Strange noise
 

Been trying to isolate a strange noise I get on decel/coast from 65 down to 10 mph. It is speed dependent and slows down as speed is decreased.

Sounds like a bent rim causing the lugs on the mud terrain to make noise on rotation or a wasted ball joint on the front end, kind of a wha, wha, wha noise.

Ive replaced the rims, tires, ball joints, tie rods, all u joints and all wheel bearings. Ive verified that the rims are not bent or any of the tires are out of round.

Today when getting off the freeway I put the truck in neutral to see if hear the noise more clearly reflecting off the off ramp wall and realized the noise was gone! Tried it a few more times and if the trans (TH350) or t case (NP205) is in neutral there is no noise.

The trans is rebuilt and the adapter has new bearings and seals which brings me down to the t case, coupler, rear end or drive shaft.

Drive shaft looks to be the original with a slight amount of play in the splines, it still has the original HO52 and NP205. I was going to replace the rear with a 14 bolt out of a 74 1 ton as there is a bit of moaning at speed coming from somewhere.

Is there any way to isolate the noise before I keep throwing cash at it?

Re: Strange noise
 

Can you just pull out the front drive shaft and drive it? See if the noise goes away?

Re: Strange noise
 

I had the same problem on an old 78 dodge power wagon, i noticed it would stop when I put it in neutral while driving,plus a bad vibration turned out the me the front driveshaft CV/u joint (forget the correct name) but a day later it finally let go driving to the store.

Re: Strange noise
 

i forgot to mention i already pulled the front shaft as i thought the same.

I am thinking about pulling out the rear shaft and just run the front for testing but Im not sure if it will tell me if the drive shaft vs. the output shaft bearings vs. pinion shaft bearings are the problem.

If I swap in a 14 bolt does the drive shaft need to be lengthened or shortened?

Re: Strange noise
 

maybe chains streched in the transfer case, I had a 4x4 that did that and the same thing, on decel, it kind of sounded like something was rubbing. Let my old man hear it, he told me to pull the transfer case apart, and sure enough the chain was stretched and slapping the case.

Re: Strange noise
 

oh, i just read that it is a 205, i think only the 208's have chains, i believe 203 and 205's are gear to gear. still, might be worth inspecting, maybe a bad bearing or a chipped tooth from engagement

Re: Strange noise
 

You said you still have the HO52. I had a problem with my HO52 many years ago. Only thing I noticed was a faint growling noise from the rear of the truck, under deceleration. Only heard it at low speeds but the truck gets so loud as it speeds up that the noise may have been there but drowned out. Also never experimented with putting it in neutral so no help there. Local mechanic found a pitted pocket bearing on the end of the pinion gear. It's been good ever since.

Re: Strange noise
 

Anyone else have any ideas? Would a worn slip joint in the drive shaft cause this type of noise?

I would love to keep the HO52 but the bearings are expensive. Its over $250 just for a pinion bearing and I would hate to waste the funds if thats not the issue.

Any other experience greatly appreciated