740 prop shaft movement

jamesinc

My 740 has some vibration in the prop shaft. Based on the amount of play in the shaft, I think the centre bearing is worn out.

My main concern is the apparent play in the output shaft of the gearbox (near the end of the video). Is that normal?

Spac

The bush in your auto's extension housing is buggered, and is most likely your source of vibration. Quite surprised it hasn't chopped out the rear seal and isn't pissing out ATF. Don't know what is involved in replacing it on an AW7x.

The rubber support for the centre bearing is tired. Doesn't mean the bearing itself is buggered. If its like a 140 or 240 (and im pretty sure it is), the rubber can be replaced fairly easily - a much easier task than dealing with the bearing itself.

jamesinc

@Spac I actually have a full set of U-joints, bearings and rubber boot. Figured I may as well just renew the whole thing at once and not worry about it again. Are you referring to the tailshaft bushing mentioned in this article? http://www.volvoclubofbc.com/technical/tailshaft_aw71.html

jamesinc

Man I just called up the dealership and the bushing is NLA.

http://www.ebay.com/itm/141001363226?item=141001363226 maybe?

Spac

That article is talking about exactly the bush. Just to continue the persistent theme: I have a spare AW71 (72?) here. Worked great, but don't know if the bush is good or not.

jamesinc

Nah my AW71 works fine. I don't mind doing the bush, looks like it'll only take a couple hours.

jamesinc

Okay so updates. In addition to the vibration, recently there's been a big clunk up the rear end under acceleration. I had a dig around, and the upper torque rod was LITERALLY HANGING BY A THREAD. The only reason the bolt hadn't left the assembly altogether is because the rubber bushing was gripping onto it. Good guy bushing.

So I put it back in, smothered it in threadlocker, tightened it to infinity Nm, and the clunk is still there.

I did one of those weird things where kickdown engages moments after the car shifts into second, and it made the most ungodly clunk and the acceleration kicked me in the face bigtime.

So yeah at this point I'm not sure. The bushings at the rear, while old, don't look worn out. Nothing looks bent. Shrug what do? Is it still just the prop shaft/gb extension housing bush?

Tigabu

Basic question, but did you check all other bolts/bushes for tightness or bentness/brokenness? Can't remember if it was you or another Bruce who had undercar sealer/deadener hiding a broken mount on the body. My 88 auto wagon did the same thing and it was also a torque rod but almost impossible to detect. I checked all the other components and found looseness of vary degrees...

jamesinc

I checked everything I could see. Did you find it easier with the suspension loaded or unloaded? I put the rear on ramps for this as I thought it would be easier with the suspension loaded.

Tigabu

I did both, to cover sprung and unsprung

jamesinc

I had a wobble around with the car on stands and on ramps, and there's nothing obvious.

The torque arm bushings look tip top - no cracks, no deformities
Bump stops look fairly new
Checked every bolt, everything tight
Shocks nice and firm, no play

Had a mate bounce the car while it was on the ramps and couldn't get it to clunk.

The consensus with my mates is that a wobbly propshaft is the cause of all my problems, so I'll leave the rear end alone unless the clunks persist after I've replaced all the worn components on the prop shaft.

Here's some pics:

Looks like I have a Dana 1030 axle?

Panhard rod upper mount:

Panhard rod lower mount:

Tigabu

Well, at least you are closer to knowing what it is by knowing what it isn't :)

Spac

So I double posted, deleted one and both went?!

The "twin rib rule" is rubbish.

Its true that all 1030s are single rib, but 1031s can be either twin or single rib.

Pretty sure all 700+ cars have 1031s.

egads (she/her)

Spac said: So I double posted, deleted one and both went?!

Only double displays, one save to the DB displays twice. Clears up when you go back in (in my experience).

Tigabu

und mein!!!

nickm

No sticker on the Diff. Should be on the passenger side might need some thinner on the goop

Poly Panhard bar is an easy mod. Uni joints good? Torque rod bolt falling out....common

precopster

If your rear springs have sagged at all the distance between the diff and the gearbox increases therefore creating the vibration because the prop-shaft isn't inserted as deeply into the splined part of the gearbox. If you want to repair this without changing the rear springs have someone machine up a spacer of around 5-8mm thickness which will insert between the prop-shaft and the differential and the prop-shaft. To work out the thickness of the shim reguired get under the car while someone jacks the rear to a standard height and see how much the tailshaft re-enters the gearbox. This measurement will be the thickness of your shim. BTW first post here so hi one and all.

Tigabu

Yoda! ;) Welcome

egads (she/her)

precopster said: BTW first post here so hi one and all.

Hi, glad you made it over!

jamesinc

@precopster thanks, that is some solid advice! And welcome