[Stinkin_V8]

On my wife's '91 S-10 4x4, there is an intermittent vibration/noise from the front end. Sounds almost like something is rubbing the tire. It seems to be on the passenger's side and I can feel it slightly on the floorboards but it's pretty tough to pinpoint. The steering is not affected by the vibration, and I have ruled out any tire interference. Hitting a bump in the road usually triggers it, and only when the drivetrain has warmed up, or the temperature outside is above freezing.

It started with a brief sound when she'd hit a bump once in a while, I figured it was the mud flap. Over the last few days, it has gotten a lot worse and will sometimes last until the vehicle stops, or hit another bump. The CV boots looked good so I replaced the right wheel bearing with no luck. I was out testing it this morning and the sound didn't come back when I drove it in 4WD. I removed the front driveshaft to try to rule it out and the symptoms returned. She doesn't use the 4WD very often, and IIRC last winter the front diff didn't seem to be engaging (classic S-10 transfer case vacuum switch).

I have two ideas left - 1) brake caliper pins need lube (but it continues to make the noise while the brakes are applied) or 2) the vacuum switch on the T-case is trying to engage the front diff while the vehicle is moving (I'm pretty sure the transfer case is not a shift-on-the-fly unit).

I'm going to head out and try looking at those two items, but I sure am stumped. Anyone have any input?

 

[1939P7]

The only thing similar to what you have explained
with feeling it in the floor, gets triggered by a bump,
and it happened to me with my van. Drove me nuts!
Have you checked the sway bar bushings ?


Dave

"There isn't anything that one can't overcome"

 

[milner]

i had a jimmy blazer in the shop a few weeks ago with a vibration and noise complaint . it turn out to be front cab mounts were gone, floor was touching transmission and transfer case. another thing to check.

 

[Stinkin_V8]

Great thoughts, thanks. The sway bar bushings look good, the sway bar feels solid in there. Body mounts are all still there and the bolts are tight. I lubed up the caliper pins and disconnected the vacuum line to the front diff actuator and it's still doing it.

I'm really stumped...

 

[Rick 5150 69]

In reading your post I remember the wifes Jeep, actually two jeeps we`ve had, had the same problem it was the panhard rod on the front axle, the only time it started to vibrate was when the jeep was warm and only when you hit a bump, the front panhard rod on jeeps use a tapered rod end that fit in a saddle off the front cross member when the jeep got warm the saddle would expand and allow the rod end to move, upon cooling it would tigthen back up, I just put a wrench on it when it was warm and it Quit. Rick

 

[Restore60s]

Strange noise

I was still working in the GM dealerships during 91 and the only few things I can remember as being strange & hard to find on cab foward problems were:
1) Front diff. plunger spring being broken and allowing fork to try and engage 4X4 which even with the engagement controls removed and the front drive shaft it could still be jarred enough to try & engage.
2) Lower ball joints. They just broke off. I think GM is still replacing them as a half way recall after all these years- a goodwill policy.
3) Front engine support bracket that holds the power steering pump it runs completley across the front of the engine. A hairline crack by the pump & hard to see that when it first starts to crack creates strange noises & vibrations because everything being attached to tends to move around, and worse as it gets heated up.
4) The "honey comb" wheels GM used on the Blazer having stress cracks.
5) Caliper rattles. Cured by filing down the slide area, lubing the slide areas & installing new caliper mounting bolts.
6) A broken front shock.
That's about the most I can remember as repairing several of.
Good Luck!:thumbup:

 

[Stinkin_V8]

Restore60s - I think you nailed it with #1. Thanks for the help!! :thumbup: