2.47 diff in a w123? - PeachParts Mercedes-Benz Forum

jsp300D · #1 08-11-2018, 02:50 PM

What job is involved getting a w126 v8 differential fit into a w123?

I know the yoke needs to be swapped over.

I heard something with driveshafts.......

greazzer · #2 08-11-2018, 02:55 PM

Yoke and pinion seal and obviously half shafts. I would replace all the seals and I would have a small assortment of shims at the ready.

Frank Reiner · #3 08-11-2018, 03:23 PM

jsp:

Because the 210mm diff is wider than the 185mm diff the half-shafts will be shorter for any given chassis.
The half-shafts from the V8-engined 107 chassis thru 1985 will be the right length for a 123/210mm diff combination.
If the diff is sourced from a 126, it will have to be from a chassis prior to 1986.

jsp300D · #4 08-12-2018, 07:01 PM

so if it comes from a w126 its a straight swap except the yoke?

Frank Reiner · #5 08-12-2018, 07:53 PM

Quote:

Originally Posted by jsp300D

so if it comes from a w126 its a straight swap except the yoke?

Cliches are truisms:
"When all else fails, read the directions." [All the directions.]

jsp300D · #6 08-12-2018, 08:09 PM

lol

chrisgt · #7 08-12-2018, 10:37 PM

How is driving a 617 turbo with a 2.47 diff?
With the 3.07 it's not exactly fast off the line, does the 2.47 make it sluggish?

Diseasel300 · #8 08-12-2018, 10:52 PM

The 603 with the 2.88 isn't exactly a rocketship off the line either, and it has more power AND torque than the 617 does. I'd suspect the 617 with the 2.47 could be borderline dangerous...

jsp300D · #9 08-13-2018, 01:05 AM

I want some quiet cabin sound at 60-80mph. I dont need to reach 100mph.

vstech · #10 08-13-2018, 06:27 AM

Many have done the swap.

All say off the line loss isn’t noticeable. I think the line launch abilities are the turbo latency itself, not the gearing. We have tourquey motors... but low horsepower, and turbo lag... the choices are, retrofit in a transmission with overdrive, or swap dif... the diff swap is simpler.

greazzer · #11 08-13-2018, 08:48 AM

I tried the 617NA with the 2:65LSD with a 5 speed for over a year. Everyone said the car which be as sluggish as sluggish could be and I would hate it .... Well, I tried it since I like the idea of trying things out.

I loved it Not sluggish at all. Very peppy and your top speed is dramactically increased ... I went over 100 MPH on the interstate before I chickened out and got scared of the cops. I had a lot of rack (throttle would be the first term I would use but for all the hawks out there) left. However, keep in mind that I had manual steering and 5 speed. An auto tranny robs power and the manual steering saves you a few horses too.

I have a 2:47 differential under the crawl space of my house with the correct W123 yoke and seals all nicely boxed up. Had a project in mind but that went away.

So, if you want to buy that yoke and seals, please PM me. Or, you will need to hit the JY to get that yoke. A new one is a smidge under $150. I bought one a number of years ago when I was in a time crunch and could not find one anywhere ...

dieseldiehard · #12 08-13-2018, 10:35 PM

I had a 116 diff swapped in my '79 300TD after I had a '85 turbodiesel installed and running, that 3.65 (or was it 3.47?) ratio was really awful, I cold burn rubber with it and it was screaming loud at anything over 55MPH. The key point I want to make is SHIMS!
Be sure to have as many shims available for the half shafts, or a full set if you can find one, because that was the only major issue encountered with that particular swap. A good friend had a set of shims squirreled away at the shop where I worked occasionally in exchange for using the lift. I think they are NLA so if you don't have the right shims your camber is going to wreck tires. And you will want to go back to the previous diff!
After owning an '83 300D for several years I found a 2.87 for it and had it installed, man! was the change dramatic, quicker overall, quieter at freeway speeds and fuel consumption was somewhat less, not as much of an improvement as I hoped but also if I now drove faster that added to the reduced fuel mileage.
And because 80 was now a breeze then yes, one could say that makes it more dangerous

I always said that is the ratio MB should have put in the 617 turbodiesels in the first place, unfortunately they waited until late ;84 and the last year of production in '85 to do that.

Oh, did no one mentioned another aspect associated with swapping the diff that is the speedo error that results?
Rather than try to find the right instrument cluster, I had my speedo cal'd to make it read the actual speed.

Quote:

Originally Posted by Diseasel300

The 603 with the 2.88 isn't exactly a rocketship off the line either, and it has more power AND torque than the 617 does. I'd suspect the 617 with the 2.47 could be borderline dangerous...

re: .... a 603 isn't a rocketship off the line.
Well, to the subject matter at hand, the other day I drove my '87 300D and was a bit tweeked as someone took forever getting their car out of a parking place at the entrance to a parking lot, so finally when they got clear I stepped on the accelerator like I do in the '79 with the 617 turbo engine in it and to my shock my Rt rear tire broke traction and I squealed a few feet up to the parking place - wow burning rubber in the diesel made me feel like a teenager all over again!
I felt a little embarrassed as I walked back to see the streak I just left on the pavement. I was a bit curious as this doesn't happen often, probably because I don't intentionally floor it that much but I didn't see anything that would contribute to the experience so I might go back and try it again as a controlled experiment. I'll follow up with the results here later.

SD Blue · #13 08-14-2018, 12:54 PM

To clarify, I did the swap 84 300SD (W126) from a 87 420SEL. The SD has the wider differential so it required the axle half-shafts as well. It also required swapping the yoke from the SD.

The biggest difference I noticed was how smooth and quiet it became on the highway. There was a slight difference of off-the-line feel but I'm not interested in the traffic light races. Merging in to traffic was not an issue.

jsp300D · #14 08-14-2018, 04:02 PM

Quote:

Originally Posted by greazzer

I tried the 617NA with the 2:65LSD with a 5 speed for over a year. Everyone said the car which be as sluggish as sluggish could be and I would hate it .... Well, I tried it since I like the idea of trying things out.

I loved it Not sluggish at all. Very peppy and your top speed is dramactically increased ... I went over 100 MPH on the interstate before I chickened out and got scared of the cops. I had a lot of rack (throttle would be the first term I would use but for all the hawks out there) left. However, keep in mind that I had manual steering and 5 speed. An auto tranny robs power and the manual steering saves you a few horses too.

I have a 2:47 differential under the crawl space of my house with the correct W123 yoke and seals all nicely boxed up. Had a project in mind but that went away.

So, if you want to buy that yoke and seals, please PM me. Or, you will need to hit the JY to get that yoke. A new one is a smidge under $150. I bought one a number of years ago when I was in a time crunch and could not find one anywhere ...

I will pm you

jsp300D · #15 08-26-2018, 04:17 AM

I sourced a 2.65 now. Is it possible to change the yoke on the tailshaft?