Welcome to the North American Subaru Impreza Owners Club Tuesday March 19, 2024
Home Forums Images WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Archives > NASIOC Archives > Technical Forum Archive

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.







* As an Amazon Associate I earn from qualifying purchases. 
* Registered users of the site do not see these ads. 
 
 
Thread Tools Display Modes
Old 05-21-2000, 12:39 AM   #1
late_apex
Scooby Newbie
 
Member#: 861
Join Date: Feb 2000
Location: Huffman, TX, US
Vehicle:
2000 2.5RS
BRP

Exclamation Viscous coupling hammering the drivetrain under hard acceleration?

Anybody know how the center diff is designed? As far as my understanding of the way a locking coupling works, it should lock when under load and release when not under load.

Yesterday I was just playing around and did a hard launch in the rain. When the tires broke loose, I heard that familiar 'thunk' sound like when you shift hard, but this time it did it about 9 or 10 times, like it was locking when the tires spun, but releasing and locking again about 2 times a second until the tires all hooked up. It sounded terrible, shook the whole car!

I have a MY00, could it be the LSD? Has anyone experienced this before? I haven't noticed anything wrong or any noises from the drivetrain, but it just didn't sound healthy for the car.

-Jason
* Registered users of the site do not see these ads.
late_apex is offline  
Sponsored Links
* Registered users of the site do not see these ads.
Old 05-21-2000, 12:51 AM   #2
Tarmac RS
Scooby Newbie
 
Member#: 1020
Join Date: Mar 2000
Location: Russia with Love
Post

You know why it didn't sound healthy?
One guess, because it WASNT.

It was probably the drivetrain components bouncing off the chassis due to their flabby rubber composition.

There is no end to the abuse that people will put their car thru to get the tires to spin after they bought a car that you shouldnt spin the tires on.

I have driven in snowy/icy conditions and put ALL the diffs to their ultimate tests and if yours made noise it was from abuse.
Tarmac RS is offline  
Old 05-21-2000, 09:11 AM   #3
IMPRZIV
Scooby Newbie
 
Member#: 628
Join Date: Dec 1999
Location: Maryland, USA
Talking

Jason,

What you are hearing is the driveline "bouncing" against the car's chassis. The above post is right, the wimpy tranny and engine mount bushings in the US spec cars allow alot of movement (Driveline twists and the hard parts meet), and under the situation you have described, that is what happens. Swap in some STi Tranny and motor mounts, and you won't here that noise again...

~Scott
Rally Blue MY99
Owings Mills, Md.
IMPRZIV is offline  
Old 05-21-2000, 10:01 AM   #4
Tarmac RS
Scooby Newbie
 
Member#: 1020
Join Date: Mar 2000
Location: Russia with Love
Post

Yep, the other above post is also right, swap in the stonger mounts and hear the parts they attach to the car hitting the pavement

You know what else is a bad sound?
Standing 5 feet from a car dumping its clutch and listening to the rear diff and both axles deciding they weren't up to it.

Dont know what was worse, the sound of the mechanicals failing or the sound that WE all made after it happened.

Tarmac RS is offline  
Old 05-21-2000, 11:32 AM   #5
M a t t
Guest
 
Member#:
Post

TarmacRS, that sure was a bad sound.
 
Old 05-21-2000, 04:29 PM   #6
late_apex
Scooby Newbie
 
Member#: 861
Join Date: Feb 2000
Location: Huffman, TX, US
Vehicle:
2000 2.5RS
BRP

Question

If my unmodified stock rs has now suffered drivetrain abuse by doing a wet launch, then how do the cars hold up to being turboed?

I've seen Shiv mention in a post about breaking all four tires loose while testing/tuning. He's running like 280 HP, how is it he is not blowing up diffs and trannies?

I'm just concerned about the durability of the drivetrain, now. AliBenn just had his MY98 tranny frag, and the dealer gave him hell because of the aftermarket clutch.

I'd really like to know what kinds of other disasters have occurred as a result of drivetrain abuse.
late_apex is offline  
Old 05-21-2000, 07:01 PM   #7
Tarmac RS
Scooby Newbie
 
Member#: 1020
Join Date: Mar 2000
Location: Russia with Love
Post

It al depends on how you apply the power.

You dump the clutch ,something is going to fail eventually.

YOu ease on the power with some respect for the mechanicals of the car you should be ok.

There is difference between driving hard and abuse.
Tarmac RS is offline  
Old 05-21-2000, 07:39 PM   #8
Revision
Scooby Guru
 
Member#: 242
Join Date: Sep 1999
Chapter/Region: MWSOC
Location: Carol Stream, IL USA
Vehicle:
MY05 PSM GGA !STOCK
MY99 RS-RIP / MY95 MX-5

Post

Hey Tarmac RS, you were 5 feet away, I was the passenger when the diff and axles failed...

What an ugly horrible sound.
Revision is offline  
Old 05-21-2000, 09:20 PM   #9
Pilot
Scooby Specialist
 
Member#: 513
Join Date: Nov 1999
Post

Sounds less like drivetrain problems and more like tire hopping to me. Not that it wasn't the drivetrain but I think we should consider the possibility that it was tire hop. I wasn't there so I can't say for certain but the description sounds suspiciously like the effects of tire hop.

Pilot is offline  
Old 05-21-2000, 09:24 PM   #10
RallyGuy2k
Scooby Specialist
 
Member#: 1146
Join Date: Mar 2000
Chapter/Region: International
Location: Houston/LA/NYC
Post

I'm agree with Pilot...sounds like tire hop...more prevalent with the MY00 with the LSD.
RallyGuy2k is offline  
Old 05-21-2000, 10:26 PM   #11
8Complex

Moderator
 
Member#: 922
Join Date: Feb 2000
Chapter/Region: MWSOC
Location: Schaumburg, IL
Vehicle:
16 WRX (white)
04 FXT (red)

Post

It's tire hop guys... I've done it time and time again and it drives me nuts every time it does it. Best thing is to get off the gas and take off a little easier.

I've had cars where the mounts and such were all so crappy that I've bounced the driveshaft off the underbody of the car before, I know that sound all too well (usually meant an $83 driveshaft rebuild soon).
8Complex is offline  
Old 05-21-2000, 10:56 PM   #12
late_apex
Scooby Newbie
 
Member#: 861
Join Date: Feb 2000
Location: Huffman, TX, US
Vehicle:
2000 2.5RS
BRP

Post

Well, I'm starting to feel better about it, now. Tire hop sounds possible. The bottom line is, that this is the first AWD car I have owned, and the noises that the drivetrain makes when it is looking for traction are just something I am not used to.

I don't normally beat the hell out of the car, but I did play around in the mall parking lot one rainy night when the security guard was parked on the opposite side of the mall. I got into some big long sideways drifts with all four wheels spinning, but I never heard the 'bang'bang'bang' sound I heard the other night. The car handled beautifully. It was so predictable.

I was just really curious if anyone had experienced it before.

-Jason
late_apex is offline  
Old 05-21-2000, 10:59 PM   #13
late_apex
Scooby Newbie
 
Member#: 861
Join Date: Feb 2000
Location: Huffman, TX, US
Vehicle:
2000 2.5RS
BRP

Talking

Oh, by the way, I will be getting the STI engine/tranny mounts for Father's Day.

Hmmm. I better place my order..
late_apex is offline  
Old 05-22-2000, 12:02 AM   #14
Tarmac RS
Scooby Newbie
 
Member#: 1020
Join Date: Mar 2000
Location: Russia with Love
Post

If ya want the tires to spin in the wet, jsut crank the wheels to one side or the other and then hang on.

Wheel hop or driveline lash, either way be nice to your car
Tarmac RS is offline  
Old 05-22-2000, 09:24 PM   #15
rschwarzwalder
Scooby Newbie
 
Member#: 29
Join Date: Jun 1999
Location: NJ, USA
Vehicle:
2005 Baja
Satin White Pearl

Post

I just had the STi Engine/Tranny mounts installed tonight, by RalliSpec.

I wouldn't have believed how flimsy the US spec mounts are unless I saw them myself. No wonder the drivetrain flops around in the cradle!

The mounts make a huge difference in how the car behaves, and the amount of feedback on what the car's doing. Idle vibrations travel into the car now, but it's worth the trade off. Swinging the car into a turn is much smoother, as the engine and tranny are connected to the car instead of being hung on rubber bands (well, in effect anyway).
rschwarzwalder is offline  
Old 05-23-2000, 02:41 PM   #16
nizz
Scooby Specialist
 
Member#: 188
Join Date: Aug 1999
Location: New York
Vehicle:
2004 Forester XT
24k gold on white

Post

I don't know if any of you guys have experience with LSD's before and I may be ignorant but I always thought that's sound that the LSD makes when you launch the car. I haven't been able to launch the RS that hard due to the power/traction ration but I would frequently get that continuous thudding when I launched my Integra Type R. This would not happen when I did the same with an Integra GS-R which has an open-end diff. Please someone enlighten me.

nizz
nizz is offline  
Old 05-23-2000, 03:24 PM   #17
Pilot
Scooby Specialist
 
Member#: 513
Join Date: Nov 1999
Post

Wheel/axle hop is not as prevalent (almost nonexistant) with open diffs. It isn't the LSD per say but the LSD allows enough traction to create the wheel hop.
Pilot is offline  
 

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
squeaking sound under hard acceleration/shifting Jasper Brakes, Steering & Suspension 3 11-02-2005 10:03 PM
Grind From Front Of Vehicle Under Hard Acceleration nickgomez Transmission (AT/MT) & Driveline 0 10-10-2002 04:17 PM
grinding under hard acceleration gbaby Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 10 09-27-2002 02:04 AM
P-Brake light goes off under hard Acceleration Extraze Brakes, Steering & Suspension 10 09-01-2002 03:20 AM
Loud thud when shifting under hard acceleration PhilG Normally Aspirated Powertrain 7 03-11-2001 04:26 PM

All times are GMT -4. The time now is 03:16 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2024 Axivo Inc.
Copyright ©1999 - 2019, North American Subaru Impreza Owners Club, Inc.

As an Amazon Associate I earn from qualifying purchases.

When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission
Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.