Yet another 80 Series Vibration Thread. Replaced almost everything but the truck.

[ajax1]

You said you did the exhaust, is the bracket tight on the upper engine where it holds the y pipe? Mine occasionally loosens and slidesdown cause ing bad rattle sound. You can see it from top of engine bay on pass near and below the rear fire wall

 

[RAYJON]

Go pro underneath?? there are also some vibration monitors that read the resonance and convert it into area’s to look… I always think it’s something simple, motor moving and exhaust hitting body/frame…etc..

 

[12bit]

1) What tire pressure are you running?
30 PSI currently.

2) Bearings in front axle "preload set" to what?
set to around 12 lbs on a fish scale (torquing the inner nut to 45lbf the last time around)

3) Did the front trunnion bearings get changed out?
Changed bearings and races with new Koyo.

4) What is your toe-in and how was it measured?
will post a pic of my readout. The rear left 'toe' reading seemed a little odd to me.

5) What are your camber / caster numbers?
will post a pic of my readout

6) Are the rubber/plastic cups still under the springs after the new springs installed (IDK if you did them or a PO)?
I swapped the coils. There is a rubber insulator on the top of the rear coil, but no plastic cups under any coils.

7) Have you checked your nuts? (On the bottom of the L/R steering knuckles)
Torqued to 71 lbf

8) Have you lubed your shaft? (On the driveshafts - I see you have new OEM)
Yes.

9) Are your DS in proper phase? Front 90° out of phase, rear in phase
Yes. Front is out of phase, rear in phase.

10) What tires and wheels are you running?
Right now, 305s BFG K2s (E rated) on factory alloy wheels. I have also ran 285 K2s (E rated) & 265 Michelin Defenders (SL rated). In each case at around 30 PSI.

Will take some pics of the undercarriage.

View attachment 3926713

I stuck this on the backburner and am now revisiting the issue.

Does the 0.23° toe reading on the rear left wheel seem weird? What would cause that? Bent axle housing? Bad bearing?

 

[FJ80HI]

I have a 92 all stock and just starting to do deferred maintenance. I would think if you get caster up to about 3 degrees that will help with handling. That is what my all stock is. My son has a lifted 90 pickup with solid axel swap and we had all kinds of handling problems until we increased caster. Also on my 80 lc I installed new ome steering stabilizer and also tightened up the sway bar down links. These both made huge difference. I should replace sway bar bushings. Next project. Also check none of your exhaust is vibrating onto the frame or other parts

 

[FJ80HI]

I stuck this on the backburner and am now revisiting the issue.

Does the 0.23° toe reading on the rear left wheel seem weird? What would cause that? Bent axle housing? Bad bearing?

It would be interesting to see how shop made measurements. Did they take from wheel rim. Rim could have slight imperfection or rim might not be mounted perfectly due to variation between hub and wheel rim. When your on highway driving straight and take hand off wheel what happens