240d or 300d - PeachParts Mercedes-Benz Forum

linski · #1 08-21-2004, 04:04 PM

Hello everybody, got a question, I have a '61 240d, that drives great, but untill we got a '83 240d, didn't know what kind of compression the '61 was lacking. It has 250,000+++++. Now, I could get a 300d engine, that was RAN OUT OF MOTOR OIL, for free and rebuild it, or, rebuild the 240d. Would the xtra cylinder in the 300 be a problem for the 4 speed manual transmission ? Making me want a 5 speed, that I can't get in the states ?

thanks

300SDog · #2 08-22-2004, 12:53 AM

Lower gear ratio in the rear end would solve any problems with the tranny that you anticipate. You want a 300D pumpkin instead of what's in the 240D.

oldnavy · #3 08-22-2004, 01:35 PM

Quote:

Originally Posted by 240DieselDog

Lower gear ratio in the rear end would solve any problems with the tranny that you anticipate. You want a 300D pumpkin instead of what's in the 240D.

A lower gear ratio will slow the car down, if you want to drop top end RPM's and maybe pick up some speed then you need a higher ratio gearing in the rearend.

If you have the stock 5.5 inch rims with 175/14 tires, you can have the same effect of changing gear ratio by going to a 205/70/ and gain almost 2.5 inches over all with taller tire like a 215/70. It will drop RPM's big time on the road, I speak from experience. In my case the speedo is now only 1.5 MPH slow, but the engine no longer is screaming at 65 MPH as it did with the 185/70's. I have a 1.5 inch taller tire now, with much more tread on the ground. I bought Yokohama 205/70 Avid's, installed at local shop for $305 M&B, RH, lifetime free rotation and balancing, and of course taxe's.

300SDog · #4 08-22-2004, 05:56 PM

I think the 300D comes with something like a 3.27 rear end ratio... whereas the 240D is equipped with possibly a 3.69 ratio or higher.

"Taller" gears mean lower gear ratios in the final drive. Higher gear ratios are the ones that will slow the car down........ 1st gear in your tranny has the highest gear ratio of all (4.56?) - whereas 4th is practically direct drive, something like 1.1:1

Surf this board to find one particular thread a month ago that runs for severall pages about converting a 300D automatic into a 4-spd 300D. The same rules apply to your car.

What you want is the 300D (low gear ratio) pumpkin and not the higher ratio 240D differential.

Old Navy, your larger tires actually lower the final drive ratio. If you want to raise the ratio, then you should probably be using 13" wheels that will slow down the car considerably.

oldnavy · #5 08-22-2004, 06:22 PM

Quote:

Originally Posted by 240DieselDog

I think the 300D comes with something like a 3.27 rear end ratio... whereas the 240D is equipped with possibly a 3.69 ratio or higher.

"Taller" gears mean lower gear ratios in the final drive. Higher gear ratios are the ones that will slow the car down........ 1st gear in your tranny has the highest gear ratio of all (4.56?) - whereas 4th is practically direct drive, something like 1.1:1

Surf this board to find one particular thread a month ago that runs for severall pages about converting a 300D automatic into a 4-spd 300D. The same rules apply to your car.

What you want is the 300D (low gear ratio) pumpkin and not the higher ratio 240D differential.

Old Navy, your larger tires actually lower the final drive ratio. If you want to raise the ratio, then you should should probably be using 13" wheels that will slow down the car considerably.

You need to get your tems straight, 4:11 rear gears are lower ratio then 3:50 gears. A taller tire will slow your speedometer and will effectly raise your final gear ratio with tires making less revolutions per mile. A smaller tire make's more rev's lowering the effective gear ratio, speeding up the speedo.

I take it you don't have much experience with car & truck tire size changes. I use to think it funny when some twit would put the big mudder tires on his truck then get several speeding tickets before he figured it out.

300SDog · #6 08-22-2004, 06:51 PM

I think you are looking at this in reverse.... taking proportions from rotation of the wheel against revolutions of the engine instead of taking ratios the way they are documented as proportional to engine revolutions compared with wheel rotations.

You really have no clue in the world as to where I've been and what I've done with Mercedes Benz automobiles, have you?

oldnavy · #7 08-22-2004, 07:17 PM

Quote:

Originally Posted by 240DieselDog

I think you are looking at this in reverse.... taking proportions from rotation of the wheel against revolutions of the engine instead of taking ratios the way they are documented as proportional to engine revolutions compared with wheel rotations. In 40 plus years I never heard a 4:11 refered to as a taller gear then 3:50 in racing circles.

You really have no clue in the world as to where I've been and what I've done with Mercedes Benz automobiles, have you?Nope, and you can say the same for me.

I did not mention MB's and the fact that what you stated in your first para informs me that you have know idea what you are talking about, just quoting something from a book.

That's great, I love books and have learned a lot over the years from them, but I have put them to everyday use.

I'm here to tell you if your tires make 500 rev's less per mile at the same speed, then you have raised your final drive ratio. Loved all those engineering books and courses I read or did over the years while at sea.

:p

300SDog · #8 08-22-2004, 07:29 PM

Yep, a great place to learn automobiles has gotta be on board a sea-going vessel in the middle of the ocean.....

Everybody please note: None of the bold print add-libs in the quote above are mine. As I have said, tallest gears are those with lowest ratios..... thus the 300D 3.27 is taller than the 240D 3.69 pumpkin.

And to the author of this thread - USE THE 300D DIFFERENTIAL - and you will be fine.

oldnavy · #9 08-22-2004, 08:08 PM

Quote:

Originally Posted by 240DieselDog

Yep, a great place to learn automobiles has gotta be on board a sea-going vessel in the middle of the ocean.....

Everybody please note: None of the bold print add-libs in the quote above are mine. As I have said, tallest gears are those with lowest ratios..... thus the 300D 3.27 is taller than the 240D 3.69 pumpkin. Hahaha, you never run dragsters have you dude. I bet you would want your stoplight street rod with 2:79 gears instead of say 3:92 gears, Hahahahaha

:p

And to the author of this thread - USE THE 300D DIFFERENTIAL - and you will be fine.

You bet, there are lots of reduction gears between the main engine and ships screw. Not to mention there are lots of gears in the lathe's in a machine shop, makes my head hurt just thinking where one might find gears onboard a ship. I was mostly on repair ships and we had lot's of little gear driven things on those ships.

300SDog · #10 08-22-2004, 08:35 PM

(((((yawn))))) C'mon down and visit sometime..... we've got the Ohio (River) Valley Speedway that holds open events every weekend. Nitrous bottles can be refilled for $4.85. And there's also the Knob Creek Range nearby which holds its semi-annual machinegun shoot and subgun competition on the weekend of Oct. 4th.

ZZZzzzzzz....

linski · #11 08-23-2004, 01:18 AM

Thats what I wanted to hear, Ill grab the differential from the 300 while Im there. thanks for the info.

oldnavy · #12 08-23-2004, 09:53 AM

Quote:

Originally Posted by 240DieselDog

(((((yawn))))) C'mon down and visit sometime..... we've got the Ohio (River) Valley Speedway that holds open events every weekend. Nitrous bottles can be refilled for $4.85. And there's also the Knob Creek Range nearby which holds its semi-annual machinegun shoot and subgun competition on the weekend of Oct. 4th.

ZZZzzzzzz....

I built a '70 Maverick for H modified production class on NHRA strip, used a 240 CID in line six cylinder, with full lift Cane cam, Holly tri-power carbs, Clifford reaserch headers, used the pushrods from a 427 Ford V8 so as not to bend things.

I had two rear end options for the car, 3:50's for normal street use and road racing, and the 1/8th mile gears were (if memory serves me correctly) 5:10. They were too low for 1/4 mile runs, because I would max out log before I would get to the finish line. It was fun blowing doors off basiclly stock Boss Mustangs and Z28's at local non NHRA strip in "grudge runs", those were the days.

Edited for a final comment.

What is really bad, all my pictuires from this time in my life were lost in a government move from SC to VA, along with some other personel items belonging to the wife.

Left that pretty much behind when I finally got rid of my '66 Impalla SS 396 with 375 hp (stock rating) with Holly spreadbore double pumper, Isky cam, headers, close ratio 4sp, an 4:11 positrack rear gears. I changed rear gearing to 5:13 for 1/8 th mile use, sure did suck on the road. The 5:13 gears made the car basiclly undriveable on the highway, and dangerous in the curves of the hilly country roads in the Ozarks. I eventually replaced the 5:13's with my old 4:11's and sold the car, and started driving a '98 Olds boat

, but it did have a 455 CID. Would pass everything on the interstate except a gas station.

Sold the car after 57,000 trouble free miles.

Brian Carlton · #13 08-23-2004, 10:29 AM

Quote:

Originally Posted by 240DieselDog

Lower gear ratio in the rear end would solve any problems with the tranny that you anticipate. You want a 300D pumpkin instead of what's in the 240D.

Quote:

Originally Posted by Old Navy

A lower gear ratio will slow the car down, if you want to drop top end RPM's and maybe pick up some speed then you need a higher ratio gearing in the rearend.

Old Navy is correct. Taller gears have lower numerical ratios and will allow the vehicle to have more speed for a given rpm. Shorter gears have higher numerical ratios and will cause the vehicle to have less speed at a given rpm. 240's have lower gear ratios than 300's because they have less horsepower than 300's so the lower gear ratio provides the 240 with more torque to the pavement, something that it desperately needs.

The confusion is caused by the terms "high ratio" and "low ratio". These terms are ambiguous. A "high gear ratio" has a "low numerical ratio". A "low gear ratio" has a "high numerical ratio". Stating simply "high ratio" is very confusing to most people.

oldnavy · #14 08-23-2004, 03:40 PM

Brian has hit the nail on the head, that's why I originally said he had the term's wrong. But you are correct it can be confusing and I often wondered as a kid why it was the that way, then I thought about how things worked and then I understood.

My inch an a quarter taller tires has made the car have more top speed and less RPM's for the normal driving speed of 60 to 65 on the highway. I sure it cost me some take off speed, but I'm not in any hurry nowdays. :p If I was, I would have bought something else to drive besides a 240D.