Hi Everybody,

I am experiencing a mild vibration that I think is from my driveshaft. It occurs only at higher speeds (highway), and only when I release the throttle. Throughout acceleration and constant speed, it is undetectable. However, if I ease off the throttle it becomes slightly apparent, and if I release it completely, I experience a short grinding/vibration sensation. It only lasts about 1 second, but occurs every time I do this. The problem is undetectable at lower speeds. I have indeed lifted the vehicle (P38) about 2 to 2.5". Is this something to worry about, or is it simply a side affect of the lift. I intend on eventually upgrading the driveshaft(s), so can it wait till then?

UPDATE:
So I replaced the U-joints on my front drive shaft this weekend. Although that seems to have made general driving smoother, it has not yet cleared the problem.

I have confirmed that I can feel it at speeds above 70km/h. When I release the throttle immediately, I notice a short (but quite noticeable) vibration/grinding sensation. I also realized that if I slowly release the throttle to right before I reach 0% throttle, I can actually cause the sensation for a prolonged period (as long as I keep the throttle in that position).

Could this still be the drive shaft? If it is at it's maximum angle would this be a symptom, or would it not be a more constant sensation?

Thanks very much,

John.

 

Yes to all of your questions.

Have it inspected.

 

Uh Oh!

A fellow P38 owner informed me that they had similar problems, but it turned out to be their front diff. They had a whine on deceleration, and had similar unloading vibrations. Mine has that whine on the highway when I coast. It's had it for years though. However only fairly recently has the vibrations become noticable.

As well, I've really started to notice the shudder and such while braking. I thought it was brakes before, but now I think it's the same problem. It happens when I have to brake harder than usual, and becomes noticable within the last (and hardest) couple meters of braking. I get a shuddering sensation that has become quite noticable, and can be felt underneath me as I drive (LHD). Could this be a shoddy diff? I'm going to check the U-joints first, but unfortunately this is going to be mostly performed by a mechanic, and will probably cost me quite the penny if I have to open up the diff's as well... I hope it's not as severe as it seems!

 

UPDATE:

So I replaced the U-joints on my front drive shaft this weekend. Although that seems to have made general driving smoother, it has not yet cleared the problem.

I have confirmed that I can feel it at speeds above 70km/h. When I release the throttle immediately, I notice a short (but quite noticeable) vibration/grinding sensation. I also realized that if I slowly release the throttle to right before I reach 0% throttle, I can actually cause the sensation for a prolonged period (as long as I keep the throttle in that position).

Could this still be the drive shaft? If it is at it's maximum angle would this be a symptom, or would it not be a more constant sensation?

Thanks

 

I am not familiar with the P38, do you have a locking t/case, also does your drive shaft have the double cardon style shaft? If so, did you replace the centering ball? Also if you have the CDL case, remove the front shaft and drive on the rear only to see if the vibration goes away.

 

had this on my 95 D1, figured it was driveshaft after it was there in each gear.

It turned out to be not a worn uni at front of rear dirve shaft but one that was tight.

Have to drop rear driveshaft down to check uni by hand, cheap to replace

regards
OZ

 

The P38 has a Borg-Warner auto locking transfer case. My drive shaft is not double cardon style, rather a basic single u-joint at each end.

 

So it was the tight u-joint on the rear shaft that was causing the problem? I'll check to see if it's in every gear, but I don't think it's in the lower end gears as I mentioned it only happens at higher speeds..?