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Bevel Gear Failure

20K views 58 replies 10 participants last post by  lookforjoe 
#1 ·
Hi guys,

been awhile...I was the guy who posted the how to on bevel gear maintenance and I have religiously changed gear oil in the bevel gear every spring. I just changed it a few weeks ago. Anyway, today I got in the car and the SERVICE light was on and the car would kind of bind up in the driveline when I backed it up. I put it on the jackstands and found a lot of slop where the driveshaft goes into the rear of the bevel gear
. I suspect that the bevel gear is toasted, but am not 100% certain (I guess it could be the joint in the rear driveshaft where it mates to the bevel gear, but I doubt it...the slop seems to be inside the back of the bevel gear).

So here is what I am thinking...if it is the bevel gear that is toast, I would like to convert the car to FWD (I have read threads where people talked about this somewhere). What I was wondering is, does anyone know of a writeup or a thread concerning this modification on a first generation V70XC? I've searched like crazy and can't find anything. If anyone can help with pointing me in the correct direction on this conversion...I sure would appreciate it.
 
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#27 ·
Re: Bevel Gear Failure (JRL)

Thanks for the reply - wheel bearings have been checked, and are good. Any advice for determining if it is in the trans, or is the bevel gear? Currently, I have ~135k on the car, and I'm relatively certain it's likely to have the original fluid in the bevel gears; would changing this fluid be an advisable first step? Not sure about the trans fluid; it is mostly red, it seems likely to have been changed at some point, but it is a little over-full (I've been planning on correcting this, likely at next oil change in ~2-3 weeks).
 
#28 ·
Re: Bevel Gear Failure (CassMori)

Change them both and see how it is in a couple of hundred miles
 
#30 ·
Re: Bevel Gear Failure (JRL)

Quote, originally posted by JRL »

Sorry, that is not "proof"
My (and all the other 2000 R's) do not have a Tracs or STC button, guess what, pop a button (either one) IN THE PREWIRED DASH and voila you have TRACS!
Yours is also prewired for it, it's just that an AWD really doesn't need a traction control defeat but they are all prewired and the software is already in the computer

plug and play m'boy, plug and play!
Your car has a working (albiet, crude) traction/STC working already in the system.
When I turn the button OFF I now can actually slide her a bit if I want to

Jim,

I respect you and all you've done for the Volvo community but I do not agree with this gospel.

If the car was meant to have TRACS, it would have came with it from the factory. The AWD system uses a mechanical torque transfer diff. to distribute the power where traction is available. Therefore, a TRACS or STC system in a AWD equipped X70 is paradox. Why have two systems working to do the same thing?

Sure, for economic reasons Volvo would not program different software into their AWD X70 vehicles, but it's deactivated for a reason.
 
#31 ·
Re: Bevel Gear Failure (CassMori)

Hi there!

Here's the way to tell if the noise is the bevel gear: It's a little tough to determine whether the transmission is making the noise or the bevel gear without putting the car up in the air and driving it so you can hear exactly what is making noise. That said, most likely it is that sleeve in between the bevel gear and the prop shaft that has worn down and as the worn "teeth" engage each other it creates noise; or the internals of the bevel gear are wearing and the same concept applies. You can be pretty sure it is something related to the bevel gear if once you start hearing the noise it gets more pronounced as you press down on the throttle and add power to the rear wheels.

I don't mean that the noise gets louder as speed/RPMs increase the way a wheel bearing does, but when you give it throttle, the AWD system transfers a bit of power (this is normal) and the noise gets louder; then when you let off the noise should still be present as things are still spinning in the AWD system, but should quiet down slightly as the power transfer lessens.
I hope that helps and is comprehensible.

Changing the fluid in the gear would not help this noise problem as the teeth themselves are already worn. Probably time to replace the angle gear or at the very least, that sleeve that I mentioned before.

Additionally, the prop shaft's carrier bearing can start to whine as it is on it's way out.

Always good to flush the transmission fluid and try not to overfill it - no need to add even more pressure to the system by increasing volume.

895meztz94:
I am actually sorry to have to respond to you again because I feel like this post was meant for nlemerise who is having an issue w/ his AWD system and arguing over how the TRACS system works on the AWD cars is irrelevant to his post, but since you seem to want to talk about it a bit more, I'll entertain.

On the 1st page of this thread, I quoted you from VADIS how the TRACS system works for the Front Wheels by utilizing the ABS system to apply the brakes on wheels that slip when the car is traveling under 25 mph. That is "gospel" and there should be no argument there. Again, this applies to 1998 model year cars.

Your XC from 99 could have been equipped with STC which is pre-wired in your car - please trust Jim on that one. However, it was an option much the way the DSTC was an option of newer Volvos like the 2005 and 2006 S40 until Volvo (and most car companies) made it standard in 2007 for safety.

Again, the mechanical side of the AWD system has nothing to do with TRACS on the 98 model or STC on the 99+ models. The AWD system transfers power from front to back based on wheel slip and the changing characteristic of a fluid in the Viscous Coupling. It is a very simple system. The TRACS has to do with keeping the vehicle moving in a straight line when slipping up a hill or braking on an icy road etc. I hope this settles this so we can get back to the original poster/other people w/ similar problems question.

Cheers.

Modified by Big Will at 6:26 PM 6-15-2008
 
#32 ·
Re: Bevel Gear Failure (895meztz94)

Quote, originally posted by 895meztz94 »


Jim,

I respect you and all you've done for the Volvo community but I do not agree with this gospel.

If the car was meant to have TRACS, it would have came with it from the factory. The AWD system uses a mechanical torque transfer diff. to distribute the power where traction is available. Therefore, a TRACS or STC system in a AWD equipped X70 is paradox. Why have two systems working to do the same thing?

Sure, for economic reasons Volvo would not program different software into their AWD X70 vehicles, but it's deactivated for a reason.

You can disagree as you darn please, the fact remains that if you remove the blank switch cover there is wiring there for a tracs switch that when installed, WORKS when pushed.
SEVERAL guys over on V70R.com have done this
 
#33 ·
Re: Bevel Gear Failure (CassMori)

Quote, originally posted by CassMori »

It sounds to me like a gear whine, and as I said, I've been told this is normal due to the AWD system. I've put about 7500 miles on since Feb (mostly highway), and the noise has not changed, either for better or for worse.
Could this be the bevel gear making this noise? And, is it in fact normal?

I concur with JRL, this isn't normal.
 
#34 ·
Re: Bevel Gear Failure (JRL)

Quote, originally posted by JRL »


You can disagree as you darn please, the fact remains that if you remove the blank switch cover there is wiring there for a tracs switch that when installed, WORKS when pushed.
SEVERAL guys over on V70R.com have done this

I back up JRL on this also and he is right been there and done it .

Also sold some extra buttons to others and it works fine
 
#35 ·
Re: Bevel Gear Failure (nlemerise)

Thanks for the advice, guys, sorry if I'm throwing the thread off topic.

Big Will, I tried the acceleration test as you suggested (several times on my way home from work tonight), but I did not notice the symptoms you described. Just the increase in noise as speed increases. And, honestly, it's not very loud, most times my tire/wind noise is slightly louder, or about the same. Sometimes it is more noticeable than others, but when I hear it easiest is when driving by an object (building, another card, etc.) with the window open; I also notice it by its absence when I slow down for a stop (this is when I realise how loud it actually is/was). I can pick it out from the other noises in normal driving, however, if I listen for it.

I'll get the car up on a rack when I do the oil change in ~2 weeks, and I'll run it while it's on there, to see if I can pinpoint the source from underneath - it should be easy to locate from that vantage point, correct? (I'll have someone in the car, to vary RPMs as needed, also).

I have also looked at the driveshaft, at the last oil change; there was some play to it, at the front/transmission end only, but nothing that seemed excessive, definately not as nlemerise described in his initial post. How much, if any, is normal for these cars?
 
#36 ·
Re: Bevel Gear Failure (JRL)

Quote, originally posted by JRL »


You can disagree as you darn please, the fact remains that if you remove the blank switch cover there is wiring there for a tracs switch that when installed, WORKS when pushed.
SEVERAL guys over on V70R.com have done this

I'm not arguing about whether it's there or not guy. I understand it's there, as I previously stated. Also, please don't explain to me the fundamentals of the systems, I know them.

The fact remains though, the TRACS and STC systems were not installed on AWD X70 models from the factory for a reason. Try to put that through your thick heads.
 
#37 ·
Re: Bevel Gear Failure (895meztz94)

First of all,

I don't think any of us appreciate being called "thickheaded" and there are other ways to get your point across that don't require insulting others on the forum.
I apologize if you were offended by my attempts to explain how the AWD system and the Traction Control System work - your posts made it seem like you didn't have a full understanding - however, I think it benefits everyone to talk about how the system works b/c there are often questions like the one that started this thread which has gone so horribly awry.

If the "AWD 70 series cars did not come equipped with TRACS from the factory" then why did my 1998 V70 AWD come equipped with TRACS from the factory in Belgium? So did every other 1998 V70 AWD that I have ever seen.

Once again, I will refer to my quote from VADIS in an earlier post (which is the software that Volvo created for Dealers and Independent mechanics to use to look up parts, repair procedures, and general and specific information about the design and function of their cars) which states that in the 70 series AWD cars that the front wheels are used in conjunction with TRACS and the rear wheels utilize the rear differential.

I don't understand why you keep arguing that the AWD cars weren't meant to have a traction control system.


What is it that you think is overlapping between the TRACS/STC and the mechanical AWD system? Please explain your thinking and I'll try to respond later. http://********************/smile/emthup.gif
 
#38 ·
Agreed they come stock in the car and its just as simple as adding the button .

I think some of us
<<<< Me
Have total stripped out a V70AWD and it was in there.
Oh and the V70T5 had it also along with my
98 V70 R also acutally both of them
 
#39 ·
Re: (Chilled Man)

Just a quick one guys...my car isn't here and I can't look at it. If the bevel gear was taken out of the car, is the car still drivable (and if not, why not)? From what I remember when I pulled the driveshaft off, it wouldn't be...but I am not certain.
 
#40 ·
bevel gear help out holding in the passenger side drive shaft.

that and it seals the tranny up
 
#41 ·
Re: (JRL)

There should be no noticeable play in the pinion output of the bevel gear. if you can move it around, the pinion gear is likely toast. It will only make noise until the pinion gear is mashed, then it will be quiet - ask me how I know.

From your description, the BG is shot, not the driveshaft - even if one of the joints is bad, it won't cause play in the BG pinion.

I got a used BG from Stranberg auto $650.

Driveshaft Doctor (coloradodriveshaft.com) sells the front D/S CV joint and /or the boot kit in either size (early/late).
 
#42 ·
CassMori,
I'm not an expert but have had and fixed a problem with the front flex joint in the rear driveshaft, saving several $100 at least. The sound mine made was a metallic ping-ping-ping coming from the console area that sped up with vehicle speed. Check the play in the front between the driveshaft and the large shaft that comes out of the bevel gear, and look for thrown grease above the cat muffler and a leak in the boot in the joint, and flex in the joint (should be none). I think it sometimes fails because of heat from the cat. It's a little hard to see, but I posted some photos above if you want to take a look. I lost the part no of the repair kit a few hard drive generations ago. This may not be the problem for you and nlemerise but it's easy to check and a cheap repair if it is.
 
#45 ·
Thank you Big Will and Mogatu'r!

I guess this is the end of the road...the bevel gear is toast...gone. I drained the fluid the other day and it looks like silver paint - full of obvious metallic particles. Anyway, I want to thank everyone because this story has a happy ending (at least as happy as I can imagine it). Through Big Will (see his posts in this thread trying to help me out) and email he sent me, I was able to find a bevel gear with 30k miles on it and a driveshaft for less than the cost of the driveshaft alone! I should get the parts this week and then I will begin the removal and install of the new parts. I suspect I will take pictures and do a write-up to help the next poor bugger remove and replace theirs!

Onto another one of my questions concerning the install...When I removed the driveshaft from the bevel gear, I marked both the bevel gear flange and the driveshaft so I could reinstall the driveshaft in exactly the same orientation. Now that I will be using another driveshaft, how do I know what is proper orientation?


Modified by nlemerise at 1:08 PM 6-22-2008
 
#46 ·
It will say front and rear plus if you install it wrong the center mounting spot wont line up

theres two 12mm bolts where the exhaust hangs from
 
#48 ·
Re: (Chilled Man)

Quote, originally posted by Chilled Man »
It will say front and rear plus if you install it wrong the center mounting spot wont line up

theres two 12mm bolts where the exhaust hangs from

No, I didn't mean front to back
I was worried that the balance would be off if the driveshaft was put on any other way than the way it was taken off. Other driveshafts I have removed I always have marked the differential, the tranny output, and the driveshaft so that I could get it back in as assembled. I guess I'll find out how picky Volvo's are soon enough.
 
#49 ·
Re: Bevel Gear Failure (2000S70AWD)

Quote, originally posted by 2000S70AWD »
Jim,

Do you think my 2000 S70 AWD is prewired for a TRACS button?

Joel
Probably, just pull the switch blank out and see...
If it is, you will see the wiring harness sitting there waiting for the switch!
Your system is no different than a 2000R and every one of those is prewired
Remember adding a switch allows you to TURN OFF Tracs/STC, it's already on and working
 
#50 ·
Re: (nlemerise)

Are the angle gear and Prop shaft both out of Juan's car? If so maybe he marked them when he removed them? If not...like you said, I guess we'll see how picky Volvos are


By the way, glad I could help. I always say that's the best part about these forums.
 
#51 ·
you cant put in the drive shaft backwards it wont fit lol

and the bolts all weight the same its pretty idiot proof installtion
 
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