Pfadt diff bushings and gear noise

[Stealth 2010 2SS/RS]

First off I love the pfadt parts that I have installed the car drives great no wheel hop and the rear is planted on launches. I just got around to driving the car for the first time since I got done with the solid sub mounts and diff bushings about two weeks ago and at 60 to 70 the rear gears sound like a circular saw. I expected some gear noise but not this much. Any help or advice would great.

[10camaross]

You have the stock gear?? Maybe the new found traction is hurting the rear?

[jmart53]

Did you put new fluid in when you changed the diff bushings? I just installed a bunch of Pfadt stuff(diff bushings, solid subframe mounts, trailing arms, rear tie rods, and engine mounts) as well but forgot new fluid so had to reuse what I drained and now I have some gear whine but alot of people on here say a fluid change really helps. Either the GM brand with the additive or something like Royal Purple which I bought but have yet to install. Also, give it some time, it settles in a bit as well.

[Stealth 2010 2SS/RS]

Stock gears. Have not changed the fluid yet. I have a friend thats a gm mechanicand might have him check the diff for the right preload and backlash.

[Apex Motorsports]

When you go with harder differential bushings there is always the potential for increased gear noise. I say increased because it was always there but your mushy stock bushings were insulating it. Right of the assembly line some rear ends are set up more "loose" than others so it can vary from car to car.

As has been mentioned, a fluid change and adding an additive can help. I would make sure your buddy has plenty of experience messing with gears in a IRS car before he goes in there.

[Blue70SS]

Originally Posted by Apex Chase

When you go with harder differential bushings there is always the potential for increased gear noise. I say increased because it was always there but your mushy stock bushings were insulating it. Right of the assembly line some rear ends are set up more "loose" than others so it can vary from car to car.

As has been mentioned, a fluid change and adding an additive can help. I would make sure your buddy has plenty of experience messing with gears in a IRS car before he goes in there.

I had the LPE 3.70 gears with Jannetty posi fix, almost all Pfadt bushings (except used the BMR ones that came with trailing and toe arms and kept Pfadt ones for down the road changes). I have the Pfadt solid subframe bushings and at the time Pfadt's softer "street" diff bushings for the 2 front bushings and ran the harder "strip" rear diff bushing due to my increased power. Had some gear whine, but was told mine was nothing compared with Richmond 4.10s others had. Cracked the diff open once to inspect and everything checked out, including wear pattern.

Here's the interesting part... when removing the OEM diff to replace with LPE 9.5" I found the rear diff bushing extremely loose. Before removal I could rock the car back and forth using the tire while parking brake off and tranny locked in 1st gear. I could see the rear of the diff move up/down about 1/4" total. A little off topic here... but ended up replacing the 85mm long "torque to yield" mounting bolts that had shouldered ends and skinnier middle part, with 90mm 12.9 hardness black bolts that were the same thickness from end to end. It got rid of about 1/2 of the movement. HOWEVER, the harder diff bushing fell out of the diff when the unit was removed. IMO, Seemed like the impregnated lubricant was almost squished out of the bushing. It had grey grease on it, but I had used clear Sphon lubricant. The 2 front bushings were nice and tight.

I installed Pedders HD bushings on the LPE 9.5" diff mainly just to show it off with red bushings. The MAJOR difference I noticed (WHICH MIGHT LESSEN NOISE TRANSMISSION), is the center metal cylinder the bolt runs through is Shorter on the Pedders bushing. The Pfadt one makes contact with the subframe mount, while the Pedders one does not extend to the outside edge of the bushing. And if centered in the bushing, leaves the metal cylinder recessed about 1/8". On installation, the new bushings slipped into the subframe very tight (good). I had the 9.5" installed last week with 3.73 gears and have absolutely no rear end noise now. I'm sure most of it's the better rear end, but believe Pedders HD bushings should be quieter compared to Pfadt's "Strip" bushing - solely based on design differences I saw.

It would be interesting to compare the 2 harder version bushings in the same car, without changing anything else. I do know that Pfadt's street version was made solely because of increased noise found using the "strip" version, when combined with Pfadt's solid subframe bushings.

[Blue70SS]

Originally Posted by Stealth 2010 2SS/RS

First off I love the pfadt parts that I have installed the car drives great no wheel hop and the rear is planted on launches. I just got around to driving the car for the first time since I got done with the solid sub mounts and diff bushings about two weeks ago and at 60 to 70 the rear gears sound like a circular saw. I expected some gear noise but not this much. Any help or advice would great.

Are your Pfadt diff bushings the harder "Strip" version or the newer "Street" version. Initially they only had one version, which was later deemed the "Strip" version. Plus all the origional bushings were one piece, and later the rear bushing became a 2 piece which helped with sound insulation.

You also might try contacting Pfadt. Both Pedders and Pfadt are more than willing to help troubleshoot their products and give expert advise.

[Stealth 2010 2SS/RS]

Originally Posted by Blue70SS

Are your Pfadt diff bushings the harder "Strip" version or the newer "Street" version. Initially they only had one version, which was later deemed the "Strip" version. Plus all the origional bushings were one piece, and later the rear bushing became a 2 piece which helped with sound insulation.

You also might try contacting Pfadt. Both Pedders and Pfadt are more than willing to help troubleshoot their products and give expert advise.

The pfadt diff bushings are the street version.

[Blue70SS]

Originally Posted by Stealth 2010 2SS/RS

The pfadt diff bushings are the street version.

Here's what I would do if it were my car

1st - Experiment with Pedder's street version of diff bushings. Obviously more work, but you can always sell them easily for 15 bucks or so less to another member if needed. If completely pulling the diff to do this, then I would inspect the inside - but I doubt you'll find anything, since the problem didn't show up till after the changes. It's nice to say I have a Pfadt car or Pedders car, but sometimes it's just what works the best. You might also try contacting Aaron Pfadt to see if they're experimenting with something different on the rear diff bushings. They do change things based on feedback. You might even mention the differences I noticed between brands of bushings.... he might experiment for you.

2nd - Try running 85w-140w rear diff fluid. Jannetty had mentioned to try this and helped some. I'm not sure if different brands work better, but heavier wieght makes sense - solely based on the colder diff seems to be quiter until the fluid gets warmed up and thinner.

3rd - Dynomat the trunk and below the rear seat. Might as well realize harder bushings are better for performance, but will transmit noises that were not noticeable beforehand. (not that they always transmit noise.... it has to be a "hidden" noise getting amplified)

Other things to consider.... outside temps. Minnesota is obviously colder right now, but your noise level comparisons should be done at roughly the same temps. Colder will be louder and suspension will be stiffer. So again, make sure you compare at same temps, same roads, and don't be fooled by the first few minutes of comparison on 1st drive of the day. I've notice rear end noise not being there at first, then once the rear is diff warmed up, noise comes back.

Hope this helps...

[Blue70SS]

Originally Posted by Stealth 2010 2SS/RS

The pfadt diff bushings are the street version.

If you want, I'll be in Minneapolis this week around 35W/494 area and could possibly meet up one night to give you my impression of the noise.

[Stealth 2010 2SS/RS]

thanks for the input Blue70SS, like i said i knew that some gear noise would transmited to the cabin but never thought that it would be that much. I think that i'm going to try and see if me friend can take a look at the rearend and make sure everything is ok and then do some fluid changes, might also look into the LPW diff cover. I think that when the time comes the lpe diff is what i'm going to put in it.

[PfadtRacing]

Hey folks. As has been mentioned earlier in the thread a few times, our differential bushings don't create noise that wasn't already there. One thing the factory bushings do well is isolate noise from the differential, and when you move to a harder bushing material for performance reasons you run the risk of increasing noise transmission into the cabin. An instance we have seen of this came with a husband and wife who each purchased Camaros about the same time and did the same differential bushing install, one saw an increase in cabin noise and one was whisper quiet.

Sometimes when moving to a set of aftermarket gears the noise can be lessened due to the amount of attention to detail that can be paid by the tech setting up the differential. There has also been some success reducing noise by changing the stock differential fluid and going to the OEM Fluid for limited slip differentials, or perhaps an aftermarket fluid that's slightly heavier in weight. When troubleshooting noisy differentials in Corvettes and Camaros typically the dealership will start with their differential fluid with the limited slip modifier, and this has proven to take care of quite a few noisy differential issues.

We have experimented with different durometer polyurethane for the differential bushings and it can be a "catch 22" scenario. The ideal product will be be extremely stiff whilst transmitting absolutely zero road noise and gear whine. Unfortunately, there is no magical solution as a bushing that is soft enough to transmit no noise will also deflect more, and therefor is not much of an "upgrade" to begin with. Our differential bushing kit only currently ships in a street version which during our testing we found to have the best combination of performance gain and smallest chance of increasing NVH. Ultimately we find that most bushing kits are being installed into folks looking for a serious performance gain, and that's certainly realized with these bushing kits.

[Bruce@raymondsperformance]

Most performance upgrades are a compromise of ride comfort for performance,as Pfadt said above the bushings didn't cause the noise they just made it more noticable inside of the car.

[Blue70SS]

Originally Posted by PfadtRacing

Hey folks. As has been mentioned earlier in the thread a few times, our differential bushings don't create noise that wasn't already there. One thing the factory bushings do well is isolate noise from the differential, and when you move to a harder bushing material for performance reasons you run the risk of increasing noise transmission into the cabin. An instance we have seen of this came with a husband and wife who each purchased Camaros about the same time and did the same differential bushing install, one saw an increase in cabin noise and one was whisper quiet.

Sometimes when moving to a set of aftermarket gears the noise can be lessened due to the amount of attention to detail that can be paid by the tech setting up the differential. There has also been some success reducing noise by changing the stock differential fluid and going to the OEM Fluid for limited slip differentials, or perhaps an aftermarket fluid that's slightly heavier in weight. When troubleshooting noisy differentials in Corvettes and Camaros typically the dealership will start with their differential fluid with the limited slip modifier, and this has proven to take care of quite a few noisy differential issues.

We have experimented with different durometer polyurethane for the differential bushings and it can be a "catch 22" scenario. The ideal product will be be extremely stiff whilst transmitting absolutely zero road noise and gear whine. Unfortunately, there is no magical solution as a bushing that is soft enough to transmit no noise will also deflect more, and therefor is not much of an "upgrade" to begin with. Our differential bushing kit only currently ships in a street version which during our testing we found to have the best combination of performance gain and smallest chance of increasing NVH. Ultimately we find that most bushing kits are being installed into folks looking for a serious performance gain, and that's certainly realized with these bushing kits.

Thanks for the feedback. The husband/wife owners are Lingenfelter owners in New Mexico. The husband had the noise problem with OEM gears, while the wife that had LPE 3.70 gears. They have since both gone to Ford 9" rearends. However, the early changes from "strip" to "street" bushings did help them alot.