Aluminum Vs Steel Driveshafts

[Meep-Meep]

The diameter, length and material selection has to do with keeping the shaft from going into the first critical. Meaning, if you turn a perfectly balanced drive shaft fast enough eventually the center will start to whip and cause vibration, and the speed at which the first critical happens depends on the length of the shaft.

 

[Bruzilla]

In 20+ years of driving Interceptors with aluminum shafts, I've only had one failure and that was because of a faulty U-joint, and most of my cars were driven 300k miles before I retired them, so I know the thing are durable. I'm just wondering how they'll hold up when I go from 235-325 HP to 400+.

 

[Meep-Meep]

It's really the torque input that matters. And worse if you apply that force abruptly (dump the clutch at high RPM kind of stuff or try to pull the Queen Mary) you may twist it into a pretzel. Other failures would be resonance related, which result from improper U joint angles or running the shaft too fast for it's length. For a street car you may be OK because you are likely to not glue it down with slicks so the rear tires are your fuse. Just don't put 4.30 gears and go 100 MPH! Most new V8 cars and trucks with OD and tall gears likely never see over 2 KRPM on the freeway so the drive shaft is plenty safe.

 

[67Satty]

I use the Dodge truck units, but another source is always good news.

Can you tell me which model Dodge truck you get the driveshafts from? I'm intrigued by this idea and might want to do some junkyarding. What else do you need to do to them before they can swap into a B Body? Thanks!

 

[Meep-Meep]

Can you tell me which model Dodge truck you get the driveshafts from? I'm intrigued by this idea and might want to do some junkyarding. What else do you need to do to them before they can swap into a B Body? Thanks!

This likely will need to be shortened and balanced before you can use it as I'm sure it's not a direct bolt in. By the time you spend the time scrounging and then have it modified to fit you might as well start from scratch. Plus how many drive shafts have you seen in a yard that have been subjected to the forklift?

 

[q-ship]

Can you tell me which model Dodge truck you get the driveshafts from? I'm intrigued by this idea and might want to do some junkyarding. What else do you need to do to them before they can swap into a B Body? Thanks!

Though I'm sure a list exists somewhere, I don't know what years had aluminum vs. steel.

I read somewhere, years ago, that they were an easy/cheap alternative to locating stock B body big block driveshafts, so I picked one up out of a 2 door late 90's/early 2000's truck. --- the only reason I ever messed with them in the first place is because I sold off my stock BB cars when they became ridiculously valuable to others, and bought replacement SB cars for cheap that I could do rotisserie re-builds on as BB clones, and still be money ahead (as numbers matching has zero value to me personally).

It cost me $30.00 (pic-a-part) + $90.00 to have it shortened and balanced and worked perfectly.

Since then, I have used 3 others, plus have a spare laying out back (just in case).

My brother-in-law grabbed one for his 66 Plymouth (as per my suggestion), and he was only into it for $90.00 total after purchase, shortening, and balance (different state).

I don't have any idea how "race" usable they are as I quit racing years ago except for the rare "test and tune" nights on street tires, but I have gone 12.94 with borrowed DOT drag radials, and have probably 200,000 miles on my three 60's cars (with the aluminum shafts in them). --- All my cars are daily drivers.

They may be a good race addition, but I can only attest to their "performance street" durability. However there are numerous trucks that live quite happily running nitrous, computer flash, and other mods and run low 11's week after week.

I hope any of that helps.

 

[Bruzilla]

The nice thing about aluminum driveshafts is they are a breeze to find in the junkyards since they don't rust or corrode like steel ones. Look for a shaft that a nice silver color, and you can bet it'll be an aluminum one.

 

[67Satty]

It cost me $30.00 (pic-a-part) + $90.00 to have it shortened and balanced and worked perfectly.

That sounds a lot better than $500 or so for one from Denny's Driveshafts. I've got a junkyard a few miles down the road so it's worth a shot to me. Thanks for the info!

In one of my old High Performance Mopar magazines their test mule car is very close to mine, only it's a '67 Dodge B Body. They did a back to back strip test and found that the aluminum driveshaft was worth a 1/10 in the quarter. Every little bit helps. If I can get another tenth off for around another $100 and a little bit of my time, I'll do it.

 

[tpodwdog]

with the horse power of a 440...do ya REALLY think 20 pounds makes that much of a difference? with the juice my 440 has...i would not trust anything but steel.

 

[Bruzilla]

I knew guys in MD who used to drill a bunch of 1/2" holes in their hood hinges to reduce weight. What does that add up to? An ounce or two?

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It cost me $30.00 (pic-a-part) + $90.00 to have it shortened and balanced and worked perfectly.

When the U-joints failed in one of my Interceptors and the driveshaft got all tore up on the *** end, the local Ford junkyard wanted $90 for one, and the u-pull-it charged me $20, which was about what the U joints cost. ;) I got the shaft, installed it, and all was good. Only problem I had was there was a mama copperhead snake laying under the car about where the drivers seat is, and wouldn't move for nothing. I threw sticks and stones at her, but she wouldn't budge. I finally said "you don't bother me, I won't bother you" and I got the shaft off while she just watched.

 

[RustyRatRod]

I remember when I went to driveline school at GM, they said that EVERY drive shaft vibrates. The trick is getting it to NOT vibrate within the "useable range" as they called it. In other words, spun above the threshold of normal opreation, they are imbalanced. You gotta stay away from that critical. It'll booger you up everytime.

The diameter, length and material selection has to do with keeping the shaft from going into the first critical. Meaning, if you turn a perfectly balanced drive shaft fast enough eventually the center will start to whip and cause vibration, and the speed at which the first critical happens depends on the length of the shaft.

 

[tpodwdog]

I knew guys in MD who used to drill a bunch of 1/2" holes in their hood hinges to reduce weight. What does that add up to? An ounce or two?



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When the U-joints failed in one of my Interceptors and the driveshaft got all tore up on the *** end, the local Ford junkyard wanted $90 for one, and the u-pull-it charged me $20, which was about what the U joints cost. ;) I got the shaft, installed it, and all was good. Only problem I had was there was a mama copperhead snake laying under the car about where the drivers seat is, and wouldn't move for nothing. I threw sticks and stones at her, but she wouldn't budge. I finally said "you don't bother me, I won't bother you" and I got the shaft off while she just watched.

every snake i ever knew drove a Ford

 

[67Satty]

with the horse power of a 440...do ya REALLY think 20 pounds makes that much of a difference? with the juice my 440 has...i would not trust anything but steel.

It's not so much the total weight savings, it's more that there is less rotational mass from what I understand that makes the aluminum driveshaft an advantage - less weight to get spinning. They are also supposed to be smoother. From surfing around today, some other Mopar racers are claiming junkyard aluminum driveshafts they've pulled from Dodge and Chevy trucks and Ford Crown Vics have stood up to 600 HP in 3400-plus pound cars at the strip.

 

[RustyRatRod]

I knew guys in MD who used to drill a bunch of 1/2" holes in their hood hinges to reduce weight. What does that add up to? An ounce or two?

Those are the kinda guys that win. Names like Yunick and Garlits come to mind.

 

[HT413]

I knew guys in MD who used to drill a bunch of 1/2" holes in their hood hinges to reduce weight. What does that add up to? An ounce or two?

I hear ya, but when it counts, all those details add up to some big numbers. Example: I always liked to go backpacking but as i get older my back just cant take it. So after pouring through my gear and removing every single oz i could, then doing again and again, I took a 33 lb pack down to 19 lbs. this includes 6lbs of water and enough food for 2 days. Even drilled holes in my toothbrush lol. And i'm not the kind of guy that buys a $300 titanium pot, i spent a total of like $50 on a smart combination of new gear and old army surplus (those guys know their stuff). My whole gear kit cost less than my buddy's parka but i pack several pounds less than him.

Every ounce counts when you carry it all weekend.

 

[Supershafts]

Who was bein smartass? I am dead serious. GM used fiberglass drive shafts in almost all their half ton trucks from 88-98.

Here is but one of many companies that offer them.

http://www.strongwell.com/selected_markets/comp_driveshaft/

They used .065 wall AL shafts wrapped in CFF to keep the flexing of the AL down since it will make a pinging noise everytime the shaft is loaded.
fiberglass without the CF would crack in that environment

Is there any balance between weight savings and a loss in rotating balance and inertia? You know, could something with that kind of length to diameter difference be TOO light for the application if strength is equal?

I replaced my driveshaft last year and the driveline shop said a mild steel shaft in 3" diameter was just as good as a smaller diameter chrome moly steel shaft and he claimed it balanced and perform better than a 2.5" shaft due to decreasing the length to diameter ratio, so now I have a 3" mild steel shaft on my car. I didn't check out aluminum shafts but I know that the Denny's driveshafts are super expensive.

Anyone else running 3"?

That is not correct, a 3 stl shaft will see higher rpm than a 2.5 cm stl shaft, and the strength is not better really, the rpm capabilities and strength between the 2 are very close.

lets use 50" long as an example and 3", 3" stl will be safe to 6500 and the 3" CM stl will be safe an additional 150 rpm, in 2.5 you lost some tq capability and you lost 1000 rpm and are going to have a issue at 5500 rpm rather than 6500 with reg stl 3".

AL shafts because the weight is less can experience more rpm than stl at the same diameter.

with the horse power of a 440...do ya REALLY think 20 pounds makes that much of a difference? with the juice my 440 has...i would not trust anything but steel.

When you lose half the weight of the shaft Stl vs AL you can expect .007 to .010 of time loss in acceleration, and you'll gain rpm and mileage.

Stl to AL is 99.9% always at the least half, in some cases it is even more weight loss depending.
If you have a 20 lb shaft in stl it'll be 10 lbs in AL which is a lot of weight loss in the driveline and pounds lost in the driveline are equivalent to 10's lost carrying, so losing 10 lbs is like losing 200 lbs carrying.

I don't use anything but AL in my performance stuff, and trucks are far heavier than your car and making more tq than you, and i have many race boats on AL which are far more abusive than cars and trucks.
I have AL shafts in heavy 3700 lb cars doing in 8.0s and cars in the 1.1teen 60's and even adrl pro cars in the .9 area.
AL is not weak.

CF shafts are as light and in some cases a little lighter than AL, but CF unlike Stl and AL have no flex at all within the tube, and if they break and they are designed right they will kinda rag and splinter, if they are built for far more than they need to and break by having something contact them they can keep there form.

.

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As for the original question of the ford shafts, those are made by visteon, and if they are the .110 tube they are ok for some good power, stay away from the AAM AL shafts and some of the visteon shafts which you won't know they're junk till you see your local driveline shop and they confirm.

The aam shafts many of them are mostly .068 and that's fine for your car if it's not performance , if you have a stock 340/360/383/440 they'll be fine, once you're past the 500hp area those shafts become your risk.

Many of the truck AL shafts will be 4", 4.5", 5" and 6" shafts, of which 5" and 6" shafts are going to be a problem in the car unless you have no rear suspension, some of the 4.5" may also be a issue.
Then there are the swedged tube AL shafts, that come in some trucks and when they are shortened you can't use the weld yoke in the larger part of the tube and between the right yoke and machining you're far better off having your local driveline shop make you a new AL shaft.

Stay away from oil soaked used AL shafts that will need to be shortened, AL is kinda porous and oil/whatever soaked shafts i stay away from with shafts like that because the contaminants soak into the AL and cleaning them with other solvents and scrubbing them with particular stainless stl still makes a 50/50 chance, and heating tubes used in driveline to clean or burn out contaminants is not a good idea with AL and when welding you'll see the problem and it could work and it could fail and instead of having a shop say they aren't going to guarantee that and a problem does happen you're better off leaving that filthy piece right where it is rather than chance it.
.

 

[Bruzilla]

The HP on the Interceptors has been going up over the years, so would it be more likely the better aluminum shafts would be off later Interceptors vice say 92-97 cars?

By the way... Crown Victorias all have steel driveshafts. Only the police interceptor package cars from 1992-1998, and the Police Interceptor named cars from 1999-2012, had the aluminum shafts. There are lots of ways to tell the Interceptors from the Crown Victorias, but it's a lot easier to just look for a dull silver driveshaft in the junkyard. They're usually just lying around.

 

[RustyRatRod]

They used .065 wall AL shafts wrapped in CFF to keep the flexing of the AL down since it will make a pinging noise everytime the shaft is loaded.
fiberglass without the CF would crack in that environment

I replaced a buttload of broken ones when I worked at the local chebbie dealer back in the late 80s and early 90s. There was no aluminum in the shafts. Only on the ends.

......on reflection, I really cannot remember. I know the yokes were aluminum. I just don't remember there being an alumium shaft there at all.....approachin 30 years ago so I really do not remember.

 

[Cranky]

I'm one of those guys that like to drill holes! More ways than one . Took my 66 Belvedere down from 3370 to 2950 and the ac was still on it. Glass hood, no front bumper, a lot of the interior gone and punched holes. The car even had those heavy cop car wheels still on it. I read up on AL shafts many years back and will keep that option open.

 

[68 Sport Satellite]

The diameter, length and material selection has to do with keeping the shaft from going into the first critical. Meaning, if you turn a perfectly balanced drive shaft fast enough eventually the center will start to whip and cause vibration, and the speed at which the first critical happens depends on the length of the shaft.

Just theoretically, is that length at which first critical happens indepenent of diameter? I would think if say the diameter was very close to the length, which would of course never happen for a driveshaft, that that speed at which first critical occurs would go up. I know nothing about this - just curious since my background is engineering.