Vibration.....Driveshaft?

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aengineguy

aengineguy

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Mt. Zion, Illinois
Still not resolved. Took the Dart out yesterday and was hard on it till about 95 mph. Not super horrible, but pretty good vibration, even after letting off till speed decreased. It is not wheel speed and not engine speed as I have had it over 6600 rpm in first and second...does not occur. The shaft was built locally with spicer 1350 and Mark Williams slip yoke on a 3" tube. They say they have built hundreds for local racers, but they only spin them to around 2000 to balance them. Running a 904 and I am afraid it could bust the extension housing. Rear end is a Moser with 4:10's. I don't dare do a 1/4 mile stint with it as I will be pushing the 120 mark. Does this sound like something associated with the driveshaft to you??

Thanks for your feedback!!
 
I would check the pinion/driveshaft/trans angles! Check for another post on this here as there is a free smart phone app to use on this.
 
I had my driveline balanced at a race shop that touted all the same crap and it was still out of balance $140 later.
 
aengineguy said:
I had another driveshaft builder tell me that the incorrect angles would not cause a vibration.....was he not correct?
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He absolutely was not correct. Maybe he was talking about something other than driveline angles? Here is a nice short YouTube video that explains the angles and how they relate to vibrations, etc. Check this out:
 
68gtxman said:
He absolutely was not correct. Maybe he was talking about something other than driveline angles? Search the forums for a nice short YouTube video that explains the angles and how they relate to vibrations, etc.
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That is a little encouraging, since the guy told me that I have put changing the pinion angle to the bottom of my todo list. I did measure everything a couple of years ago and if I recall I was out on the pinion by about 2 1/2 degrees...can't remember which way. I will look for the video.....Thanks.
 
No slop in splines?
Rear trans mount getting mushy?
Any different installed 180 degrees out?
 
aengineguy said:
That is a little encouraging, since the guy told me that I have put changing the pinion angle to the bottom of my todo list. I did measure everything a couple of years ago and if I recall I was out on the pinion by about 2 1/2 degrees...can't remember which way. I will look for the video.....Thanks.
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I edited my post with the link in it. Here it is again.

I chased down a bad speed related vibration by myself and it turned out to be a pinion angle that was too nose high.
 
68gtxman said:
I edited my post with the link in it. Here it is again.

I chased down a bad speed related vibration by myself and it turned out to be a pinion angle that was too nose high.
Click to expand...

Outstanding video. I am a mech engineer and can fully understand. Looks like I have some things to check. Also, I am running Caltracs with about 1/4" play for the street, so I have to take into account my pinion movement.
 
Darthomas said:
No slop in splines?
Rear trans mount getting mushy?
Any different installed 180 degrees out?
Click to expand...
Everything was brand new when I put the car together, probably only have about 2000 miles on the car, I did check for any spline play a while back, but good. Thanks.
 
aengineguy said:
Outstanding video. I am a mech engineer and can fully understand. Looks like I have some things to check. Also, I am running Caltracs with about 1/4" play for the street, so I have to take into account my pinion movement.
Click to expand...

Funny, I am a mechanical engineer too! Glad I could help you!
 
I've been in the web printing business since 1988, and have seen many a driveshaft blown or thrown.
I used lightly damaged press driveshafts for the backyard fence posts.
No, or not enough angle for the ujoints to work is just as bad as too much angle, and can let vibrations run amok.
 
Darthomas said:
I've been in the web printing business since 1988, and have seen many a driveshaft blown or thrown.
I used lightly damaged press driveshafts for the backyard fence posts.
No, or not enough angle for the ujoints to work is just as bad as too much angle, and can let vibrations run amok.
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That's funny on the fence posts. I still have the original one out of the car you can add to your fence. It would probably look like a candy cane if I put it in the Dart now.
 
aengineguy said:
Were you a flier in the Air Force? I never got that far, but had my civilian CFII and Twin Instructor
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No, I wasn't a pilot in the USAF - just a civil engineer. I did get my multi-engine instrument rating though. I bought a gyrocopter years ago (just like the one in the original Mad Max) and it's on my To Do list to get it flying in the future. Till then I just fly my buddy's Archer. I'll bet that since you are an instructor, you probably fly a lot of different planes. Is that what you do for a living?
 
I only kept shafts with mildly damaged flanges.
1466964414061.jpg
 
68gtxman said:
No, I wasn't a pilot in the USAF - just a civil engineer. I did get my multi-engine instrument rating though. I bought a gyrocopter years ago (just like the one in the original Mad Max) and it's on my To Do list to get it flying in the future. Till then I just fly my buddy's Archer. I'll bet that since you are an instructor, you probably fly a lot of different planes. Is that what you do for a living?
Click to expand...
No, my brother and I own a manufacturing company of about 20 people. I am the engineering mgr. Work with CAT, John Deere, Toyota. I did fly an Archer once and about 30 other planes. Best ride though was in the back of a P51-D. Friend of mine had 2 of them. He had taken the fuel tank from behind the pilot and put in a jump seat. As you know the bubble canopy is quite constraining for someone behind the pilot. Also, flew along side Rudy Frasca's P-40 Warhawk for a while.
 
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