So I recently inherited a 2001 Mazda B4000 truck and I am currently trying to rehab it. So far I have replaced the front pads and rotors, replaced an ABS sensor, and the EGR DP sensor. But the one thing I can't seem to fix is a rumbling noise that is present anytime the truck is moving(I can feel it through the floor). I have already checked the front and rear bearings, they all seem good. So I put the truck up on jack stands, all 4 tires off the ground, had the wife put it in 4WD and step on the gas. But much to my surprise NO noise!!! So what I got is a rumbling noise I can feel through the floor anytime the truck is moving but not when its up on jack stands. Any ideas?

I don't know anything about the history of this truck, but I did notice that the passenger side wheel hub had been replaced.



2001 Mazda B4000 4.0L 4x4 5-speed manual

 

Sounds kinda like the U joints are shot. Try redoing them next. Maybe the drive shafts are out of balance to.

 

Don't mean to Hijack your post, but I think I have a similar problem... there's a bit of a rumble when the truck is under load. Cruising in any gear is smooth, but accelerating has a dull rumble to it. Is it transmission slipping or U joints going out?? Not sure if I understant how the U joints going out would rumble, but that's why I'm here asking....

 

Best way to check is slide under the truck, grab a driveshaft and yank it side to side, if there is play then it a bad ujoint. Do each side of each driveshaft.

 

if there's no play in the driveshaft??? = Bad news?

 

No play means it's not the ujoints and you have some more trouble shooting to do

 

To the OP, it's just a rumbling noise? Like the truck itself doesn't feel "wrong" in some way? Like squirrely or non-responsive?

 

The vehicle seems to handle and respond fine, I can feel the rumble through the floor but not through the steering column or peddles. That being said it can be difficult (for me at least) to jump into a vehicle that one has never been in before and has no experience with and be able to know what constitutes an abnormal sound. My wife seems to think the sound could just be normal road noise, but I have a hard time believing that could be the case. When I first heard the sound I thought it could be a seized brake caliper except usually you can feel that in the steering and when I did the brake pads and rotors I found nothing wrong with the calipers. Really the fact that the sound isn't present when I have the truck up on the stands could mean my wife is correct, but I know that can be right.

 

What kind of tires do you have?

 

Goodyear Wrangler RT/S standard size for the truck per the door sticker

 

Have they been balanced at a tire shop?

 

Have the tires re mount and balanced and rotated maybe?

 

Not sure if they have been balanced, although I did see some weights on them. I would think an out of balance wheel would be fairly evident when running the truck while on jack stands. Rotating the tires is a good idea never the less.