gear ratio question - Page 2 - PeachParts Mercedes-Benz Forum

Frankenbenz · #16 10-31-2005, 08:26 AM

I have 2.24 in my 300sd came from an 85 500sel. The only time I notice a power problem is when I am running the A/C. It's peppy in the winter (colder air intake, no A/C). I filled up yesterday 418 miles 13.99 gallons. I have been taking it easy on the throttle, and it was 80% hiway. Let's see if I can do it again next tank. If I could find the elusive 4.25 first gear for the 722.3 Transmission It would be a perfect set up!
P.S. Mine was not a LSD, but the donor did have German words on the cruise stalk

t walgamuth · #17 10-31-2005, 10:14 PM

16 valve 190s have a 3:36 posi.
and the old 6.9 and 6.3s have them i think. really high ratios perhaps higher than the 2:24. i just checked, the 6.9 is 2:65. i dont know if these will bolt into our more modern cars but i bet they will with some work. i have seen them used offered in hemmings for about $1000. they are expensive to set up and repair. not for the inexperienced i would think.

tom w

Hit Man X · #18 10-31-2005, 10:30 PM

Quote:

Originally Posted by rwthomas1

Everything I have read states that maximum fuel economy with a diesel occurs if the engine is operated at or just slightly below its torque peak when at cruising speed. I believe the 617 torque peak occurs at 2800-3000rpm. The factory 2.88 gears are almost perfect for 70-75mph cruising. This gearset with slightly taller tire to lower apparent gearing to @ 2:70 or so would probably be perfect. I think going to a 2:24 would lower the rpm so drastically that it would be hard for the engine to build enough rpm to start spooling the turbo up when you encounter a steep grade, like you do in CO. The 2:47 gears are probably a little too tall as well for mountain use but would likely work well in a places that are flat. Just my 2 cents. RT

If I could cruise at 2200-2400rpm @ 70mph I'd be happy. Remember the torque converter doesn't lockup so it has to slip a few hundred RPM and when you give it a bit more fuel it's going to flash up...

Check this pic for a 617 dyno...

BioBens · #19 10-31-2005, 11:43 PM

I've got a 2.47 diff from an 85 SEC with 137k on it, for sale at $140 including shipping anywhere in the US.

DslBnz · #20 10-31-2005, 11:53 PM

I find it quite interesting how I have heard claims of such excellent mileage figures from "egging" our old diesels. Perhaps this gearing is one of the main reasons the CDI's are so economical.

Consider this: In a US spec(2.65 w/0.83 OD) E320CDI, 70 mph is only 2K on the tach. The peak torque of these cars ranges from 1800 - 2600 rpm. 40 mpg? Impossible to achieve? Maybe not, if conditions are ideal.

Frankenbenz · #21 11-01-2005, 12:58 PM

I run about 2100 @ 70MPH. Hills are no problem, but I live in central Texas. They are just that hills.

Hit Man X · #22 11-01-2005, 01:39 PM

Quote:

Originally Posted by Frankenbenz

I run about 2100 @ 70MPH. Hills are no problem, but I live in central Texas. They are just that hills.

So do all US 500SELs have the taller diff with limited slip?

What about the Euro ones?

Frankenbenz · #23 11-01-2005, 03:37 PM

My 2.24 was not LSD. I did have some kind of aluminum ring around the inboard CV joints. I went ahead and put them on my car. I can't tell any difference.

Hit Man X · #24 11-01-2005, 03:52 PM

Hrm, do you happen to know if any 2.24:1 are LSD equipped?

Also, any ideas on fuel economy cruising about 65-70mph?

Thanks!

Frankenbenz · #25 11-01-2005, 10:25 PM

I'll have to check tomorrow. It's all in the service manual. It tells you what ratio goes with which model. I sure the 2.24 comes in LSD. I'll just hafta check.

Hit Man X · #26 11-01-2005, 10:42 PM

Ah excellent, keep me posted!