| Author |
 Topic  |
|
|
kevintee
New Member
United States
5 Posts |
 Posted - 03/30/2009 : 10:24:02 AM
|
Ha guys and gals,
I am a nu-be here but I do drive. I am the bus driver/maintenance man for a Boy Scout troop. We have a 1989 Bluebird on a GMC 6000 chassis. She has a 366 engine, 5 speed trans and split rear axle. I have all the exact specks at home they would help. We have a drive line vibration that starts around 55 MPH in 5th gear High range and continues through about 68 MPH. We have had all the shafts rebuilt and balanced which helped for a while.
I am a retired mechanic and know the shaft angles could make a big difference. I did not do much drive line work and am not real familiar with the angle setup however I do know how and have the tools to measure them.
Any thoughts.
We are also talking about changing the dif gears to pull the revs down some at highway speeds. |
|
|
bwest
Administrator
United States
3820 Posts |
Posted - 03/30/2009 : 12:02:27 PM
|
If you were one of my drivers the first thing I would say is: how do you know it is vibrating above 55? Just a little ribbing there. I guess being a retired mechanic you have already checked the carrier bearings? This it the first thing that I check. I had one that was vibrating and I could not even make the carrier bearing move up and down. I checked every thing and even let the driver run it for a wile thinking it would get worse and be easier to find. I then was frustraited and raised the rear wheels (use all the precausions here for saftey. I know we are all experienced mechanics) and put the axle back down on stands. I started the bus and put it in drive (it was an automatic, you might have to have someone help) I carfully crawled under the bus and put a long screw driver to my ear and each carrier bearing. I found one that sounded rough and replaced it. This fixed the problem. I know what some of you are going to say, save all those comments for a novice.
There is a chance it could be a bearing in the trans. or a problem with the clutch and/or related. But I try to go after the easy stuff first if possible.
Good luck. |
Bryan |
 |
|
|
origcharger
Top Member
United States
619 Posts |
Posted - 03/30/2009 : 12:07:14 PM
|
| Also check to make sure the sections of driveshaft have been properly lined up and yokes slid on the splines so the ujoints are correctly "in phase". In otherwords each section of shaft must have the ujoint journals on each end on the same plane. |
Operating; Seven T444Es, One MaxxForce 7, One VT365, Four DT466s, One E-450 6.0 and one Mercedes in a C2. |
Edited by - origcharger on 03/30/2009 12:09:32 PM |
|
|
|
kevintee
New Member
United States
5 Posts |
Posted - 03/31/2009 : 3:56:49 PM
|
bwest,
Seeing that we are a boy scout troop instead of a school we can do the speed limit, which I do.
At first we removed the rear shaft and spun her up. We removed one at a time and with just the front shaft in it bounced all over. We ended up taking all the sections to the local machine shop and had all u-joints and bearings replaced as they balanced the shaft. We even had the brake drum balanced. Some one had replaced two of the bolts in it with the wrong ones. They were 1 oz heaver than the other two so we replaced all 4.
When we got the shafts back they had put paint alignment marks on them so I think that is OK but I will double check.
We thought we felt some play in the trans output shaft bearing but could not verify that.
I do believe the next thing is to put her up on stands and go under with the shafts spinning.
O, one other thing; Sounds this site is one that can handle some ribbing. I should fit right in.  Nothing like a little fun when figuring things out.  |
Kevin Tee.
Troop 311 Driver |
Edited by - kevintee on 03/31/2009 3:59:48 PM |
|
|
|
Wolf0r
Top Member
USA
2181 Posts |
Posted - 04/02/2009 : 06:35:09 AM
|
| These are fun to diagnose. Yes I would try the jackstand method first. Don't rule out the angles, motor mounts can wear down and change the angle. |
“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson |
|
|
|
whe8913
Advanced Member
United States
301 Posts |
Posted - 04/02/2009 : 07:54:56 AM
|
It could just be the roar of that gas engine  They used to remind me of a rocket about to take off.
From my experience, high speeds (more than 55) and school bus gearing/drive shafts, etc. don't mix well at all in the first place. A gasoline-burning bus doesn't help things either. Does the vibration get a little better when you let off the accelerator when coasting down a hill? That's what a bus I drove once did and it was the carrier bearings was the culprit.
|
|
|
|
NWCROWN
Advanced Member
USA
461 Posts |
Posted - 04/02/2009 : 09:59:58 AM
|
| Because of the speed mentioned (above 55) don't rule out a tire balance issue. Back when I worked at a Chevy dealer we had a P-Chassis van come in that had been to two driveline shops and had the tranny replaced. The tires were overlooked because, according to the customer, he didn't think that mattered on a truck. The tire balance fixed his issue. |
|
|
|
kd4jfd
Top Member
USA
1168 Posts |
Posted - 04/02/2009 : 6:15:17 PM
|
Kevin,
E-mail me with a phone number and we'll talk Scouting |
539 - Repair work in progress! |
|
|
| |
Topic |
|
Driveline Vibes
