2.47 / 3.07 diff swap on '83 300CD - Page 2 - PeachParts Mercedes-Benz Forum

Alberta Luthier · #16 08-23-2007, 05:30 PM

Quote:

Originally Posted by LUVMBDiesels

I bought a 2.47 diff last winter but have not time to do the work yet. I am looking for a speedometer from a 420SEL with that rear end and will swap the speedometer at the same time. I am looking to reduce the revs on my commute as well as I can't drive under 80 on the Thruway without being rear ended by a semi

Did the revolutions go down by a significant amount? I am looking for around a 900 RPM drop

Tell me more about the issues you had lining up the new differential.
It seems strange that it would not just line up properly.

If I have done the math right ?? And I am quite ready to be corrected if my math is wrong

80. mph is nearly 129 kph. and is right in the sweet spot.
I went from a 3.07 diff to a 2.47 diff
I believe that when my speedo reads 100 kph I am now doing 124.3kph or just over 77 mph
I find it pulls really nice at 105 - 110 kph on my old speedo and up.
thats about 81--- 85 mph. I forget what the rpms were ... maybe 3200 or so

DslBnz · #17 08-23-2007, 05:36 PM

Quote:

Originally Posted by Hit Man X

Drive a 300SEL, that first gear is REALLY useless.

You think so? I always thought the M103 was a bit peaky and gutless unless revs were above 4.5K rpm. That first gear could get me out of hairy situations in my old 300SE.

I, personally, would strive for an overdrive transmission of sorts before any differential swap.

I think a 3.07 with overdrive is perfect for any car, gas or diesel, with peak power nearing 5K rpm. If your car is slightly gutless at lower revs and gets its max power around this speed or above, it seems perfect.

The E300 turbodiesels are just wonderful in this regard with shortly spaced gears and a tall overdrive. If I ever got back into a W210, it would be that model and nothing else.

Alberta Luthier · #18 08-23-2007, 06:03 PM

Quote:

Originally Posted by LUVMBDiesels

I bought a 2.47 diff last winter but have not time to do the work yet. I am looking for a speedometer from a 420SEL with that rear end and will swap the speedometer at the same time. I am looking to reduce the revs on my commute as well as I can't drive under 80 on the Thruway without being rear ended by a semi

Did the revolutions go down by a significant amount? I am looking for around a 900 RPM drop

Tell me more about the issues you had lining up the new differential.
It seems strange that it would not just line up properly.

Sorry I meant to address your question about lining up the diff but got lost trying to calculate the kph mph rpm things, and posted before I caught myself.

The diff I took out was 3.07 and the 'small pumpkin'. Any diff we are going to put in this car is either going to go on with four studs or be way more difficult to swap than I would consider. There are three different pumpkin cases that I know of that will bolt up to the car (sorry I don't know which come from which cars) but if it doesn't have four studs on top you don't want it.
There are two small pumpkins one with bolt on side covers and one without bolt on side covers.
The diff I used is, I think, from an 83 380se 2.47 ratio.
It is a bit bigger, has the vent on the body not on the cover, has a few cooling ribs on the cover, and does have the same four studs on top and big lug on the cover for the rear rubber mount.
The input shaft is about 5/8 inch (about 15 m.m.) lower when it is just bolted up to the car. (side note here the input flange is a different size but you just change them and put your old input shaft on the donor diff).
So what I did was no spacers on the front two studs.
about 1m.m washers on the rear two studs.
about 2 m.m. spacers between the rear rubber mount and the car.
That tipped the diff up a smidge and pointed the input shaft at the correct angle towards the front engine mounts.
I spaced the 'rear engine mount'/(I would have called it the trany mount)down about 4 m.m.
and I spaced the drive shaft support bearing holder down about 6 or 6.5 m.m..
I don't know what would happen if you didn't make these corrections but didn't want to find out. What is important is it runs as smooth as silk! And I love the change. I will admit I would like a bit more power now. I will be fine tuning the turbo/engine stuff to see if I can find just a few more ponies. Taking the slack out of the IP linkage got me quite a bit

But I don't think I will be sending my IP for a Finland holiday or anything like that though it will disapoint my 16 year old boy.

LUVMBDiesels · #19 08-23-2007, 06:07 PM

Thanks for the info. It will definitely come in handy when I get around to doing it on my car. 3200 at 85 would be great. it is somewhere in the 4000 range at that speed now.

When you start out does it stay in 1st longer now? Mine starts in 1st then goes 2-3 almost immediately. I am hoping that the new gear will let it hold in 2nd longer.

t walgamuth · #20 08-23-2007, 06:30 PM

I have two cars running a 307 rear and a stick tranny. my 82 300cd and my 83 240/300d. the coupe seems content with the 307 gear, the 240/300 cries out for a little lower gear. I don't understand yet why but that is based on my seat of pants observation.

I think maybe my throttle linkage is a little amiss on the 240/300 not giving me full power.

I would not recommend the 247 with a stick.

Tom W

Alberta Luthier · #21 08-23-2007, 06:42 PM

Quote:

Originally Posted by LUVMBDiesels

Thanks for the info. It will definitely come in handy when I get around to doing it on my car. 3200 at 85 would be great. it is somewhere in the 4000 range at that speed now.

When you start out does it stay in 1st longer now? Mine starts in 1st then goes 2-3 almost immediately. I am hoping that the new gear will let it hold in 2nd longer.

1st is better and second even more so.

Alberta Luthier · #22 08-23-2007, 06:45 PM

Quote:

Originally Posted by t walgamuth

I have two cars running a 307 rear and a stick tranny. my 82 300cd and my 83 240/300d. the coupe seems content with the 307 gear, the 240/300 cries out for a little lower gear. I don't understand yet why but that is based on my seat of pants observation.

I think maybe my throttle linkage is a little amiss on the 240/300 not giving me full power.

I would not recommend the 247 with a stick.

Tom W

When I adjusted my IP linkage, I lengthened that rod that goes down to the IP 2 full turns (just taking all the slack out) and it made a very significant difference at WOT. More than I had hoped for.

bgkast · #23 08-23-2007, 07:18 PM

Quote:

Originally Posted by Alberta Luthier

That's really handy. Do you happen to have that info for a 3.07 rear end?

Yes:

12.28
10.5915
6.9075
3.07

I have a 3.46 I plan to put behind my 4 speed next time I am doing some work back there.

bgkast · #24 08-23-2007, 07:22 PM

Quote:

Originally Posted by winmutt

*cough* This is not entirely true, not all manual transmissions had the same gearing. But as a generality.....

Really? I thought both the iron and aluminum boxes that bolt up to the 61X engines had the following ratios:

1st 4
2nd 3.45
3rd 2.25
4th 1

The 5 speed has the same ratios for 1st - 4th also, correct?

t walgamuth · #25 08-23-2007, 08:53 PM

There are several versions with slightly different ratios. In my experience you cannot tell the difference, I don't think. The fiver has essentially the same ratios from one to four.

OTOH the stick four speed in my 300cd seems to have very close together first and second gear ratios.

Tom W

Markp · #26 08-23-2007, 09:24 PM

I drive over 600mi a week in my 82TDT. I am currently chaning the diff from 3.07 (?) to 2:88. The main reason I am chainging it is since the current diff is worn out (carrier is worn, pin is very loose/damaged). I am glad to be going to a 2:88, I drove the donor car home last night and it felt good at 90 (in terms of gear ratios anyway) I don't know if I would change it for the heck of it, but I am glad its happening, these cars seem much happier when not screaming at 80. I drive alot of hills, but think the 2:88's will be fine, the parts car ran very strong on the hills.

Bringing the donor car home from Mass to VT (2.5 Hr) last night was a challange. It sat for long time, got her running and realized trans cooler was mixing with rad. I changed/flushed fluids and filters and installed another rad I happened to have. The one fluid I was not able to check was the diff-the part I really need. could not get the damn fill plug out.

I left Mass around 10 after various repairs and got on the highway. I soon got pulled over for no license plate lights and loud exhaust, at which time the brake pedal went to the floor, fortunately it still had enough brakes for a slow stop. I told the cop it was a parts car I was limping home and he was cool with it, let me go!

back on the road for a bit and the exhaust dropped out, drovea few miles to the VT welcome center and pulled in to fix that and my wipers. There was a guy there from Sask CAN who just bought a really niceTDT in Mass and was driving it back, he was into it and fully understood the parts car transport, was pretty funny.

I passed two more cops with no exhaust and can't believe they did not pull out, made it home around 1:00AM

Car ran strong, I'm gonna dismantal it this weekend and get the diff in my car. I'm also going to pull the motor and go through it so I can mate up my manual trans and then drop it in my 82 when I get a chance. paid about 500 total with all the fluids/filters. body is not too bad, but I need the parts, she took her last drive.

Alberta Luthier · #27 08-23-2007, 11:50 PM

Does anyone know the different weights of the 300SD, 300TD, and 300CD?

And I'm going to get a set of these Vogtland springs to lower the CD... Is it going to change my top speed with better aerodynamics?

winmutt · #28 08-24-2007, 01:01 AM

Quote:

Originally Posted by bgkast

Really? I thought both the iron and aluminum boxes that bolt up to the 61X engines had the following ratios:

1st 4
2nd 3.45
3rd 2.25
4th 1

The 5 speed has the same ratios for 1st - 4th also, correct?

FI posted a list of gear boxes and rear ends for most models. After 83 (I think that was last year for federal 240D right?) the sub 300D's (200,220,240) came with a much shorter 1st and 2nd gear. A perfect match for a 2.47 rear. If I could find one I would swap it out in a heart beat.

t walgamuth · #29 08-24-2007, 06:03 AM

Quote:

Originally Posted by Alberta Luthier

Does anyone know the different weights of the 300SD, 300TD, and 300CD?

And I'm going to get a set of these Vogtland springs to lower the CD... Is it going to change my top speed with better aerodynamics?

Yes.

By my calculation it will raise your top speed.......one third of a mile per hour.

Tom W

partsman225 · #30 01-13-2013, 09:24 AM

I do have a 3.69 rear end out of a 82 240D with the matching speedo for sale.pm me