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Waterloo · 01-17-2019, **(Subject: Elusive vibration )**

(01-17-2019 )Mrkentee Wrote:
(01-17-2019 )Waterloo Wrote: Throw in new Cam and Crank sensors and see if that helps, they are the same part# and inexpensive. Prior to my in frame at Rawze's, mine had similar issues. Sounded like gravel under the floor board but only at certain RPMs. But, I had all of the wrong parts under the hood, along with worn bearings from what looked like a dry start.

Might be worth a try. I wonder could an unbalanced brake drum cause this, and how would you check it?

You doing some hard braking, riding them rolling down Grapevine, trailer on fire? Honestly, I doubt it is your drums.

ynot · 01-17-2019, **(Subject: Elusive vibration )**

I was told by an old mechanic that specialized in finding vibrations, that a wheel end vibrations will show themself at 50-55mph then as you go faster will stop an show them selves again around 80+ mph.

You mentioned you've got all new drive line parts have you checked your driveline angles an made sure it was all in phase? That can cause vibrations as well

flatbed94kid · 01-17-2019, **(Subject: Elusive vibration )**

How do you check the angle?
Just curious.

Mrkentee · 01-18-2019, **(Subject: Elusive vibration )**

Update: at 65 mph, loaded, I put it in neutral, the engine went to idle and had the definite vibration. When I brought the RPMs up to 1000 it went away. So it’s got to be the engine. I’m thinking vibration damper, front motor mounts, or the clutch. Or...??

ynot · 01-18-2019, **(Subject: Elusive vibration )**

(01-17-2019 )flatbed94kid Wrote: How do you check the angle?
Just curious.

These videos should help

https://youtu.be/Idk3BVDVHq4
https://youtu.be/TUFzehQBDPI
https://youtu.be/f1m-Fh5kiRU

An spicers calculator
https://spicerparts.com/calculators/driv...calculator

ynot · 01-18-2019, **(Subject: Elusive vibration )**

This video explains that first video better

https://youtu.be/jaaTyL099RA

Mrkentee · 02-22-2019, **(Subject: Elusive vibration )**

Success!! I finally found the source of the vibration. It was the output shaft from the front diff to the rear drive shaft. And it could be changed from the outside without taking the whole diff out on this DSP40 differential.

JMBT · 02-23-2019, **(Subject: Elusive vibration )**

So how did you end up finding it? What led you to pull the output shaft?

Mrkentee · 02-23-2019, **(Subject: Elusive vibration )**

(02-23-2019 )JMBT Wrote: So how did you end up finding it? What led you to pull the output shaft?

It had a new yoke put on about 6 months ago, and a new seal. The old was difficult to get off. The splines were a little goofed up on the end. The guy had to use a file to clean them up. Then run the yoke on with the nut. (It was a Friday afternoon, and we thought the diff had to come out to replace that). Recently was in warmer weather and the seal started leaking a little. I found out it comes out from outside the housing, and the parts were only about $220. That new yoke already had a groove in it, so it was replaced again, also.
Even though it felt tight, it just started making sense that if it was tweaked a little, it could be causing the front yoke of the rear driveshaft to be out of whack. Figured it was worth a shot.
(It took me so long to figure that out. I should have known about it and done it when I replaced the diffs. But I was just worried about getting it done. Knowledge is king!)