluneV between my 4R70W and Atlas. I like it. Small diameter, light, everything on it is good for 5500ft lbs of torque but the output shaft so I have the opportunity to upgrade to 4340 output but the company quit making 8620 due to manufacturing costs. I'm hoping that I will get some numbers from the designer of the unit so I can see if it will hopefully not be the weak link.

I've run the NP203 gear doubler before. Great doubler, is stoopid strong, just bulkier/heavier and I'd like to keep the 2.7:1 ratio of the KluneV if possible since I'm selling my Atlas 4.3:1 (115# dry) and going with a NP205 (135# dry).

If guess if I had the chance I would have one made out of 8620, but all I have around me are tractor supply houses! lol

I started the 300M output shaft mass buy 15+ years ago from Chuck. It was an excellent product...survived all the punishment I gave it...it worked great in 4 different Dana 20 housings : ( until I went with the Atlas.

Thanks again...

 

[5001craig]

I upgraded my Atlas output to 300M when I ordered it.

There is a local company to me called Branik Motorsports (link here). They can and do build stuff from billet 300M. I saw them taking a huge billet of this stuff to make axle shafts. All I could think was that there was so much in shavings... Some of the stuff they make is amazing like a 9" carrier with D60 guts. Stan and Brandon have been great to me.

And I AM NOT a metallurgical engineer.

 

[nvrstuk]

Thanks for the link, I'll call them Monday.

 

[pcf_mark]

Cylinder head bolts are 300M so that is some tough stuff!

 

[ntsqd]

Never, ever heard that. ARP's "ARP 300" is a stainless steel, not 300M.

 

[welndmn]

Jack at CTM also does a lot of custom shafts out of 300m.

 

[nvrstuk]

Thanks welndmn, I'll call him tomorrow. Got a call in to Branik's today.