Thread: Isuzu MSA Gearbox to LT230

Originally Posted by Lotz-A-Landies

The shaft won't be heat treated?

Is this O.K. for durability?

Durability as in strength or wear?

Don't believe strength is going to be an issue here. Unlike axle halfshafts your not getting any torque multiplication when in low range. Hence I believe the material strength is sufficient - which I meant to be 4140 (not 4130 as I miss typed...)

Can see some benefit in wear reduction by flame hardening to Rc 50 from Rc30.

How about I get them hardened and provide a warranty - if you break it I replace it? Uh oh sounds like a challenge to me.... Obvisouly price will go up.

Originally Posted by Lotz-A-Landies

Some friends had adapter shafts to mate New Process manual boxes behind Ford V8's to Land Rover transfer boxes and while the untreated shafts worked for a while they did break in less time than some were happy with.

Material? Design? Dimensions? Stress raisers? Internal spline to NP box or flange mount? Alignment? Tolerances? Surface finish? LT230 transfer case or series? May not necessarily be that the breakage occured due to un(heat)treated shafts.

Originally Posted by Dougal

You are aware of different output splines on the MSA boxes?

No I wasn't, but shouldn't matter as longer as the output flange is the same. And if it isn't a bit of a measure up and a different shaft is easy enough.

I have a MSA-5G here that I am adapting. I believe this is the same you have Dougal?

Originally Posted by the_grubb

Durability as in strength or wear?

Don't believe strength is going to be an issue here. Unlike axle halfshafts your not getting any torque multiplication when in low range. Hence I believe the material strength is sufficient - which I meant to be 4140 (not 4130 as I miss typed...)

Can see some benefit in wear reduction by flame hardening to Rc 50 from Rc30.

How about I get them hardened and provide a warranty - if you break it I replace it? Uh oh sounds like a challenge to me.... Obvisouly price will go up.

Material? Design? Dimensions? Stress raisers? Internal spline to NP box or flange mount? Alignment? Tolerances? Surface finish? LT230 transfer case or series? May not necessarily be that the breakage occured due to un(heat)treated shafts.

I believe the originals were hi-tough the same stuff MaxiDrive (now Hi-Tough Engineering) used for the axles, but will find out.

Mal Storey used to have a lot of trouble finding people who would harden the shafts so all his axles were sent to Sydney. I believe this continues with Hi-Tough axles.

4140 is normally supplied in the hardened and tempered condition.

However, with heat treatment of large section there is some reduction in strength from the outside to the core (because the core can't be quenched at the same rate). If you are starting with large diameter to suit the Isuzu flange OD, there will be some reduction where it is machined down to the 10 spline section.

It should be ok, but a hardness check will tell all.

Originally Posted by the_grubb

No I wasn't, but shouldn't matter as longer as the output flange is the same. And if it isn't a bit of a measure up and a different shaft is easy enough.

I have a MSA-5G here that I am adapting. I believe this is the same you have Dougal?

The output flanges appear to be the same. My conversion has removed the output flange and gone from the gearbox spline to the transfer input spline.

I don't believe your shafts will stand up if not hardened. I forget the exact hardness mine was done to, but I was looking for a material with at least 1000 MPa yeild, the concern being stress concentration causing fatigue at the start of the splines.

The final material I received had a yeild when hardened of almost 2000MPa. Overkill, but it boasted minimal distortion in heat-treatment and the cost difference was minimal.
I received quotes from $NZ350-750 to make my shaft, in the end the workshop that started didn't finish it, I had to do the final machining and heat-treatment. Total cost around $NZ600.

I'll see if I can dig up my original calculations, but the FEA study I ran at the time shows 650 MPa bulk stress with 1450MPa max stress concentration at the start of the splines. The computer simulations tend to exaggerate stress concentration as computer modelled geometry tends to have sharper transitions than actual manufacturered parts.
This is with 2000Nm applied to the shaft. 2000Nm was the shaft torque required to light up wheels on tarmac. It represents 345Nm applied by the engine in first gear or 666 Nm applied in second gear.

Originally Posted by Dougal

The output flanges appear to be the same. My conversion has removed the output flange and gone from the gearbox spline to the transfer input spline.

I don't believe your shafts will stand up if not hardened. I forget the exact hardness mine was done to, but I was looking for a material with at least 1000 MPa yeild, the concern being stress concentration causing fatigue at the start of the splines.

The final material I received had a yeild when hardened of almost 2000MPa. Overkill, but it boasted minimal distortion in heat-treatment and the cost difference was minimal.
I received quotes from $NZ350-750 to make my shaft, in the end the workshop that started didn't finish it, I had to do the final machining and heat-treatment. Total cost around $NZ600.

I'll see if I can dig up my original calculations, but the FEA study I ran at the time shows 650 MPa bulk stress with 1450MPa max stress concentration at the start of the splines. The computer simulations tend to exaggerate stress concentration as computer modelled geometry tends to have sharper transitions than actual manufacturered parts.
This is with 2000Nm applied to the shaft. 2000Nm was the shaft torque required to light up wheels on tarmac. It represents 345Nm applied by the engine in first gear or 666 Nm applied in second gear.

Good points Dougal. I get the same numbers as you.

Although I believe the MSA/shaft setup will be stronger than say the LT85 , considering with upgraded axles, diffs and now gearbox this shaft will now be the weakest link (when in high range, not so when in low range) in the system so might as well go as much extra strength as possible without breaking the bank.

Will speak to the supplier monday about getting some hy-tuf and getting it heat treated.

Been having problems uploading progress pics.....

Shafts = EN26 Heat Treated

Originally Posted by Dougal

Are the 110 chassis rails further apart than a rangie?

Dougal, how does your starter motor compare to these pics? I can get my fingers b/n starter and chassiss in all locations. This is with the Isuzu Flywheel cover but not with the gearbox in yet.