My 2004 F150 (XL 2WD) occasionally makes a startling "bang" when in reverse. It sounds and feels like I backed into a pedestrian or a fence post. This is sometimes followed by a slight dragging. I thought it was the parking brake, but that seems not to be the case. The truck has a limited-slip differential. Any suggestions?

Phil

 

Same happens to me in my 07 awd Harley. Scares the hell outta me. Pretty sure it's the limited slip

 

Block the wheels, put it in nuetral, crawl underneath. You want to check the driveshaft. Make sure the u-joints are still tight. And, if you have a 2-piece, check the carrier bearing and slip yoke. The carrier will move some, but the bearing should be tight. The slip should not have a huge amount of movement. Also check that the pinion on the axle has no movement up and down.

If that all checks out, you could jack up a rear wheel and rotate a tire back and forth. You would be checking it doesnt have excess movement. Around 1/8th turn or less before the driveshaft rotates is usual. Dont be underneath the tire or make sure you use a jack stand.

If it only does it right after start up, it is probably the trans pumping up to pressure. Reverse takes the most fluid to engage. Ive had several transmissions slam reverse when cold.

 

Thanks. I'll check those things. The reverse bang comes only once, and not every time. It seems to occur more when I have a load on truck bed.

Phil