617+manualtransmission 240D= stump puller. - PeachParts Mercedes-Benz Forum

spamman450 · #1 09-10-2009, 12:36 AM

I have recently completed the install of a 617 turbo engine in my manual transmission 240D. It has the stock 3.69 rear end. The car has incredible torque and i can get it to peel out on asphalt if i gas it while cornering. That said, first gear feels like a granny gear. I feel like i could pull redwoods stumps out of the ground or haul around a couple of bulldozers. While i definitely like the torque around town, it is not to good on the highway. At 65mph it is maxed out. I know a rear end swap is probably on my future although i am wondering if i can get away with using a larger tire in the rear to lower highway rpm. I currently have P205/70R14's on there now. What is the biggest sized tire i could safely fit in the rear wheel well? would this work at all? Any and all input is appreciated!

Brandon_SLC · #2 09-10-2009, 12:44 AM

Do you know the rear end ratio of the donor car?

I don't understand why your top speed would be any lower than a NA 616. My 4 spd manual 240D goes 85+ with the same transmission.

spamman450 · #3 09-10-2009, 01:14 AM

donor car was a 300SD with a 307 or a 308 differential. Before the swap the car could do 75 all day long. Now it sounds very maxxed out.

Ian White · #4 09-10-2009, 01:19 AM

Sounds? Very correct rpms at highway speeds and report what you find.

pawoSD · #5 09-10-2009, 01:33 AM

It could probably be pushed up to 75-85mph....but that is just crazy with a 3.69 diff....its needlessly running the engine at 4000+rpm......not good IMHO....just adds a lot of wear. I'd swap in a 3.07 or 2.88.

spamman450 · #6 09-10-2009, 02:38 AM

what kind of car would one find a 3.46?

#7 09-10-2009, 03:10 AM

Are you saying that it will go no faster than 70 MPH or that it sounds as if it's wound too tight at 70 MPH? A five cylinder will sound as if it's running faster than a four cylinder at any given RPM because you have 25% more cylinders firing in the same amount of time.

As Brandon says, if it was doing 85 with the four, there is absolutely no reason that it shouldn't do 85 with the five. If it won't then, there is a governor problem or something that is preventing it from spinning up.

With a turbo engine, changing ratios will not have that much effect on fuel mileage. That said, will it start out well in second gear? If so, then determine the first and second gear ratios and do some math to determine what the effective rear ratio is when in second gear and pick a rear ratio that will give you that same overall ratio in first. THEN fourth should be a really good cruise gear.

There are plenty of different ratio center sections available for these cars and there are plenty of them in the salvage yards to pick from.

BTW, it sounds like a fun ride.

johninva · #8 09-10-2009, 07:44 AM

check here for rear end ratio / year model info

http://www.peachparts.com/shopforum/showthread.php?t=212286

lutzTD · #9 09-10-2009, 08:45 AM

Quote:

Originally Posted by 82-300TD

3.69 tops out at 90mph, 3.46 at 96mph, 3.07 at 108mph and 2.88 at 116mph. All at 4800rpm.

3.46 is good for a 4-speed, 3.08 is good for the highway but sometimes lugging in town, 2.88 will wear out the clutch quickly unless its a highway machine.

2.47 in mine is fine on the clutch and gives very nice all around performance. You just wont be a quarter miler due to the tall first gear but these cars were never meant for that anyway. takeoffs are not that hard to get used to and after you get rolling it is awesome. you will still be better on takeoff then a 240D

#10 09-10-2009, 10:19 AM

I drove my 240D with a stick and 3.69's about 450,000 miles before my son took over. I drove that thing 80 and 90 MPH all over five states. I was late for a flight one time and saw 100MPH on the speedometer. I must have been on a downhill stretch.

The engine lasted 380,000 miles before overhaul. The 616 and 617 engines don't seem to mind RPM. The only problem is your getting used to the noise. If I were to change the rear axle I would probably go to the 3.46 or possibly the 3.07. I would NEVER put the 2.88 in it.