Vibration between 55mph-62mph

gstacky

gstacky

Member
Re: Vibration between 55mph-62mph

This is exactly it, a tire or balance issue should shake all the time, not just at one small speed range. Exactly why I suggested throwing the stockers back on to see if anything changes. If it doesn't, then you know it's due to the lowering.
 
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raman117

Member
Re: Vibration between 55mph-62mph

gstacky said:
This is exactly it, a tire or balance issue should shake all the time, not just at one small speed range. Exactly why I suggested throwing the stockers back on to see if anything changes. If it doesn't, then you know it's due to the lowering.
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That's exactly what I was wondering. I did not check the pinion angle after I lowered it. I believe the pinion wedges are *under* the lowering blocks. Do they need to be above?
 
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raman117

Member
Re: Vibration between 55mph-62mph

DaveP said:
Back to the thread. The OP's vibration began when he changed wheel/tires AND installed lowering blocks that probably changed the rear driveshaft u-joint angles.

The vibration is in a very narrow speed range. A wheel rotates about 685 revs per mile. At 60 MPH that's 11.4 times per second. 11hz. That is a very low frequency.

The driveshaft rotates 3.42 times faster (the axle ratio.). That's 38hz. However, the u-joints 'bind' 4X per rev, so a driveline vibration caused by u-joint procession will be 150hz. So much higher than tire imbalance.

With a little thought and attention to the problem, you should be able to "feel" whether it's 11 or 150 hz, or both, and therefor where to focus your attention to solving the problem. But the very narrow range (55-62 MPH) is typical of driveline imbalance or u-joint angle procession. Tire imbalance tends to increase in severity, the faster the vehichle speed. It's driveline u-joint angles, IMO.
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We have a business called "Driveline Specialists" up here, all they do is driveline stuff. If I brought it up there, would they be able to tell me what's up? IE, is it something that a professional should be able to spot right away? I don't have a pinion angle tool or anything.
 
turbodig

turbodig

Active member
Re: Vibration between 55mph-62mph

raman117 said:
We have a business called "Driveline Specialists" up here, all they do is driveline stuff. If I brought it up there, would they be able to tell me what's up? IE, is it something that a professional should be able to spot right away? I don't have a pinion angle tool or anything.
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Honestly, you really should check pinion angle. Just because you put the wedges back in doesn't automatically mean that the driveline angles stayed the same.

You can't look at it and tell, unless it's really obviously out of whack.
 
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raman117

Member
Re: Vibration between 55mph-62mph

turbodig said:
Honestly, you really should check pinion angle. Just because you put the wedges back in doesn't automatically mean that the driveline angles stayed the same.

You can't look at it and tell, unless it's really obviously out of whack.
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Agreed, I'll bring it up to them and see what they find.
 
BigBadSmoosh

BigBadSmoosh

Picking fights on I-65 since 2013
Re: Vibration between 55mph-62mph

DaveP said:
Back to the thread. The OP's vibration began when he changed wheel/tires AND installed lowering blocks that probably changed the rear driveshaft u-joint angles.

The vibration is in a very narrow speed range. A wheel rotates about 685 revs per mile. At 60 MPH that's 11.4 times per second. 11hz. That is a very low frequency.

The driveshaft rotates 3.42 times faster (the axle ratio.). That's 38hz. However, the u-joints 'bind' 4X per rev, so a driveline vibration caused by u-joint procession will be 150hz. So much higher than tire imbalance.

With a little thought and attention to the problem, you should be able to "feel" whether it's 11 or 150 hz, or both, and therefor where to focus your attention to solving the problem. But the very narrow range (55-62 MPH) is typical of driveline imbalance or u-joint angle procession. Tire imbalance tends to increase in severity, the faster the vehichle speed. It's driveline u-joint angles, IMO.
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exactly my thoughts.. replace the u-joint it will go away..

i had to do the same thing when i installed lowering blocks.
 
gstacky

gstacky

Member
Re: Vibration between 55mph-62mph

GM TURBO said:
But the OP also said the tire shop claims flat spotted tires...
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Probably not flat spotted, you wouldn't be able to drive the thing much less hit 60 on a flat spotted tire. Tire shop is probably just trying to get him into a new set of tires.
 
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raman117

Member
Re: Vibration between 55mph-62mph

I don't think that's the case. TWO tire shops told me they were flat spotted, in fact one said they moved one of the tires from the front to the rear to make it go down the road better. Although I admit, I told the second shop that the first shop told me they were flat spotted, so I may have colored their thinking.
 
gstacky

gstacky

Member
Re: Vibration between 55mph-62mph

raman117 said:
I don't think that's the case. TWO tire shops told me they were flat spotted, in fact one said they moved one of the tires from the front to the rear to make it go down the road better. Although I admit, I told the second shop that the first shop told me they were flat spotted, so I may have colored their thinking.
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I think the best and cheapest route so far is to get the driveline checked first. The kit you put in, what did it consist of?
 
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raman117

Member
Re: Vibration between 55mph-62mph

gstacky said:
I think the best and cheapest route so far is to get the driveline checked first. The kit you put in, what did it consist of?
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I went with the following:

1" Lowering Blocks - http://www.jagsthatrun.com/Pages/Parts_S10-Lowering-Blocks.html
Axle Setback Plates to keep the wheel centered - http://www.jagsthatrun.com/Pages/Parts_S10-301.html

And I also kept the stock pinion wedges. I believe it gave me a total of around 1.375" of lowering.
 
BigBadSmoosh

BigBadSmoosh

Picking fights on I-65 since 2013
Re: Vibration between 55mph-62mph

raman117 said:
Talk about lots of different recommendations. It is of your opinion that my u-joints may be bad?
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when you lower the truck you are effectively changing the angle of the u-joints, basically after a period of time the u-joints get "worn in" to the angle they are being used at. When you change that their rotation changes, which causes a vibration.

If you install new u-joints they will wear in to the new angles of the rear end and driveshaft.

I had to do it and I didn't believe it either until i made the change.
 
gstacky

gstacky

Member
Re: Vibration between 55mph-62mph

raman117 said:
The blocks were not tapered.
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That might be the problem, there should be a taper to them to change the angle just a bit.
And follow the advice above too, that is an excellent point, especially if the truck is new to you, you never know when they were changed last, and they are cheap, easy to do, and give you peace of mind.
 
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raman117

Member
Re: Vibration between 55mph-62mph

gstacky said:
That might be the problem, there should be a taper to them to change the angle just a bit.
And follow the advice above too, that is an excellent point, especially if the truck is new to you, you never know when they were changed last, and they are cheap, easy to do, and give you peace of mind.
Click to expand...

I thought keeping the stock pinion wedges would take care of the angle?
 
alwayscode390

alwayscode390

pppssssshhhhhtttttttttttt
Re: Vibration between 55mph-62mph

My tires sat for a year in the SAME SPOT ... I went to have them balanced ( and only on the inside, I hate the damage caused by outer weights ) ... rides a LOT better , but I definately feel a shudder on the highway ( its speed sensitive for sure ) ---
 
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