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  #1  
Old 02-26-2005, 12:45 PM
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240TD 4 speed to 5 speed gearbox swap

Hi guys,
I am new! Hi.

I have a 1982 240 TD and it has a 4 speed manual. I was hoping you could tell me what 5 speed will fit?

I have heard the Mercedes vans from the 80's will fit, not sure if you get them in the states.

Thanks and regards
Adam

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  #2  
Old 02-26-2005, 01:04 PM
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Is your ' TD ' a wagon ?
What are you wanting to accomplish by changing to a 5 speed ?
Where do you live and drive your car ?
It helps on lots of questions to have your location listed in your name....
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  #3  
Old 02-26-2005, 01:04 PM
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Welcome!
Try a search on 5 speeds...and then hop in at the end of the line
Cheers,
-M-
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  #4  
Old 02-26-2005, 01:18 PM
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Quote:
Originally Posted by leathermang
Is your ' TD ' a wagon ?
What are you wanting to accomplish by changing to a 5 speed ?
Where do you live and drive your car ?
It helps on lots of questions to have your location listed in your name....
Yes it is a wagon, I thought changing to 5 speed would be obvious? Better MPG, less noise, less stress on the engine etc
I live in the UK.

Thanks
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  #5  
Old 02-26-2005, 01:22 PM
Diesel Power
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I had a Eurospec 240D 5 speed for a while. You should be able to find a donor 240D 5 speed over there, and swap everything straight across.
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  #6  
Old 02-26-2005, 01:40 PM
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" less stress "

is one of those things which can be counter intuitive... if you understand that your transmission and the work to the rear wheels can be compared to a ramp (or in the circular a screw )... with more turns of the engine taking less force but longer travel... and understand that your engine dynamics include lots of physics which end up with a pretty fixed area of rpm / load relationships then you can see that under some driving situations you can be putting more stress on your engine by lowering the rpms.....

Often for a small engine like you have the difference will be in the speed limits which your country imposes....and whether you follow them... if you have access to the Autobahn in Germany or some of those unregulated Montana,USA roads... fine... but if you shift too early to 5th and run it you will not be doing your engine a favor...
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Old 02-26-2005, 02:08 PM
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Quote:
Originally Posted by leathermang
" less stress "

is one of those things which can be counter intuitive... if you understand that your transmission and the work to the rear wheels can be compared to a ramp (or in the circular a screw )... with more turns of the engine taking less force but longer travel... and understand that your engine dynamics include lots of physics which end up with a pretty fixed area of rpm / load relationships then you can see that under some driving situations you can be putting more stress on your engine by lowering the rpms.....

Often for a small engine like you have the difference will be in the speed limits which your country imposes....and whether you follow them... if you have access to the Autobahn in Germany or some of those unregulated Montana,USA roads... fine... but if you shift too early to 5th and run it you will not be doing your engine a favor...
"but if you shift too early to 5th and run it you will not be doing your engine a favor"
So your saying if you drive badly you will damage your car? But I can do that anyway!

The way I see it is this, less RPM as cruising speed = less fuel used = less rotation of the engine = less wear = less noise. Simple.

Oh and I wouldnt class a 2.4TD as small in this country, maybe in the US or Australia where you need big torquey engines that do high miles and cruise all day but not in little old England with its twisty roads and qaint village pubs!
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Old 02-26-2005, 02:56 PM
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[QUOTE=briitts]" less RPM as cruising speed = less fuel used = less rotation of the engine = less wear = less noise. Simple."QUOTE]
It's not necessarily that simple.
One needs to look at the brake specific fuel consumption curve for any CI engine (rpm on horizontal axis, bsfc on vertical axis) to see that it is trough-shaped. That is, it is higher in the lowest rpm range, slopes down to a minimum at some engine speed (near the peak-torque speed), and then climbs upward in the rpm range above that.
You want to run at the "sweet spot" as much as possible. So you want to gear it so that the sweet spot coincides with your most common cruise speed.
The only thing true for certain in your equation is "less RPM as cruising speed = less rotation of the engine".
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  #9  
Old 02-26-2005, 02:58 PM
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Actually, not even that is quite true. You will get lower rotational speed of the engine, but the same amount of rotation for a given number of miles driven.
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  #10  
Old 02-26-2005, 03:08 PM
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The above may all be true in tech world and on paper and when one has far too much spare time on ones hands, but in the real world you cannot possibly know the consumption curve while driving. I dont know about you but I have been driving a stick shift all my life, its kind of second nature to know when to change gear and when not.

Unless you can change gear perfectly at the optimun consumption curve 100% of the time its pretty pointless pointing out the fact in the first place. While we are at it lets factor in drag coefficient, tyre condition/pressure, outside temperature, amount of fuel (after all carry only half a tank you will weigh less), condition of engine etc etc

In the real world, having a lower revving engine is good. Period
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Old 02-26-2005, 03:09 PM
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What????

Ted, I think you need to re-consider your math. If the engine has a lower rpm for any given speed, it also means that the engine will turn less revolutions for any given distance traveled.

Steve.
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  #12  
Old 02-26-2005, 03:12 PM
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Quote:
Originally Posted by TedG
Actually, not even that is quite true. You will get lower rotational speed of the engine, but the same amount of rotation for a given number of miles driven.
So if you drove from Dallas to LA in first gear and then drove back in 5th gear your engine would have done the same amount of rotation on the return journey?

Er no.
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Old 02-26-2005, 03:41 PM
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I think I misread your statement/equation

OK. I see now where wording has caused perhaps a misinterpretation on my part.
"Less RPM as cruising speed" is a bit confusing, now that I re-read it.
I was thinking simply that you were saying "less rpm", which would mean lower cruise speed. But I guess you mean "less rpm at cruising speed, implying gearing, in which case you will have fewer rotations for the same distance traveled. You will also have less consumption if you don't drop too far below the sweet spot. But you could also have more, if you do drop below the sweet spot, as well as more wear (as leathermang said, "under some driving situations you can be putting more stress on your engine by lowering the rpms....."
Yes, drag is a factor also. But if we are talking about gearing a car for one specific road speed, drag is a constant.
The bottom line is that it will be helpful to know what engine speed each of the transmissions will give you in the road speed range at which you spend the most time.
At that constant road speed, lower engine speed could give you higher fuel consumption. This is a fact borne out by simply looking at the bsfc curve for the engine.
Sorry for the confusion.
I hope this is helpful.
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  #14  
Old 02-26-2005, 04:09 PM
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"its kind of second nature to know when to change gear and when not. "
"In the real world, having a lower revving engine is good. Period "--Briits
----------------------
I do not care what you do with your car or engine... but I am going to post concerning this for others...

It is not second nature for the many people who have driven gas engined cars all their lives and then get into a diesel.... and the problem can be aggravated by it being an old car with the hood insulation gone and a high gear ratio rear end needed to make the 240d servicable in all sorts of driving conditions... diesels should be shifted at lower rpms than gas engines...but still should not be lugged at any time...

Your last statement is patently wrong and most of the people on this site know that... and at some point in your life I am confidant you will figure that out also.... but I won't be holding my breath....
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  #15  
Old 02-26-2005, 04:12 PM
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You guys are just trying to steer him away from the 5 speed gearboxes because you want to horde them all for yourselves. I've seen the greed in people's eyes when they imagine those sweet, sweet, 5 speed manuals.

peace,
sam

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