None of the 727/618/47RH series have a mechanical OD. The 47RH has TCC and OD, but both are electrical. That transmission came in the 94-95 year models. The rest of the transmission is hydraulically controlled via govenor housing.
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mechnical overdrive
I heard about a mechanical overdrive (four speed) automatic tranny made in the mid 90's which might work in my 1990 Cummins 5.9 250. It currently has a 3-speed automatic. I have also been told there is a mechanical overdrive tailshaft I could use on my current tranny. Do you folks know which model numbers I should be looking for?
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Yes, on a 47RH there are only three wires that run to it. One is a 12v +(hot) and the other two are the grounding circuit for the TCC and OD. You can do something as simple as putting a switch connected to ground and connect to transmission. When you flip the switch, it engages.
If your current trans has lock up TC then it all should interchange. Ofcourse driveshaft changes.Thanks again,
Are you aware of any fitment problems? The truck has the Cummins adapter for the 3-speed. I suspect I will have to use another driveshaft or shorten the one I have. What about the torque converter and pilot shaft?
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Whoa! For that price he could buy and build himself a nice 47RH.gearvenders makes a od that goes on the back of your current trans they are 2500-3000 bucks if i remember right.there was one for sale on here not to long ago you might look back in the forsale section and see if its still there.
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Check on the classifieds here and CompD as often a 47RH will pop up. All 47RH are locking TC.
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No you want one from a diesel. The govenor weights , VB ,and internals are different.I had a thought. Since I will be engaging the OD with a manual switch, could I use a transmission from a gas model, like a V10 or 360?
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