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Author Topic: pinion angle vibration  (Read 1900 times)

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mopar 318

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pinion angle vibration
« on: August 18, 2010, 00:06:46 »

So its been about a month since I swapped a 8 1/4 into my fifth. Since the rear was out of a cherokee I had to set the pinion angle. At about 110+ kph I get a bad vibration, which I think is caused by an incorrect pinion angle. I have air shocks on the back of this car and I was wondering whether lowering the car via the shocks could correct this vibration?
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doomedgame

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Re: pinion angle vibration
« Reply #1 on: August 18, 2010, 01:37:39 »

What is the pinion angle set at? any more the -2 will make a vibration
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GrissomRacing

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Re: pinion angle vibration
« Reply #2 on: August 19, 2010, 18:51:00 »

From my personal experience, incorrect pinion angle will ,more often than not, cause a vibration when starting from a dead stop, not at high speeds.  I think I would look elsewhere for the vibe.  Possibly tires.  One thing about tires that most don't know is that it is not possible to perfectly balance a wheel/tire combo for "all speeds".   When balancing a tire, all you are doing is moving the imbalance to a speed that is not normally driven.  This is the same principal as a harmonic balancer on an engine.  All it does is move the imbalance to a speed beyond what the engine will ever run.  I really don't think it will end up being pinion angle.  Tires, driveshaft, steering parts, etc.
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mopar 318

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Re: pinion angle vibration
« Reply #3 on: August 19, 2010, 23:24:30 »

I have a feeling that it might be tires also, since my driveshaft was just balanced about a month ago and new u joints were installed at the same time. I am going to replace the tires on the front and get the rear tires rebalanced.
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S-type

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Re: pinion angle vibration
« Reply #4 on: August 22, 2010, 14:28:45 »

So its been about a month since I swapped a 8 1/4 into my fifth. Since the rear was out of a cherokee I had to set the pinion angle. At about 110+ kph I get a bad vibration, which I think is caused by an incorrect pinion angle.
If the vibration started right after the axle swap, I would guess that is a good place to start. If not, tires/wheels would be my vote at that speed.
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mopar 318

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Re: pinion angle vibration
« Reply #5 on: August 23, 2010, 01:26:45 »

Well heres the story,my first combination in the car was a 360 magnum with a 904 and 71/4 rear with some odd ball 2.45 gears (with no vibration issues). Then I swapped in a 518 transmission and shortened the driveshaft myself (With minor vibration but, I was going to change the rear so I waited to get the driveshaft properly balanced). Next I put in the cherokee rear and I had a bad vibration. Upon further research I found out I had been running the wrong flexplate, so I swapped out the flexplate for the B&M unit.  The vibration is now minor and only exists at higher speed.
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doomedgame

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Re: pinion angle vibration
« Reply #6 on: August 23, 2010, 11:55:14 »

It could be the tires but could be the pinion angle or a combo of the to If you have a angle finder it would be the angle
driveshaft angle + rear end angle from the u joint saddle = pinion angle
ds should be +
rear should be -
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