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Gear Whine / 3 link rear end

1495 Views 42 Replies 16 Participants Last post by  Harryburroughs
Hey Guys,

Ive been chasing down terrible whine / gear noise for months. I will post a link to the noise and hoping to see if anyone else has had something similar and if they resolved it. The noise is there all the time but cannot really hear it until 50mph then when she's in overdrive its overbearing... If I dip the clutch the noise goes away.

I have a quick performance 9 inch rear end with less than a 1000 miles on it... Its got 3.70 Motive gears along with a SOT 3 Link kit. My current shop said it may be the diff or 3 link so I had the centre section removed and the back lash set up again, axle straighten and I still have those dam noise. Quick performance are blaming the suspension company, the suspension company have said they have not had this issue previously so im just in the middle with a great driving restomod which I cannot stand to drive on the freeway....

Work ive done...
Suspension is new.
Diff is new
Back lash has been set up again
Axle has been checked and straighten
Axle bearings have been replaced
Tyres are brand new
Driveshaft has been balanced
New UJ's

Cheers.
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That's interesting. I didn't know that. Glad you mentioned it. I was doing some research after reading your post and it seems there might be 2 lines of Motive, the high end made in Italy and second tier made in Asia. I have a set of Richmond gears in the box I plan on using. It looks like Richmond has a second tier version called Excel. Looks like Richmond still has a facility in SC. , hope they work out. (y)
I bought a set of the low end motive gears for my truck and they whined from day one and tried to adjust for it and it never went away. I only paid $25 for them so other than my time it was a lesson learned not to buy cheaper gear sets. I eventually installed ford gears in my truck and no more noise.
 

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Discussion Starter · #22 ·
I bought a set of the low end motive gears for my truck and they whined from day one and tried to adjust for it and it never went away. I only paid $25 for them so other than my time it was a lesson learned not to buy cheaper gear sets. I eventually installed ford gears in my truck and no more noise.
The motive gears aren't cheap. I think my next move is to get a set of OEM gears but its so confusing when people are blaming everything else but the axle.
 

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The motive gears aren't cheap. I think my next move is to get a set of OEM gears but its so confusing when people are blaming everything else but the axle.
If it was the SoT 3 link design it wouldn't be "just you" with the issue, it would be everybody. You only have one rubber end on the link bars and none on the Watts link so more noise is going to transfer. I don't think it's bad on my car. My SoT setup is way quieter than any Fox body or Camaro I have been in with a factory link type rear suspension that has had the bushings replaced with Poly or heim joints. On the other hand you have a gear set with a gear ratio from a company with known noise issues with that setup.
 

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OP its very clearly gear whine - common issue with aftermarket ring and pinion sets. I would look at a US gear ring and pinion set in one of the the known 'quite' ratios.

The mesh photos look ok, but it dosent matter sometimes regarding noise. When the backlash was reset was it changed? Was the runout of the ring gear verified ok?
 
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The 3rd Link is transmitting the noise from a faulty/noisy gear set.

We've sold 100's of 3-Links and Strange built center sections. None of them come back.

I know you like to drive your car. If you want to enjoy it again and fix this issue, I would try a complete different gear set built by someone different than the previous manufacturer/builder.
 

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Discussion Starter · #27 ·
OP its very clearly gear whine - common issue with aftermarket ring and pinion sets. I would look at a US gear ring and pinion set in one of the the known 'quite' ratios.

The mesh photos look ok, but it dosent matter sometimes regarding noise. When the backlash was reset was it changed? Was the runout of the ring gear verified ok?
I sent the centre section to a local shop and they said everything was ok...
 
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I sent the centre section to a local shop and they said everything was ok...
Well it's obviously not based on the noise in your video.

I would try a different ring and pinion set, new bearings, all from a different supplier and built by a different builder.
 
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Do you know anyone that has a 9" third member that you could install to prove that what you have is causing the issue? It's just a thought.
If I can find some local enough I was going to try that.
Good idea and one that I've already suggested in an email exchange. Annoying problem for sure Harry but myself and the brain trust here are all pointing to the gear set.

Maybe you can find another Mustang owner, perhaps at a local meet/Facebook group. Maybe throw them some money and see if they'll let you pull their center section out and try it in your car. Few hours of labor and some gear lube and you'll have your answer. Use Lubelocker gaskets and you won't have to mess with RTV again!
 

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Wow. I’m outta here. Got better things to do.

ex-Global West GM
1991-1995
 

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I came across a article about 9” gear whine. What the article said was what makes the 9” strong is what makes it whine and that’s the hypoid angle. With more tooth contact comes more friction and whine from the friction. They went on to say with a lot of today’s builds with roll bars and suspension, it can act like a tuning fork amplifying the noise.

As far as setting up the gears they said you can set them up contact patch as per specs but still be noisy. What was suggested was more of trying different settings for what works best. The shop has their own rear axle dyno to test and make adjustments
 

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Discussion Starter · #35 ·
Well it's obviously not based on the noise in your video.

I would try a different ring and pinion set, new bearings, all from a different supplier and built by a different builder.
Yes I agree. something isn't right. Its good to see people with the 3 link without the problem so I can show the shop this. so I dont just get 'this is what happens when you add solid joints and a 3 links direct to the body' or 'its normal for a 3 link to to this'
 

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I know from racing that solid joints add noise but not the hellacious whine that you're experiencing. I have no business spending your money, but if I did, I'd be calling Strange Engineering.
 

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Looking at that pattern, I would pull the center and remove the pinion and recheck all the specs and preloads. I used my center section as your example, pointing at the spot that looks suspect on your setup. Do you notice the top of the your tooth doesn't have any pattern on it, the half moon is below the top edge of the tooth. It looks like the pinion gear is centered, but too deep on the ring gear. That would make the pinion and ring too close, and tight (and whine like crazy). Your ring preload might be overly tight, or your pinion too deep, or a combo of both. Understand, a change of .002-3 is noticeable.
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Discussion Starter · #39 ·
Not to mention they’re only solid on one side. I agree with @Nailbender. Or you could raise hell with QP and make them send you 3.89’s.
Ive spoken back and fourth with them for months. they've just blamed the solid joints. I guess the only way to find out is replacing the gears with some which hopefully dont whine as much.
 

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Ive spoken back and fourth with them for months. they've just blamed the solid joints. I guess the only way to find out is replacing the gears with some which hopefully dont whine as much.
Dealing with QP can be like pissing in the wind. If you whine enough they will do anything you ask. I PM with forum member who has had similar issues as I have had and has the patience to deal with QP. I have a relatively short fuse and Strange Engineering is 60 miles North West of me and Moser 120 miles South. Quality of life.
I have the exact same rear suspension as you with 3.25 gears from "QP" and zero whine. As I have stated repeatedly, you're gonna get a little bit more noise with less rubber insulation, but it has not been offensive in my case.
 
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