New drivetrain issue

[powderfinger]

Well, I have fixed the noise problems I was having after replacing the release bearing and pilot bushing but in the process I seem to have created a new problem. The truck has developed a vibration that only seems to happen during deceleration and when in gear. It's worse when hitting bumps specifically dips in the road that compress the suspension some.

 

The fact that it does it worse when the suspension compresses made me think maybe I somehow screwed something up when I reconnected the driveshaft figuring the angle was changing when hitting dips in the road making the vibration worse but everything looks fine and it seems to me if it were the drive shaft it wouldn't do it only when decelerating. Also the fact that it doesn't do it when in neutral or when the clutch is pressed also doesn't seem like a drive shaft issue. I connected the driveshaft the exact same way it had been previously, I marked the intermediate shaft and the driveshaft just in case it mattered. I have had the transmission out before and didn't have this issue but this is the first time I have taken the clutch off.

 

Could a warped pressure plate do this? I was in a hurry and forgot to take the bolts out of the clutch a little and a time in a star pattern until the tension was off and instead took them out one at at time. I didn't think about it until I was on the last bolt and then realized what I had done. Hopefully I didn't damage it. If that was the issue it seems to me it would always do it instead of just when decelerating. 

 

It also seems like the source of the vibration is too far forward to be the driveshaft but vibrations can be tricky to pinpoint the location of.

 

If anyone has experienced anything like this before please let me know. I'd like to get this thing back on the road so I can keep the miles off of my big truck and stop going through so much diesel at 17mpg.

 

 

Edited January 28, 2020 by powderfinger

[datzenmike]

Warped PP would not alter it's balance.

 

Worse on dips on the road leads me to think the driveshaft. You had it out, is the rubber surround on the carrier bearing rotted away?

 

Has the truck been lowered? This will upset the driveshaft angles and cause vibration specially on dips.

 

Does the driveshaft have any dings or dents on it? Is it bent? Put in neutral and lift one wheel off the ground. Have someone spin the wheel while you watch the driveshaft spin. Anything?

 

Inspect it to see if any of the balance weights have come off. Usually a clean spot where it was.

 

Swap the front wheels with the rears and see if this helps.

 

Split the rear driveshaft from the front and turn it 180 and install. Test drive it.

 

Check that rear lug nuts are tight.

[powderfinger]

Truck is not lowered and the driveshaft is definitely not bent. This vibration didn't start until I replaced the release bearing and pilot bearing. It started immediately after that. I have never taken the rear driveshaft out, just the front. I removed the front shaft and let the rear shaft rest on a bungee cord while the truck is up on my lift. I put the front shaft back on the rear shaft in the exact same orientation.

 

The carrier bearing and rubber surround is in good shape, less than a year old. I'll check to make sure no weights came off the shaft and while I am at it I'll swap the wheels too just in case.

[powderfinger]

I believe something is missing here LOL. How many leaf springs did these 2wd 720s have stock? I have seen pics of new ones online with 4.

 

 

[datzenmike]

 Three, on a 2wd, a main full length with a similar, though shorter one under it, and a thicker over load leaf at the bottom. There was an optional 4 leaf.

[powderfinger]

oh well, i guess there isn't one missing. I thought there must be because the suspension feels way too soft and this vibration issue I am having is worse when the suspension compresses. It also seems to do it worse when I turn sharp to the left if I swerve back and forth in the road so maybe it's a wheel bearing. It feels like it's directly under me though. Turning sharp compresses the suspension as well so that could still lead back to the driveshaft. I replaced the u-joints even thought they felt fine and that didn't fix it.

 

I'll get the truck off the ground and see how the wheel bearings feel.

[datzenmike]

Climb on the rear bumper and jump up and down on it. Get it going and jump off. If it's still bouncing when you hit the ground it probably needs new shock absorbers.

[wayno]

Has this truck been lowered?

It doesn't look lowered in the photo but the body may be jacked up with a floor jack.

[datzenmike]

Asked 6 posts back. Lowering upsets drive shaft angles.

[I'm BLUE]

On 1/27/2020 at 5:14 PM, powderfinger said:

 I was in a hurry and forgot to take the bolts out of the clutch a little and a time ....

 

 

 

^^^ After reading this, I'd go back and check the torque on each fastener touched ....parts as well....first before looking at other avenues before blaming on a new problem. Seems like the problem came on quite suddenly ?

 

Good luck man

Edited February 8, 2020 by I'm BLUE
Blah

[powderfinger]

Guess I never updated this! It ended up being a tire. I would have bet plenty of money that a tire could not make the truck do what it was doing. My brother rode in the truck with me and felt it and once I fixed it and told him what it was he barely believed me.

[Rat-a-tat-Dat]

I can believe it. That happened to me once as well. Sorry I hadn't read this post earlier.

My rear right tire was the issue, but prior to discovering what really cause the problem, took some time to figure out.

A long story and sadly, plenty of cash spent before a (freak) accidental find.

 

Glad to hear its resolved.