I have a noticeable driveline vibration when accelerating from a stop up to 40 m.p.h., after that speed it goes away. I have driven it up to 75 m.p.h. on the highway with no vibrations at that speed. It only does it from 0-40. I have checked the u-joints and driveshaft run-out and all is good. The truck was lifted 6" by the P/O. The pinion angle looks too high to me. (It has 6* shims under the springs).Front u-joint angle is 1/2*, while the rear is 2 1/2* in relation to the driveshaft. If this is the case, wouldn't the vibrations get worse, not better, when speeds increase above 40 m.p.h.? Any suggestions of what else to check would be appreciated.

 

Check your tranny

 

Thanks for the suggestion, Roverdon. Trans and mount are both in good condition.

 

If you let off the gas does it still vibrate at let's say 40 down to 30 mph?

 

No they wouldn't if your pinion angle is out you are going to feel the vibrations under load when the driveline angle is under torque. Once you get up to cruising speed the torque is relieved and it settles into an acceptable angle. During accelleration that pinion is going to pull upward, if you are already at the outside range of acceptable then it's going to push that 2 1/2 up to 3 degrees. Which direction is the fat end of those 6 degree shims pointing?

 

LivingLarge, it only does it while accelerating, not coasting.

Sammie, whoever did the lift installed the shims correctly, thick-end towards the rear of the truck. I have a feeling the blocks might be tapered as well, although I haven't had the time to verify that yet. If that's the case, the pinion angle is way off, as it looks to be. I'm going to measure the blocks later today and see what they are and order the correct shims.

 

If the front end of the pinion is pointing too high then to shim it down you need the fat end facing the front of the truck. That being said if the PO put in too large of a shim (facing rear) then he basically shimmed it up too much and may just need a smaller shim so it doesn't push the front of the pinion so far up. I'm pretty sure I'm reading your description correctly but sometimes it's very hard to tell, when you say 2.5 degrees.

Give this a read - helped me a great deal with I was measuring mine out and fixing some things "others" did to my truck.
Driveline 101

Here is copy and paste of one section that is very helpful.
Installing a shim between the axle and spring is the easiest way to correct the driveshaft angle (here's a convenient on-line source for custom-built axle shims). But which way does the shim go in to fix the problem? It depends on the spring and axle configuration, namely Spring-Over-Axle (SOA) or Spring-Under-Axle (SUA). The following table summarizes the direction of pinion tilt vs. axle configuration. and which way the "fat end" of the shim faces:
<center> <table border="3" cellpadding="3" cellspacing="3"> <tbody><tr> <td>Tilt/Config</td> <td>Front/SUA</td> <td>Front/SOA</td> <td>Rear/SUA</td> <td>Rear/SOA</td> </tr> <tr> <td>UP</td> <td>Backward</td> <td>Forward</td> <td>Forward</td> <td>Backward</td> </tr> <tr> <td>DOWN</td> <td>Forward</td> <td>Backward</td> <td>Backward</td> <td>Forward</td> </tr> </tbody><caption align="BOTTOM">Pinion Tilt vs. Spring Configuration</caption> </table> </center> Its best to visualize the spring as fixed flat surface under the vehicle. Then the shim will sit between the spring (top or bottom) and the axle, which then must rotate up or down to align the spring perch of the axle with the angle of the shim.



Vibrations that get worse say going uphill or accelerating at speed than when going the same speed on the flat or downhill, or vice versa, might be due to a slight alignment issue.

• If worse uphill/accelerating, the lower u-joint angle may be moving too high as the axle and pinion tip up under load, if so, tip the static pinion angle down a little lower than it is now.

 

Problem solved... the P/O over-shimmed the rear axle. I removed the 8* shims and dropped them down to 4*. No more vibrations.

 

That's great! I know that happy dance feeling very well when you solve a vibration.

 

Mine is doing the same thing, but it is a dually not lifted and does it between 45 and 55 when it shifts into over drive. I have a 2wd transfer case solenoid code, number 2 cylinder something can remember, but I got some sea foam and that seemed to help a little bit,maybe dirty injectors? ReplaceD egr valve. It's not front end,, had that checked out, new tires shocks, brakes, calipers rotors, tie rod end

 

Ok I’m stumped, this is driving me nuts. I get a vibration from 5 mph till about 35, but it goes away as my Rpm’s rise Between 1500-2100 rpm. It’s more noticeable with ac on and going up hill.

under light acceleration it’s not bad, nail it and it feels like something is going to leave my truck from underneath. Just replaced all U joints.

I forgot to grease the damn splines though, not sure if that could cause this. Everything under this truck is tight as a drum, it’s been very well maintained. Pretty much all original except cosmetics and the normal maintenance stuff like U joints, ball joints, it’s all either new or in very good condition.

Im thinking it could be an injector/stiction issue?
I really noticed it after new tires and wheels.

on the freeway it’s none existent, the 6.0 runs incredible, SCT X4 tuner, egr delete.
just changed the oil and added archoil, I use Hot shot at every fill up.

Im sure I’m forgetting something.

oh I was ASE certified on gassers back in the 90’s so I’m mechanically inclined, diesels are a bit new to me, but most of the suspensions the same anyway, just bigger it seems.

anyway, I’m lost I think at this point, I shall never give up, but I’m hoping someone might have another idea for me to check. Any response is much appreciated 🇺🇸

 

I have fought vibration issues a couple times. For me they both went away after replacing the tires. only run michelins now because of this issue. Good luck let us know when you figure it out.