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Author Topic:   vibration
wag3
Member
posted September 08, 2003 07:08 PM
Have a jet Phantom stockcar that vibrates at 4800 5000 rpm. Feels like it is coming from the drive shaft.So I purchased a .85 thick shaft from bushore, and a direct drive powerglide. Changed the engine, no change.changed pinion angle to 5 degrees down 5 diffrent gear sets in 9in floater.found some factory yokes that were no good. If run in low gear slows down vibration with 3.50 gears. In drive ran 6.50 and 6.00. Dont know what else to try. took all the rotating stuff off the motor like pullys, fan.Put engine mounts on 1/2 in rubber. No change ,But what is wierd is that it shakes with out axles in the floater. so all that is turning is trans, shaft, gears.if any one has had the same problem like to know answer. About to cut car in half and give to junkman.


fastride
Member
posted September 08, 2003 07:55 PM
how far is the drive shaft out of the tranny?Had mine out to far caused a vibration.Try a nother trans if you can get one and check the clutch and flywheel when you swap it.


wag3
Member
posted September 08, 2003 08:46 PM
Had internal balanced 406 in there with manual set up. have 355 in now with powerglide. Every thing is brand new in the car. only raced 10 nights.I cant buy the problem away.This car has a engine plate between the motor and trans. changed the way it mounted no difference. I drilled a 1/2 in hole in the tunnel to watch the driveshaft spin. It spins perfect, but at 5000rpm the drive shaft swings in the center a good 1/4 in . Just like strumin a guitar string. Once you go above or below this rpm the shake is gone.drive shaft is out a 11/2 of the trans.


ryan
Member
posted September 08, 2003 09:18 PM
It's nothing simple he's been fighting it all year. Did you finish what we were working on Sun. or did you say to heck with it. Before you get to the point of cutting it in half bring it over I could use a spare.

[This message has been edited by ryan (edited September 08, 2003).]

mod4
Member
posted September 08, 2003 09:43 PM
Pull the driveshaft and run it - if it still vibrates it's engine (you already changed trannys) if it doesnt it's driveshaft or rear. It's one of three things, dont give up and let us know.


wag3
Member
posted September 08, 2003 09:43 PM
took night off. Borrowed diff trans to try low . finish what we were doing tomorrow.


wag3
Member
posted September 08, 2003 09:49 PM
took off drive shaft.no shake.I can take car down road run up to 6000rpm kick out of gear shut engine down. and hear drive shaft buzzing under car acts like u-joint binding.put trans,driveshaft,yoke into a different car no vibration in there. so that leaves the gears or the housing or the car.


wizzard
Member
posted September 08, 2003 10:07 PM
been there did that. I have had 3 stock shafts rebalanced. I have purchased 2 brand new shafts from bushore.21/2 .85 wall


FastEddy
Member
posted September 08, 2003 11:40 PM
Just by chance how closely have you looked at the transmount rubber? That seems to be the only thing that you have not mentioned here. Otherwise, I have no idea. You have done everything so far that I would have. Motor, trans, driveshaft, u-joints(you did replace, right?), rear end, pullies, etc... Could it be possible that your frame is bent? I may be way off base there. I'm sorry but the only thing I can think of is maybe a trans-mount. But I dont see how that could effect it by what you are describing. Check the frame for being true using a plumb bob. You should be able to make a rectangle and the corners should be close to 90 deg. I dont know what the tolerence should be though.


gahainsey
Member
posted September 09, 2003 06:20 AM
The tranny and rear end must be parrallel to each other. Your driveshaft does not spin at a constant RPM. The varying RPM comes from going thru a U joint at an angle. If your rear U joint is at the same angle(rear and tranny parallel), then any speed gained at the front will be lost at the back and vice versa. Ever wonder why front wheel drive cars use a CONSTANT VELOCITY joint and not a Universal joint?? It is to get away from the sinusoidal rotatational speed that comes from driving thru a ujoint at an angle.


racer2
Member
posted September 09, 2003 07:39 AM
gotta long pilot bushing in there?


ryan
Member
posted September 09, 2003 04:12 PM
Eddy if I remember right he runs a midplate with no rear tranny mount. He is a body man and frame guy so he knows how what to check for on his frame besides its done it since he got it and he bought it brand new from jet. I know he has had a bunch of different trannys he tried in there auto, manual, direct drive glide


wag3
Member
posted September 09, 2003 08:12 PM
just got back from working on the car. Took pinion angle from -5 to 0 to see if better.
hung strings from rear end yoke 2 spots on drive shaft, tailshaft on trans, copler to motor, to check if alignment strait. frame is square. Driveshaft is 2 degrees down. Nothing Changed. On everybodys rearend yokes how much move ment in joint. On every yoke I have there is about .20 movement. There should be some for grease but that much.Had one yoke that was machined of center.Is this common. ????



FastEddy
Member
posted September 09, 2003 11:47 PM
I am sorry but I dont have an answer for you. When ever you figure out what the problem is, will you post it? Thanks!


racnfool
Member
posted September 10, 2003 11:37 AM
That metric rear must not have changed anything huh. Did you ever try putting in a rubber rear tranny mount?


wag3
Member
posted September 10, 2003 05:44 PM
had rubber mount and crossmember both bushore told me to take them out so dont bust case.did not finish stock rear did not have right length of shaft. could the place ment of the motor mounts have anything to do with it. could there be anything in the housing that could do it is only thing that remains in the car.


wizzard
Member
posted September 10, 2003 07:10 PM
driveshaft is off to the right 2 degrees. still shakes. are all of you running in high gear or low. I might have to run in low nothing else works.


MEANGENE83
Member
posted September 10, 2003 09:46 PM
When I had this problem I fixed it with a longer yoke on the 9 inch, my driveshaft was out too far. My car made the buzzing sound you're describing. I think an inch and a half out of the trans is pushing it on the driveshaft length(unless you have a longer than stock slip yoke). Also look at the bushing that the driveshaft rides on in the tail housing of the trans to make sure the slipyoke isn't walking around. Does it get worse with more load on it(heavy track)? Also, I know a lot of people run top gear with no problems, it's more RPM but less torque through it. Did you mean .020 play in the ford yoke? if so that's loose but should be OK, if you did mean .2 something is wrong there.

[This message has been edited by MEANGENE83 (edited September 10, 2003).]

MEANGENE83
Member
posted September 10, 2003 09:58 PM
Just reread that you tried the stuff in another car, how far did the driveshaft slide in on the other car?


wag3
Member
posted September 10, 2003 10:55 PM
it was 11/2 on that car to. it does it on jack stands. on the track it did it the worst rolling on to the right rear putting the ponys to it. also have tryed longer yoke witch set the yoke out 1/2 out of trans no difference.


S@Bracing
Member
posted September 11, 2003 02:33 AM
I also run a phantom and had the same problem. I run the long yolk on my 9in(the one that allows the use of a stock chevy u-joint) I had to have a driveshaft made for mine to fix the problem. But it sounds like you have gone this route. Did Jet install the engine and midplate mounts? The only thing you haven't said you checked was the angle of the engine and trans. When I was fighting mine I was told to check this. I remember a guy at Jet racing telling me that the engine/trans angle can have an adverse effects on the u-joints and driveshafts isit is not correct. Hope this helps


outlawstock17
Member
posted September 11, 2003 07:09 AM
S@B is correct. the driveshaft must angle down from the transmission and up from the rear end yoke. if it the engine is too low or is angled down in the rear so much that the driveshaft angles up from the transmission to the rearend, you have a condition known as "broken driveshaft syndrome". check this carefully.....usually this will cause severe problems, but if yours is borderline, it might be your problem. try tilting the rear of the transmission up a little.

[This message has been edited by outlawstock17 (edited September 11, 2003).]

powerglides
Member
posted September 11, 2003 10:23 AM
Powerglides- car vibrates in the shop with no axles in and the pinion angle doesn't change.


wag3
Member
posted September 11, 2003 06:01 PM
my driveshaft is angled down out of the trans and off to the right toward pass side
did they put the mounts in your car. cause I run a stock length driveshaft and have to use the short wide yoke on gears


S@Bracing
Member
posted September 12, 2003 01:54 AM
They did put my engine and rear engine mounts in my car too. But my car was one of the first built tho. Before they started useing a midplate. I also don't run a crossmember under the tranny. I would call Jet and ask the guys building his cars what they think it could be. The main builder he has for the mods has been building race cars for a very long time and I'm sure he could help you.

[This message has been edited by S@Bracing (edited September 12, 2003).]

S@Bracing
Member
posted September 12, 2003 01:57 AM
Since I run the long yoke I have to cut about an inch off my driveshaft and have it balenced.


wag3
Member
posted September 12, 2003 05:25 PM
I have called jet they have no idea. they said they have never had a car vibrate. so I must be the only one. my car is made number 27.


S@Bracing
Member
posted September 12, 2003 10:12 PM
The only other thing I can think of is have you checked your flexplate to see if it is straight? I had a nasty vibration under a load another time and it turned out that my flex plate was bent. I had someone look at the flexplate while I turned the engine over to check mine. If it moves back and forth that could be your problem.


wag3
Member
posted September 12, 2003 10:42 PM
my flexplate is good. shook with a manual flywheel also.


dirttechguy
Member
posted September 14, 2003 12:10 PM
nine times out of ten if you are having vibration problems and you have located eveything else that it might be as far as rotation you next best probable cause will be a broken crankshaft


wag3
Member
posted September 14, 2003 09:19 PM
i have had 3 different motors in the car so what are the odds of three broke cranks when I have had the cranks out and checked after the vibration started


FastEddy
Member
posted September 14, 2003 10:54 PM
This has to be an angle problem between tranny and rearend. You have tried so many different things on this car with the same reseult. You have taken the same eguipment and put it on another car and the issue is gone. I know you have checked it probably a 100 times but that is all that it can be because you eliminate all physical equipment when you put it in another car and it works fine there. The only differnce has to be mounting and the angle between the tail of the tranny and the rearend.


widebody
Member
posted September 16, 2003 09:12 AM
were dealing with this now. But I know my issues are, 1. 1/2" lead on RR,2. 8* pinion angle and 3. alot of pinion angle movement, runing a pull bar 3rd link...
Id have to agree with the last post about it being a drivline angle problem, either statitcly or dynamicaly.


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