96 C2500 Rear End Clunk (video)

[Frank Enstein]

The Redline gear lube will make the sound significantly quieter. It cushions the metal to metal contact.

 

[Schurkey]

When I take off from a stop I get a jerky feeling in the driveline.

It's just when I take off from a stop

Driveshaft slip-yoke in the transmission/transfer case.

or shift from R to D.

Start with the driveshaft yoke. See what happens.

That axle has some play, but I don't think it's all that bad. You'll know more when you pop the cover.

 

[Vanishing Point]

It seems you, and I have or had the same problem,
I also own a 1996 2WD C2500 single cab long bed (SCLB), not an (ECLB). My 5.7L 58,000 mile and not 128,000 like yours 8 Lug Semi Float rear axle, which is attached to a 4L80E Automatic, made similar noise,
so I checked the fluid level at the rear passenger side differential site (fill) plug, and it was level with the bottom opening of the site (fill) plug, which it should be, and upon further inspection found out the u-joints were completely dry/noisey and decided to go ahead and replaced them. With new front and rear Heavy Duty Spicer 5-1350X U-Joints with no zerk (grease) fittings at $29.99. And then a one each Center Load Bearing, Spicer U-Joint Coupler C3-3-399 on my two-piece Driveshaft with new rubber dust cover and zerk (grease) fitting rebuilt for $65.00 at my local driveshaft shop. And that seemed to have taken care of the situation of which I left alignment marks on both my rear axle differential housing flange and automatic transmission tail housing yoke before removal. And to help aline and reassemble everything back up so that I wouldn't create an imbalanced driveshaft vibration noise, and that sure did make a difference. So I hope this helps you in determining your concern and have the same luck as I did in remedying the situation.

 

[kennythewelder]

Pull off the diff cover. After draining out the oil, have someone you trust do the same thing as in your video, and see what is going on inside of the diff. Maybe you can set up a camera to film it. Me, I would have mt wife move the truck as I watched the diff without the cover so I could see in there, and see what is happening. You may be able to put it on jack stands and do this or not. It may only show under load, IDK. It could be a broken gear, of like mine a broken carrier bearing mounting post, although mine did make a lot of noise. Ether way, with the cover off, you will be able to see what is jerking around in there.

 

[kennythewelder]

Here are a few pics of my rebuild.

 

[Justin2500]

Good stuff everyone! Lots of stuff to investigate.

It really wasn’t the noise that was a concern it was stoplight —> foot off the brake —> gas —> slight hesitation then lurches forward.

 

[Erik the Awful]

Hell, just throw some saw dust in there and run it! JK

Actually, I saw a Chevy Monza at the race track (the Speedy Monzales race team) a couple years back. An hour into the race their rear end started howling. They pulled into the pits, opened the diff, plopped an entire can of anti-seize into it, put the same gear oil back in it, and drove the entire rest of the race - at least twelve hours - with the rear end howling.
www.murileemartin.com/UG/LECR14/419%20-%202014%20North%20Dallas%20Hooptie%2024%20Hours%20of%20LeMons%20-%20IMG_7028.jpg

 

[454cid]

Actually, I saw a Chevy Monza at the race track (the Speedy Monzales race team) a couple years back. An hour into the race their rear end started howling. They pulled into the pits, opened the diff, plopped an entire can of anti-seize into it, put the same gear oil back in it, and drove the entire rest of the race - at least twelve hours - with the rear end howling.
www.murileemartin.com/UG/LECR14/419%20-%202014%20North%20Dallas%20Hooptie%2024%20Hours%20of%20LeMons%20-%20IMG_7028.jpg

That doesn't make much sense to me. What did they think the anti-seize was going to do? It's not a high speed lubricant, in fact some of them have ingrediants that would become an abrasive in that application.

 

[Erik the Awful]

I thought the same thing, but I can't argue with "it worked".

 

[Justin2500]

just discovered the glove box codes. Rear diff is 14 bolt SF 4.10 posi.

truck sat for 3 days while I refreshed the front end. Drove it this afternoon and there was no clunk at all. Maybe it only does it when warmed up, I only drove 10 min. I’ll see tomorrow. I’ve only had the truck for 2 weeks. I’ve spent most of those 2 weeks fixing it up. Why would anyone want a new truck? Gmt400 for life.