Driveshaft balance/vibrations/angles

[allan5oh]

Having problems with vibrations. They come on after using a lot of power, going over the crest of a hill for example. Just a real quick VRRRRRRR then it's gone.

1) My tranny mounts are probably needing of replacment

2) I think the carrier bearing(right wording?) is too low

3) My ride height is EXACTLY where it needs to be

I think I should balance the d/s's, raise the carrier bearing(I say it's low because my dad has a truck with exact same driveline, and his is a notch higher, plus the angles don't look good) and maybe change the tranny mounts (huge job on a volvo).

It also seems like if I lower ride height a bit(lower then spec) the vibrations go away.

What do you folks suggest? What angles should I be looking for?

The yokes on the rear d/s should both be pointed "up" correct?(in comparison to the d/s) How much?

Any tips/tricks?

[bob h]

Having problems with vibrations. They come on after using a lot of power, going over the crest of a hill for example. Just a real quick VRRRRRRR then it's gone.

1) My tranny mounts are probably needing of replacment

2) I think the carrier bearing(right wording?) is too low

3) My ride height is EXACTLY where it needs to be

I think I should balance the d/s's, raise the carrier bearing(I say it's low because my dad has a truck with exact same driveline, and his is a notch higher, plus the angles don't look good) and maybe change the tranny mounts (huge job on a volvo).

It also seems like if I lower ride height a bit(lower then spec) the vibrations go away.

What do you folks suggest? What angles should I be looking for?

The yokes on the rear d/s should both be pointed "up" correct?(in comparison to the d/s) How much?

Any tips/tricks?

Is this happening each time you move from "accel" to "decel or coast"?

If you've already determined that you have worn rear engine mounts, they obviously need to be replaced.


I'm expecting you've already looked at the basics; endplay at each u-joint on each 90 degree plane?

Take a close look at the u-joint cups inboard of the yoke ears to make sure there is no tiny cracks on the outer walls.

Check closely for loose yoke nuts and straps (1/2 round yokes?).

Check the drive axle suspension for shifting; loose u-bolts, etc.

Do you have an angle gauge to measure the shaft/yoke angles?

[allan5oh]

No gauge, but I'm sure I can get my hands on one.

It vibrates when the cruise comes off full throttle to maybe 5-10% throttle. Happens maybe once a day.

I know the front pinion on the front diff has a little bit of play axially, but the transmission shop said it was fine.

I'll check the rest tomorrow.

Thanks.

[allan5oh]

Checked everything out, seems ok except the hanger/carrier bearing(can never remember what it's called).

It was way too low. Apparently the driveshaft is supposed to be level from the tranny to the rear, and it was way down. Raised it up 2 bolt holes, and man the difference is unreal. What I thought was the road was really the front yoke on the front diff. Every time I hit a bump, it would vibrate a bit, but it felt like road bumps. Sort of weird to explain it.

Also, the wear pads are worn, causing the front yokes on the diffs to have too much angle. I'm replacing those.

This volvo suspension is weird, as the pads wear, basically you're supposed to lower the ride height with them. Otherwise your angles go to hell.

Don't have angles, but I know they're supposed to be 2.5 degrees and 13 degrees. I'll get them checked after I change the wear pads. I'll probably have to reset the ride height as well.


Do you have any idea what kind of angles the yoke off the tranny and the yoke off the carrier bearing are supposed to have?

[Bandit102]

In my experience, you do NOT want your driveshafts to be perfectly straight (meaning 0 degree angles). If the U-joints can't 'work' you will wear them out very very quickly.

[allan5oh]

Yeah I know, but nowhere in the specs does it say what the angles are supposed to be. I guess they never counted on someone re-installing the bearing way too low.

The problem is the front yoke never sees any angle from the suspension either, the angle stays the same 100% of the time.

[NotSteve]

Can't you just measure another truck and use that as an example?

[allan5oh]

The problem with that steve is the other truck isn't necessarily right.

But it did get the ball rolling. I looked at my dads truck, which is almost exactly like mine, and noticed the carrier bearing was much much higher.

The problem is even slight wear on the wear pads will change the angles of the pinions on the diffs. Damn Volvo and their suspensions.

[logical]

Driveshaft vibrations come from the ujoint angles not canceling each other out. In order to set the angles you will need to know the angle (as if you draw a straight line through you tranny) and then your 1st shaft and your 2nd shaft and your diff. the working angle on your 1st joint is the difference between the tranny and the shaft. (ie if the tranny is 10 and the shaft is 12 you have 2 degree angle) If one goes down and the other up then you would need to add the two numbers together.
Now then to get the ujoints to cancel out each other and not vibrate, you need to have the working angle on each shaft + or - 1 degree of each other. Remember that you have a shaft off the back of your 1st diff to make sure it doesn't get out of wack. Make sure that all the mounts are in good condition before you start, and check the play in you slip yoke and your u-joints, if any of these items are worn out they will need to be replaced before you begin setting up your angles, also make sure the joints are all in time, if someone removed your slip yoke and did not put in back in time you will have a vibration from that. Take them to a competant driveline shop that has a balancer and get them checked and fixed if you don't know how.

[sbatson]

I posted in new drivers but probably should of posted here but I'm having the same problem as allan5oh with the grinding noise in my 05 century, what is wrong? Also with a trailer on ( loaded or not) it sounds like it bottoms out in the rear when I hit a bump, small or big any ideas?

[Doghouse]

When did you have the carrier unit lowered or adjusted. The housing isn't supposed to be adjustable. It shoud be mounted to the frame. I suspect you have a funky u-joint and changing that angle just took away the sound, but not the problem.

[allan5oh]

It is mounted to the frame but has several different mounting holes.

It seems much better now. I'm also going to change the leveling valve, I noticed my ride height seems to vary too much.

All of the yokes are in phase as well, thanks for the tip.

[allan5oh]

I bought one of those magnetic angle thingys, but am confused on how to use it.

How do you calculate yoke angles where the other side of the yoke goes into the tranny or the diffs? It's impossible, as there's no flat surface on the yoke.

The way I understand it is this:

You want the tranny yoke to be level, with the first driveshaft level to the hanger bearing. From there it should go down slightly to the front yoke on the front diff. That d/s is measuring 2 degrees UP to the first yoke. Then the rear d/s should be 13 degrees, both yokes pointing slightly "up" in comparison to the d/s.

[Doghouse]

I'm not sure about that. My 9400 has a solid set between the trans and the carrier bearing, then after the CB the shaft dips at a shallow angle to the frint diff, then the front to rear diff line up at a steeper angle.
I would check with your dealer.