Hello everybody,

I am new to these forums, I'm very happy to see that there is in fact a "Diesel Discussion" forum where us dieselers can help each other out... Excellent! I myself own www.crownvic.org, a UBB board about a DOHC V8 swap I did in a '96 Lincoln Town Car Cartier w/an engine out of a Lincoln Mark VIII. This swap added about 120HP to that car!

Anyway, enough about that... I own a Mercedes Benz 300D Turbo 4 door sedan, has been my father's car since 1983 when he bought it brand new, I've had it for the last three years but it's been sitting in a warehouse w/no use.. I know I know, not a good thing, but financial situations stopped me from using the car and polluting the environment...

Well, the time has come to set the 300D free again on the California freeways (this is not a CA car, it was originally bought by my Dad in Orlando Florida) and I wanted to ask you guys about the gear swap. I know that it revs awfully high (around 3100 RPM) at 70 mph, and I really do want to kick the ratio down to the lowest available gear set. I'm not concerned about acceleration, this car only has 100K miles on it and it's FAST for a 300D. Given that most of the car's usage will be on the I-15 at ~80-90 MPH, I am concerned about the 4000 RPM operation when the redline is ~5100RPM.

What gears can I buy that will work in this vehicle? I am serious about this, I'm not posting to "find out" how much it will cost or what not, I will do the work myself. I just need to know for sure what parts I need and if this is even possible.

I would like to have 70 mph at around 2300-2400 rpm if possible. This may be impossible, but hey, at least I'm asking.

Please let me know, on this forum if this is possible.

Thanks!
Oh feel free to register on my www.crownvic.org board if you want to talk about 4.6L V8's in Lincolns! LOL


Chris

glad I don't have to ride with you daily at 90 mph on crowded freeway, but the car and engine are certainly made to run at that speed all day long with out damage. If there are such gears of a higher ratio you would loose a lot of aceleration.
William Rogers.........

William,

I work I-15 and can attest that if you aren't doing 85-90 for the most part you will get run over . ABout the only times traffic seems to slow is in the greater San Diego area, or near Ontario and the I-10 split - or Northbound between the Cajon Summit and Las Vegas on any Friday after about 12 noon (southbound on Sundays).

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

I'm reasonably certain that the 300D turbo's had the lowest gear ratios available in the U.S. marketed diesels in the 123 body.

The gasoline powered 123's (230 and 280E) might also be worth looking into, since they rev higher (like up to 7000+) and hence would have different transmissions etc. I don't know any of the specific gear ratios on any of these cars, just throwing out routes that you might investigate.

Alternately, you might do some research and look for the rare 5-speed that was available on the Euro models.

- Nathan
'83 240D "Steiner"
'00 New Beetle TDI

I feel a certain kinship here, as I’ve played Dr. Frankenstein more than a few times myself.

You may want to check into the 1985 model year for the turbodiesels. The rear end ratio was lowered. If memory serves me correctly (and there are no guarantees ) it was reduced about 8% or so. Not much, but it makes a little bit of a difference. Apparently, the HP & torque ratings were higher for 1985, so it could pull a lower gear. Speedo calibration should be fairly straight forward – no big deal there.

Another possibility, but a long shot & potentially expensive – IF the early five speed automatics are hydraulically controlled (not electronic) and IF the top gear ratio is an overdrive (less than 1:1) and IF it has the proper bolt pattern… well, you get the idea.

Good Luck! Please keep me/us informed as to your progress!

RTH

PS: FWIW, If anyone has tried to contact me during the last couple of weeks, my (old) email address is no longer functioning due to being compromised, most likely due to a freakin back-door VIRUS. Words of Wisdom: Keep your virus definitions up to date! If this could happen to me – it could happen to anyone. I have always been careful to not download anything unless I knew who sent it, yet despite this diligence, I got hammered.

My Euro 240D has no tach, but is obviously very low geared. I drove it 380,000 mostly highway miles in the 75 to 85 MPH area, and it reached 100 once with the same engine screaming like a Banshee the whole way.

These engines will take the RPM's without worry as long as they are properly maintained.

Good luck,

The 1985 300DT did have an 2.88/1 rear axle ratio. That would make a nice change at 70mph, but still not down to 2500rpm. Orig ratio was 3.07/1

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

What about like a 280SE or some other gasoline car?

Can I get a ring and pinion out of a Benz of that vintage and have it replaced? I'm no stranger to gear swaps, trust me, I went from 3.07's to 3.55 to 4.10 in my '96 330HP Lincoln, so I know what you're saying about the 70 mph RPM's.

I knwo that the 4th gear ratio on the Benz is 1:1, whereas on my '96 Linc for example it's a .70 ratio. I would really like to get a 2.2X ratio in that 300D.

Best regards to all
Chris

I don't think yhat you will like that car at all if you change ratios . however you might go to taller tires all the way around....
William Rogers.......