Just reviving this thread for a minute. I have an '81 300SD with the 1:3.07 rear end, and would like to put in the 1:2.47 rear end from a 420SEL I found. I have heard that they just drop in, but upon further inspection I see that the mount is different. What have you guys been doing to solve this? Can you swap the back-plate of the differential where the mount is? Looking for ideas, thanks!

Re: Well - I have found the MB diesel "easter egg"
 

My 1983 300D revs a little lower than that in stock form. I can go 70mph or a little over at 3k rpms, 65mph is about 2850rpms. My 84 had the normal rear end in it, the car itself was a bit faster but it could never touch the mileage the 83 got. Not many of us here can claim our turbo W123 got 33-34mpg several tanks in a row with a mix of 50/50 city and highway driving. At any speed under 10mph I'm in first, I have it set so under normal acceleration at about 43mph it shifts into 4th. If I want to keep it in third I just push the pedal down, I can hold it until redline if I want to.

What I don't understand is how does it now take off in first instead of second? It has no way of knowing the rear ratio and the trans has to start turning for at least a few times before it can figure out what gear it needs to be in.

Without rereading the thread I believe he changed to a more highway friendly rear end, this means when taking off from a stoplight you'll probably push the pedal down further. Since the pedal goes down further the tranny keeps it in gear longer or if possible in a lower gear.

Guess I'm just use to the 240D where even with the better low-end gears, you're still pushing the pedal all the way down :D

I don't have a 240, but I still drive wityh the pedal all the way down.:D
Thanks
David

Bump!
 

Here's the scene: I have a '85 SD, and a 82TD. The TD has low miles (135K) and plenty of power, and it's primary use is ultra flat highway runs to Grandma and Grandpa's house- 180 miles one way. Love to have the lower RPM of the the later model rear ends. The SD is a luxury (no pun intended- with three MB's and one driver in the household) so I can use it as I wish. The engine and mechanical systems in the SD are very good. The tranny is less than three years old. I'd like to change the rear end in it to the 2.46 of the 420-560 sel's, use it's 2.88 for the TD. I have the best yard resources in the country it seems- there were 7 W126's in the three WPB yards last weekend, so getting parts is no problem. Is this a DIY???


BTW, I'm now seeing quite a bit of ebay MB parts being pulled and sold by people in both WPB and South Florida- moparmom is one. Many people are PM'ing (and emailing) me to find out about these yards and asking me how they can get to them. Like a good surf spot, you want to tell only your best friends. I have and will continue to "share the wealth" with little reserve, but please do ask me for information of the yards if you are going to pull parts and ebay them. I was taught not to poo-poo where you eat, if you catch my drift. :mad:
I pull parts for members who ask with little profit to me. Enough to trim some fuel costs to the yards. This year's revenue over expenses (NOT including yard, shipping or packing time, tool costs or wear and tear to the '80 wagon ) will be less than $100. Keep asking, though, because I will find what you need, even if it takes bit of time. :sun_smile

William

MTU, it should be a fairly easy DIY to swap the rear diffs with the only real hard part of the job is needing some good muscle to do it. The diffs I can imagine are quite heavy because the axle shafts alone are like lifting some medium weight dumbells when working on your back with the rear of the car lifted. Since you'd be just swapping the diffs you wouldn't probably even need to remove the shafts completely, only from the wheels. There aren't that many bolts holding the diff to the chassis either. Just get a very good jack to secure the diff when lowering it from the car.

W126 diff to W123?
 

So what are we saying here? Can we post a table of "working diff swapout combinations" such as:

Source = W126, Destination=W123, ratio swap= 3.68 to 2.88, notes: difficulty / easy / things to watch out for?

blah blah.. PER success?!

So far, I am thouroghly confused as to WHAT source cars and ratios could (should) be used in my 230TE !.. I also suspect other members might be interested!

thanks!

>Joe

This is interesting.

What ratio does my 1992 300Sd 3.5L has ?

this thread has got me all twitterpated :D ...sounds like something i might like to try in my 85 SD...mine has the 2.88, as opposed to breckman's former 3.07...i have a few questions about this...say i switch from my current 2.88 to the 380's 2.47 diff...what kind of increase in top speed would i see? any? i assume i would almost always need to run it in 3rd gear for city driving to keep it in a decent powerband, for anything under 40-45mph i run in 3rd now....might there be any ill effects on my transmission by doing this? would i be sacrificing much on the low end? right now im pretty satisfied with the low end power, even with starting out in 2nd a lot of the time...first gear is quick, it never runs over 3500rpm before shifting, even with WOT...i dont know what thats about...its always done it though...all other gears shift at around 4500rpm....so what seems to be the general concensus on this swap? think its worth it? a new diff isnt all that pricey, esp. a used one....i think im gonna bite the bullet and try it out, right after i get the beast back on the road...should be interesting at the least

"Golden Egg"

It's staring us all in the face...............wake up...........

Why do we need to start in second gear? Because first is way too low!

Was first gear intended for an entirly different rear ratio, that we don't get here in the USA.........They do refer to us as STOOPID AMERICANS!!!

Is this why the dots on the speedometer set for gear changes seem to be foolishly high, I mean, wouldn't your engine red line before it got to the first dot (approx 35 mph) probably!

What would be the right ratios if 2000 rpm is the proper shifting point for 35 mph in first gear, and dots for second, third and fourth, respectively? :eek:

I just got 28 mpg. I drive like a jerk. The car is never sooted up. What's the point in a different differential? SDL with 2.88. Just weighed it today(fer kicks on a CAT scale) on a full tank of diesel. Car was completely empty otherwise(I wasn't in there), came out to be 3960 lbs. Not bad mileage for the weight and season, eh?

Even my 300SE seems perfectly suited to it's 3.46. Plenty of balls, and a wonderful German gutteral I6 sound at 80 - 90 mph.

Most Mercedes are geared optimally straight out of the box. The diesel and the gas six cylinder run top speed at their peak hp levels.

I actually agree with the general personally conflicting philosophy: "keep it stock, stupid!" :P

In this case, at least.

First is not at all too low. I always start in 1st, likely due to a bad kickdown solonoid. :rolleyes: I can't imagine how slow and painful it would be to start from second anytime I'm not in L. With my 3K turbo on, I'll hit 9psi by the 1-2 shift at 3K. BTW, 722 tranny won't go past 3800 rpm in 1st. It will shift to 2nd by 4K.

I was just trying to make an observation! First gear in my 190E, 87 300D, and my prior 83 300D, all seemed to have extremely low first gears, lower than any car I've ever driven, however my 80 450SL is only a 3 speed and first is not quite as low.

Do you think the dots on the speedo are practicle points to shift gears?

Is it possible that a lower ratio differential might have been intended, but not introduced to the US market?