DriveATransAm

ive heard that steel driveshafts are hard to balance vs. aluminum. would an aluminum one be better for a daily driver that sees 120+ mph pretty often?

trackbird

iTrader: (4)

In most cases, the aluminum will have a higher "critical speed". THe critical speed is the maximum rpm that a driveshaft is rated to see. At the critical speed (it is like a harmonic frequency) it will vibrate and usually break. At 1/2 the critical speed it will also vibrate (it is a 1/2 harmonic). I suspect the aluminum version will be less prone to vibration (which is easier on u-joints, trans seals, etc). Just my thoughts....good luck!

DriveATransAm

hmmm. I have a strange chromoly one right now. i just replaced the trans bushing since the old one got worn out for some reason. i have a spohn torque arm, and it was checked and set to about -1.5. I have 3.73s in a strange 12 bolt and i drive on the expressway quite a bit. the last bushing seemed to last about 1200 or so miles after i put the steel driveshaft in. im wondering if maybe steel is just a bad choice for a pretty steep gear and high speeds. i set the cruise to 80 and it was fine at that speed for some time...but anytime i wanted to bring it past 100 it was pretty annoying, and if i brought it to about 130 and let off it was getting kinda bad.

Pro Stock John

iTrader: (34)

You mean you are getting a lot of vibration with your new HD one, at high speeds?

trackbird

iTrader: (4)

The aftermarket chromoly shaft should have a fairly high critical speed as well, I find it suprising that you are having issues with that one. (I thought you had a stock steel one). You may want to call the manufacturer about that one....Just my thoughts.

trackbird

iTrader: (4)

If you are wearing trans bushings, it is either the pinion angle causing a bind or it is vibrating and wearing them out. If it is vibration, it will likely be worn all over, if it is the pinion angle, it will likely be worn in one spot (where the yoke is rubbing).....

DriveATransAm

the pinion angle was set by a speed shop in front of me. i had them show me how to set it too. originally the driveshaft was a little short imo, and a few other people thought so too. the company that i ordered it though sent me a new one without asking any questions. very cool of them and awesome customer service. i figured that was a main cause of it. the bushing was replaced (it was totally gone) and put the new driveshaft in (which looked like a much better fit). it seemed ok, but i didnt go too fast. this weekend i drove to iowa (bout 4 hour drive) and there were a lot of wide open straights needless to say, my car saw 4th gear often 4th gear is about 130ish with 3.73s. i wanted to run it up to the top of 4th but i didnt want to break in the middle of no where. i would think that the driveline would have been a little less vibrationy.... on the way home i had an acura that wanted to play around a little so i ran it up to 120+ a few times and something just doesnt seem right. i shouldnt be afraid to run my car to 150 mph, lol. i set the cruise to 80 and it was at there for over an hour and was fine at that speed.

i will pull the shaft and see if the bushing looks worn. if it is, then i dont know what the heck is causing the vibration. maybe i just drive too fast.

maybe -1.5 is a bad angle for high speeds?
maybe the trans is messed up? i already broke the stock alum shaft and tailshaft with it. i was told that if it was a trans issue that it would vibrate from the beginning and wear the bushing almost instant.
maybe chromoly is bad

anyone

trackbird

iTrader: (4)

That is what I was trying to say, is that -1.5 may be pushing the limits of the driveline. I'm not sure how far you can go before you run into a binding problem on the driveshaft and yoke. I'd think you are getting close (probably not dangerous, but close). I'd reset it to -.5 degrees and see if it cures your noise...then work up from there. Good luck!

And, Chromoly is fine.....

2001CamaroGuy

iTrader: (6)

Steel:
stronger (more torque handling)
heavier (can't be spun as fast/harder for engine to spin)

Aluminum:
weaker (less torque handling)
lighter (spin higher/faster)

The only reason people use steel driveshafts anymore is they don't have the money to go aluminum. If people need the strength of steel (can break an aluminum one), they tipically go with carbon fiber or chrome molly (both lighter than mild steel).

Change out the stock steel shaft. The car will drive better (less vibration) and will perform better (more power) because of the reduced ratation weight.

trackbird

iTrader: (4)

He has a strange driveshaft....not stock....(I thought that too at first).

DriveATransAm

ill set the pinion angle to 0. it was closer than 0 when the bushing first went out.

trackbird

iTrader: (4)

Just don't go "positive"....

Pro Stock John

iTrader: (34)

Don't use stock steel one it's not high speed balanced.

scottknight

A note on running angles for u-joints. You don't want to run 0º or the u-joint will destroy itself. Anywhere between .5º and 1.5º is where you want the running angles to be for optimum u-joint life and strength.

Also, an often overlooked source of vibration is the difference between the running angles of the two ends of the shaft. They need to be as close to each other as possible, or you get that torque induced drone. The u-joint is not a constant velocity coupling and it causes the driveshaft to speed up and slow down twice for each revolution. If the two running angles are not the same, you will causing the trans and pinion to accelerate/decelerate twice for each rev...lots of vibe.

DriveATransAm

wtf. dont run 0 now? why cant anyone give me a straight answer. i just want to be able to drive my car up to 150 mph with no vibrations!!!

trackbird

iTrader: (4)

Back to my earlier suggestion.....I think it is the best idea....I agree, don't go positive (and I'd stay away from a setting of less than .5 degrees).

Kevin

Derek 357i

iTrader: (1)

Here is a link that is on Inland Empire's site:
http://www.iedls.com/ptsetup.html

and another
http://www.streetrodderweb.com/tech/0203sr_driving/