rotational noise at 70+ mph

[70chevellemalibu]

Here’s tonights math I think I’m pretty dang close .5 of a degree out with the trans lifted about an inch.

I might even be there if you think I have less uplift with my poly bushings versus the rubber.

[andrewb70]

The output shaft of the transmission and the pinion gear need to be parallel.



Andrew

[70chevellemalibu]

Ive been playing with it a bit more and i think i have have her licked.

1. Angle at the block 2 degrees down.

2. Driveshaft angle at transmission output .5 up towards diff.

3. Driveshaft angle at diff .5 up towards diff.

4. Pinion 2.5 down

Engine operating angle: = 2 - 0.5 = 1.5
Diff operating angle: = 2.5 -.5 = 2.0

Add pinion uplift using 1.5 degrees because of poly bushings (is this acceptable?)

= -2.5 + 1.5 = -1

New rear operating angle = -1 - 0.5 = - 1.5

Final outcome:

Front operating angles + 1.5 degrees
rear operating angles - 1.5 degrees

[andrewb70]

Go drive it...LOL

Andrew

[70chevellemalibu]

whoo hoo!

thanks Andrew I'm going to get a spacer built and test it out.

thanks again for your help, your detailed description helped me understand what i was actually doing instead of just following a tutorial.

[70chevellemalibu]

one comment i do have is why didnt i feel any vibrations why was i only hearing a rotational sound?

[andrewb70]

one comment i do have is why didnt i feel any vibrations why was i only hearing a rotational sound?

Beats me? Maybe you did all this for nothing and it is something else entirely :-)

Andrew

[70chevellemalibu]

So everything is set up and the noise is still there it’s definitely smooth and I feel confident taking it up to higher speeds but the noise is still there maybe the pitch of the noise is not as loud at 65-70 as it was before...

The noise definitely is not there until 65-70 and is there up to about 85 I didn’t push it any higher but seemed the noise got louder the faster I went.

Any ideas on what to try next?

[sccacuda]

Put it on a 4 post drive on lift, raise the rear axle, and drive it up to speed. See if the noise is still present with no load on the tires or wheel bearings. You can get under it while it's making the noise and hunt around with a stethoscope. Driveline noises are tough to find because they transmit through the drive shaft and axle. Have you tried changing lanes suddenly when it's making noise? This can help identify a wheel bearing by loading/unloading one side for a second.

[raustinss]

Without reading everything here , have you checked u joints and axle bearings as well

[70chevellemalibu]

All wheel bearings and axle bears are new and u joints are new and tight.

How would I convince someone to get the car on a 4 post and bring it up to speed? To check with a stethoscope? Does it need to be going 70-80 mph on the hoist or will it be able to be heard at a slower speed?

One thing to note that has me wondering is my x pipe is touching my cross member, it doesn’t rattle but is there a chance there’s noise coming off that at 2000 rpm?

[raustinss]

Convince then with beer , slide them some money , strap it down good , pray to teenage jesus and giver

[70chevellemalibu]

Would this type of rhythmic noise that I’m hearing be tire noise?

I can’t swap my rims front to rear due to the stagger, my truck has a bad mud tire noise but it’s constant throughout all speeds which makes me think this isn’t the case with the chevelle, correct?

[raustinss]

Where are you located

[Peter Mc Mahon]

Sounds like pinion gear noise. Fairly hi pitched? If it is doing it at a steady speed, and you then accelerate does it go away?
Same scenario, if it is doing it at a steady speed and you let off the gas does it go away?
Shift to neutral at speed and it goes away?

[70chevellemalibu]

I’m in Manitoba.

Peter i have pinion gear noise at 50 mph +\- 5 mph high pitch whine.

The noise I am hearing is 100% rotational oscillating (on off on off on off) no vibration baby smooth up to 80 mph feels safe but the noise is there. The noise starts at 70 and gets faster the faster I go.

It’s not a constant bad bearing noise all all speeds or if I jerk the steering it doesn’t go away. It’s strictly related to the speed I am traveling.

[Peter Mc Mahon]

Still sounds like what I have had in the past. Try the questions that I asked and see what happens. Mine was smooth as glass, no vibration, on off on off.

[70chevellemalibu]

The oscillating sound isn’t high pitched, it does it 70 mph threw to 80 probably does it above but I have gone that fast yet doesn’t go away until I’m below 70.

What you are describing happens to me at 50 mph +\- 5 mph.

[andrewb70]

Just out of curiosity, what tires are you running?

Andrew

[70chevellemalibu]

Just out of curiosity, what tires are you running?

Andrew

Im miss matched for now.

new falken azenis rt615k 255/40/17 in the front.
older Nitto nt555 285/40/17 in the rear

i bought the rims used and they came with bald fronts and newer rears.