Bevel Gear / Angle Gear...Gone Bad?

DAK · Post by **DAK** » 15 Jun 2012, 10:34

Hello Again... ('98 V70XC, 150Kmi) ... finally got around to figuring out an intermittent problem when turning at low speeds (tight turn radius), and why I would get a rear wheel shutter or wheel skipping during turns like this.... I went through the rear parking brakes - adjusted several different ways and several times - again, IN MY MIND, the problem went away for a while. The last time I tried this- it didn't go away. All fluids were changed out, rear differential appears to be OK from what I can see, Viscous Coupling tested OK, wheels are new and same diameter, etc....

So...I broke down and removed the Prop shaft, again. The noise, wheel skip, etc...went away and hasn't come back. My guess is the Angle Gear is bad? (FYI...there was no noise from the gear box when the shaft was in, no whining, clunking, etc....)

I see there are some options for rebuilding these, or I have a line on a used one from a salvage yard. I saw that the splined coupling may be the problem child? (There doesn't seem to be excess bearing play, no seal leaks, etc...on the gear box...) If so, would this change out of the splined coupler be preferred to putting in a used gear box? (Any good repair links are appreciated!)

Also, can someone give a quick overview of why this is happening? My understanding is that the Angle Gear is a direct mechanical setup to turn the Trans rotation 90deg's and move it through the Prop shaft to the rear Diff. I understand that the Transmission would allow the front wheels to spin at different rates when cornering, and the Rear Diff allows for this same rotational difference, so.......why would the Angle Gear cause this shuttering/skipping of the rear wheel since (in my mind again) the rear differential should allow for some freewheeling? Is the Angle Gear Binding and causing the the Prop shaft to rotate at a rate that the Rear Diff cannot overcome? Why are these gear boxes so weak? (All the same old questions...)

Thanks for the help - any solid advise would be great regarding throwing in a used gear box, or just replacing the splined coupling, or other options(?)....

Post by **jimmy57** » 15 Jun 2012, 11:34

No the viscous coupling is the much more likely candidate. The VC is supposed to yield with some resistance to slow speed speed differences between front and rear axles and stiffen to transmit torque to rear when the front slips and overspeeds the rear. The VC has a silicone gel and wavy discs alternately connected to input and output in the disc stack with the gel around them. The gel seems to be weeping out over time and leave the gel more as a powder and locks up the VC.
You can test by jacking up rear and putting a breaker bar with the right socket on the nut for the flange where you undid the prop shaft at rear. With the parking brake set TIGHT you should be able to turn that nut with constant force and should move smoothly.
Dried gel will make it impossible to move with normal human force or it will move with high force incrementally.
The intermittent part is likely that it does this after a long highway drive or after short drive with lots of turns or even after a few 180 turns at the ends of parking lot isles when the other conditions are not met.

Post by **JRL** » 15 Jun 2012, 14:24

Or a bad propshaft

DAK · Post by **DAK** » 18 Jun 2012, 07:34

Thanks for the replies...

*There is no fluid leaking, or ever leaked from the VC - all appears to be dry and clean in this area
*Tested the VC per the Volvo Procedure several times - both sides lifted (one at a time), and it appears to be right on spec' for torque indications
*Has anyone rebuilt the Angle Gear versus putting in a used one? (New ones are about $1500, so I don't think that is an option right now.

Thanks Again

DAK · Post by **DAK** » 18 Jun 2012, 07:35

....and Prop shaft was replaced with a CO rebuilt - all is good there, as well.

Thanks

Post by **JRL** » 18 Jun 2012, 07:46

Bevel gear's usually don't "shudder", they whine (bearings going) or just break

DAK · Post by **DAK** » 18 Jun 2012, 09:21

Would a binding Bevel Gear cause the Prop Shaft to lock up and the rear wheels would skip/shutter on tight slow turns? Or, is this more of a sign of the VC?

(Just trying to narrow it down so I'm not throwing parts at a problem....thanks to everyone for the inputs and advice.)