Loud whine under partial load - Dorkiphus.net
Navigation » Dorkiphus.net > Technical & Track Disussions > Porsche Technical Discussions » Loud whine under partial load

Porsche Technical Discussions Porsche related technical discussions and questions go here.

Reply
 
Thread Tools Display Modes
  #1  
Old 11-01-2019, 08:52 PM
Modian's Avatar
Modian Modian is offline
 
Join Date: Jul 2007
Location: Bristow
Posts: 284
Modian
Default Loud whine under partial load

Driving the 964 home from the track on Saturday, I was getting a loud whining noise at ~2800 rpm in fifth gear under partial load. It went away when I let off the throttle or when giving it more gas. Not wanting to take chances, I parked it until today.

This afternoon I changed the gear oil from Redline to Mobil Delvac. There was the usual sludge on the drain plug but no metal pieces. Driving it afterward, it made no difference with the noise, but I did confirm if I shift to fourth at the same speed, the whine is still there but quieter.

I did recently change to stiffer engine mounts, but I did not hear the noise Fri or Sat morning, so I don't think it's those.

Anything else I can look at? If not, who is good to take it to? Keeping in mind if it does get torn down, I may end up putting in shorter gears and a better LSD. ASG?
__________________
Aaron

Ď93 964
Reply With Quote
  #2  
Old 11-03-2019, 11:52 AM
scott's Avatar
scott scott is offline
 
Join Date: Apr 2003
Location: Sykesville, MD
Posts: 695
scott
Default Fill in the blanks...

Couple of missing data points to fill in

What is the mileage on the transmission?

What wieght gear oil and synthetic or dino.

Does it go away coasting in neutral?

My initial take is ring and pinion or the lsd ... but these typically have a slow crescendo... you hear it grow louder over time.

Scott
__________________
Scott

1982 SC
1991 Vanagon wrx
1962 Beetle
2001 MR2 Spyder
2005 Scion XB
2006 Audi a4
Reply With Quote
  #3  
Old 11-03-2019, 02:07 PM
Modian's Avatar
Modian Modian is offline
 
Join Date: Jul 2007
Location: Bristow
Posts: 284
Modian
Default

Quote:
Originally Posted by scott View Post
Couple of missing data points to fill in

What is the mileage on the transmission? 108k total, 17k since last rebuild

What wieght gear oil and synthetic or dino. Redline 75w90ns to Mobil 1 Delvac 75w90. Both are synthetic

Does it go away coasting in neutral? Yes

My initial take is ring and pinion or the lsd ... but these typically have a slow crescendo... you hear it grow louder over time.

Scott
Everything Iíve researched points at those too, but I was curious if there was a way to narrow it down with taking it apart.
__________________
Aaron

Ď93 964
Reply With Quote
  #4  
Old 11-03-2019, 05:42 PM
Der ABT's Avatar
Der ABT Der ABT is offline
 
Join Date: Oct 2007
Location: Arlington,VA
Posts: 1,289
Der ABT
Default

Should be able to jack up the rear and test what it takes to move each side.
If it doesnt grab enough may be shot,
__________________
Evan
87 911 E stock
GONE.......: 84 911 Estock
2015 E stock national champion
Close Motorsports - Driver Coaching and Data Equipment sales
Website coming soon
Old
http://retaliatemotorsports.blogspot.com/
Reply With Quote
  #5  
Old 11-13-2019, 09:17 PM
Modian's Avatar
Modian Modian is offline
 
Join Date: Jul 2007
Location: Bristow
Posts: 284
Modian
Default

So changing the fluid did reduce the sound by quite a bit. I still took it to ASG to look at it and a couple other things. Jeff drove it around and said the noise is there in every gear, and is probably the r&p or carrier bearing, I think. He said If there was no metal in the fluid (there wasn’t) to just keep an eye on it.

I hate not taking care of something right away, but I’m also not ready to do a whole bunch of while you’re in there that I want to do... So is it something to watch or something I should get done now?
__________________
Aaron

Ď93 964
Reply With Quote
  #6  
Old 11-14-2019, 10:45 AM
racer's Avatar
racer racer is offline
 
Join Date: Jul 2004
Location: South Riding, Va
Posts: 6,879
racer
Default

Quote:
Originally Posted by Modian View Post
So changing the fluid did reduce the sound by quite a bit. I still took it to ASG to look at it and a couple other things. Jeff drove it around and said the noise is there in every gear, and is probably the r&p or carrier bearing, I think. He said If there was no metal in the fluid (there wasnít) to just keep an eye on it.

I hate not taking care of something right away, but Iím also not ready to do a whole bunch of while youíre in there that I want to do... So is it something to watch or something I should get done now?
hmm.. your mechanic (whom you trust?) says to watch and wait. It will only get worse, but it could take a while after all. But if the mechanic isn't looking to take your money, why just give it to him?

vs your "ocd" need to have everything perfect (which means opening up the transmission and doing a full update, maybe with shorter gears for even more fun!)

Your money.. your choice

(I fall in the cheap camp and wait for more reasons to fix)
__________________
Dave
- 1970 914-6
Past
- 2000 Boxster
- 1987 944
- 1978 911 Euro SC
- 1976 914 2.0
- 1970 914 1.7 / 2056cc
Reply With Quote
  #7  
Old 11-14-2019, 12:02 PM
Roo's Avatar
Roo Roo is offline
 
Join Date: Aug 2011
Location: Driver, VA
Posts: 461
Roo
Default

Generally speaking:

Gears whine
Cause: lower finish surface standard, spalled surface, chipped tooth; after changing fluid, which flushes some debris, mating surfaces will "re-acclimate" and only get noisier over a long time. I've seen heavy equipment drivetrain gears with chipped teeth and spalled surfaces that worked noisely for hundreds of hours of continued us (still fully functional)

Bearings rumble/roar
Cause: spalling roller elements, get worse rapidly as damage increases exponentially

In either case, continuing to operate the transmission will potentially create new debris that can damage other parts (that's why helicopters have chip detectors in their gearboxes; chip-detected, land soon)

We're approaching the off-season, good time for a tranny refresh as noted by others.
__________________
CT

83 911SC
08 Outback wagon
04 F250 SD
85 Celica GTS convertible
82 Targa
68 Firebird convertible

Truth be it known, I just like working on cars - Slick Henderson
Reply With Quote
  #8  
Old 11-14-2019, 12:42 PM
HoodPin's Avatar
HoodPin HoodPin is offline
Building a Worm Hole.....
 
Join Date: Dec 2004
Location: Monrovia, MD
Posts: 10,386
HoodPin
Default

X2 what he said ^.
__________________
- Tony P.

Currently
- 1984 944 SP2 racer
- 1977 911 KM Special vintage racer
- 1989 944S2
- 2012 Cayman R (also the wife's)
- 2000 Boxster S (the wife's)

- 1995 993 (garage queen)
- 1979 RX7 enduro
- 2017 F350 (tow monster)

Gone but not forgotten
- 1986 944 (under new mgmt)
- 1991 944S2 (in car heaven...)
- 2001 Chevy Suburban 2500 (FIL's beast now)

"Keep your eyes on the road and your hands upon the wheel." - The Doors
Reply With Quote
  #9  
Old 11-14-2019, 12:59 PM
Otto's Avatar
Otto Otto is offline
 
Join Date: Jun 2012
Location: Chantilly, VA
Posts: 815
Otto
Default

change transmission / diff grease often
__________________
Otto

#906
2014 Cayman S
2012 Cayman S - retired
2006 Boxster S
Reply With Quote
  #10  
Old 11-14-2019, 02:28 PM
BlackTalon's Avatar
BlackTalon BlackTalon is offline
#polishforprez
 
Join Date: Dec 2002
Location: Alexandria, Virginia
Posts: 14,354
BlackTalon
Default

Quote:
Originally Posted by Roo View Post
(that's why helicopters have chip detectors in their gearboxes; chip-detected, land soon)
So when helicopters fly over you, and detect you, they have to land?
__________________
David D.
'87 Targa

- 2019 quickly disappearing...
Reply With Quote
Reply

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