Sounds like I might have some rear differential problems on 98 Chevy 1 ton.

wtd

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The other day when I went to drive the truck, I put it in gear and heard something clank in the rear. I didn't think too much about it but as I was driving, I periodically could hear a metallic sound coming from somewhere, but I thought it might be the large floor jack that was in the bed.

I drove it around more that day and every time I went from park to drive or reverse, I would get a loud clank. When you first take off you can hear a metallic sound for several seconds and it goes away. I got under the truck and tried moving the driveshaft around first in park to see if maybe the Ujoints were loose but there were no movement from them. In neutral you can hear some noise at the rear end and inside the transfer case when turning the driveshaft by hand.

I put the rear of the truck up on jackstands with the front wheels blocked and ran it in gear and could hear a slight noise at the rear end and nothing at the transfer case but nothing metallic sounding on either. Truck has a little over 122,000 miles on it.

Does anyone know if there are any weak areas on these 14 bolt full floater rear ends or the Borg Warner transfer cases? I have an appointment in a few weeks to get it looked at. One guy that listened to it when I put it in gear and heard the loud clank says it's the pinion but the shop owner who is going to be looking at it said that bad pinion bearings have a whine sound more so than what I'm hearing. I've had bad pinion and carrier bearings in the rearend of my 98 Chevy 1500 with the 10 bolt and it didn't sound anything like what this truck sounds like and did have a large whine.
 
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If you have your foot on the brake, and zero on the gas,does it make the sound? Does it get worse with mild acceleration then quit?

Not definitive but I had something that drove me bat-sh&t like this until I realized it was the (a) cat.
 
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Make clunking sound when on and off the gas pedal?

Consider universal joints and check entire exhaust system.
 
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Pull drive shaft. With arse end off the ground and emergency brake released see if there is any in and out movement on the pinion yoke. If so then there is a problem with pinion bearings and/or pinion nut backing off. Is this the G80 locking differential? May be something busted there also. Either way my opinion is the rear cover should come off for further diagnosis and repair. For what it’s worth I’ve seen a few universal joints appear tight but actually be going bad and make a clanking clinging noise. They will feel crunchy and tight when moved. Trans yoke and rear joint should be checked. Does this truck have a mid-ship drive shaft bearing???
 

D60

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Could be the drive chain in the BW transfer case which is it's only weak point.
The chain really should sit idle in 2hi. If the 4wd fork hasn't slid back to tie the chain to the rear output, the chain itself is none the wiser as to what is happening at all.

OP, I think you took care of it later (on jackstands) but don't bother checking u-joints in Park. When in P the rear d/s is your chock so it's bound up and you won't be able to detect any play by hand.

Is this a slip yoke at t-case, or slip shaft within the d/s? Is there a carrier bearing?
 
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10- 1/5 incher is likely still dry, spalled u joints. Check them first. Easy 15min job. Next the cover comes off for a look see, also if this unit has a magnetic drain plug you can check for the iron hedgehog.
 
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The chain really should sit idle in 2hi. If the 4wd fork hasn't slid back to tie the chain to the rear output, the chain itself is none the wiser as to what is happening at all.

OP, I think you took care of it later (on jackstands) but don't bother checking u-joints in Park. When in P the rear d/s is your chock so it's bound up and you won't be able to detect any play by hand.

Is this a slip yoke at t-case, or slip shaft within the d/s? Is there a carrier bearing?
Some of the old Chevy's were full time 4wd...
 
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As someone that went thru waaaay to much to get a differential fixed, I will offer this one piece of advice. Take it to a shop that specializes in Rear Ends. Not a trans shop, not a general mechanic, not anything except someone that really knows rear ends.
 

wtd

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Thanks for the replies. To answer some of the questions, the driveshaft does not have a mid ship support bearing. Driveshaft is one piece from transfer case to rear end. It does have the G80 locking rear. The U-joints do appear to be original but not totally sure.

Does not have full time 4x4. I did check the exhaust and shook it but can hear no clanging or noise. Both Cats are fairly new as well as the muffler.

I bought the truck back in 2007 with about 94,000 miles on it and changed the rear diff fluid shortly after that. There are no signs of leakage of the rear diff anywhere. I will have to check level though to make sure it's still full.

I will have to put the rear back up on jack stands and see if there is any in or out movement of the pinion yoke. In neutral on the ground, there is some slight back and forth movement of the yoke. There is also no movement at either U-joint.

The shop that I'm taking it to replaced the pinion and carrier bearings in the rear of my 98 K1500 years ago so I'm familiar with their work. They are an off-road shop that installs lifts and repairs drivetrain parts.
 
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Thanks for the replies. To answer some of the questions, the driveshaft does not have a mid ship support bearing. Driveshaft is one piece from transfer case to rear end. It does have the G80 locking rear. The U-joints do appear to be original but not totally sure.

Does not have full time 4x4. I did check the exhaust and shook it but can hear no clanging or noise. Both Cats are fairly new as well as the muffler.

I bought the truck back in 2007 with about 94,000 miles on it and changed the rear diff fluid shortly after that. There are no signs of leakage of the rear diff anywhere. I will have to check level though to make sure it's still full.

I will have to put the rear back up on jack stands and see if there is any in or out movement of the pinion yoke. In neutral on the ground, there is some slight back and forth movement of the yoke. There is also no movement at either U-joint.

The shop that I'm taking it to replaced the pinion and carrier bearings in the rear of my 98 K1500 years ago so I'm familiar with their work. They are an off-road shop that installs lifts and repairs drivetrain parts.
Don't forget to check trans and motor mounts when you are under there. - and shot isolator bushings in spring eyes or control arms/links
 
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As someone that went thru waaaay to much to get a differential fixed, I will offer this one piece of advice. Take it to a shop that specializes in Rear Ends. Not a trans shop, not a general mechanic, not anything except someone that really knows rear ends.

Transmission shops usually have at least one guy that's good with differentials, The crafts kind of go hand in hand.
 
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14bolt ff is a pretty stout axle. I believe the snout of the pinion also has a bearing to help with load. The g80 in the 14 bolt used the same mechanism but different design than the 10bolt and is much stronger as well.
 

wtd

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My fiancé's dad got under the truck while I put the truck in forward and reverse and he says it's definitely in the rear end. Before looking at it, he thought it might be the U-joint because he said as other have, that the 14 bolt FF is a pretty stout rearend and you usually don't see problems with them. I guess I just got un-lucky as usual. He did say that the front U-joint has some movement in it but that the rear one did not.

On the 12th, the truck is going into my front end guy to get the Pitman arm replaced under warranty and possibly the lower steering shaft depending on what he finds. The truck has been wandering all over the place lately and I had him look at it last week.

On the 24th, it's going in to get the rearend looked at so sometime after that I will know more.
 
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