Yeah... so i thought waiting for three weeks for the proper shims and parts would make this work flawlessly, but...

the rear end of my car is now singing like an opera star... the pitch is independent of engine rpm, but is based on vehicle speed... the higher the speed, the higher the pitch...

it's about 5-10x louder than my tilton, and it's really ****ing annoying

after talking to Z1 Auto on AIM, he seems to think it's driveline backlash due to improper shimming.

just wondering what exactly causes this, where exactly the noise is coming from, and how i can explain it to this guy so that he can do it properly.

thanks in advance!

 

update:

after talking w/ Z1 some more, it comes from improper toe mesh of the gear/pinion and improper distance between the gear and pinion

car is back at the shop getting tuned up a bit... we'll see what they say

but, if you can deal with the noise (which i can't... the tilton has become normal, but this is above and beyond)... this thing hauls *** now!

 

The noise comes from gear alignment which is too far out of spec. There are two gears that intermesh. A ring gear and a pinion gear and they have to be very closely aligned. Lash is how much play there is between the gears. Lash can play an important part of gear noise. Besides the lash, there is also a pattern between the gears where they touch. When you turn the pinion gear it makes a pattern on the ring gear and that pattern is determined by the lash, pinion preload and pinion gear depth and location. You want the shape and location of that pattern to be very precisely centered on the teeth. Those all have to be adjusted to very close specifications in order for the gear to function properly. If you have a lot of noise, your gears are not aligned properly and you are generating a lot of extra heat and wear.

If its making that much noise, I would not drive it anymore other than to take it to another driveline shop.

A competent driveline mechanic would not have to have that explained to him. The 3.9 should make a little more noise than stock, but nothing more than having to turn the stereo up a notch.

 

awesome, thanks for the info -- i'll see what they come up with tomorrow... only problem is that there aren't a terribly large number of driveline shops in the area, even Tidewater Z (easily the best Z shop around) outsources their driveline stuff -- i can't remember the name, but i'll have to call and ask because if they don't get it perfect this time, i'm driving straight up there.

can't wait to ditch the 400 pound singing lady in the trunk and really rip into this baby

 

oh, and even the cusco RS pops and bings a bit, but i imagine that's just break-in and will subside once i get her out to do figure 8's and swap out the diff fluid

thanks again,
-nick

 

We have the sims here in stock so if you find out what you need exactly let me know. I would love to offer a shim kit but there are about 20 different sizes and they are about $12.50 each so to offer a complete kit with 1 of each of the shims would be a bit pricey....and there is a posiblity of need 2 ofthe same size. Every housing is different.

 

sounds good -- they already charged me for 13x $9.13 washers (i imagine that's their lingo for shims)...

can i have the guy give you a call if he's having trouble? i really want this to go well and not destroy the rear end of my car

 

back in the shop getting re-shimmed

dwnshift: they may start sourcing their shims through you, since you've got a better selection / availability than anyone in north america

thanks!
-nick

 

I had ordered a couple of all the sizes a while ago. It took a some time to get them in.

 

yep, when i do my writeup of this, i'm going to advocate making sure you have all the shims PRIOR to taking the car anywhere -- had to wait three weeks for the other shims to come in, and hopefully won't have to wait as long for these!

 

ok, got the car back again...

it's still making a ton of noise (albeit less than before)... i'm going to take it up to Tidewater Z tomorrow and have them listen to it and see what they can do... luckily i've got a crapload of shims, so if it needs to be redone, they can do it.

another Q... would changing fluids make the sound go away? thanks!

-nick

 

Drive her up here and well get it straight.

Sounds like something isnt right.....should not be hearing it.
The backlash can be set a little loose which will really help rear end temps and will ahve a little bit of noise but nothing annoying.......but if is making that much nosie....its not set up correct.

Cheers
BJ@350EVO.com

 

BJ, i would in a heartbeat if i didn't think that driving it all the way up there would blow up the rear end

believe me, i've learned my lesson about not having you do the driveline stuff

 

BJ, you've got a PM -- i'm having the stock stuff put back in, at least they can do that, i'm going to ship everything to you -- if you don't mind

thanks,
-nick