Hey guys, I posted a couple of weeks ago about a mysterious noise whenever I put the truck in reverse. It was a knocking sound. I got some feedback saying it might be a motor mount.

Well, I had the wife get in the truck drop in in R and hold the brake while at the same time hitting the throttle. The motor didn't move at all, leading me to believe it may not be a motor mount. Second I couldn't hear the noise.
After she turned off the truck I climbed under it and poked around. This is what I found(Bear with me because I'm no mechanic) The Ujoint where the Tranny connects to the driveshaft seems to have play in it. I could turn it back and forth by hand (slightly) and it did seem to move slightly when I pulled it back and forth. This seems like the cause of the noise to me, what do you think?

 

Turn back and forth a little is ok... as long as everything is going back and forth together...It's sideways play in the little u-joint caps that you don't want..... (the inner part of the u-joint will move sideways inside the captive caps)

 

Is it only a knock when you put it in gear/P/R/etc or a constant knocking? Slop in the joints or gear will just make one clunk when you take up the slack - unless you have a real bad U-joint that will click all the time & vary as speed does.

What about a broken spring leaf?

If it didn't make the sound while your wife was holding the brake then maybe the truck needs to be in motion to make the noise? Therefore the noise is related to part of the drive line or something the driveline affects right? I don't recall your first post so I'm not sure of the characteristics.

 

Just found your earlier post. You described it as a tapping noise towards the front right I think?

When you put it in gear the trans will slow the idle down some which will allow you to hear different sounds and changes the vibration which causes different sounds and rattles, etc - but it should do this in D too I would think.

Did you have the hood up and were you standing by the fender when your wife put it in R?

Gotta be the exhaust or something like that...

 

Hey guys, thanks for the input so far. When driving the truck, it sounded like the noise was under the hood to the right, about where the turbo and exhaust is located. When my wife hit the gas when it was in gear, I couldn't hear the noise. I could still hear it while in the cab, but not when I was outside standing by the truck.

It only makes the noise while in Reverse.

 

Rockfoot, there is some sideways play in the joint. Not much but I can move it slightly.

 

I'm stumped.

Can't hear it outside, only inside.
Only in reverse...

 

do two wheel drive have a rear trans mount and/or drive shaft carrier bgrn?
Clark

 

Yes... a transmission mount and a centerbearing.... If its a click and in reverse, it could be u-joints.... try greasing them real good and see if there is a change in the tone...

 

Maybe a grossed out tranny mount that rocks the opposite way in R?

 

Make sure your jack is in place and fastened down tight. Mine made a rattle a while back and it took me a couple of weeks to track it down.

 

This is probably your brake pads slapping around in the calipers. If it's annoying you can take them apart and check the anti rattle spring is in place. There is also an adhesive you can use on the back of the pads to stop the rattle.

Otherwise it causes no problem it's just annoying.

Edwin