Gear Ratios

TH350
2.52:1
1.52:1
1:1

C6
2.46
1.46
1:1

A727 (A518 also, OD is 0.69)
2.45
1.45
1:1

There really is not a noticeable difference in gear ratios from any manufacturer. Gaps are all essentially the same.

Anyway I would be very surprised if the A727 and A518 planetaries were not interchangeable. They look identical. Look them up on PATC and see if the part #'s are the same.

 

I'm not an expert on anything, and the mysteries in that transmission casing are just that.. but..

that planetary and supporting cast is responsible for varying gearing possibilities.. for instance, our rigs have seven different ratios.. first gear may be x, then shift to second gear, but when it goes back to first, it may be one of two ratio's.. I've no clue under the sun how this works, but the planetary has something to do with it.. well, the planetary and the sun.. no pun intended..

so, moving to a device that offers MORE planetary gears offers MORE possible ratio's, right? am I wrong? how the hell does this work? at some point you lose strength because of diminishing material for each planetary, but where is that cut off? is this the reason for the legendary strength of the 727?

 

It's the size of the gears that determines ratio. More planet gears make the unit stronger. (we have four planet gears in ours, you can get five, or even six planet gears to put in instead. same gear ratio.) there are also some optional ratios available...... Lower first/second gears. I think we had someone on here that was doing trans gears, instead of regearing the axles for larger tires.

 

I used this to get an idea of how the planetary gears work.

http://auto.howstuffworks.com/automa...ansmission.htm

 

i read on another forum that all the 900 series transmisison(30rh, 31rh, 32rh) had 2.74:1 first gear ratio and 1.54:1 second gear ratio from 1981 and newer.