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#1
11-24-2004, 12:37 AM
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Gearing on 722.321 transmission
Does anybody have the gearing ratios for the 300SDL transmission?
It is just a curious matter, as I have no outside reference to look at. From what I gather, and what my GPS reads, it seems gearing would be something like this, with the 2.88 diff. 1st @ 3.90:1 Shift at 30 - 31 4700 rpm 2nd @ 2.51:1 Shift at 48 - 49 4700 rpm 3rd @ 2.49:1 Shift at 81 - 82 4700 rpm 4th @ 1:1 -- max velocity Am I correct, or not? This is just a guesstimate. I assume Mercedes governs most 603's to shift at 4700 rpm's past kickdown. That would line the gearing up with what I assume for the V8's. 
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#2
11-24-2004, 12:45 AM
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__________________
Check out my website photos, documents, and movies!
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#3
11-24-2004, 12:58 AM
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Thank you, Dave. Much appreciated!
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#4
11-24-2004, 01:15 AM
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Oh, I don't mean to nit-pick but 2nd gear just doesn't seem to line up.
All the rest of the ratios fit great, but 2nd gear seems a lot shorter than it is depicted in the charts. Take a look at an '86 560SEL vs an '89 560SEL, and you'll notice 2nd gear ends differently. The rest of the ratios fit great.    I swear 2nd gear has to be 2.59 in the older ones. It would make sense. Also, I just noticed that 3rd gear HAS to be a 1.51 or so. Look at the gearing of the 560's. Assuming tire size is 25.49 inches in diameter, and using a handy differential conversion calculator at prestage.com, I can figure this stuff out in a flash with less paper to throw out. Don't mean to criticize their documentation, but it can't be entirely universal. 
Last edited by DslBnz; 11-24-2004 at 01:29 AM.
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#5
11-24-2004, 01:20 AM
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A 2.59:1 second would have the 560SEL shift at 70 - 71 mph.
A 2.41:1 would shift at about 76 - 77 mph. Both with 2.47 differentials. Makes sense, right?
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#6
11-24-2004, 11:28 AM
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Interesting! I was doing similar math for top speed purposes a couple of weeks ago, and the numbers weren't coming out as I expected them to. I suspect there is a few hudred RPM of slippage due to the torque converter when WFO - but I don't have a way to confirm that.
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#7
11-24-2004, 04:37 PM
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There seems to always be a lot of slippage in these diesel cars, but all should lock before the next shift occurs. I don't know about the mechanical speedo in the 124 but in the W126, the speedometer is slow to recognize acceleration or deceleration and tends to lag behind or ahead a bit.
I have managed, down a hill, to run about 56 mph on the GPS at what looked like 5400, +- 50 more or less, in 2nd gear. I just figured my transmission gearing would be identical to the S-Class of the same years. For 2.88 and 2.47 differentials, it appears to be equivalent. Now, that gearing mentioned in the charts is more along the lines of the '91 350 I have. Definitely identical to those numbers for the 722.3. BTW, what were the results of your topspeed run? You know, what did she clock at speed vs rpm, and did she have anymore wind left in her sail(but you ran out of room)? Did you do it with your current rims, or stock 195/65/R15 tires?
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#8
11-24-2004, 04:41 PM
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I guess we can only hypothesize, for now.
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#9
11-24-2004, 07:13 PM
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I saw an indicated 120mph, but the GPS said 125mph max - speedo reads low. I had 225/45/17 tires on. There was nothing left at that speed, and sadly I was too busy watching the road to note the RPM, darnit. I'm planning on finding more power, so if it wasn't an RPM limit, it might pull a little higher. I suspect it would pick up a few MPH just by switching to the skinny stock tires (which also weigh 15lbs less each - 35 stock vs 50 for the 17x8 Carat wheels). I now have 17x7.5 W203 wheels that are a little lighter, 46 lbs or so...?
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