Loud "bang" from the back?

[devilsfan]

I know this is a major long shot, but you never know. I had to make a fast U-turn off the side of the road yesterday after I missed my turn. There were about 5 big rigs speeding in my direction so I threw it into reverse and backed up fast. As I was doing so, I heard a huge BANG from the rear of the truck. I got out of there and it seemed to drive fine.

About an hour later, I had turned the steering wheel hard to parallel park and heard it again. Nothing seemed out of place, nothing dripping. The sound is as if I backed into concrete post at 40 mph. It's crazy loud.

Ran it a bunch today and nothing seems an issue - steering and suspension seem fine, no rougher ride than usual, no drifting.

I can't think of a reason to take it in to the shop if there's nothing wrong with it, but those noises are NOT normal and I'm worried I'll be on the freeway when whatever it is that possibly went bad decides to break for good.

Anyway, to get to the point - has anyone ever experienced this with their truck before, and if so, what did it turn out to be? Truck has a 12" suspension lift and aftermarket exhaust, if that helps any.

Stacy

[jsbihn]

does this happen only when you drive in reverse? or when you shift from drive to reverse or vice versa? have you checked all your connections and links for any look bolts or anything?

[HUMTECH]

If your hard on the brakes and then reverse direction it might be rear driveshaft slip yoke binding in transfer case output shaft. Braking hard will change driveline angles which could cause yoke to cock on output shaft. When it releases will be rather abrupt. Worn trailing arm bushings will make this condition even worse as they will allow diff to rotate out of position more.

[devilsfan]

HUMTECH - so, in laymans terms - is this something I need to take it into the shop for?

[guruerror]

Originally Posted by devilsfan

HUMTECH - so, in laymans terms - is this something I need to take it into the shop for?

If it was my rig...I'd say 'yes...definitely.' Having something like that snap on a trail would be a major PITA. Especially since most rural part stores near where we wheel are on bible-belt hours during the weekends.

If you're strictly a pavement pounder I'd say it can prolly wait a while since you typically wouldn't be stressing it the way you did with the hard brake and reverse, and if it does give you'll be easily accessible for a tow.

Originally Posted by HUMTECH

If your hard on the brakes and then reverse direction it might be rear driveshaft slip yoke binding in transfer case output shaft. Braking hard will change driveline angles which could cause yoke to cock on output shaft. When it releases will be rather abrupt. Worn trailing arm bushings will make this condition even worse as they will allow diff to rotate out of position more.

You, sir, are a wealth of knowledge. If you ever get bored here, feel free to check out clubhummeroffroad.com.

[jsbihn]

Originally Posted by guruerror

You, sir, are a wealth of knowledge. If you ever get bored here, feel free to check out clubhummeroffroad.com.

I completely agree.

[BUNNY15]

Devilsfan I remember your lift because I was a huge fan and thought I would be using the same system and set-up. In the end though, I decided against it due to towing concerns, but let me ask you, have you ever noticed any fluid dripping from where the yoke meets the transfer case? Even minor drips?

The reason I ask is because I ended up going with the Fabtech 6" and 40x15.50 but experienced this problem with the pinion angle being too aggressive causing more slippage than expected, soon to fail if not corrected. To make a long story short, I did not notice any loud noise with the problem, but I agree with HUMTECH. You may want to look at that for sure because mine was driving just fine too, and I just happen to notice the SMALL leak by chance one night in the driveway.

I have noticed that unless you just crack the case, then the problem can lie within the early cases and you not even know it until it's too late. There was no sure way for the tech to tell me why it failed or when, but that I had sheared some of the original casting where the later models have a rubber bushing. The early cases did not have that. Keep us posted. I know I'd be interested in the root of the problem. Good luck!

p.s. I ended up having to replace the entire back casing of the tcase and lengthen the stock driveshaft about 1.5". The shop that did the lift (biggest national company around, wink wink) said they had not encountered this kind of problem on the H2 using a 6 and 40x15.50s in the past.