Is your NVH (gear noise) almost unbearable with stiffer/solid mounted rear suspension parts?

[Cory S]

My buddy has been through 3 gear sets and an entire new rear end as well. After an outing at the drag strip, his rear end gear whine gets ridiculously loud (once the gears break in).

He has cradle lock outs, solid mount control arms and diff bushings etc. I have suggested to him that the increased noise is because his rear suspension has almost zero isolation into the unibody, and 70% of the massively increased noise is indeed from the changes he made.

I have read numerous postings about this being so bad in cases, that many wish they had never done so many of these suspension mods.

I am trying to save him $7500.00 because he wants to do SRA conversion to get rid of the noise.

So does anyone have an really bad rear/gear noise on video or a good detailed example of this so I can show him, that's where the problem is?

Sponsored

 

[Cobra Jet]

Cory,

Has he swapped the entire pumpkin out for another (new or used)? If not, it’s possible the current pumpkin has a manufacturing defect, which could explain the constant problems.

Is he also using TIMKEN bearing assemblies when rebuilding the rear? Or can you tell us what gear sets he’s buying that are self destructing?

 

[Cory S]

Cory,

Has he swapped the entire pumpkin out for another (new or used)? If not, it’s possible the current pumpkin has a manufacturing defect, which could explain the constant problems.

Is he also using TIMKEN bearing assemblies when rebuilding the rear? Or can you tell us what gear sets he’s buying that are self destructing?

The first two sets were new KOYO (OEM) bearing sets. He’s been building and setting up rears for 25-30 years. They are perfect. After the 2nd set he did, 2 launches at the drag strip and the gear noise gets 50% louder. So he bought a brand new FRPP loaded housing. Drove it fine for 700 ish miles on the street and the noise is barely audible. Went to the drag strip. 2 runs. Gear whine increases again. Returned the new center section, and setup yet ANOTHER ring and pinion..(KOYO)…… then yesterday, leaving the track the increased NVH was back for the 4th time. Note*. This time he had a machined solid spacer made, because he thought it was because of the pinion losing pre-load. Didn’t change a thing.

I personally believe once the ring and pinion/bearings seat (mostly on launch at the drag strip) in after a large load, the surfaces mate closer together and create much more transfer of sound. This coupled with his cradle lockouts, delrin/solid bearing suspension components, amplify everything by 50-60% because there’s now basically zero isolation from the differential/housing/subframe etc to the body.

 

[Cobra Jet]

The first two sets were new KOYO (OEM) bearing sets. He’s been building and setting up rears for 25-30 years. They are perfect. After the 2nd set he did, 2 launches at the drag strip and the gear noise gets 50% louder. So he bought a brand new FRPP loaded housing. Drove it fine for 700 ish miles on the street and the noise is barely audible. Went to the drag strip. 2 runs. Gear whine increases again. Returned the new center section, and setup yet ANOTHER ring and pinion..(KOYO)…… then yesterday, leaving the track the increased NVH was back for the 4th time. Note*. This time he had a machined solid spacer made, because he thought it was because of the pinion losing pre-load. Didn’t change a thing.

I personally believe once the ring and pinion/bearings seat (mostly on launch at the drag strip) in after a large load, the surfaces mate closer together and create much more transfer of sound. This coupled with his cradle lockouts, delrin/solid bearing suspension components, amplify everything by 50-60% because there’s now basically zero isolation from the differential/housing/subframe etc to the body.

He's certain the NVH isn't from the driveshaft center support bearing (if still on a two piece factory shaft) or that the front trans flange isn't damaged?

Just trying to think of other parts along the driveline that would contribute to the additional or persistent NVH. Also has he read through the huge "driveshaft vibe" thread? There were instances where folks had brand new warranty replacement pumpkins installed - then after some accursed miles, the roar or NVH was back and pronounced again. In some instances the NVH is really pronounced in the 55-75 mph range, if exceeding 80 it disappears and if going lower than 45 it also disappears. There was a LOT of DIY fixes and tech that had helped others in that thread.

Mind you, it's a very large thread - so gotta be patient weeding through it, but like I said there was quite a bit of tech and pics embedded in it.

 

[Cory S]

He's certain the NVH isn't from the driveshaft center support bearing (if still on a two piece factory shaft) or that the front trans flange isn't damaged?

Just trying to think of other parts along the driveline that would contribute to the additional or persistent NVH. Also has he read through the huge "driveshaft vibe" thread? There were instances where folks had brand new warranty replacement pumpkins installed - then after some accursed miles, the roar or NVH was back and pronounced again. In some instances the NVH is really pronounced in the 55-75 mph range, if exceeding 80 it disappears and if going lower than 45 it also disappears. There was a LOT of DIY fixes and tech that had helped others in that thread.

Mind you, it's a very large thread - so gotta be patient weeding through it, but like I said there was quite a bit of tech and pics embedded in it.

He’s gone through the whole aftermarket driveshaft trial. The QA1 he tried first killed his rear end. It was out .022”. He’s been back to the stock unit since then.

 

[shogun32]

So does anyone have an really bad rear/gear noise on video or a good detailed example of this so I can show him, that's where the problem is?

the Steeda and BMR diff 'pucks' or AL solid bushings sing something fierce. Use Whiteline's total replacement part instead. The IRS isolation also from Whiteline is the best solution. Yes you will hear the diff but it's a low-key growl in the background.

Beyond choosing inserts that are simply too hard, I would guess whomever is building his diff is probably doing something wrong? That it gets much louder after 2 runs suggests to me the parts are coming out of alignment - deformation of parts or load surfaces. Is he using aluminum or cast iron pumpkins? Has he checked the internals after the noise sets in and confirmed mesh clearance, preload, and axial play?

 

[Cory S]

, I would guess whomever is building his diff is probably doing something wrong?

Definitely not. Just found he installed BOTH the subframe mounts and differential mounts. They both have the stiff bushings in them. He did everything all at once. Cradle lock outs as well. So there's literally zero isolation now.

 

[shogun32]

Just found he installed BOTH the subframe mounts and differential mounts. They both have the stiff bushings in them. He did everything all at once. Cradle lock outs as well. So there's literally zero isolation now.

Both my GT and EB had all the bushings replaced with Whiteline (Diff+IRS+Trans) and the noise is just background. But I don't drag race so haven't 'bent' anything in the diff.

He needs to check post-run clearances. He'll find stuff has moved. What ratios is he installing?
If he's that hard on the diff, I think he would benefit from more support - the Steeda front bracket and thru-bolting the rear ears.

You still haven't said (conclusively) if he cut the old bushings out, or is using the 'puck' systems.

 

[Cory S]

He needs to check post-run clearances. He'll find stuff has moved. What ratios is he installing?
If he's that hard on the diff, I think he would benefit from more support - the Steeda front bracket and thru-bolting the rear ears.

You still haven't said (conclusively) if he cut the old bushings out, or is using the 'puck' systems.

He's using the full bushings. He cut out the OEM bushing sleeves. He's been installing 3.55's each time and sets them up to perfection. It sounds like the Differential and subframe are now all welded to the floor. It's that stiff. Super amplification of any noise.

 

[shogun32]

He's using the full bushings. He cut out the OEM bushing sleeves. He's been installing 3.55's each time and sets them up to perfection

that's a standard Ford size - A10 trans I'm guessing? Then he's also using an aluminum pumpkin. Have him change to cast iron.

If he's using BMR's Aluminum bushings at both IRS and diff then yes, it's going to make serious noise.

The hint that he's bending things is that the noise profile changes after a couple runs. That's not "breaking in the teeth/mesh" it's from stuff getting bent/deformed/clearanced. New gears is not the answer - identifying where the deformation is occurring is.

 

[TrackMustang]

The diff bushings make most of that noise, go to a softer one or get rid of them. Or, understand that performance is loud… if it’s a DD car and he goes to the track for shits n gigs, put the softest ones in. If he’s so annoyed by it at this point he’s completely over the issue, go back to stock.

 

[Cory S]

that's a standard Ford size - A10 trans I'm guessing? Then he's also using an aluminum pumpkin. Have him change to cast iron.

If he's using BMR's Aluminum bushings at both IRS and diff then yes, it's going to make serious noise.

The hint that he's bending things is that the noise profile changes after a couple runs. That's not "breaking in the teeth/mesh" it's from stuff getting bent/deformed/clearanced. New gears is not the answer - identifying where the deformation is occurring is.

Is a PP1 car. Iron housing. Yes 10R80.

 

[Cory S]

The diff bushings make most of that noise, go to a softer one or get rid of them. Or, understand that performance is loud… if it’s a DD car and he goes to the track for shits n gigs, put the softest ones in. If he’s so annoyed by it at this point he’s completely over the issue, go back to stock.

Yep. I have him almost convinced to buy an entire new subframe (They come with the OEM rubber bushing sleeves pre-installed) for $900 and start over. Only add the parts he NEEDS..... Which is very few in realty for a 95% street car.....

 

[jeniffergate]

I came across this old post and wanted to share my experience. I had a similar issue with my rear end after doing a bunch of mods. The noise was unbearable because of the minimal isolation from the unibody. My friend used NVH isolators from Mantaline, and it really helped cut down the noise. If your buddy’s dealing with excessive gear whine, showing him how much isolation impacts noise might save him from spending on an SRA conversion. It’s worth checking out if he wants to save some cash and reduce that annoying sound.

Sponsored