On Sat, 4 Jul 2020 19:32:15 +0000 (UTC) Max Dillon via Mercedes <mercedes@okiebenz.com> wrote:
> Dave M. has a spread sheet of differentials on his website, I know it > covers 124 and 126 cars, don't know that it covers 123 cars. Fred beat me on Dave's file, but here is one from Stu below. Craig ============================================================== Original source (see post #11): http://www.mercedesshop.com/shopforum/showthread.php3?t=80104 This is an article from Stu Ritter, of the infamous Ritter/Easeley MB list. Stu is also a veteran MB technician and shop owner, and Technical Editor of MBCA's "The Star" magazine. My comments are followed by "-dm". ================================================================================ General info on MB differential setup... if you're thinking of swapping the ring and pinion to change gear ratios, read carefully. -dm ================================================================================ There are two ways to change the differential ratio in our MB's. First is to swap the entire differential and the second is to swap out just the ring and pinion for the ratio you want. In order to swap the gears, you must have ALL the measuring tools from MB to set up the pinion seating depth, the backlash and the case spread (bearing preload). While you can cob up some of the tooling you cannot cob up the pinion depth setting arrangement. The zero point for the pinion exists in space, inside the case. The only way to arrive at zero and the deviation from zero etched on the back of the pinion is to have the gauges. You could of course attempt to assemble it and blue the gears and read the pattern and take it apart and put it together, but OHMYGAWD, what work. The factory sets up each ring and pinion in a test jig. This test jig allows the operator to move the pinion in and out of engagement with the ring gear. The purpose is to determine the point of quietest operation. When the gears are at their quietest they also are at the point of maximum mesh and longest wear with most contact. This is the ideal point you are looking for if you blue and pattern a set of gears. The operator of the test jig moves the pinion in and out with microphones pointed at the ring/pinion set. Watching dB meters, the operator finds the quietest point. The test jig is set up so that the deviation from the zero point is noted in hundredths of a millimeter. Your job when setting pinion depth is to match that same point. You can't do it without the MB tools. The measuring tools cost me $3,600 in 1986. I have no idea of what they cost today. As far as I know, RennTech and another shop in Florida along with my olde shop own the measuring tools. There is no other way to change the gears by themselves. Also, when you buy new gears, or take them from a junker, you must also take the ring gear carrier because each ratio uses a different thickness carrier. Keeps the engagement spot the same. So much for the limited appeal of changing ring and pinion. ================================================================================ The following describes Stu's process of changing ratios in his 400E (124.034). There are a number of minor technical errors, see my "Edit" notes below. -dm ================================================================================ In my car I obtained a 3.07 [gearset] from a 1973 450SL. Let me explain. There are several sizes of differentials used by MB and they care categorized by the oil capacity of the differential, or in other words the size of the case. There are 1, 1.1 (185mm), 1.3 (210mm), and 1.4 liter cases. [Edit: This is not entirely correct. The common case sizes in the 1980's and 1990's are 0.7, 1.1, 1.3, 1.4, and 1.6L. The 0.7L case has 168mm gears. The 1.4L and 1.6L use "reinforced" 210mm gears. There is no 1.0L case. -dm ] The gears are not interchangeable between cases. You must use 1.3 gears in a 1.3 case. The case on the V-8 124 chassis is the 1.3 liter case, used since the first V-8's in 1972. [Edit: True... but although the case fluid capacity is 1.3L, it is NOT the same case as used in the 1970's-1980's W116/W126/R107. You may be able to use the ring & pinion gears, but you can't swap the entire housing. -dm ] The jump from the 1.1 liter case to the 1.3 liter case occurs at 200 horsepower. Everything with over 200 horsepower has the larger gears in the 1.3 liter case. [Edit: The change was based on torque, not horsepower. The W140 S350 diesel only had 134hp, but used the 1.3L case. I believe the change happened when the engine torque rating exceeded approx 210 lb-ft, regardless of HP. -dm ] The 103-engined 124 chassis has the 1.1 liter case. The introduction of the 104 engine in the 300CE brought the 1.3 liter case to the 124 chassis. Every 104 and 119 engined 124 has the 1.3 liter case along with a much beefier rear subframe assembly to hold that 1.3 liter diff. [Edit: Only the M119/W124 had the stronger subframe, not the M104/W124. -dm] Any gear that fits in a 1.3 case can be used in any E-class car that came with the 1.3 liter case, provided you own the tools to make the change. [Edit: Be careful here - check the EPC to ensure the gearset you want to use, was actually used in the housing you plan to install it in. And when Stu says "E-class car", that means W124 only, not W210 or W211. -dm ] If you don't own the tools, then things become a bit different. You must have the same case to fit the rear subframe to make it work. In other words, you can't go to the junk yard and get a 73 450SL diff and install it. Won't fit and besides, there is no ABS sensor hole in the case. I took the 3.07 pinion to my cam/crank grinder and we ground down the pinion to accept the 3.07 stator for the ABS system. Just had him copy a pinion from another ABS equipped car. No sweat. $50 for the grinding. The 3.07 stator just slipped right on as it was supposed to. All 124 and 140 cars use the same diff case so any ratio in the 1.3 liter case will work. [Edit: The 1.3L case on the 124, 129, and 140 is interchangeable, but only for certain years, and only if you match ABS and ASR. You cannot use an ABS diff in an ASR car, and vice-versa. -dm] So, to sum it all up: If you want to swap cases, it has to be a 1.3 liter case from a 124, 129 or a 140 chassis. The later 126 (86 and later) won't fit. Different design. Those are the limits of your choices. [Edit: Not all 1.3L cases from a 129 or 140 will work in a 124. There was a change in approximately 1995, only the "early" cases work in a 124. And you still need to match ABS/ASR, as noted previously. -dm] Yes, the speedo gets modified. It is done at the speedo head and is an $85 proposition in Denver. No big deal. You just tell them which ratio you went to. My speedo is accurate to about 1 mph after the change from 2.24 to 3.07. [Edit: 124 V8 models use an electronic speedo, and the change can be done with an electronic converter box (~$100). All other 124's have mechanical speedos, and the easiest fix is to swap the entire speedometer head to one that matches the rear axle ratio. -dm] I show 3,500 rpm at 84 mph. I knocked 2.2 seconds off my 0 - 60 time in Denver. Went from 9.3 to 7.1. I would imagine I am sub 6 seconds at sea level if I could stop the tires from spinning. The acceleration when passing from 50 - 100 is really strong. Stu _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
