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 03-20-2002, 02:40 AM
Registered User
 
Join Date: Jan 2001
Location: Tucson, Arizona
Posts: 758
Does Your 300 Turbo downshift on grades?

Greetings All,

I know, another tranny question, but just curious to see if things are operating as they should. I have done the search option about tranny shifts etc. etc. but none of them really mention whether a load on the engine will cause the tranny to downshift automatically without punching it to the floor to engage the downshift button. If your '84 or so 300 turbo senses the load and downshifts without the pedal to the floor, can you tell me what it is that actually needs adjustment to make it happen for me? The car seems to shift fine from a stand still, firm and predictable, but going up a hill as you loose speed, shouldn't it downshift without the downshift button being engaged? Give me your thoughts or experienced ideas as to what I need to look into adjusting, or perhaps yours is the same way and you find it to be just normal.

Thanks,

Charles

__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan

Last edited by can-do; 03-20-2002 at 01:12 PM.
Reply With Quote
  #2  
Old 03-20-2002, 10:32 AM
NIC
Guest
 
Posts: n/a
charles,

Brrrr, 39 degrees in your town this am as I respond. Sometimes its great to be in the South.

One of the things I like best about my car is that it does not downshift on hills in general. If I'm going slowly up a steep hill (in town or in the mountains), it does shift automatically to a lower gear without fully depressing the pedal. But normally, on the highway or interestate at speed, never needs to shift down to maintain the speed. Lots of easy torque.

On the other hand, my wife's subaru outback, which is all-round a great car, goes crazy on the interstate every time we encounter any type of material grade. Will downshift when in cruise at 70 plus mph and turn around 4,500 rpms in the process. I hate that.

Nic
'85 300CD
Reply With Quote
  #3  
Old 03-20-2002, 01:35 PM
Registered User
 
Join Date: Jan 2001
Location: Tucson, Arizona
Posts: 758
Thanks Guys for the responses,

From what I read on both your posts I assume that your car doesn't downshift either unless pushed to the floor. I am comparing how my turbo drives with vacuum shift to my non-turbo with mechanical shift. At highway speeds of 60mph meeting an extremely steep grade with a length of perhaps a 1/4 mile or more the turbo will slow to a speed of about 50 mph with the same gas pedal height held. Yeah, I'd say it has torque and plenty of power to churn right up the hill no downshift needed, or at least it doesn't. The non-turbo can be mechanically downshifted simply by pushing on the pedal slightly more. Even traveling the hilly coutryside of this state and you are forced to slow to perhaps 25 mph for a turning vehicle, the turbo will stay in 4th gear and slowly accelerate back up to your cruising speed while the mechanical non-turbo will downshift a gear to get your rpms up so acceleration is somewhat quicker. I know all these are observations but I am still curious to know if Mercedes incorporated any sensing device or anything at all that will cause the vacuum operated tranny to downshift? I figured if it was designed to upshift at specific vacuum set points, it should also downshift at relatively the same set points. It would seem strange that the mechancal linkage trannies were designed to do it buy the upgraded vacuum operated ones won't. Something to think about isn't it?
Anyone else out there have any input or can shed some light on this topic please jump in.

Charles
__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
Reply With Quote
  #4  
Old 03-20-2002, 02:07 PM
BWatson's Avatar
Registered User
 
Join Date: Jan 2002
Location: Los Angeles
Posts: 222
Mine doesn't really downshift all that effectively. My tranny upshifts smoothly at nice intervals so I don't think there is any problem but it is sort of older technology. No computer chips, which is why they are not all that expensive to fix. I drive mostly in th city, Los Angeles, and the big thing I notice is when I am accelerating and then someone slows down in front of me. I am already in 4th gear and get slowed down to 25 mph and then the road opens up and I step on the gas and it stays in 4th. NO power! If I slow down almost to a stop, it will downshift but since this happens at least 5,000,000,000,000,000,000,000,000,000,000,000,000,000,000 and 99 times a day when driving in this over crowded mess, I am just in the habit of grabbing the shifter and pulling it down to the "S" setting. It will at least go down into 3rd and give me some more rpms to get back up to speed.
__________________
1982 300D Turbo "Helga"
380,000 miles
Reply With Quote
  #5  
Old 03-20-2002, 03:25 PM
Gary F.'s Avatar
Registered User
 
Join Date: Feb 2002
Posts: 110
I have a 85 300d. From my own experience, I have found that my trans. downshifts without punching it to the floor. There is a rather steep hill about a 1/2 mile from my house. I am generally going about 20-25 when I hit the hill. I try to keep it steady going up the hill and near the top the trans down shifts.



Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime
__________________
Gary
85 300D Ivory, 202,000
Beatus exsisto Jesu, verus et Deus verus Vir
Reply With Quote
  #6  
Old 03-20-2002, 10:30 PM
Registered User
 
Join Date: Jan 2001
Location: Tucson, Arizona
Posts: 758
Nothing like a day off to bond with the Benz

Greetings Guys,

Among other things, seeing as the day was somewhat warm and I really needed to adjust my valves anyway. I tinkered with the throttle downshift cable. I found that screwing out the plastic threaded cable end causes the tranny to delay it's shift points to some degree as well as downshift on uphill grades where rpms are needed to maintain a preset speed. Yes, it takes some tinkering and readjusting to get it to shift right, and also feel right, but I think I have found a happy medium. I also did a bad thing and plugged the vacuum line going to the EGR valve. Don't know if there will be any benefit to this, but we'll see.

Charles
__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
Reply With Quote
  #7  
Old 03-20-2002, 11:58 PM
Senior Member
 
Join Date: Feb 2001
Location: Canton,Texas
Posts: 987
Mine will downshift but only when I have it on cruise at about 45mph (county road) on a hill. It won't if the rpm's are higher but they are pretty low already at 45.
__________________
1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k
Reply With Quote
  #8  
Old 03-21-2002, 03:35 AM
Registered User
 
Join Date: Oct 2000
Location: California
Posts: 209
Yes, mine downshifts on a hill if speed is dropping and it does it without pushing the pedal down far enough to engage the switch.
I've had the transmission replaced, and when it was first installed it worked very well. I'm now on my third transmission in a year and a half (replaced under warranty), and now it downshifts even if I'm going 70mph - it shouldn't do it then.

__________________
Dave
1995 C280
1999 Triumph Daytona 955I - my speed fix.
1982 300TD - Gone, but not forgotten.
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Will the 300 Turbo fit in a 110/111 Heckflosse? autobahnfahrer Diesel Discussion 2 12-27-2004 02:21 AM
1982 300 Turbo For Sale chief_noseeum Mercedes-Benz Cars For Sale 3 11-11-2004 09:35 PM
1982 300 turbo diesel/orlando fl jada Mercedes-Benz Cars For Sale 0 08-26-2003 12:17 AM
240 to Turbo 300 Tim the Taxman Diesel Discussion 19 11-11-2002 09:58 PM
Turbo adjustment on 87 300 SDL invisik Diesel Discussion 1 11-12-2001 09:09 PM



All times are GMT -4. The time now is 09:26 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page