Axle hub flange runout

[Hemi_Roids]

I replaced 2 out of the 3 U-joints in the main drive shaft (I boogered up a bearing cap on the 3rd new joint, gotta get another one). It made quite a difference. The old joints were definitely bad - there were grooves worn into the machined ends where the needle bearings ride. But there was no easy way to tell that without actually removing the old joints - they all felt fine when manipulating them by hand with the driveshaft on the ground.

The truck still shakes at certain speeds on the highway, but I think I have that narrowed down to a bad slip yoke bushing in the transfer case extension housing. See here: https://www.cumminsforum.com/threads/vibrations-around-65-70mph.2258009/

Will report back once I get that replaced.

I replaced the 3rd U-joint along with the slip yoke bushing and seal. Truck feels tighter/smoother, except it still shakes/bucks at certain speeds (around 45 and 65 mph). So the problem lies elsewhere.

 

[D60]

I replaced the 3rd U-joint along with the slip yoke bushing and seal. Truck feels tighter/smoother, except it still shakes/bucks at certain speeds (around 45 and 65 mph). So the problem lies elsewhere.

You're sure this is driveline and not a misfire issue?

 

[Hemi_Roids]

You're sure this is driveline and not a misfire issue?

I'm an amateur - I'm not sure of anything ;-) I checked for stored misfire codes, found none.

 

[D60]

I'm an amateur - I'm not sure of anything ;-) I checked for stored misfire codes, found none.

If this occurs 45-65 under high load (which means low RPM and heavy-ish throttle, ie before downshifting) I might suspect misfires.

Driveline will often cause a vibe or harmonics but you also say "bucking". This can mean different things to different people but it's rare for driveline to cause bucking. Sometimes (particularly on Ford 7.3 diesels) the torque converter can cause these symptoms, so I guess that's driveline

 

[Hemi_Roids]

If this occurs 45-65 under high load (which means low RPM and heavy-ish throttle, ie before downshifting) I might suspect misfires.

Driveline will often cause a vibe or harmonics but you also say "bucking". This can mean different things to different people but it's rare for driveline to cause bucking. Sometimes (particularly on Ford 7.3 diesels) the torque converter can cause these symptoms, so I guess that's driveline

It seems that lots of Ram owners deal with this same thing, whether gas or diesel: https://www.cumminsforum.com/thread...-65-70mph.475016/?nested_view=1&sortby=oldest

I would love to have a shop with one of those vibration analyzer systems do an analysis, I just have to find somebody in my area (central MD) who offers that service.

 

[Hemi_Roids]

It looks like D60 was right about it not being a driveline issue.

I replaced the control arms, and that seems to have made a big difference. The shaking has largely abated - I can confidently drive at 60-70 mph again. The truck still rides like ****, but it never was very smooth, and a lot of the remaining roughness can be attributed to old shocks and less-than-perfect tires.

Of the 8 old control arm bushings, the rubber was cracked to some extent on all of them, but only 1 was demonstrably "bad". I could flex that one noticeably with a screwdriver through the bolt hole.

I may eventually replace the leaf spring bushings as well, but that's a lot tougher job than the control arms.
I will also need to rebuild my front diff because the pinion seal is leaking pretty badly.