Its been doing this for quite awhile but is just getting progressively worse. When I put the truck in reverse it makes a loud clonk noise and then it takes a few seconds to register before it starts moving itself but if you hit the acceleration it will move immediately. I've been told several things from "your rear end is going out" to "your transmission sounds like it's about to need to be replaced or rebuilt" and very often I'll notice transmission fluid leaking out from under the front of the truck and when I check my transmission fluid levels it all seems to be okay so idk the problem. Any help?

 

I'm guessing you have never looked under your truck... maybe look at the tranny and see if and where it's leaking from... when was the last time you serviced the rear end ...if ever ??

 

I bet it is your rear output seal on your transfer case that weeps when it wears out only a drop now and then and the clunk is probably from the backlash in your rear end (play between the ring and pinion gear) which is common when vehicles age. my truck has it

 

I've had the truck a year and can say I haven't done anything as far as the rear end goes

 

except listen to it get progressively worse.

 

id took it took a mechanic and he couldn't find any leaks or anything wrong and told me not to worry about it so I didnt until I saw it leaking again and today when I started it and put it in reverse it shifted smoothly and didn't make that annoying "clonk" noise

 

that would be caused by backlash like I am saying. if ring and pinion gears already have pressure on the reverse side then you won't get a clunk but if you have it on the forward motion side then shift to reverse you will. the way it can be fixed is using shims to move the ring gear closer to the pinion. it is a pretty intensive job for what it is worth. many vehicles will drive like this for hundreds of thousands of miles and never really have a problem

 

I assume you/they inspected the driveshaft and u-joints while under there?

 

Yeah...a bad u-joint would clunk too...

 

^^^+1 check them too