Hey everyone...first post on here but long time lurker. I've got the most annoying grinding noise from my front end OR engine compartment that I can't figure out. I've never been at such a loss to figure out a problem. The truck is a 1995 F350 7.3 Diesel 4x4. Here's the deal:

Once the truck gets "warmed up" and whatever is grinding gets loose, it grinds under ANY of the following conditions:
Turning left
Hitting a bump (grinds on suspension compression)
Braking (suspension compression again)
High speeds (50 mph+)
Reverse

If I turn the engine off, the grinding stops, even if I'm still moving while doing anything listed above. It does it in both 4x2 and 4x4. If my buddy and I sit in the truck with the engine running, parking brake on, tranny in park and sway front to back (not left to right) to force the truck forward, we can hear the grind. If I get out and press down on the front bumper, no sound. If I get behind the truck and push it forward, no grind.

Recently replaced:
All front end ball joints, both u-joints, needles bearings, front bearings, power steering gear.

I can feel the vibration through the floor but it also sounds like its coming from behind the dash.

What in the world could cause this? Nothing about it makes sense. Thanks!

 

Well the only thing that I can think of is the rotor backing plate rubbing the rotor on and off, but it sounds that would have been spotted with the front end work. Post what you have done for mods and a little more info on the truck so we have a better idea of what we're workin with. Someone else will be along with a better suggestion.

And welcome to FTE!

 

As weird as this sounds check the two bolts that hold the fenders on at the top of the fenders near the hood hinges. There have been several users on here that have had this problem, and the fender bolts were loose allowing the fenders to move causing a popping, grinding noise.

 

Thanks for the reply and welcome! The truck is a 95 crew cab long bed 4x4 with 35x12.50" tires. Not too sure how much lift...front leafs are stocks with no blocks and 4" rear blocks. Brand new Bilstein shocks all around. Just changed oil, front diff fluid (did with front end work). Also has the auto hubs. Auto transmission. 184k miles. New water pump, starter, glow plugs, batteries, 6637 filter....I think that's all I can think of

I'm leaning toward power steering pump but is it even capable of GRINDING? I've heard them whine but not grind. I'm wondering if the suspension travel is being transmitted through the pitman arm, through the gear and into the power steering pump and causing the pump to grind if its messed up?

 

Ill go check those, thanks for the suggestion! The reason I think its something power related is that when I turn the truck off, the grinding stops.

 

Do you have a stock down pipe? or has it been changed? if it has been changed to a 3" down pipe maybe it is hitting the cab and making the noise?

 

It is a stock DP as far as I know. I can go out and look. I recently bought this truck and so far am under the impression that the only exhaust modification is a cat delete. How can I tell if it's stock?

 

it will be flat, aftermarket DP are round and much better than the stupid flat one. Its gonna be my next mod.

 

I'll have to take a better look tomorrow when its light and my engine has cooled off. From a quick glance I'm pretty sure it's stock based on the level of modifications on my truck (rest of the system is stock) and the amount of rust on the downpipe.

I checked out the fender and tightened it up and while it does rattle, it doesn't make nearly enough noise to match what i'm hearing. When it's really grinding, I can feel it pretty good in the floorboards.

 

My money is on the down pipe. Under the conditions you say, those all say the body moves or flexes enough for the dp to hit the firewall, and it WILL sound like grinding. It's easily remedied by losening the clamp at the cat delete pipe and losening the clamp on the turbo (just loose, not off) From underneith the truck, wiggle the dp and break it loose from the turbo. (soot and time will fuse it to the turbo) Once loose, have someone tighten it at the turbo whill you put a little downward pressure on it. Don't run it into the up pipe, but some downward pressure to assure it's not hitting. Then retighten the clamp at the delete pipe. Take it for a drive.

 

Thanks RubberDuck...I'll focus on the DP next time I'm out there workin after class. Would this explain the nonstop grinding at highway speeds though? It seems pretty rhythmic like it's tied to the engine RPMs and i was thinking any suspension travel, especially high-speed bumps in the road, are being absorbed by the steering gear/power steering pump. That could explain why the noise stops when the engine stops, even if the truck is still moving. I'm close to replacing the steering pump out of frustration but I'd rather not spend the $75 if I don't have to.

 

I'm almost 100% sure that's your problem. Yes, if the body bushings compressed after your last turn/bump etc. you will hear it running down the road. It's ficle like that. I had a dp CLEARLY rubbing the firewall after some tranny work, and it did all the things you described to a tee. Just rearanging the angle of the dangle on the dp was all it needed. It took me a few tries but I got it. But each time, I knew it was working because the grinding/vibrating would change every time I messed with it. Good luck to you man. And let us know.

 

I really appreciate it RubberDuck...I'll be sure to let you know what I find out!

 

I've been poking around under my truck for a while and comparing it to my buddy's 97 and I'm sure now that I have the stock downpipe. It doesn't *appear* to be rubbing on anything unless that pipe can move backwards by about 1".

While under there I tried turning my front driveshaft (im in 2wd) and it would only turn about 180* before the hubs stopped me. Shouldnt the shaft spin freely with auto hubs (no switches, manual t-case) when in 2wd? I put a piece of tape on the bottom of the shaft and drove in 2wd and that tope is no longer on the bottom. Seems like my hubs aren't disengaging, right?

Could that cause my grinding noise? What would explain the fact that the grinding stops when the engine does?

 

I dont think the hubs are nessasarily related to the grinding, Hoever based on what you stated Id say they are bad too. Even when your in 2 wd drive your drive line will rotate going down the road due to surface contact of the gears in the tcase. However the hubs should not hold the driveline unless they're stuck they are operated by full power from the driveline in 4wd, where as in 2wd you will have so little that while the drive line may turn in 2wd youd be able to grab hold of it and stop it. So it sounds like it time to upgrade to manual hubs. Also something tells me you should look at your fan shroud maybe the fan is leaning into it and grinding there. Another possibe thing to look at while is eems unlikely is your motor mounts, if they're bad the motor can move around some. Might look for signs of movement on your up pipes.