Discussion Forum - Northstar Chevelle Club

bowtie · Secretary

grinding noise

John D · 2K+ Club

Hunk of rust/grunge got knocked loose from the wheel change, and is between the drum and backing plate??

Lost in the 60s · President

Do you have a driveshaft safety loop ?

bowtie · Secretary

Forgot to add, the noise is spradic. Does not change with vehicle speed, not noticeable at idle.

Wheels have all been off, nothing grinding at the rotors, they spin freely and quietly.

I have a driveshaft loop, might possibly be hitting on the top side, there's tons of room below.

I'm definately leaning towards driveshaft yoke/trans snout area the more I think about it.

Lost in the 60s · President

The amount of travel of the shaft in the trans is minimal but if it was made for the car with the rear that high it could be bottoming out. I'd look at the loop first, myself.

dashboard · 2K+ Club

Are you running/using any kind of spacers for lift in your springs?

What have you used to achieve that tall stance? I like the look and want to raise my front end two to three inches.

Chris R · 2K+ Club

Find a quiet parking lot or a side street and coast or get the noise to act up. Put it in neutral and shut off the engine and coast with the windows down to hear the noise. It actually works good in a parking lot thats empty because then you know your souroundings better in case you need to start the engine again. Obviously no engine means no P/S and maybe a few stops on the brake system until the pedal becomes hard to push, Unless its manual brakes that is. Ive had to do this on tons of customers cars over the years. Without the engine running, it can really open up your ears to where the noise is coming from.

Ive also coasted past a partner standing on the ground slow enough to communicate with him, like only a few MPH if that, walking speed perhaps, and gotten thier take on where its coming from. That is if the noise will do it that slow.

Ive seen several dried out u-joints make that kind of noise.

SteveS · Super Poster

I would be thinking drive shaft too, but that should change with vehicle speed. Have you tried to put it into a lower gear when it's making the noise to see if the change in RPMS effect it? If you think it has to do with drive shaft angle maybe throw some weight in the trunk and see if that makes the sound change?

Bowtieman427 · Active Member

Perhaps look for marks on the drive shaft if it is hitting I would think there would be rub marks on it. Even in park car off move suspention up and down listen for noises. May not grind then but may clang and bang: )

bowtie · Secretary

I haven't gotten up to speed more than once (in a neighborhood mind you), to see any changes or more than a 1-2 gear change.

I like the idea of weighing the trunk down which should make it constant I bet, but I will be looking at the shaft for witness marks first. Assuming the driveshaft is hitting the loop, I can do some gravity fed adjustments with the floor jack.... shouldn't take much.

Scott Parkhurst · Super Poster

You'd see 'machining' marks on the driveshaft for sure. The 'not changing with vehicle speed' thing is odd. The first thing I thought was a brake dragging or one of those fat new tires rubbing a bit too- but you've checked all that out. Weird.

Enganeer · Mega Poster

I would double check / replace your u-joints if nothing else pans out. Your new pinion angle maybe stressing them.

I had a 76 firebird that would make a noise occasionally more like a grinding sound with a loud pop sound followed by a vibration like out of balance tires. Checked the U-joints and seemed ok (but I was like 17, did not know what to look for). Needless to say, two weeks later with a car full of friends, passed a semi at 70 and BOOM! Rear U-joint caps busted apart and the drive shaft shifted in the yoke...talk about being in paint shaker Was able to pull over and stop and the drive shaft just fell out of the rear.

So any older used car I buy, I replace the u-joints as part of the maintenance procedure.

bowtie · Secretary

Definately will be looking at u-joints too, they were done with the driveshaft cut/rebalance back when I did the engine/tranny install.

I did look at the tire sidewalls right away too since they're tucked under and it seemed to come on with a swerving motion vs straight ahead. There aren't any cut/slice marks.

Enganeer · Mega Poster

Check your routing of the emergency brake cabling setup also and see how close it is to anything moving...yoke to yoke and whether the wind could push anything into contact with your drivetrain.

bowtie · Secretary

Definately the top half of the loop. Since it was already on the highest set of holes, I took the top half out for now. I'll be working on a fix, but after a test drive, we're back in business again.

John D · 2K+ Club

Home Depot has a "metal center" in the hardware aisle. Get a length of 1/4" x 1-1/2" (?) and make an "extension"... basically a square of metal with 4 holes.

OR

Just make a new upper loop with more Clarence, clearance.

-- Edited by John D on Saturday 12th of May 2012 08:16:50 PM

bowtie · Secretary

Here's part of my solution. Factory rubber mount instead of the Energy Suspension Polyurethane mount. I saved a good 1/2" I would bet:

Bowtieman427 · Active Member

What is you pinon angle with the change ? I would think 1/2 drop would change it.
Is the loop you have like this ?

http://www.jegs.com/i/Lakewood/620/18000/10002/-1?parentProductId=751248

I had to alter mine a little to work.

bowtie · Secretary

Yep, pretty much the same piece.

As for pinion angle, I haven't checked. I have Southside Machine upper and lower rear bars which have a drilled location for one of the brackets used. It would take some work to re-do it if it's too far off but I'll get to that eventually too.