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Diff gear whine - 1030 rear axle

aristg

aristg

El Greco Capitano
300+ Club
Joined
Sep 19, 2013
Location
Greece
Here is a really "new" noise problem for me, with a "time wait" solution as it seems, as we concluded with Gary. Maybe someone else has the same problem or even a solution so, share it !!

The past year i had my open diff replaced with a TrueTrac, as well as the carrier bearings and cover seal. Everything was perfect, no noises or whine. Backlash was set "textbook" perfect -luckily- according to the greenbook. I had it used for over 2000 kms, while not really abusing it. My wheels were 14's with 185/60/14 old tires.

So a month or so ago, i decided to go poly all around, R-brakes mod on the rear (and front) - while kept the old rotors hat to use it as a e-brake (solution by Homer), use 35mm rear hub/wheel centric spacers to install 8,5 inch 30 offset wheels with 235/40/18 tires. Also i used a 25mm rear IPD sway bar, adjustable TRs and panhard (that in the beginning i had them set at equal length as the original - keep that in mind for the "noise"). However, despite all these mods, the diff-axle-pinion-driveline-etc was not at all altered! Not even changed diff oil !

When i took it for a test drive there was a noise with the following characteristics:

- Starts at 80 km/h no matter which gear peaks at 90-100 and disappears at 120-130. No connection to the revs, no matter if i am on 3rd 4th or 5th
- It is heard ONLY when on gas with gear engaged and clutch not pressed, when i let it go it is not heard. (so i think this proves it is no bearing .. since would do it when gaining or loosing speed ..)
- No matter if it is a turn
- It is definitely not road noise or anything "external" to the car.
- As said above changes over speed, but only when on gas and not pressing the clutch ! So if i am on a downhill accelerating and press the clutch it is lost. Same when loosing speed.
- I noticed that when i start moving from stop or sometimes when i press the clutch a sound is heard once. Something like two metals are hit and lock together, no echo of course, just a short sound. Something like if there is a gap on a u-joint.

After seeing all these, i tried to test some things:

1) Raised the car on jacks where i put the 2 jacks under the rear axle so that it takes the weight of the car on its own springs. NO noise at all..
2) Changed the rear u-joint -proved that was not needed though- with a new one. No real change
3) Opened up diff and found that backlash is perfect as in the first moment. 0.15mm. It is even perfect by volvo's specs. The teeth are used on all their length, as back then, so i could see nothing more in there.
4) The big change: Adjusted the panhard (with the use of wheel alignment machine) and TR using a level indicator: +3 on the gearbox plate , -3 degrees on the diff plate , got them in parallel perfectly. Also checked the u-joints with this guide http://www.hurst-drivelines.com/files/Universal_Joint_Alignment_Proc_111606.pdf suggested by Gary and everything seem in order. The calculations gave me 1 degree u-joint operation which is good! The noise changed a bit but not much. Reduced by 30%.
5) Used Motul 90PA Mineral for lsd + 200ml of MotorCoat. Not much changed. Maybe a 10%.

I have been driving with this setup for 1000kms, Gary suggested that this will go away since the gears may re-mesh after 5000 miles or so.. Is it a waiting game ?

So after all these .. my question is "why now" ? Why is the noise introduced now, since i changed nothing in the diff ? Anyone can think of any reasons?
 
My suspicion is gears remeshing since everything else appears to be in line. Can't think of anything else really. One of the downfalls to reusing gears.

No noise with the rear up in the air may be due to minimal load on everything would be my guess.

One thing that just clicked though...you had the TT in while still running the old tires correct? Any noise at that point, or only when you swapped to the 18's?

Has it changed at all since you got it on the road?
Positive it's diff and not possibly coming from the M90?

For those just jumping in, Aris is in Greece so yeah, he gets the cool stuff. Car is a modded 242T with a bunch of goodies from here in the states. We've been building this thing up, between my parts sources and suggestions and his blood, sweat, and time. :)
 
I've seen several threads over the last 5+ years on TB, whereby the NVH sensitivity of the 2 series rear assembly suddenly peaked......in every case, the owners had installed poly bushings. I specifically remember a couple threads (can't recall whom) where they were on the verge of madness.....grabbed a couple JY upper torque rods that still had OE rubber installed, and the waters went quiet.

OP, I'm doubting your diff. setup has caused anything (the forcing function) that wasn't already there.

Find some spare TRs with rubber, and test. Did you install 100% poly, including the rear lower control arms also?
 
change back to rubber and see if the noise goes away...

You could try one of the factory dampened driveshafts.
 
@Gary: I run the car with the M90 and same of the rest setup for 2000kms with the 14s and there was absolutely no noise. As i mentioned in the initial post, there were specific things that i changed: poly, rods, panhard, sway, R-brakes, wheels, spacers. Before that the car run with no problems (noises) with the same setup.

@DET17: I also suspect the polys transferring noise, but it is definitely the diff. Weird thing is though when the car is lifted off the ground there is absolutely NO noise at the same wheel speeds. My feel is that since the distance between wheels got bigger the leverage through the two stub axles got bigger resulting in different gear-meshing-force. However we are talking about a noise so loud (initially) that covered the sound of a 3" free flow exhaust .. Could this be silenced by some rubber bushings ?

@blkaplan: i already have the thick rear stock driveshaft with the rubber "suspension" in it. But anyway this was not modified at this point.

My TR's were the ones that IPD sold in the past with the yellow poly bushings. I could go back stock if i bought some new rubber bushings and fitted on them. I need to make sure though before i ruin the polys ..
 
@DET17: Forgot .. Yes it is now 100% poly .. including the lower arms ! I used the full SuperPro kit for the 200 series ..
 
I've done just about the same mods that you did and my diff suddenly became noisy. Poly is crazy stiff and sends everything into the body. That's the price to pay for response and precision in the handling department.

The only difference is I haven't done anything with the diff, it just didn't make any noise with "stock" suspension, and now with all poly/boxed arms/adj bars it wines. Nothing unbearable, but alarming the first time I heard it.
 
Only issue I have with it being the poly...even my 140 is running full poly and I have absolutely no whine in the diff, either with the stock gearset or the new Richmond gears when the TruTrac went in, and those are also with the smaller hourglass style torque rods. Granted the ones Aris has have the yellow poly which is a touch stiffer, but still, it shouldn't overpower the exhaust note.

Just my .02...
 
At last i managed to capture a video with the whining noise.

I tried to stay at low boost, very low throttle, so that i capture the noise between 90-120 or 130. At some point i changed gears, let the throttle unpressed, accelerated and decelerated a bit. The noise always remains the same (@same speed) and depends on load and speed.

As far as i remember the gears on the video are 4th and 5th.

https://youtu.be/lD7Oe9gNF9s

I have a feeling though that as time passes and the car is used with this setup, the whine is getting quieter.
 
I'm going to say that poly bushings have nothing to do with it. My buddy has a 242 with the same noise, at all speeds though, and he has all stock rubber in the back.
 
Did you change the pinion bearings and check the pinion preload?

The carrier bearings see much less wear and abuse then the pinion bearings do.
 
No, i did not. I did not mess at all with the pinion. I only changed the diff and the carrier bearings + spacers to adjust backlash.

But remember the case: this noise appeared suddenly when i changed to R-brakes + big wheels + poly + spacers, without messing with anything else. Before that i had thousands of kms with no noise at all.
 
aristg said:
No, i did not. I did not mess at all with the pinion. I only changed the diff and the carrier bearings + spacers to adjust backlash.

But remember the case: this noise appeared suddenly when i changed to R-brakes + big wheels + poly + spacers, without messing with anything else. Before that i had thousands of kms with no noise at all.
Click to expand...

It was making the noise the entire time, you just couldn't hear it before.

You should do the pinion bearings and crush sleeve.
 
I dunno Ben, sounds way too much like gear whine. Pinion bearings as part of the work perhaps, but it just sounds like gears that are wearing into a new spot, even if just so slight.

I had the same thing when I did the trutrac install in my wagon. Same gearset, new bearings all around, took it about 10k before they had really quieted down, still hear a little whine every once in a while.
 
Any noise it made with the old bushings will be amplified with poly.
I'm sure that rear is making noise, it's pretty common when you reuse gears to have noise.
I would do what Ben says, replace the pinion bearings, races and crush sleeve. That may help.
otherwise you can always pick up a new set of gears and install them.

Also keep in mind that after you make changes to a car you are going to be far more sensitive to any noise or vibration you think might be new.
 
badvlvo said:
Any noise it made with the old bushings will be amplified with poly.
I'm sure that rear is making noise, it's pretty common when you reuse gears to have noise.
I would do what Ben says, replace the pinion bearings, races and crush sleeve. That may help.
otherwise you can always pick up a new set of gears and install them.

Also keep in mind that after you make changes to a car you are going to be far more sensitive to any noise or vibration you think might be new.
Click to expand...

:nod:

I just put together a 1031 for vwtechs 245 ls powered drift car, he has my spherical torque rods on his car and spherical axle bearings. He has had a noisy rear end for the last 2 years. After installing new pinion bearings and a solid shim for the pinion preload, his rear end is dead quiet with using spherical torque rods which transmit any noise the rear makes.
 
gsellstr said:
I dunno Ben, sounds way too much like gear whine. Pinion bearings as part of the work perhaps, but it just sounds like gears that are wearing into a new spot, even if just so slight.

I had the same thing when I did the trutrac install in my wagon. Same gearset, new bearings all around, took it about 10k before they had really quieted down, still hear a little whine every once in a while.
Click to expand...

It probably is the gears whining but they could be whining because he could use fresh pinion bearings.
 
When i did my diff, truth is that i was afraid to mess with the pinion, since i was told that it is a huge pain to get it back in correctly. Also Volvo's instructions on the service manual seemed too difficult to follow, since it needed some special tools, which i don't have, plus i understood that the whole axle should be removed to do it. So i left the pinion alone..

Questions:
Is there an easy way to do it? Any instructions with common tools ?
Do i need to remove the axle ?

Plus one more: As you may know, i did a big project of restoring my car. After i finished with the engine + gearbox part of the project, i needed to have my engine run for 4000 kms with a rev limiter @ 4500 rpm and 0,5 bar boost (phase 1). When this period finished, i installed the brakes, poly, wheels, spacers, TRs etc (phase 2)
Before started the project i run the car for another 2-3000 kms with the TT and the diff mods only.

So if we see the facts:

-Pre-project period with TT: no noise
-Phase 1 of project finished: no noise
-Phase 2 of project finished: noise

I understand that i should have done more to the diff but the logical question is "why on phase 2 and not earlier".

So i assume that something was changed (TR angles hence pinion angle, poly, something else like weight due to spacers/wheel distance).

I ruled out TR angles since i got them initially at the same length as in stock, no change.

So poly remains, or "something else option". I will try my old TRs despite being a bit ruined, to check poly option, and shoot a video again.

The "something else" option falls into Gary's words, which the car may be used to and stop after a while..
 
Not yet. Just tried stock length. My next move is to swap to the stock to rule out the poly thing.
 
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