Driveshaft or rear end noise...?

[dc2r]

[edited for clarity]

car is a 2011 GT brembo pack with stock 3.73 rear end. 6spd man.

just did the following:

4" Aluminum Axle Exchange driveshaft
Blowfish trans bracket
MGW Gen2 shifter
BMR adjustable rear upper mount


For the first few days everything seemed fine, but recently I am starting to hear a "chirping" noise coming from the rear end when cold. I am assuming it's driveshaft or diff related.

Driving straight, turning, clutching in, coasting in neutral, foot brake or parking brake applied while moving... the sound remains, but it only lasts about 1-2 minutes at most, and then goes away like it was never there. Oddly enough it dosen't make this noise in reverse?

I've been under the car on a hoist several times now and nothing is leaking or wet. Because I have to drive to the shop it won't make the sound once the mechanic gets to it and I haven't been able to leave it overnight because it's my only ride.

I'm at a loss here... help?

 

[Mr.Window]

Stock suspension?

 

[TEG-84]

Dumb question, but do you still have a LSD? If so, was 4 oz friction modifier added after the gear install?

 

[dc2r]

sorry, i wasn't clear. let me try again...

rear end has never been opened up.

oem 3.73 gears. fluid that's in the diff now is whatever came from the factory.
stock LSD.
factory brembo car.

in addition to the above, BMR LCAs, relocation brackets, panhard bar and brace, lowering springs. eibach adjustable rear swaybar, but all this was installed prior.

useless pic of the mechanic wondering wtf i am complaining about...

 

[TEG-84]

So, you replaced the uca mount and kept the factory non adjustable uca? I'm curious about the pinion angle? -2ish? What hole is the uca mounted in? Just a thought.

 

[dc2r]

lowered on bmr springs.

sorry... both the mount and the uca were replaced with bmr hardware. not sure what you mean by "what hole"... i'm missing something obvious here argh.

according to the mechanic his angle finder says -2 on the nose... but having said that, this is the first aluminum driveshaft he's done and he was going by the instruction sheet.

 

[stang99x]

Just a thought, but if it's only when cold for 1-2 minutes then it is likely related to something that heats up pretty fast which either expands and no longer creates a contact point (that is squeaking when touching) or after settling overnight and getting cold needs to heat up and vibrate to allow for movement (like a bushing that is sticking until is warms up or makes that first movement that creates a more fluid movement) Perhaps try one morning taking off really hard immediately and seeing if the noise remains.....that might indicate that it's something sticking (like a bushing) that has to "heat up and break loose" through a few minutes driving.....but only settles after cooling overnight? I've seen that before in a bushing that simply need a little lubricant.

 

[TEG-84]

lowered on bmr springs.

sorry... both the mount and the uca were replaced with bmr hardware. not sure what you mean by "what hole"... i'm missing something obvious here argh.

according to the mechanic his angle finder says -2 on the nose... but having said that, this is the first aluminum driveshaft he's done and he was going by the instruction sheet.

Aye, I saw the lower springs portion after I posted.
From another forum by bmr

"Bascially, the LOWER hole in the UCA Mount is designed to provide better Anti-Squat Geometry on a stock height car. As a matter of fact, if someone has a completely stock vehicle...and uses the lower hole, with everything else stock (even the OEM UCA) it will aide in better traction.

The UPPER position is designed specifically. It is the only position on the market, of it's kind, and it is designed for a car that uses RLCA Relocation Brackets in any of the 3 positions. (I usually say for lowered cars, because most lowered cars have RLCA Brackets)

On some occasions, a "slammed" car will use the LOWER hole on the UCA Mount in drag race applications, to achieve maximum AS values.....but they MUST use a very good double adjustable rear shock, and the car should be an automatic Trans."

https://youtu.be/9TbwRZqEtxQ

I would also check to ensure all your bushings and such are properly lubed ( I'd recommend amsoil grease). Id lean more towards this since it goes away after a few minutes. The pinion angle you'd most likely feel a vibration as well.

 

[stang99x]

After I posted this, I realized it was you. I know that Panhard bar is newly replaced, double check the bushings.

 

[dc2r]

confused... it's the panhard bar that's doing this? how?

 

[TEG-84]

Could be....not tq correctly or need more lube!!

 

[stang99x]

I wasn't specifically saying it IS the panhard bar Ben, but those bushings are new as I remember you sold the steeda one and went BMR. Possibly those new bushings, after sitting overnight in the cool weather get a little sticky. Then when you drive, they work their way loose in a couple minutes and don't have any further noticeable noises until it sat overnight again. This would make sense as we know you've recently replaced it and those bushings are going to be moving constantly. Of course, under that train of thought, it could also be the upper control arm you replaced. If any of those poly bushings didn't have enough grease they could "stick" overnight, but after a couple moments driving the flex could be enough to loosen them up and make no further noise. It should be pretty easy to remove the panhard bar and grease the bushings and then the next morning would give you a definitive yes or no answer as to whether or not that was it. After that, grease the UCA the next day. Anything else you changed with poly bushings do one thing each day until either the problem is solved or you will eliminate the bushing theory. You know, just a shot in the dark diagnosing a sound like that from 2000 miles away behind a computer. But that's where I'd start, and I've been solving issues like that for years.

 

[dc2r]

i am going to hazard a guess and say it's not suspension related because as i increase or decrease vehicle speed, the chirping sound increases and decreases at the same rate...

 

[stang99x]

Well, only wheels brakes and driveshaft rotate faster or slower. Any changes to those?

 

[dc2r]

nope still the same old... using both parking and normal brakes made no difference to the noise.

i think i will have to suck it up and go to the dealer... sigh. bad things always happen when i'm there.