Shake on acceleration after setting 1" rake on torsion bars

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BigMaineWomen

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Jun 2, 2018
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Hi all. I asked this on my alignment post over a week ago but didnt get any responses.

2004 LX with 248K. Hydraulic suspension was professionally swapped for conventional 2 years ago without touching the torsion bars. I finally got around to cranking them to increase the front height because it was 3" lower than the rear. I'm at 1" lower in front now. Vibration appears to be a common result of too much height on the front end from cranking the TBs, but can someone tell me what causes the vibration? I measured my droop to be 4" on each side, which is 100mm and a fair bit beyond the recommended 50-70mm. Do i need to go back to the TBs and crank the front end back down until i am at 70mm droop in order to remove the vibration? Lets say this puts me at a 2" height different between front and rear... Do i just live with it that way? (With the 3" i started with it rode awful and headlights pointed down) Does a 2 degree (should be 3 degree+) camber from my alignment come in to play on any of this?

Thank you!
 
BigMaineWomen said:
Hi all. I asked this on my alignment post over a week ago but didnt get any responses.

2004 LX with 248K. Hydraulic suspension was professionally swapped for conventional 2 years ago without touching the torsion bars. I finally got around to cranking them to increase the front height because it was 3" lower than the rear. I'm at 1" lower in front now. Vibration appears to be a common result of too much height on the front end from cranking the TBs, but can someone tell me what causes the vibration? I measured my droop to be 4" on each side, which is 100mm and a fair bit beyond the recommended 50-70mm. Do i need to go back to the TBs and crank the front end back down until i am at 70mm droop in order to remove the vibration? Lets say this puts me at a 2" height different between front and rear... Do i just live with it that way? (With the 3" i started with it rode awful and headlights pointed down) Does a 2 degree (should be 3 degree+) camber from my alignment come in to play on any of this?

Thank you!
Click to expand...
All kinds of s*** can cause that.
Ride height/rake/droop are FAR down the list of things I'd consider.
The caster/camber shouldn't cause it. (based off the readout you posted in the other thread.)
But like others said, it looks like they (IMO half-assed) the alignment and just did "Toe and go". Not a full alignment. If you do have a lifetime, I'd make them do the full thing.

But back to the vibration.
Since your "Before" measurements had ALOT of Toe-Out. I wouldn't be surprised if they are cupped and worn all to hell and THAT is causing the vibration now that its fixed. (unless these were new tires)
Wheel somehow now out of balance? I've seen weights fall off, crap get stuck to the inside of a wheel, some offroad/AT tires randomly become off balance as they wore, crappy tech not balance correctly.
Worn/dead bushings.
One of the links/joints going or are bad? Wheel bering can cause this too, but if its bad enough to cause a vibration you'd have to be deaf not to hear it.
Thrust angle is all off and its "crab-walking" that is supposed to be 0.00.
And the more I look at the rear axel the worse it gets. Ideally they should all be 0.00. (Toe per wheel no more than +/-0.8, Total no more than +/-0.15) (Camber +/-0.50)(Thrust +/-0.10)

Things to look at and I hope helps.
 
Thanks for the reply. When I was cranking my TBs i would crank them, drive to work the next day, drive home, measure. Repeat. For three days in a row. On my drive home day 2, i didnt have a vibration. Cranked my TBs, left the house the next working and had a vibration. I can slowly accelerate up to 70mph without any vibrations but if i get on the gas, the truck starts shaking as soon as the RPM climbs even though i'm only doing 20mph. This all happened before the alignment, which i had scheduled for after i got the rake correct because i expected to get a caster change from turning the TB and wanted them to correct it in the alignment.
 
BTW.
Something I just thought of.

When you swapped out the AHC for the normal static one did you also change the torsions to the regular ones?
The AHC ones are too small (low spring rate) for the normal suspension. 25.4mm(AHC) vs 28mm(non AHC).
 
You don’t mention the starting or ending wheel well to hub height or that they are adjusted to spec. In that you've changed the height by multiple inches, all “horizontal” suspension and control arm bushings would have to be re-clocked now to the new ride height with a new alignment. Then, torsion bars that are correct will be the final key to the puzzle.
 
I think you guys are right. I voiced my concerns when new torsion bars weren't on the quote and the shop said they purposefully don't swap out TBs in order to maintain a more LX like ride quality (as opposed to the LC100). Lex Connection is supposed to be the best shop in Maine. I travel over an hour 1 way for them and I haven't been real impressed. Shortly after the suspension conversion I tried to have them do some evap troubleshooting. They refused, said they would just replace everything fuel related from the filler neck to the engine bay, or suggested as an alternative I scrap the truck and they knew a guy that would take it from me. I checked receipts and the suspension work was 3.5 years ago, so this was 3 years ago they said to scrap it. Admittedly, i did have to put a new (used) fuel tank in 1.5 years ago as it was leaking at the seam, but outside of that its been nothing but routine maintenance in 3 years. It isn't THAT rusty... i did get my torsion bars to crank after all and passed inspection last month too. I think i'll crank the TBs back a bit to stop the vibration and split the difference between ride height and droop until i can source some used/new bars.

Thanks for the input!
 
Just a super easy thing to check is greasing the zerks on your prop shaft. The angle changes could have squeezed some out. I had extremely old grease in mine and after I serviced my prop shaft my acceleration vibrations went away. Also hit your u joints while you are there w the grease gun.
I don’t think this is your issue, but it will check a box.
 
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