Universal joints 47 1/2 ton

[dgrinnan]

I think I have some bad u-joints on the drive shaft.  Under load the truck runs smooth.  As soon as I let off the clutch or decelerate I get a noticeable vibration.  Not as much in deceleration. I would guess one of the u-joints has some play and when the drive load is removed it can shift around, under deceleration with the clutch engaged it shifts out of position but doesn't shift around.  I have been told the u-joints look like the modern u-joints but are more complicated?   Does anyone have any experience change the u-joints on their drive shaft?  Any pointers or advice? I have not taken a good look at them yet but wanted to gather some information before I crawl under the truck. 

[Los_Control]

What you describe could be u-joints. I had one on a toyota do what you describe. Under load it was fine, put in the clutch to freewheel and the rear end would bounce all around. .... The u-joint actually froze &  would not move. There was not any play in it, only way to find it was to pull the drive line.

 

Be interesting to see if you have modern u-joints or the old Cleveland style.

 

48-50 we had them, I would assume a 47 would also .... I could be wrong or yours may have been changed .... no idea.

My plan after I finish painting the frame is to grease everything replacing plugged zirks as I go ..... The drive line I am going to remove and disassemble the u-joints, clean all the old grease out of them & inspect while putting them back together with fresh grease.

May sound like overkill ... I know 5 years ago it was almost impossible to find replacements, then a few years ago I heard of a supplier & they were about $80 each ..... I dunno what cost or availability is on them today. So I figure it is worth the effort.

 

If I end up doing a rear end swap & need some drive line work done, I will spend the extra cost to replace them at that time.

 

[dgrinnan]

Mine are similar to what you have pictured.  Yes, DCM now carries replacements.  $75 ea.  Some places are asking well over $100 for them.  Trying to decide if I just bite the bullet and go ahead and replace both while I am at it.  Even if one is still good I think they are both original.  It won't be too far behind the first one to fail. 

[Los_Control]

Tough call. couple years ago I had 1 start to make noise on my chebby truck I replaced both & the center carrier bearing. Figured it was time.

 

The old Dodge at $75 each ..... I'm so cheap I would rather spend a day cleaning & greasing them before they go bad

 

 

 

 

[Veemoney]

On my 47WC I have the same style Cleveland joints as Los shows for his truck. When I pulled the driveshaft while changing out the rear gearing and servicing the axles, I could not get the rear joints of the driveshaft out. I remembered reading a thread here where a member had added weight to the bed of his truck to get the required clearance by compressing the leaf springs. I started stacking what was closest till it came down enough to clear.  My u-joints had dried grease which I cleaned, greased and reassembled. Make sure the front and rear u-joints are phased correctly which could be creating your vibration problem.  

[dgrinnan]

Good information on the phasing.  I had never heard that before.  I googled it and found an nice video on what it is and how to check it.