Quote:
Originally Posted by Frank Reiner
Lt:
For purposes of comparing the overall 1st gear ratios, as corrected for tire size,
the following calculations can be used:
final drive ratio x 1st gear internal ratio / tire rolling radius
For the Benz: 3.07 x 3.68 / 12.65 = .89
For the Jeep: 3.07 x 2.45 / 14.44 = .52
A gear correction of 1.71 would be required to equalize them; hence the Jeep would need a 5.25:1 final drive to achieve a corrected overall 1st gear of .89!!
Substituting a 180 cu.in. engine for a 360 cu.in. engine makes things tough.
If the Jeep has a 2.76:1 final drive ratio, as some did, it makes the correction even more extreme.
We should note that the stall speed of any given TC is a function of the torque applied; a TC that stalls at 2500 when driven by a 360 in. engine,
will stall at a rather lower speed when driven by an engine of half that displacement.
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I will start off with a clear disclaimer : I have never owned a domestic car and don't know more than the average joe about transmissions . For a living I have been building custom turbo systems for all sorts of applications and doing engine builds . I'm not at all afraid or too proud to ask for help when I have no idea what I'm talking about . Now with that out the way ....
As far as picking out a stall all I've been ever told is that you have to match the ENGINES torque peak to the stall rpm range . Gearing is a secondary attribute of the mechanics which relies on torque and HP to determine its end result which is the moving of the mass . So if you have an engine producing peak Tq @ 1400rpms then depending on your desired outcome you'd get a TC which ranges about 500rpms pass that point so somewhere from 1400 to 1900 will work . Any respectable TC shop will give you that range because that also helps account for some gearing and other add-ons such as mid cams or headers . In the case of the om617 it appears it makes its peak around 2500 , so a TC ranged from 2500 to 3000 should work just fine for my application which is daily driving . I'm not a rock climbing guy or muding guy , if I want speed and head-banging lowend torque I can just build me some twin turbo V8 or import inline 6 and call it a day . Gearing is another issue for another day , installing this wrong TC was my mistake . I was "sure" I had grabbed the correct one which is why I didn't even think about it . I do appreciate your post and thanks for taking the time out to reply .