I posted a thread a few days ago about my rear diff going out. I was hearing a noise in the back, the owner of the tire shop test drove it. He said he thought it was the rear diff. I took my truck into that shop today to get a ball joint replaced. The mechanic took it for a test drive afterwards. He said he thought it was the transmission. The mechanic said he checked the fluid in the rear diff and there wasn't any metal or anything in it. It shifts fine, no slippage or anything. Is there any way to tell which it is? Is there anything I can put into the tranny to doctor it up long enough to get it fixed?

 

Can you describe the noise. You never described the noise in your last post. Whine, Clunk, Screech? When does it do it? All the time? When cold? When hot? Does it stop after a while? Does it only do it around turns? More information will net you better answers / suggestions.

 

Another question....does it change with engine RPM, or axle RPM.

 

It's more of a whine. The pitch of it goes up the faster I go. It only does it when the truck is moving. Hot or cold doesn't matter. It doesn't stop. It doesn't do it with the truck in park.

I looked under the truck earlier. The tranny is right under the front seats. Right? The sound sure seems to be coming from the back of the truck. I'm back to thinking it's the rear differential.

 

That sounds like the rear differential for sure

 

My thinking is if its the tranny, I would hear it coming up through the floor. But I don't. It's from the back. 99% certain about that.

 

Another thing to think about it the fuel pump. Since its in the tank it will be hard to tell if it that. You can always jack the truck up onto stands or find someone with a lift and put the truck in drive and listen around.

 

Anyway to tell if its the fuel pump for sure?

 

sure turn the truck on, crawl underneath and take a listen around the top of the tank. If you hear the noise you talked about then there you go. If it is the pump, change the filter why you are inside.