Well - I have found the MB diesel "easter egg" - PeachParts Mercedes-Benz Forum

Breckman99 · #1 01-26-2004, 07:24 AM

Some of you may know that an "easter egg" is something cool hidden in software (basically). Well I think I may have stumbled upon something that the MB engineers may have hidden in the MB diesel. I swapped out the rear end with a 300 SE. I can't believe the difference! Instead of running at 3K at 65 its just a hair over 2.5K, right at the edge of the turbo catching - absolutely perfect for cruising at 100 where before I was afraid of blowing the engine. Even the 160 MPH speedometer dropped right in without any recalibration (hard to believe). I know what you are thinking - damn that thing is slow off the line now - the funny thing is it seems like this is a whole new car - instead of shifting from second it will always start in first and run through the gears - once the turbo kicks in it will work any other 300SD on the road! (well, have only tried her against the roommates car). It seems this may have been the rear end that was originally designed for this car and they had to change at the last minute. I always knew something was a bit off. I have been working on these cars every day for a long time now and this is the best thing I have ever done to one. Why did they do this? Was this a US requirement or did they not want the diesel 5 model to be faster than the gas 6? Hmmm I would like to talk to these engineers….

engatwork · #2 01-26-2004, 08:12 AM

What year model was the SE?

Breckman99 · #3 01-26-2004, 08:23 AM

I'm not sure - it could have been a 380 SE too. I bought the rear end awhile ago from a member on this site. One small note: This morning I got to try it out on some fresh snow - Didn't fare as well as the low rear end but once you are going its all good - probally be fine with some snow tires as I am running bald summer tires .... (car is getting ready for some major upgrades and restoration - photo is new interior)
I will try to get some shots of the rear end next time I have the car in the garage.

Breckman99 · #4 01-26-2004, 08:26 AM

seats (excuse the dust

)

Rick Miley · #5 01-26-2004, 09:35 AM

Quote:

Originally posted by Breckman99
Why did they do this?

Perhaps you're too young to remember the 55mph national speed limit that was in effect when these cars were built. MB tuned them to have the sweet spot between 55 and 60.

Breckman99 · #6 01-26-2004, 09:52 AM

Yes I am far too young to remember those times, this car happens to be the same age as me. It seems like the rear end they fitted to the car was not tuned at all, always starting in second gear and already in fourth by fifty or sixty. I think that may have been a quick fix for some government-supplied law, no? The SD was a US only car correct? They only had the 5 CYL turbo in the euro 123s? I have seen a couple 123 diesels that drove like this perhaps the SD was so de - tuned because of the US only status? I am just very surprised that with a simple gear change the car feels like it is finally in balance. Each gear shifts at the perfect point right back to ~2500 all the way up. Definitely hits the power band of this engine like I always thought it should be. As you can tell I am very excited, I was working on replacing the tired automatic with a five speed for this very reason, now I think a rebuild is all she needs….

Rick Miley · #7 01-26-2004, 10:01 AM

Quote:

Originally posted by Breckman99
...always starting in second gear and already in fourth by fifty or sixty.

Yes, that is EXACTLY what they intended! 2nd gear start was to improve fuel economy. And the car had to be in top gear by 55 because that's as fast as we were allowed to go - anywhere in the United States, ever! In the mid 80's I had a job that involved travelling to Ft. Hood, Texax. I was advised to drive 53 mph on INTERSTATE highways in TX, because 56 would get me a ticket. Times have definitely changed.

84300DT · #8 01-26-2004, 11:17 AM

hee i do remember those days. if you had a yankee plate you had better slow down to 55 or below when you hit the mason dixon line going south

it took soooo long to get to florida in the bug

fredjj · #9 01-26-2004, 11:20 AM

I'm very interested in this. How difficult was the rear end swap? Was this a weekend job? Did you swap out the rear end housing or just the differential and assorted other gears?

#10 01-26-2004, 11:42 AM

How did you adjust the speedometer? How was the top speed affected? Has MPG changed much? Last question for now, what is the ratio of the SE gearing?

R Leo · #11 01-26-2004, 12:16 PM

Can you give us the final drive ratios of your old and new pumpkins?

mjstef · #12 01-26-2004, 12:18 PM

Cool!!!! I have a 380 SEL parts car and i would love to do this!! Do you really have to change out the spedo too or can you leave the factory one in?? Also what kind of fuel economy could you expect doing this?? 35mpg??

Telecommbrkr · #13 01-26-2004, 12:49 PM

Me Too!! Me Too!!!

wolf_walker · #14 01-26-2004, 04:14 PM

The 85 300D had a way taller rear gear as well, I've wanted to know what one felt like. I feel the 300D's are geared way too low as well. Though we don't have the second gear problem..

DslBnz · #15 01-26-2004, 06:35 PM

R107
---------
380SL,SLC RATIO 1:2.47

380SL,SLC,560SL RATIO 1:2.47 ABS

450SL,SLC RATIO 1:2.65

450SL,SLC RATIO 1:3.06

W116
----------
280S,SE RATIO 1:3.69

300SD RATIO 1:3.07

450SE.SEL RATIO 1:3.06

450SE.SEL RATIO 1:2.65

W123
----------
230,240D RATIO 1:3.69

280E RATIO 1:3.58

300D RATIO 1:3.46

300DT 85 RATIO 1:2.88

300DT TO 84 RATIO 1:3.07

W126
----------
300SD 85 RATIO 1:2.88 ABS

300SD TO 85 RATIO 1:3.07

300SDL RATIO 1:2.88 ABS

300SE,SEL RATIO 1:3.46

380,500 RATIO 1:2.47

380,500,560SEL RATIO 1:2.47 ABS

420SEL RATIO 1:2.47

W124
----------
260E RATIO 1:3.27

300D 1987 RATIO 1:2.65

300E RATIO 1:3.07

Here ya' go fellas....Good reference, I suppose.

coachgeo · #16 01-26-2004, 06:54 PM

Quote:

Originally posted by DslBnz
R107....

W123
----------
.....

300DT 85 RATIO 1:2.88

300DT TO 84 RATIO 1:3.07

W126
----------...

Just to clarify. The numbers 85 and 84 in the list above represent years 1985 and 1984 correct?

DslBnz · #17 01-26-2004, 08:04 PM

Quote:

Originally posted by coachgeo
Just to clarify. The numbers 85 and 84 in the list above represent years 1985 and 1984 correct?

Yes..,

coachgeo · #18 01-26-2004, 08:21 PM

When considering a rear end swap one has to also consider the tranny ratios. Did MB change ratios of the automatics between cars in the same class (W123 for example) Did they change them much between models with same engine (W123 vs W126)

Sorry I know I should know some of this. Im still trying to stuff all this into my head. If someone has a list of trannies I will try to find time to make a spread sheet file with rear end and tranny's listed together if folk think it would help.

sixto · #19 01-26-2004, 10:06 PM

So it was a 380SE diff. That makes sense. I had a 300SE and it felt like the engine would hit redline before 100mph. The dragstrip crowd will pay plenty for a 300SE diff

Sixto
95 S420
87 300SDL

Breckman99 · #20 01-26-2004, 10:14 PM

Well it seems it was a 380 SE then. The swap was very simple. Pulled the old one out, switched the input yoke with the smaller SD one, bolted everything back in and dropped in the 160 MPH speedo. Nothing more to it.