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Discussion Starter · #1 ·
In an ongoing search for the source of a vibration in my truck, my attention is now focused on the rear driveshaft. My mechanic friend and I both agree that it's likely the shaft is out of balance from either rusty weights falling off, or the other idiot hack mechanic beating the crap out of it to replace u joints.
I have a lead on another driveshaft from a like truck, but it's an aluminum shaft and my truck came with a steel shaft. Is it a direct swap?
 

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This is just my recent past experience, so I wouldn't take it as gospel.

My 2004 extra cab has a steel driveshaft, and an 11.5", 14 bolt AAM rear end. The U-Joints are larger than those used on the aluminum driveshaft of my brother's 2003 crew cab. He also has a 14 bolt, although I don't know which one. So there may be some issues with connections at the differential, and the transfer case.

Hope this hels,

Jeff
 

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My steel driveshaft uses the U-Joints with the 1.375" caps. The aluminum shaft on my brother's uses the U-Joints with the 1.188" caps.

Jeff
 

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Discussion Starter · #6 ·
So I might have to pull off the input on the rear end to make it work? Ive never pulled one off before. Is it as simple as just getting that big nut off?
 

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Yes. Might as well replace the input shaft seal while you're at it. But google it. A lot of the diesel guys do it. They say it's a upgrade to get the aluminum.

Sent from my iPhone using Tapatalk
 

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I had my steel driveshaft balanced. It wasn't expensive. Maybe 60 bucks or so. If you are missing a weight, you would likely see a clean spot on the driveshaft where it used to be.

Unfortunately, I can't comment or provide any guidance on removing or replacing the input shaft on the diff.

Jeff
 

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There are good solutions. Balance Masters makes flexible tubing that is filled with mercury that fit over a drive shaft and continually balance the shaft, irregardless of rotational speed. Driveshafts that are shop balanced are done so at a set speed of rotation that is the average for most situations. Not bad but a continue balancing that adjusts to the conditions is a better solution. Just disconnect the shaft, slide the balancing ring on the shaft, reassemble and drive.
 

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Discussion Starter · #11 ·
So I took the shaft out and figured I would grease the splines on the slip yoke just to see what happens. During that, I noticed that the brand new ujoint on the rear was very stiff. Its supposed to move easily, The front one moves easily and its new as well.
So while I went ahead and replaced the ujoint with one I have sitting around, I noticed that during the removal, as soon as I started tapping the cap out, it started moving freely as it should. I figured this is odd. But I went ahead and replaced it anyways. As soon as I got the caps of the ne ujoint mostly in, they were difficult to get them all the way in. It required a little bit of hammer tapping to get the caps all the way in. When I got them all the way in, the new joint wouldn't move just like the old one.

So it looks like the ears on the end of the drive shaft that the caps go in, is bent. This is clearly not allowing the ujoint to move as it should. I can only assume it got bent from abuse from the hack mechanic.
 

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That's rough man. Hopefully you can get a replacement without much trouble or cost. I know I have had some issues with pressing U-joints and wheel bearings in on certain vehicles. Have gone to the use of a bottle jack more than once. Bad as it is to happen. At least now you know and it is now rear end gear related.
 

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I had the same problem. I bought one set, (MOOG brand) removed the driveline, and couldn't get the old ones out, via the tried, and true beat the crap out of them with a large socket, and hammer method. I figured if I couldn't even get the old ones out, getting the new ones installed without causing damage was going to be questionable.

The only shop that would install them for me (on a Sunday) was Pep Boys. I specifically requested that they be pressed in, and inquired as to whether they had the equipment to do so. They assured me that they did.

When I pick up my driveline, the "mechanic" commented on the amount of beating it took to get the new joints installed. The rear one was pretty stiff. But he explained that was because it was new, and "heavy duty". Having done many U-Joints over the years, albeit in different drivelines, I knew he was full of it. But I thought hmmmmmm, maybe.

In the end, the driveline shop installed a set of Splicer brand U-Joints, using a press, and at the same time that they balanced the driveline. The owner of the shop told me that the front-most one was okay, and the rearmost one was damaged from being beat in. I opted to have him replace both of them anyway.

Live, and learn I guess. The hacks are everywhere,

Jeff
 

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Jason,

Did your efforts today eliminate your vibration? I'm still chasing one as well. Although I know it's rotational, and up front somewhere.

Jeff
 

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Discussion Starter · #17 ·
As of now, the vibe is still there. I was supposed to pick up the aluminum drive shaft last night, but the guy stopped answering his phone.
So I might have to resort to the junk yard. They have a drive shaft for $150. I want to go the aluminum route. I figured the cost to have this shaft fixed would meet or exceed the cost of the junk yard one anyways.
I did however, end up having time to run over to my friends house and take a look at his 2003 2500HD LS quad cab truck. His has the aluminum shaft. The slip yoke and input on the rear end are exactly the same as mine are, so the shaft is definitely a direct swap.
I am assuming the aluminum shafts came on "nicer" trucks and my theory on that is its because the aluminum shafts dampen noise better than steel shafts do.
 

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That sucks! I'm still chasing my vibration as well. I have a set of HD CV's to install, and if that's not the source, I'm going to let it sh!t out whatever is vibrating. At that point, I will have replaced the rear driveshaft U-Joints, had the rear driveshaft balanced, eliminated the rear driveshaft slip-yoke, the front driveshaft, and the tires as sources, replaced the front wheel bearing assemblies, replaced complete tie rods, replaced the pitman arm, replaced the idler arm, and replaced the idler arm bracket. (obviously most of that needed doing anyway)

I'm not sure which trucks gets which parts, as far as the driveshafts, and the rear differentials go. When I was messing with mine, I kinda figured the steel driveshaft was used with the heavier 11.5" AAM 14 bolt, as the U-Joints in my steel driveshaft are significantly larger than those installed in the aluminum driveshaft on my brother's truck. As far as the "nicer truck" theory goes, Mine is a 2004 extra cab LT, and my brother's is a 2003 quad cab LS. Maybe it's a extra cab versus quad cab thing?

Anyway, good luck, my friend,

Jeff
 

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Discussion Starter · #19 ·
Does your brothers truck have the 6.0? The larger ujoints in your are because of the 11.5" rear end where the 6.0's have a 10.5".
 

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I doubt aluminum is used in an HD application because they are not as strong as the steel. Aluminum is generally used to reduce rotating mass. Reducing rotating mass (any parts which turn) has a large effect on fuel economy. I don't remember the rough conversion but a reduction in 1lb rotating is equivalent to somewhere between 7-9lb stationary. So if the aluminum driveshaft is 10lb lighter, the truck would drive like you removed almost 80lb from it. In other words you can make better power and fuel economy gains from a driveshaft swap or lighter wheel/tire combination than a fancy tuner that switches between power and economy modes.
They do offer conversion U-joints that have two different sizes of caps and widths. With a quick search, it looks like you are probably running the 1480 and are looking to adapt it to a 1410 for the aluminum driveshaft. Your going to want to do your own research though to make sure.
http://www.dennysdriveshaft.com/c1412_combo_jt_1410_to_1480..4_316_outside_to_4_316_outside.html

They are out there but you just need to have the information available to get the right part ordered.
 
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