Poly Rear Subframe Bushings Installed=Increased Driveline Noise?

[BluFalcon]

About 7 months ago, I had a lot of work done to my car. Poly Rear Subframe Bushings, Energy Suspension Bushing Kit installed, 5 Lug Swap w/ functional ABS, LSD 4 Bolt, Rear Wheel Steering Delete, Active Toe Elimination, and new wheel bearings on all 4 corners.

While on the highway, driving the car home, I noticed a pronounced "whining" noise that varied with RPM while in gear. It seemed to be driveline related, comning from the rear of the car. I thought it might be because of the less compliant rear subframe bushings, allowing noise from the rear end to be transferred to inside the car. I wasn't too worried, until I remembered that the rear end I had used for the car, had been sitting for about 5 years or so in my garage. I couldn't remember if I had left fluid in it or not, while it sat. I checked the fill on the rear end, and it's topped off and looks fine right now. The car has been sitting at a friend's body shop for the last 6 months getting painted, and it's almost ready to come home. I just want to get some ideas on how to troubleshoot this "issue", if it is one.

So, I guess what I'm asking is if anyone who has installed the poly rear subframe bushings on their car, experienced an increase in driveline noise? Specifically, a pronounced whining noise that's RPM dependent?

 

[jepherz]

My car got significantly louder in the rear from just filling the factory mounts with window weld. So I'd say there's not much you can do other than check the oil to ensure there's no particles in it. That, and drive it.

 

[alansupra94]

What kind of fluid are you running? I mean you can try some shockproof to see if that helps.

 

[BluFalcon]

Actually, I'm already running Redline Heavy Shockproof in the rear end. /ubbthreads/images/graemlins/banghead.gif

My only concern is if the noise is being caused by having had the rear end sitting for so long either with or without fluid in it. I knew that going with the Energy Suspension kit and poly bushings in the rear subframe would introduce some noise to the driving experience, but the damn thing kind of sounds like a rally car now. I have a spare 4 bolt I can throw in, I just wanted to try and eliminate anything that would require me having to crawl underneath the car again.

 

[1990ggsxnj]

You can always jack the car up on all fours, put it in gear, and see if the sound is just as bad in the rear while the wheels are spinning.

 

[BluFalcon]

We already did that at the shop. Put it on an alignment rack, raised it up and started it up. Couldn't hear any unusual noises that weren't drowned out by my loud assed exhaust.

 

[curtis]

Ok is it only in gear under power or just in gear and it doesn't matter if your accelerating alot or a little.
Does it do it coasting down or up a hill. Yea screw you guys if your going 80 and lift and coast car will go up a grade.

Now reason I ask all this is process of elimination at each point. I re did the grease in the drive unit on my mill a few years ago and had some badass aircraft stuff that is mixed with moly d and it made noise and I could watch the amp gauge on the mill and at max rpm was pulling about 3 amps where before was a little less than 2. So I disassembled everything again and just washed all that out with about 6 cans of brake parts cleaner and then heated up and poured in some thinner synthetic stuff and it fell back down to where it was and no noise. Could be the grease used on the new bearings was to thick or not the correct type.

Since there new there fine but could be the bearings in the diff have some pitting or wear on the case hardening. From years of aircraft maintenance I've seen alot of strange sh*t happen to bearings and when in doubt trash them and get new ones. Even one little black dot that remotely looks like pitting I trash them.

Now something else I pondered on today while thinking about this noise. Yea I read it last night and didn't respond till now. If you replaced the subframe bushings, the big bushing out on the end with a giant heim joint etc etc but didn't change or touch bearings it would be easier to figure out but you did and were stuck with this thread until the problem is solved. Cause its bugging the sh*t out of me. What I'm thinking is 4 jackstands and get it up in the air. Have some one make things move and look and listen. Don't get under the car. Could be just something is metal to metal either exhaust, sway bar etc but I really truly think the probelm is angle of the dangle is off. And in the car in the air it may go away from this but also from not having a load on the bearings The car had sagging bushings I'm sure and looking from the side had the front lower than the mustache brace area than it is now. By moving the front up you've changed the pinion angle and angle of attack on things.

Get a protractor like this. click me Doesn't have to be fancy just work. Harbor freight , Sears and other places will have one locally. Check the angle of the flange on the pinion. It should be down on the bottom. Then check the angel of the shaft and subtract on from the other. Then do the same up the shaft at the two mounts.


Someone did a great write up back a few years ago about the wub wubs and shimming these to the correct angles. So search that out cause I can't remember what the correct angle is suppose to be on this. Back to my old Mustang years we would set up 8.8 rears to 5 degrees. I would check this before I went under there pulling and swapping out a diff.

I'm on here off and all everyday all day long so if you get under there and have a quick question send me a PM we can swap numbers and I'll call. Not really my deal and I didn't do the wrench work on the car but I did do the design work on the bushings and expect some noise and vibration cause thats what polyurethane does as everyone knows but straight cut gear sound is beyond what it should be doing. Its just shore rating of 90 not a solid aluminum bushing pressed in there. Either way well get the sh*t figured out. If you have a camera get a you tube video of it and maybe that would help to see whats going on and eliminate some hassle. I really hope its not the fussion generator or the flux capacitor there damn expensive to replace. /ubbthreads/images/graemlins/grin.gif 600 dollars oh my

 

[BluFalcon]

Curtis,
I wish i could give you some more info about the noise being present when in gear or coasting or under acceleration, but I can't. I drove the car home after getting the work I mentioned in the first post done, parked it and then had my buddy drive it to his shop for the paint and bodywork. It's been there since September 2010 I think. /ubbthreads/images/graemlins/grin.gif I should be getting it back sometime this weekend, so I'll post up some more when I get a chance to drive it some more.

One thing I forgot to mention is that the carrier bearings for the driveshaft are in dire need of replacement. That was going to be my next project, once I got the car back. I only mention this because I didn't really know how bad they were until we had the car on the alignment rack. Lots of movement in the driveshaft. You mentioned that installing the subframe bushings may have caused the pinion angle on the rear to change. I'm sure the old carrier bearings aren't helping the situation at all if this is the case. I'll be sure to check this when I get a chance. I appreciate the help, and input on this. Thanks.

 

[cheekychimp]

I'm no expert but I'd concur with this making sense. My rear subframe has solid bushings and when I did a similar short test drive of my car, I had abysmal noises chiefly on deceleration. It concerned me too as I had a hybrid gearbox and rebuilt rear diff and I had visions of someone installing a 3.545 front ring and pinion with a 3.909 rear or something like that. All my rear bushings were done, in fact I am in a very similar situation, AWS delete, toe elimination kit, thicker sway bar, poly bushings everywhere, DSS driveshaft etc

I think my noises may be worse due to the solid bushings and I may well get the polyurethane ones installed but I have a strong feeling my carrier bushings are in urgent need of replacement too. It's an issue I must address when the car comes off the lift again and I can't guarantee my issue is the same as yours but given the similarity in the work done and the symptoms it seems likely we share at least some common ground.

At least you are not alone in the dark now!

 

[thecman02]

I'll tell you my results when I bolt in a rear sub frame I just restored and put PE throughout.

 

[Olson]

I know this is a bit late to the party but i would bet my money (and i would bet. Your lashings off. When you installed it did you take it apart for any reason or tighten any bolts that involve the inner working of the gears or even the huge nut on the fland where the drive shaft hooks up. If so you just threw your adjustment off. yes you can fix it by tearing apart and re lashing it but once you drove it the gears made small small groves in them and they will always be there, same with the wine.