[Chief of the 60's]

Its not a question about whether or not an aluminum driveshaft can work, they obviously do.

The question is whether its worth saving a few bucks by using a "used" factory aluminum driveshaft out of a junkyard.

I say, based on what I know and have seen, hell NO

[RocktimusPryme]

As far as the basic theory here I had in mind when I began the conversation, we are getting a bit hung up on the aluminum part of it. Are basically all OEM shafts aluminum now? Would it be difficult to find a big factory steel DS?

[JLMounce]

Originally Posted by RocktimusPryme

As far as the basic theory here I had in mind when I began the conversation, we are getting a bit hung up on the aluminum part of it. Are basically all OEM shafts aluminum now? Would it be difficult to find a big factory steel DS?

My understanding with the modern stuff is yes. There's going to be basically two types of construction you see. Either a 1 piece aluminum shaft or a 2 piece steel shaft with a center carrier bearing.

[Chief of the 60's]

Funny thing is, my Dodge Magnum Wagon has a 2 piece with carrier bearing driveshaft. Now, I don't know if all LX (300, Challenger, Charger, Magnum) cars do but mine does.

[JLMounce]

Originally Posted by Chief of the 60's

Funny thing is, my Dodge Magnum Wagon has a 2 piece with carrier bearing driveshaft. Now, I don't know if all LX (300, Challenger, Charger, Magnum) cars do but mine does.

The modern mustangs I've had S197 chassis and beyond, all had two piece shafts with carrier bearings. I know the Challenger's use two piece shafts as well.

My 2006 Tundra as equipped like that as well.

I think it's become fairly common to see that.

[Bill Eveland]

I paid around 300 for my 3" CM Strange shaft that came with 1350 u joints plus their yoke on trans and rear end . I don't see worth saving much with trying to make something else used work. Hardly any factory shaft is going to come with 1350 u joints. I know this is the street section, put pay for something good once and be done.

[RocktimusPryme]

Those strange shafts are a pretty good deal.

[ta man]

Originally Posted by AG

This. I also got the same driveshaft from Strange and I'll never have to be concerned about failure. You can look up a chart that shows the critical RPM for a given material, diameter and length to decide what you need.

I know the diameter and the length dropped the 80 percent critical rpm to just under 6800 rpm..but it can handle 1500hp if I remember.

[dataway]

The driveshaft on my 2011 GMC truck is steel, at least that's what the rust tells me.

Probably long enough to modify for any car out there.

[Formulajones]

Is it a short bed or single cab?

My understanding from our local driveline shop is it's the length of the driveshaft needed that determines the material, and if it's a long shaft and made of steel, there is a certain point where a carrier bearing is needed so the shaft can be made in 2 shorter pieces. Really long steel shafts aren't a good idea, They get too heavy and as mentioned critical speed becomes an issue, earlier I mentioned they start whipping if too long and heavy.

Think "jump rope"

Aluminum is lighter and will have a much higher critical speed before that occurs. So in some cases when the factory didn't want to use a carrier bearing to make a 2 piece steel shaft for what ever reason, they would use aluminum, make it one long shaft and done.

[RocktimusPryme]

Im in the same boat with my Ram. I feel like Ive seen some small surface rust which would make me think its steel. Its a short bed. So maybe the short box vehicles get a steel shaft.

[dataway]

My truck is a single cab, with the medium length bed ... 7'6" about. So probably shorter than some trucks.

[Tom Vaught]

Originally Posted by Formulajones

Is it a short bed or single cab?

My understanding from our local driveline shop is it's the length of the driveshaft needed that determines the material, and if it's a long shaft and made of steel, there is a certain point where a carrier bearing is needed so the shaft can be made in 2 shorter pieces. Really long steel shafts aren't a good idea, They get too heavy and as mentioned critical speed becomes an issue, earlier I mentioned they start whipping if too long and heavy.

Think "jump rope"

Aluminum is lighter and will have a much higher critical speed before that occurs. So in some cases when the factory didn't want to use a carrier bearing to make a 2 piece steel shaft for what ever reason, they would use aluminum, make it one long shaft and done.

Critical Speed, as mentioned with an example in my previous posts can not be ignored. A properly designed and fabricated aluminum driveshaft from a quality supplier or a new driveshaft modified for the proper length for the application is the way to go.

There is a point with "AGE" and "Duty Cycle" (where even the best parts fail eventually). Put a driveshaft loop on the vehicle and save your vehicle from
potential sheet metal replacement down the road.

[Formulajones]

Originally Posted by Tom Vaught

Critical Speed, as mentioned with an example in my previous posts can not be ignored. A properly designed and fabricated aluminum driveshaft from a quality supplier or a new driveshaft modified for the proper length for the application is the way to go.

There is a point with "AGE" and "Duty Cycle" (where even the best parts fail eventually). Put a driveshaft loop on the vehicle and save your vehicle from
potential sheet metal replacement down the road.

It's probably one of the reasons why, as I mentioned earlier, our driveline shop does not work on used aluminum driveshafts. He'll build you a nice shiny brand new one though

However, he'll work on and modify used steel driveshafts all day long

[AG]

The critical RPM for my Strange DS is 7800 rpm if I remember correctly and I go across the line at 6700 rpm. It is 3" CM, if I was going to a higher rpm I would have gone with a 3.5" CM shaft.

[Chief of the 60's]

Originally Posted by AG

The critical RPM for my Strange DS is 7800 rpm if I remember correctly and I go across the line at 6700 rpm. It is 3" CM, if I was going to a higher rpm I would have gone with a 3.5" CM shaft.

So your tranny is 1:1 in final gear?

[ta man]

Originally Posted by AG

The critical RPM for my Strange DS is 7800 rpm if I remember correctly and I go across the line at 6700 rpm. It is 3" CM, if I was going to a higher rpm I would have gone with a 3.5" CM shaft.

That was my way of thinking as well to stay with a 3 inch..time may tell if the rpms creep up over time with any new engine changes.

[AG]

Originally Posted by Chief of the 60's

So your tranny is 1:1 in final gear?

Yes, TH400.

[Chief of the 60's]

Originally Posted by AG

Yes, TH400.

Just curious. Some do not. That, obviously effects flywheel RPM vs. tail shaft RPM. That effects driveshaft RPM

[JLMounce]

Technically speaking, unless you’re running a lockup converter, your DS rpm will still be less than engine RPM due to torque converter slippage, even if your final is 1:1

But that’s splitting hairs of course.