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47RH 4th Gear

2K views 6 replies 3 participants last post by  Safety Guy 
#1 · (Edited)
I have a 2004 F550 4x4 at work that had a 6.0L in it. We converted it to a 12 valve about two years ago. We were using the stock Ford transmission which we replaced numerous times. We have now gone away from the Ford trans and installed a 47RH. This combination has worked very well but we are having trouble getting the transmission to go into 4th gear.
This is what I have done. I was told to install a preasure switch to activate the 4th gear at around 40 mph. Before I put in the preassure switch, I hooked up a preassure guage to see exactly what the preassure is at about 40 mph (I was told 1 psi for every mph). At 40-45 mph it was running about 90 psi (strange). So I installed a 90 psi preassure switch. The problem is that when you get to your desired cruising speed (in 4th) and back off the throtle to maintain the cruising speed, the preassure drops and it goes back into 3rd gear.
I am now thinking that if I can tap into the speedometer so that at a predetermined speed, it would put power to a silonoid and in turn activate the fourth gear.
Is this possible or should I go a differant direction?

Paul
 
#3 ·
The transmission is brand new. I checked the preassure prior to having the tranny rebuilt. When the tranny shop rebuilt it, they installed a manual switch to activate fourth gear. A couple days after we got the truck back, one of my employees was driving it and the fourth gear solinoid went out (shop replaced it free of chage). I am thinking that the young guy I had driving it did not take it out of 4th soon enough which put a extra load on the solinoid and burned it out. This is why I want to go with something more idiot proof. If I could tap into the speedo, there would be now need to flip the switch.
 
#4 ·
Ya im not to good on my electrical termanology but if i had to guess you should be able to figure out what the frequencey coming from the speedo at 40mph or your desiered speed and get a switch that would trigger at that frequencey. Sorry i cant really tell you what electrical components you need to complete that project but i know it can be done
 
#6 ·
What about using an aftermarket cruise control set up to trip it? That way when you set it, 4th engages and when you tap the brake it disengages.
 
#7 ·
That would work if I were driving it. Since it is a company vehicle, I would not know if the person driving it is driving down the freeway in 3rd gear (forgetting to go to 4th), or driving through town in 4th gear at 20 mph (forgetting to shift out of 4th). If I were to use the speedometer to activate it, it would shift into 4th at a set desired speed and then again come out of 4th when slowing below a set desired speed. I hope I am making sense, at least it makes sense in my head.
 
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