Nick Blake

I recently bought my 2000 z28. It has the following mods and I get sound at higher speeds from what sounds like would be the torque arm area when driving.

This is the list I have put together. Would any of the suspension mods be a red flag? I've read things about sound from BMR torque arms and I'm wondering what the best fix could be.
Gonna have it checked out tomorro but I'd like to have an idea of what it could be going into the shop.

Mod list:

ls1 6speed

-short throw shifter

-Borla stainless exhaust

-2in eibach springs

-Koni adjustable shocks and struts

-BMR adjustable torque arm

-UMI adjustable panhard bar

-boxed lower control arms

-sub frame connectors

-BMR trans crossmember

-drilled and slotted rotors

-factory corvette rims with new tires

-4.10 motive gears

-TA girdle

-pioneer cd player with polk audio speakers all the way around

-K and N filter

-EFI live custom tune

BMR Tech2

iTrader: (5)

describe this "rattle" a little more. Does it change with speed? Does it change with acceleration/braking? Is it a fast vibration, or just a loose sound? It sounds as if you may have incorrect pinion angle causing a driveline vibration. Otherwise, you may simply have a loose component or bad bushing in something

Dragonslate

Tell you what, I would start with the torque arm. I have a UMI adjustable one and if it's your first time doing it, and you're alone, it will probably take a few times to set it up correctly and hit the sweet spot.

If you think it might be that, basically it will sound like a clunking right under your seat. Also, when you are breaking it might feel like something is slapping the underside of your car. I wouldn't drive it much because this could cause the differential to leak at the pinion seal.

So just get it checked out if you don't know how to do it yourself!

Nick Blake

I had it checked out today and I was told the pinion angle was all set. It's worse when coasting or slowing down from high speeds.when I say rattle I mean like a vibration. I rode in the passenger seat and it's definitely from the torque arm because I felt it less and heard it less from that side. I have a BMR torque arm. Car handles on rails and doesn't cut loose incredibly easy. I'm gonna try and build stands so I can get under it and inspect every bolt especially the rear ta bolts

TA_Freak

You said you bought it recently ... so has it has this vibration/rattle since you've owned it?

Nick Blake

Yes it has

Nick Blake

It is from 45 on. Gets worse with higher speed. But it doesn't happen as much under load as it does coasting or with cruise control. Slowing down is when it is worse. Seems to be coming from under the dash so I am wondering if it's from a bad motor mount or the trans crossmember

Nick Blake

There isn't really a clunking that I notice. It's mostly a vibration that I am feeling. Would it help if I had a video? I'm gonna try and get the car on a lift soon to resolve the issue.

BMR Tech2

iTrader: (5)

That definitely sounds like a pinion angle issue. If it is worse under coasting/decel then it is too far down. Get under the car, break the jam nuts on the torque arm adjuster loose and turn it about 2 turns in the direction to shorten it. This will bring the pinion angle up about 2* and should make a significant difference in your vibration issue

Nick Blake

I just got under the car. The angle at the mounting bracket at the back of the torque arm was 2* from the drivers side. The measurement on the drivers side on the drive shaft was 2* as well. So I'm not sure what I should be aiming for but that's where I am.

BMR Tech2

iTrader: (5)

You need to be comparing the angle of the pinion to the angle of the driveline. the -2* we suggest is the difference between the angle of the crankshaft/output shaft to the pinion

Nick Blake

Why does the person in the video take the drive shaft angle into consideration then?

Nick Blake

It sounds like it's coming from the front when coasting or decelerating at high speeds.

BMR Sales2

iTrader: (40)

Because there are multiple ways to measure pinion angle.

Nick Blake

Best way to do so?

1 FMF

iTrader: (1)

ls1 6speed
check out the thread in transmission section about fix that 5/6 gear vibration. if the 6th gear cluster is loose on the output shaft that might be part of problem.

-short throw shifter
shifters can rattle under certain conditions, that's why the oem has that rubber isolator between the shifter and rod into the transmission to the rod that you grab hold of.

-Borla stainless exhaust
check you exhaust hangers and if the exhaust pipe touches anywhere. if the over axle pipe touches either the body or axle that can be noisy, i know first hand after putting in a new rear axle and reinstalling stock exhaust. and the muffler itself can just have drone and make driving miserable.

-2in eibach springs
make sure the springs clear and don't touch the panhard bar under all suspension conditions, driver's side i believe.

-Koni adjustable shocks and struts

-BMR adjustable torque arm
aftermarket tq arms with poly bushing at transmission can transmit more noise, vibration, harshness (nvh)

-UMI adjustable panhard bar
same as above considering poly bushing, worse if spherical rod end bearing

-boxed lower control arms
same as above considering poly bushing, worse if spherical rod end bearing

-sub frame connectors

-BMR trans crossmember
if you're running poly trans mount, definitely more nvh vs stock rubber

-drilled and slotted rotors
they can be noisy when braking, i had a set from ebay they never warped but would groan horribly after i put around 15k easy miles on them

-factory corvette rims with new tires
my opinion having had a 99 and now my 02 and various sets of tires, the oem goodyears were the quietest and smoothest. some tires will definitely give you a worse ride.

-4.10 motive gears
check runout on the ring gear, carrier, and pinion yoke. you can watch youtube videos of guys rebuilding all sorts of rear ends and finding unacceptable runout on new axle parts.

-TA girdle
probably no affect

-pioneer cd player with polk audio speakers all the way around
you probably listen to shitty music

-K and N filter
no affect

-EFI live custom tune
tunes are hit or miss, if it were a tune problem i would think you would have mentioned engine problems. the goal of most tunes are max hp when pedal is to the floor, my opinion the aftermarket tunes fail under light load highway cruise. also know with an aftermarket tune, the way you get more power vs oem is they lean out the a/f ratio a bit, this is bad for the catalytic converters because they can overheat. the richer a/f ratio while not resulting in maximum output from the engine, keeps the exhaust cooler and protects the cats. i mention this because the thought of broken catalytic converter internals rattling around comes to mind. normally you would have an ses light and DTC, but you have an aftermarket tune so who knows what has been tuned out.

Nick Blake

That was a great write up. A lot of those mods I knew to disregard simply because of what they are. As for tune my O2s are still on an everything. Only things turned off are air pump and EGR. Going to further tweak the tune for performance soon. I'm putting an SLP lid on. The vibration is coming from under the dash at deceleration. But it does stay around when I break 100. Gets real loud. My trap speed at 107 was real noisy. I will check out that thread. Id like to square this issue away.