awd failure symptoms Topic is solved

s70dean · Post by **s70dean** » 12 Dec 2016, 18:19

So i have this 1999 s70 awd that I've been wrenching on and when i bought it the previous owner told me he removed the driveshaft to the rear because the center support was worn and he was getting vibrations.
My whole reason for buying this car was to have awd for the winter season..So i went ahead and ordered a rebuilt shaft from Colorado Drive Shaft and installed it and the car worked fine,,,no vibrations or strange noise.
But today after the first really big snow fall here I realize I still do not have an awd vehicle!!
My simple question is What?? and Why??
My reading on this forum has lead me to believe that it's the coupler between the tranny and the angle gear had failed as i've read many people replacing the coupler a few times.. But when i called around today to a couple of trusted volvo techs in the area both of them said yes it was probably was the coupler but most likely because the angle gear itself had failed and took it out and i'd need to replace my angle gear

I haven't really done much diagnosis yet but i was wondering what is the probability of angle gear failure as opposed to simply having to replace the coupler?
Cheers

Post by **rspi** » 12 Dec 2016, 21:52

Well, the first thing I would do is get the car totally off the ground, start it, put it in drive, and see if all 4 wheels are turning.

The AWD system in the pre-2001 vehicles is somewhat passive. From what I have heard, at best the rears work at 25%. So, not really something you can tell right off.

However, if the system is not working, it usually lets you know by throwing off symptoms. Noisy as all get out, chattering, vibrations, leaking, chirping tires when parking, etc. My guess is, the system is working fine.

Post by **scot850** » 12 Dec 2016, 23:14

If the coupler sleeve fails it can damage the splines to connects to in the angle gear casing. Try Erie-VoVo for a replacement. I think there is also a Volvo used part specialist in Toronto but don't know their name. They advertised on Kijiji in the past.

The other part that could have failed is the VC (viscous coupling) which sits at the rear of the prop-shaft. As Robert advises, get all 4 wheels off the ground and see what happens.

Neil.

s70dean · Post by **s70dean** » 13 Dec 2016, 04:09

Thanks Robert, Neil
So I've never owned a awd car before so i'm not sure what performance to expect from one.
As i expected the rear tires were not being driven, i found a snow covered slippery road surface asked my girlfriend to deliberately accelerate in an aggressive manner to induce wheel spin while i stood back and observed what wheels actually spun,,,from what i could tell only left front wheel broke traction.
My next test will be to lift the car and run it as Robert suggested and observe what wheels are spinning..I let you guys know.
Cheers

Post by **scot850** » 13 Dec 2016, 15:12

Volvo does have a very un-safe test for testing the rear drive that involves having all 4 wheels off the ground and applying a torque wrench to a wheel nut at a pre-set load to see if the system is working correctly. I'm not that nuts so took it to the dealer for them to kill themselves trying the test!

Neil.

Post by **cn90** » 13 Dec 2016, 19:15

My 2 cents:

1. My 2005 XC90 2.5T AWD stripped the sleeve. I never bothered fixing b/c I know this is the Achilles heel.
Some people spend $/time fixing it, to end up with the same problem again.
So, your best bet is leave it as is, but add snow tires.
In fact, I have snow tires on the XC90 and love it.

2. The AWD testing issue. You need a 2nd person watching the tires spin.
If you don't have snow to test, there is an easy way.
Find an quiet cul-de-sac and park the car in such a way that all 4 tires are on some paper (such as the cheap yard bags), this creates a "slippery" condition.
Now as the 2nd person watches, you step on the gas.
If the AWD system works, then all 4 yard bags will fly backward.
This technique is much easier and safer than on the lift with engine running.

Post by **scot850** » 13 Dec 2016, 19:35

Nice one and a whole lot safer too (just make sure your brakes are good!!).

Neil.

s70dean · Post by **s70dean** » 13 Dec 2016, 20:54

Hey there
So tonight I jacked up the right front corner wheel and with tranny in neutral put a torque wrench on a wheel nut to see how much the viscous coupling would take...It seems angle gear passed the test with flying colors and viscous coupling slipped with a constant force of 40 plus ft lbs of twisting force applied. Left front wheel was the same.
Armed with this info i called my local factory trained Volvo guru to ask him why i can't spin the rear tires on a slippery surface.
His explaination was as rspi said,,,the early volvo awd systems are passive and in fact he was saying that although viscous coupling limits how much torque gets to the rear wheels it also kicks out a higher speeds and then your basically driving a fwd car.

Post by **cn90** » 13 Dec 2016, 21:12

To check the sleeve: an easy way is:
- Car in Park.
- Place a digital camera/smartphone on a cardboard, put it in record mode, slide the cardboard under the car so it records the drive shaft rotation. Drive the car forward about 5-10 feet.
- Park it.
- Review the video, if you see the DS rotating, the sleeve is good.

The Haldex is another story. Checking it is harder.

Want less headache: do it the way I said above, leave the car in FWD + use Snow Tires. It is like everybody else with FWD car.
I find the AWD feature in Volvo troublesome and requires so much TLC that I don't have enough love for it.