Ever since I swapped my auto for a manual transmission on my 85 4Runner, there has been this really strange scraping noise that happens when it's in reverse with the clutch depressed. My driveway is steep, so I usually just depress the clutch and let the truck roll backwards till it's in the street. If I put it in reverse and depress the clutch while letting it roll, I get what sounds like metal on metal scraping in cyclical intervals, almost like a warped rotor but much more noisy. I just recently swapped rear axles and thirds, and the same thing is happening with the new set up, so I know it's not the diff. I also had the front end apart recently to swap third members, so I know everything up there is fine. Rotors are only a few hundred miles old. The only thing I can think of is reverse in the tranny is giving out, but I'm just not sure if it would sound like this.

Any ideas?

 

sounds like you're in my boat. reverse sync
does it sound like a skitter type grind? as if a heavy metal piece is grinding on thin metal, but really fast and not a constant pitch?

 

Not sure. It's different inside than out. I was listening to it when my wife backed it out, and it sounded worse from the outside. Inside it sounds kind of like a big piece of metal dragging across a thinner one. Actually, it sounds like when you lift the front end and spin a wheel. You know how there will be some scraping from the brake pads? Imagine that once every rotation of the driveshaft.

 

BTW: I know there are some other threads about noise and rebuilding the trans. I just want to narrow down the issue and decide if it would be better to try and fix it myself or order the expensive Marlin HD version. From what I was told by the guy I bought it from, this one had about 190K on it, and I doubt it was ever touched.