I was going about 70 on the highway the other day and when i slowed down, i heard a loud cranking sound. like clack clack clack. what sounding like somehting by the rear axle. My trans already shifts hard and slips,Im in the process of finding one or rebuilding it. but the noise also happens when i break or coast at lower speeds. Could it be the rear axle ? because of the trans or is it just the trans? how could i test it or find out?
i did change tire sizes right before it started this 265 to 245s would that have somehting to do with it?

 

Thats a hard one to pick apart.. Being that both the rear axle and trans are under and towards the back, and the noise is only under DE-accelleration, I would be leaning towards the trans myself knowing that you already have some issues. I would try to open a door and listen when you let off the accelerator. But that is me and that is unsafe, so don't do anything unsafe, like me, LOL!

 

I tried sticking my head out the window and seeing if I could listin closer. But diesel truck = really noise so its kinda hard to hear LOL but goodthing I have a back up jeep untill I can get a trans, besides that I'm already missin my old lady

 

Another trick.. Not full proof.. Put the truck into neutral on the de-accel... Relieving the tension on the clutch packs of the trans may provide a result a little more definitive!

 

It would also be illustrative to shift the transfer case to neutral, to see if the noise continues.