Strange noise - The 1947 - Present Chevrolet & GMC Truck Message Board Network

RedRoad · 02-12-2015, 04:03 AM

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?

cooperhw · 02-12-2015, 08:07 AM

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

**bigmac73** · 02-12-2015, 08:53 AM

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.

RedRoad · 02-12-2015, 02:19 PM

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?

no1udknow · 02-12-2015, 03:59 PM

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.

no1udknow · 02-12-2015, 04:03 PM

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

**Stocker** · 02-12-2015, 05:00 PM

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.

RedRoad · 02-14-2015, 02:52 PM

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

02-12-2015, 04:03 AM	#1
RedRoad Registered User Join Date: Jan 2015 Location: Los Angeles California Posts: 927	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?

02-12-2015, 08:07 AM	#2
cooperhw Registered User Join Date: Oct 2014 Location: Mesa AZ (Near Phoenix) Posts: 2,302	Re: Strange noise Can you just pull out the front drive shaft and drive it? See if the noise goes away? __________________ "Life is too short to drive a boring vehicle". Later, Wayne

02-12-2015, 08:53 AM	#3
bigmac73 Senior Member Join Date: Mar 2012 Location: Chesapeake, Va Posts: 1,275	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. __________________ Mike 72 C-10 Cheyenne off frame resto and Upgraded to 4 wheel disk, Tilt, Dakota Digital Dash / Rear slider. 421 SBC / TH350 3000RPM Stall Progression Ignition /Holley 750 DP/3:73 gear Eaton Limited Slip unit / 2 1/2 exhaust glasspacks

02-12-2015, 02:19 PM	#4
RedRoad Registered User Join Date: Jan 2015 Location: Los Angeles California Posts: 927	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?

02-12-2015, 03:59 PM	#5
no1udknow Registered User Join Date: Jan 2014 Location: Sacramento,California Posts: 696	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. __________________ Built not bought! My dad always tried to convince me HEI was pointless! Welding is a lot like sex, you don't have to be great with the rod as long as you thoroughly prep the surface and your good at grinding My build : 68 C10 Short Bed Conversion

02-12-2015, 04:03 PM	#6
no1udknow Registered User Join Date: Jan 2014 Location: Sacramento,California Posts: 696	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 __________________ Built not bought! My dad always tried to convince me HEI was pointless! Welding is a lot like sex, you don't have to be great with the rod as long as you thoroughly prep the surface and your good at grinding My build : 68 C10 Short Bed Conversion

02-12-2015, 05:00 PM	#7
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,570	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. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

02-14-2015, 02:52 PM	#8
RedRoad Registered User Join Date: Jan 2015 Location: Los Angeles California Posts: 927	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



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