Another bent driveshaft thread

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Mopar to ya

Mopar to ya

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Not only have I heard of this, but I am experiencing it. I had a local shop build it. Proven Force, or as they used to be called, Clutch and U-Joint have made shafts for me in the past. I have been fighting a vibration since I put the motor and tranny in a year and a half ago. I took the driveshaft out and had PF check the balance. I took it to a different place to check the balance just to get different eyes on it. The other place didn't give me a lot of confidence, and then they counter balanced the weights. I put it on the hoist a couple of weeks ago and there was little movement at the yokes, but the center of the shaft had 1/4" to 3/8" runout. It was bent. I sent it in today. They verified the bend but were concerned on the length. The slip yoke rides well back and I was always afraid it was too short. I wanted it back so I could drive tomorrow, but they cut the yoke off so I can slide it in and remeasure to make sure I get the right length. I can wait a day if it gets rid of this damn vibration. Just a little off at high speeds can make a huge difference. My tires turn 780 revolutions per mile at 45 mph. if my math is correct, my shaft should spin 3198? How much more at 100 or 120 mph?
 
I'm having the same problem, I turned it 180 and reinstalled, this helped a lot, but it still has a vibration at 45 to 50 mph and gets worse.I sent the driveshaft back to the shop that shorten and balance it today. Try turning 180 may fix your problem its worked be for
 
Did that already. There is no question it is bent. And the driveline shop verified it. Sad, because they built it. My vibration comes in around 70 fairly lightly. Worse at 80, horrible at 90 and damn near undriveable at 100. Funny thing is that's as bad as it gets. 120+ and the vibration is the same as 100.
 
All right, I just got the drive shaft back. They had me remeasure to be sure of the length. there was .020 runout in the middle of the shaft. They straightened it and rebalanced it. Time will tell. I will throw it in tonight and take it for a test drive. My fingers are crossed!
 
Good luck, I hope that it works out for you but I dont think I would accept the same shaft back. I wouldnt think they could get a bend totally out of a shaft and they should have just cut a new tube and rewelded your ends on. Just my opinion and I hope that they fixed it properly for you. Just a FYI, I have had good luck with AA Driveline in Anoka. http://aadriveshaft.com/

On a side note, my drive shaft starts a bad vibration at 45 and only gets worse the faster I go. I have hit 100mph in the car and man was that vibration bad. I was just going to try to install new ujoints first but may have to spend for a new one all together.
 
I actually met the guy from AA in Anoka at the Ricekillers car show. I talked with him for a while and got his card. He wanted the shaft but wanted no part in diagnosing the actual issue because vibrations are so hard to track down. I don't blame him. If this doesn't help I will try him out. He was knowledgeable and personable.
 
FIXED! A year and a freaking half chasing this vibration. I had the shaft out and checked and balanced by two different places in that time. This time I insisted there was an issue and told them what it was and it magically got fixed. I knew as soon as I started driving that it was fixed. I took it up well over 120 and it was climbing smoothly ... with 4.10 gears! Gotta love that overdrive. Now I can finally hit the track.

View attachment no vibration.jpg
 
Awesome!!! Glad you got it fixed!

Wish I was only turning 3500 at that speed. Hell Im turning 3K at 60mph with 3:73 of course its only a 3 speed
 
Was the tube itself really bent or was one of the ends weld on crooked? I seems to me if the tube was bent it would be junk. You would think a shop that builds driveshafts would check runout before they shipped. You said slip yoke stuck out a little far is it possible that it was sloppy and where the run out came from? Bill
 
67cudafb said:
Was the tube itself really bent or was one of the ends weld on crooked? I seems to me if the tube was bent it would be junk. You would think a shop that builds driveshafts would check runout before they shipped. You said slip yoke stuck out a little far is it possible that it was sloppy and where the run out came from? Bill
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They had me remeasure to make sure it was the right length. It took an extra day, but it was worth it to be sure. They can straighten tubes and that's what they did. You would think they would have caught that before I picked it up ... or when I had them recheck it ... or when I took it to a different shop to get another set of eyes on it. The shaft was the right length. I believe they just shipped it bent. When I had it on the hoist, it was smooth at the yokes, but you could see it hopping in the middle. At least they did it all at no charge. Plus they picked up the shaft, brought the yoke back for measuring, picked up the yoke and built the shaft, and then delivered the shaft.
 
straightlinespeed said:
Awesome!!! Glad you got it fixed!

Wish I was only turning 3500 at that speed. Hell Im turning 3K at 60mph with 3:73 of course its only a 3 speed
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That is the overdrive. Two years ago I was 70 mph at 4000 rpm with the three speed 904. Now I have a 200R4 with a .67 overdrive. That keeps the engine rpm down, but that drive shaft is turning so fast with 4.10's that the imbalance was outrageous. I usually drive at 80 mph and 2800 rpm now.
 
Learn something new from members all the time. I didn't know that a tube could be straightened. Just thought a new one had to be made. Glad to hear you can enjoy your car now.
 
I didn't know you could straighten a driveshaft that is bent with a 1/4" to 3/8" out of round. That much of a bend should have been easy to see if the driveshaft is sitting flat on a level floor or a straight work surface. In the past if I break a rear gear or break a transmission I have always had the driveshaft checked and replace the u-joints. Even after that I did break a driveshaft pulling high gear at about 135 mph I lost both rear tires and when I got it stopped half the driveshaft was missing we never found it. It is amazing how much force has to be controlled by the driveshaft not just turning but the axle angle changing when you accelerate and brake most people do think a driveshaft can wear out but they do even on the street they can become worn out.
 
You can straighten shafts up to a point, depending on length and how much it is out, you can usually straighten a shaft that is up to .100 out, if you know how and how to deal with the heat and how to cool it and where to start.

I have told a few people on here about the issue in balancing shafts and how some shops operate with balancing and many machines aren't all that good for speed, and ordering them online there is always a 70/30 when it arrives the shipping thru the balance off and why i say to see your local driveline shop before any smooth advertizing shops.

Though the shaft having .020 run out is .010 more than is allowed, and a machine not able to spin fast enough (5000 rpm) won't be able to balance a shaft with considerable run out.

You should have went to a AL shaft this time.

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hemi446 said:
I didn't know you could straighten a driveshaft that is bent with a 1/4" to 3/8" out of round. That much of a bend should have been easy to see if the driveshaft is sitting flat on a level floor or a straight work surface. In the past if I break a rear gear or break a transmission I have always had the driveshaft checked and replace the u-joints. Even after that I did break a driveshaft pulling high gear at about 135 mph I lost both rear tires and when I got it stopped half the driveshaft was missing we never found it. It is amazing how much force has to be controlled by the driveshaft not just turning but the axle angle changing when you accelerate and brake most people do think a driveshaft can wear out but they do even on the street they can become worn out.
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You'll never seen .020 or even .100 out on a floor or table, and using the car is no good because the joints aren't 0.0 as for angle and as they turn the shaft moves just so slightly off center and the play at the slip yoke also makes every shaft seem off in the car.

However that should have been extremely easy to see when the person who is making the shaft went to balancing it if they ignored it when truing the shaft, a good specialist will know right away if he/she ignored the spec in the truing stage and didn't pick it up in the balancing stage, a shaft with an issue at the center is very evident during balancing , and the right machine you can balance it out, but you know whats going on, unless its like most shops and they hire a guy and there is no knowledge and they're using a computerized machine that can't distinguish issues and the operator is just a screen reader, kinda like a machinist of a cnc machine, it's not the same as the machinist of a manual machine shop.

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