Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 09-25-2008, 04:30 PM
Registered User
 
Join Date: Jul 2007
Posts: 517
Are my rpms too high? Speed to rpm chart?

Are my rpms too high? Speed to rpm chart?

Hi folks,

I had a 2nd replacement differential put in by Enrique. this one seems to be smoother than the first one he put in. the other one had a lot of noise from being worn out. this one makes less noise, but it still appears to be louder than my original that went out. That said, my rpms seem higher than I remember w/ my original differential. I can't quantify the original, but here's the rpms at 60 and 70 mph of the current diff:

60mph = 2500-2600

70mph = 2700-2800

Is this about right for a 87 300D? Is there a reference chart that anyone knows of?

It just seems a little noiser and higher than i remember. it too could be the $50 tires that I put on a few weeks ago. Or (gasp), could it be the transmission?

Reply With Quote
  #2  
Old 09-25-2008, 04:32 PM
79Mercy's Avatar
Registered User
 
Join Date: Mar 2008
Location: Florida
Posts: 4,131
thats normal
__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
Reply With Quote
  #3  
Old 09-25-2008, 04:56 PM
Registered User
 
Join Date: Jul 2007
Posts: 517
79:

those rpm number are normal for your 79 too? Or are you saying thats normal for my vehicle?
Reply With Quote
  #4  
Old 09-25-2008, 05:12 PM
ForcedInduction
Guest
 
Posts: n/a
Here. Add a few hundred RPM for torque converter slippage.
Attached Thumbnails
Are my rpms too high?  Speed to rpm chart?-speed1.gif   Are my rpms too high?  Speed to rpm chart?-speed2.jpg  
Reply With Quote
  #5  
Old 09-25-2008, 05:39 PM
Registered User
 
Join Date: Jul 2007
Posts: 517
Forced,

Thanks for the chart. If I am reading this correctly, the white boxes at the top are diff gear ratios. The colored bands correspond to some sort of strata like 'best, good, average, etc". But what does 1. Gang, 2. Gang, etc mean? I looked up Gang in German and it says "to be the usual thing, to be quite usual". So which Gang column do I look at? I'm assuming 5. Gang. Is that your understanding?


Reply With Quote
  #6  
Old 09-25-2008, 09:51 PM
ForcedInduction
Guest
 
Posts: n/a
Gang=speed. 1st gear, 2nd gear, etc.

For an automatic you will need 4 Gang.
Reply With Quote
  #7  
Old 09-25-2008, 10:27 PM
79Mercy's Avatar
Registered User
 
Join Date: Mar 2008
Location: Florida
Posts: 4,131
That chart can't be right. Im turning 3300 at 60mph. 3.58 rear end, 195/70 R14 tires.


EDIT: never mind, I wasn't pay attention to the Km/h, I was thinking mph.
__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
Reply With Quote
  #8  
Old 09-25-2008, 10:44 PM
babymog's Avatar
Loose Cannon - No Balls
 
Join Date: Jan 2006
Location: Northeast Indiana
Posts: 10,765
The chart doesn't have the 2.65:1 gears of the '87 300D.

Mine turn 3,000rpm right around 77mph so your numbers look about right.
__________________

Gone to the dark side

- Jeff
Reply With Quote
  #9  
Old 09-25-2008, 10:48 PM
Registered User
 
Join Date: May 2003
Posts: 2,220
It's fine....It's normal...for the 2.65 and 195/65/R15's and non-locker 722.3x.
__________________
1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)
Reply With Quote
  #10  
Old 09-25-2008, 11:21 PM
bustedbenz's Avatar
Registered User
 
Join Date: Feb 2007
Location: Valle Crucis, NC
Posts: 2,283
My 86 300SDL with unknown rear diff runs 3000 rpm straight up in the 70-80 mph range. Sounds perfectly normal to me.
__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL
Reply With Quote
  #11  
Old 09-26-2008, 02:40 AM
Registered User
 
Join Date: Jul 2007
Posts: 517
forced and other 300DT owners: thank you for posting your rpm numbers. now that i know the rpm range is normal, i'll need to figure out why it seems that there's more noise. is it the replacement diff? or perhaps the new tires?

Jeff: how noisy is it inside your cabin when you're driving between 70 and 80 mph? i know its subjective, but is it drony and loud?
Reply With Quote
  #12  
Old 09-26-2008, 08:18 AM
79Mercy's Avatar
Registered User
 
Join Date: Mar 2008
Location: Florida
Posts: 4,131
probably your ties if they're cheapo's.
__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
Reply With Quote
  #13  
Old 09-26-2008, 08:52 AM
babymog's Avatar
Loose Cannon - No Balls
 
Join Date: Jan 2006
Location: Northeast Indiana
Posts: 10,765
Quietest about 80mph-up, around 110 the wind noise around the mirror gets annoying, 130 it seems to quiet down again.

If you're getting a 4x4 tire type sound, it is usually a wheel bearing.

If it's engine noise, probably either a bad engine mount, or mis-aligned mounts (pre-stressed), alignment and stress-relieving the mounts is outlined in the FSM.
__________________

Gone to the dark side

- Jeff
Reply With Quote
  #14  
Old 09-26-2008, 12:23 PM
Registered User
 
Join Date: Jul 2007
Posts: 517
79 and Jeff,

Again, thanks for your advice and insight.

I'm ruling out wheel bearing because they were done 10k miles ago and they were fine b/f all the suspension work.

I'm going to push it up to 80mph tonight to see if it gets louder or not. probably will. I'll have the misses sit in the back to see if she can identify where the noise is the loudest.

Bob
Reply With Quote
  #15  
Old 09-26-2008, 12:29 PM
babymog's Avatar
Loose Cannon - No Balls
 
Join Date: Jan 2006
Location: Northeast Indiana
Posts: 10,765
Decide also whether it is:
Speed dependant only,
Speed and load dependant (on/off throttle changes it),
Engine RPM dependant,
Load and direction dependant (swerve from side to side gradually to see if it changes),
or does it change if you touch the brakes.

__________________

Gone to the dark side

- Jeff
Reply With Quote
Reply

Bookmarks

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 On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 07:16 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page