Gen 1 r107/w126 style 210mm 3.69 differential - PeachParts Mercedes-Benz Forum

rwd4evr · #1 12-19-2020, 11:01 PM

I broke an axle in the 450slc drift car last Sunday. It was the first major issue I've had with the car while drifting. I did break the clutch sprung hub a few years back, but in the street. Fixed it.
I kinda feel like(and hope) that it was just it's time after 3 years of abuse on a 45 year old axle. I am slightly worried about the fact that I did just increase traction with anti squat rear arms with some adjustment to increase that a little bit. It snapped off in the diff right at the spline to solid transition. Being that it's a 3.69 185mm 6cyl 280slc diff I started trying to determine if the v8 uses a larger splined portion in the diff, I know it's the same on the hub side.
I don't currently have a V8 axle out of a diff in my shop and I haven't had a chance to pull one, but as far as I can tell looking at some parts numbers and some pictures on eBay it appears that that all use the same inner and outer splines just different lengths for The wider casing on the 210 mm diff housing.
I've been wanting to upgrade to a 210mm diff for a while now and I thought I was going to be limited to a 3.46 from a 350 SL if I can get my hands on one. My gearing is about perfect and even though it's not much change, losing rpm in third gear situations is not what I want as it's on the limit of current power in third. All the poking around led me to the w140 300se which has a 210mm(I'm pretty sure at this point) 3.69 gear diff, but the case fits gen 2 subframes only. I missed out on a om606 in the pull part junkyard today so since I was an hour away from home I checked the other local ones and found a couple cars I wanted to check out for some parts including a 300 SE which had the 369 rear so I grabbed it. It was a fight rushing to beat the five closing from 3 p.m. but I got it out just at the last minute.I took the axles to which will be no good to me really since they're the wrong length and outside spline is a different type, and I didn't have my triple square bits with me to get them out. they charged me $96 for everything and I didn't even look at the receipt till I was halfway home and saw that 50 of it was for the axles I didn't want. Oh well.
So the question is, since both of these cases are 8 bolt side bearing covers, and I believe have the same rear cover bolt pattern, can I reinstall all the guts from this diff into a gen 1, 4 stud mounting type case from a 450slc? This w140 diff has ASR sensors which hopefully don't throw a wrench in it. I can probably Fab up a mount setup for it to go in a SLC/w123 subframe but I'd rather not if possible.

Code:

roncallo

PS. Massive magnetic plug is great!!!

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fonzi · #2 12-19-2020, 11:31 PM

Don’t forget that there’s the 1989 300se gen2 style (and the 560sl) subframe in your shop in case you could use it’s mounting setup on an SLC subframe. Just a thought, but I assume you know what you are doing. I figure my idea would be a last resort.

rwd4evr · #3 12-20-2020, 01:44 AM

Quote:

Originally Posted by fonzi

Don’t forget that there’s the 1989 300se gen2 style (and the 560sl) subframe in your shop in case you could use it’s mounting setup on an SLC subframe. Just a thought, but I assume you know what you are doing. I figure my idea would be a last resort.

Unfortunately after further inspection the front mount is different than
w126/r107 gen 2 front mounts. even if I can run the rear cover to locate it, ill have to fabricate front mounts. Looking at lots of different part numbers it's not looking fantastic for an internal parts slam dunk into the older style case. It could just take older style bearings on the newer carrier but hard to say. It may just make more sense as a reliability improver to just fabricate a cradle/mounts to hang it Instead of ripping two good diffs apart.

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rwd4evr · #4 12-22-2020, 07:12 PM

Well I wound up searching though part numbers again and it seems that the early w126/r107 210mm cases do use the same bearings as this w140 case. So rather than completely reworking all of the mounts to use it I think that swapping the gears is a possibility. I measured everthing again not half asleep and all the critical dimensions seem the same. The question is, how accurate is the case machining tolerance and are the fractional millimeter difference thickness washers match to that particular carrier and gear set or to that particular case? So would I reassemble with all the spacers and bearing retainer caps from the r107 case with the w140 innards or the spacers and caps from the w140 case?

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