Help Needed Vibration (rubbing) at 75mph exactly!

[02Oilburner]

I have a strange rattle noise at around 1750 to 2250 rpms. It rattles in every gear at that rmp range. I have some play in the carrier bearing. It seems to have gotten louder over the last few weeks. How do I fix this or should I take it to a shop. If I have to take it to the shop how much should it cost. Oh Im going on a 1200 mile trip on wednesday will this need to be fixed first? Thanks guys.

 

[DaveBen]

Does the noise go away if you lightly push on the clutch pedal?? If it does, then you have confirmed the throw out bearing. If not, back to looking. Good luck!

Dave

 

[02Oilburner]

Does the noise go away if you lightly push on the clutch pedal?? If it does, then you have confirmed the throw out bearing. If not, back to looking. Good luck!

Dave

i have an automatic tranny.

 

[DaveBen]

Take it to a tranny shop and see what they say.

Dave

 

[Tail_Gunner]

I'll throw my in and say that it sounds like a driveshaft balance issue.

When you get to your indicated 75 mph, the driveshaft rpm is at an out of balance harmonic. If you're faster or slower than that, the vibration is not evident. But get right at that sweet spot, and it bucks like a mule.

To use an analogy, ever hear the washing machine go into the spin cycle with an out of balance load? Initially it shakes like a muther. But as the rpm increases, the vibration subsides.

Everything there is, has a certain harmonic frequency. In school, I learned that in some aircraft, sometimes the problem is bad enough, you can't operate the engine at a certain specified RPM. At that RPM the engine sets up a harmonic vibration that will do nasty things to your aircraft. You can accelerate past that RPM or slow down past it, but you can't operate the engine continously at the specified RPM.

 

[Deadman514]

Turns out while I needed driveshaft work...that wasn't it. Seems to be something in my rear diff. Going to pull the cover/change the fluid. How much of a pain is it to change pinion bearings in these things?

 

[bigrigr]

The pinion is the last thing to come out of the diff housing, it is a major tear down. It often can result in a new gear setup(meaning backlash and gear mesh shimming) Might want to consider a complete new gear set, with that much labor, you're only out the price of parts for a new rear diff overhaul.

 

[02Oilburner]

I had my u-joints, the bearings and seal replaced in the rearend and my noise and vibration at 75 is gone!

 

[bigrigr]

Good deal, 02oilburner. At least you're ready for the trip. Sounds as though you're backing up what deadman514 is thinking