Grind/ whir sound while driving and suspension compressed ['94 LC] (1 Viewer)

[Halfpint]

Searched and can only find topic not specific to compressed suspension.

When driving and going into a dip/ low spot in road that compresses the suspension significantly (not bottoming out or anything) I can hear a grind that is almost gear-like and wondering if my birfs are jacked up or if it may be from somewhere else- it's not tire rub.

To start: '94 | I've a Woods front DC DS, 3" lift on 33s (grabber at2)
The driveshaft is new | I've recently flushed the front diff (75w-90) | filled the knuckles thru the port about ~3/4ish full to buy some time (no leaking) | greased the rear shaft

I'm doing full front knuckle maintenance and all gear oils this wknd and wondering if I should delay if it's something else to handle it while its under the knife...

Trying to think of all possibility's here that would be "affected" by compression of the suspension. I do get the "clicks" on locked turning and hard acceleration- which is why I'm doin the knuckles but its a completely different noise.

 

[BILT4ME]

If you have over-greased your DS slip-yokes, you may be pushing the shaft into the pinion bearing as well as the TCase output shaft, causing excessive pressure on those bearings.

Could also be loose wheel bearings making noise with hubs moving or axles spinning inside the spindles during a hard maneuver.

 

[tacocat]

What are you doing for caster correction? Between 3” to 4” is the weird zone for 80’s where slight driveline noise or vibration can still raise its ugly head

 

[Halfpint]

If you have over-greased your DS slip-yokes, you may be pushing the shaft into the pinion bearing as well as the TCase output shaft, causing excessive pressure on those bearings.

Could also be loose wheel bearings making noise with hubs moving or axles spinning inside the spindles during a hard maneuver.

Good call on the DS contact with Tcase. I'll assume the Wood's shaft wasnt over greased since that's their sauce- I'll start with my actions on the rear and go drive around sans zerks on the rear shaft.

 

[Halfpint]

What are you doing for caster correction? Between 3” to 4” is the weird zone for 80’s where slight driveline noise or vibration can still raise its ugly head

I've got Ironman plates on it- hoping that is doing the job. One of the reasons I got the DC shaft too...it got rid of a lot of noise down there.

 

[ppc]

I'll assume the Wood's shaft wasnt over greased since that's their sauce

I would not make that assumption. Over greasing of the slip yoke is more of a function on truck fitment versus off truck manufacturing. Removing the zerk is a simple step to eliminate the cause of a problem. Pick the lowest fruit first.

 

[Halfpint]

Drove around yesterday to get my kiddo from daycare without the slipyoke zerks in. We bombed some bulbous speed humps to get some compression on the shafts. I found (4) discoveries:

1- 4 year olds love bounding rapidly over speed humps
2- I did not find any evidence of oozed goop slung around the undercarriage
3- sound is still happening
4- I've found upon hard braking I can replicate the gear-like low whirr noise

For #4, there's no steering wheel feedback to the noise, so I'm going to not think rotors. Wondering if its just the way the DC shaft sounds like on moderate to significant compression (its less than a month old)...or if its still the axle/birf/bearing- I'll sort thru all that this weekend as my Marlin kits came in yesterday.

Finally, it sounds too "mechanical" to be tire tread which was another thought.

 

[tacocat]

Remove front driveshaft. Lock center diff. Repeat exercise.

 

[Halfpint]

Remove front driveshaft. Lock center diff. Repeat exercise.

This is what led me to where I am. I went the money route first and bought a DC shaft. The noise was better but brought out different sounds.

During the knuckle service, the moly was really loose and dripped out of the birfs/inner housing.

Also looks like my birfs took on some heat. Are these considered done?

Also found the indexing ring on the long axle was no longer in the shaft- had to use the weed trimmer wire in the breather hole technique to reinsert.

I did spin a hub nut buttoning it up...will need to cut it off or try a stud replacement on it.

Glad to say no grind or ticking sound now or feed back after a couple days!

I've got a rear hub service to do and the parking brake and mount a batwing and i should be good to go!

 

[ppc]

Also looks like my birfs took on some heat. Are these considered done?

Those birfields are completely normal. The "heat marks" are a result of heat treating for case hardening during the manufacturing process.