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Discussion Starter · #1 · (Edited)
I've swapped a 47RH into a my 98.5 cummins Please don't ask why, long story . I'm hopping someone that has done this swap can pitch in and see if the see anything wrong with my wiring or maybe point me at what to look for.

Test drove it today. It only shifts when I let off the gas pedal and the rpms drop down, didn't notice the shift rpm.
Also, have to put it in neutral when I'm coming to a stop or the trans lugs the engine till it chokes.
I used the diagram below that I borrowed from someone but I don't think he is messing with this stuff right now, least he's not getting any email on that forum.
Anyway, I also did not use the exact switch he used, I used the rocker switches in the other diagram.
I also used two hobbs the 76073 which I'll include a photo of. These are three contact type (gr, on, nc) I don't know what nc is but I presumed I was to use on and gr.
2 diodes are inline you will see but they are not marked diodes on the diagram.
Notice the ground I ran on the three rocker switches it looks like I did what he was suggesting on the diagram only I connect at the terminal, but it seems to me that it would confuse the ground signal coming from the hobbs switches.
pushing the switches has no affect but the switch lights did start working once I ran that ground wire to each three switches.
The trans is shifting to 1 2 then OD at 35mph, needs some adjustment or a different switch to up the OD shift point at around 45mph.
Then I will probably feel it shift to 3rd - TCC - then OD.

Anyone see a wiring problem here or know what these symptoms indicate?
 

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I dont fully understand what this switch assembly is taking the place of normally, but the second image of the back of the switch with 3 terminals is a SPDT momentary switch which the one side is normally closed (NC), i may be way off, but i have seen NC on electrical and it has meant normally closed. Someone let me know if i am way off.
 

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Those are the wrong Hobbs switches.

35 PSI is 40-60 PSI too low and you need NO switches, not NC.

Wondering how the I PSI/MPH BS on the 47RH keeps perpetuating. Anyone who's ever done this would know it does not work.

Maybe Hobbs has an overstock of 35 PSI switches so they started the rumor.
 

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Just get a pressure gauge put it in test port and go drive the truck. And mark the pressure at the mph you want it to lock up that's the Hobbs switch you need for that then do the same for od and whala it works.
 

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just so you know-
NO= Normally Open= normally no current will pass thru
NC= normally Closed= normally current will pass thru
GR/COM, etc=common, ground, etc
 

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Discussion Starter · #6 · (Edited)
I added toggle switchs today, the switches actually started working but like you said hobbs are too low so I have to put it in neutral before I come to a stop.
I picked up 1psi/mph from reading up on the swap. One of the threads says that.
Thanks for straightening that stuff out for me.
The switches came with the transmission so used them so I could wire up and till I found out what type I will need.

What type of store sources the hobbs switches? plumbing? air conditioning?
I wonder if I'm going to need a vaccuum switch like they show torward the bottom of the page on this site?
http://www.transmissioncenter.net/SwapInformation.htm
Some one already mentioned the hobbs type switches they sell in the pact kit are not a good selection, too low I take it.
 

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The best deals on switches for this application I have found are available on ebay. Hobbs switches have some hysteresis used in this application and they aren't as versatile as their nameplate ratings claim- A 60 psi switch doesn't accurately go from 40-80 or whatever they claim.

Expensive, industrial looking ebay pressure switches even when rated for AC loads are better than the Hobbs switches. The actual current to operate the transmission shift solenoids is very small. AC (alt current) rated switches work fine.

Best bet is the 94-95 Dodge PCM.
 

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Discussion Starter · #8 ·
This is a 98.5 3500 cummins ram.
I wonder what would be involved installing the 47rh pcm in the 98.5?
Certainly not a plug and play but really, how many wires would I need to reroute?
 

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In my opinion the money and time to do the electronics on that tranny it would be worth the effort to try the pressure switch setup. I know I am in my 47rh.
 

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This is a 98.5 3500 cummins ram.
I wonder what would be involved installing the 47rh pcm in the 98.5?
Certainly not a plug and play but really, how many wires would I need to reroute?
Just an idea- But how about looking at your 47RE control wiring diagram and seeing if you can just hook the wires that shift OD and lockup the converter to the 47RH.

Or hell, bore the connector hole out in the case and put a 47RE valve body in the 47RH and be done. There are very few differences between the RH and RE. Basicly the RH has a governor, the RE does not.

I do not know what is involved to install the 94-95 PCM in your truck. However, I do think using a factory PCM to control the transmission is the best way to do it.
 

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Discussion Starter · #11 ·
Well this hole thing began with two dead transmissions, stopped pumping fluid. could be just a pump or maybe valvebody, maybe both maybe a bad check valve. Too many possibilities to continue throwing money at it. So here I am. Had a leaky 53block too! replaced with a 12 valve this summer.
Anyway I had thought about trying out my computer and wiring the tcc and od but somebody brought up the fact of all the codes that will be set off that may hinder with limp mode. So I said hell let's get it working then later maybe try my computer.
i do have tack and speedo is working too now with this tranny, but there will still be codes that may hinder the 98.5 computer from working od and lu in this 47rh.
I think I am going to try these switches below.
Maybe a 60-120 for lu and 100-200 pressure for overdrive. Wonder if I would be safe there then just dial them in trial and error or safer with 2 60-120 switches.
sales guy said when you get with in about 5 psi of the top set point there will be hunting.
If I figure 70 psi for lu and 100 psi for overdrive maybe that would be an all round good starting point.
Here is the guys post from another thread on the swiches.
I have found the switch to end all discussion as far as i am concerned. It is a switch made by transducers direct. It is a TDPS 131CW- it has an 18" wire lead or you can order a TDPS 131CD that has a connector you can use. I chose the first one because the second adds so much length. They are 50.00 each, but they are industrial type switches. They adjust from 20-120 psi within 1 psi. The differential is 10-20%. So, if you lock up at 50 mph you would not unlock until 40-45 mph. I suppose the same switch could be used to operate OD as well. The McMaster Carr switches are not for exterior use. I spoke with a guy named Joe at Transducers Direct 513-583-9491.
They have a website at: http://www.transducersdirect.com/default.asp
 

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If you want to use pressure switches-

INSTALL A PRESSURE GAUGE! DRIVE THE TRUCK WITH THE PRESSURE GAUGE AND 2 TOGGLE SWITCHES! WATCH THE GAUGE, FLIP THE SWITCHES FOR AT LEAST A FEW HUNDRED MILES IN ALL KINDS OF CONDITIONS! ORDER THE EXACT SWITCHES YOU NEED FOR THE PRESSURES YOU NEED!

If you can't do that than order every pressure gauge they sell because you probably won't get the right one. Every single transmission is different. Governor pressure relative to atmospheric (what you will be using to operate switches) is NOT what the valve body uses for reference. It uses the pressure differential between governor pressure and line pressure which IS consistent between transmissions.

OD needs to come in first, then lockup. It will work poorly if you have the transmission do a full locked shift into overdrive every time.
 

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Discussion Starter · #13 · (Edited)
Ok I hear ya check the pressures, I will.
Do you like the exact switches over the adjustable switches?

Oh, it would be hard to set the adjustable switch exactly, I see.
 

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You need the adjustable. Your tranny will change over time and you'll need adjustability. I'm going to use 0-200 psi , also going to find one that opens the circuit with in 10 psi of setting. You'll need 3, one for OD, one for lockup, and one to continue power after the speed is to high to down shift it will continue power even if the switch on the throttle is opened.
 

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Discussion Starter · #16 ·
You need the adjustable. Your tranny will change over time and you'll need adjustability. I'm going to use 0-200 psi , also going to find one that opens the circuit with in 10 psi of setting. You'll need 3, one for OD, one for lockup, and one to continue power after the speed is to high to down shift it will continue power even if the switch on the throttle is opened.
I had read a mention of a 3rd switch but it just goes right over my head.
wait..you just lost me, where does the 3rd one go, how does it wire in and what exactly does it do?
 

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They all are plumbed in together into the drive pressure port( I think it's called). Lets say for example the pressure is whatever at 60 mph you want one switch to close and go into OD. At whatever pressure at 65 mph one switch to close to lock the lockup. These two switches, the power will come from a batt source to a switch on the throttle so if you hammer the gas it will open the switch and no power will go to the tranny and it will down shift. The third pressure switch is closed at whatever pressure at 75 mph so when you hammer the gas and your going to fast to down shift it gives continuous power to the tranny.

These speeds are just for example purposes.
 

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Very difficult to get a "passing gear" activation to work properly with the pressure switches. You really don't want to downshift from 4 to 3 very often even under full throttle, but often times you will want to run OD with the converter unlocked.

If I was hell bent on building the EMP proof apocalypse zombie vehicle with an auto tranny the pressure switches could be made to work effectively, but you'll need more than 2 pressure switches. Ideally, you'll have two or three pairs of pressure switches for OD and LU with some simple relay logic tied into throttle position switches or manifold pressure switches. I would opt for the manifold pressure switches- They are going to give more useful info.

Talk about a pain to tune though. Getting two switches set perfectly can be a nightmare in itself.

The port used to activate the switches on the switches is the governor pressure test port.
 

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Manifold pressure switch would work on a natural aspirated engine but not a boosted engine. Thanks for correcting me on the port. Why wouldn't you want to down shift? if your cruising at 1500rpms and need to pass it would be a dog without that.
 

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Discussion Starter · #20 · (Edited)
This switch is only 30 bucks but would be pretty easy to adjust. Though it is open to dirt and grime.
https://www.transducersdirect.com/H...ails.aspx?sq=Kl0ouTYd6foAbK6x1309TFUeXelt3aGL

This is the switch that was referenced to use, is 50 bucks and would be harder to tune.
http://www.transducersdirect.com/HeleoCart/ProductPage/_TDPS.aspx

I read someone saying the shift points will most likely fall within around 100 psi.
Does it seem safe to say that I can get 3 of the 20-120 psi adjustable switches ordered? The next switch up is 100 to 400 psi


Also do you think one of these vacuum switches PATC sells would take the place of the third switch? for passing?
Also there is one guy that left the thread off at the point where he mentioned he would work out an arduoino build for these switches.
But like you say the other way is fully mechanical which carries weight on it's own. Course if we come to that I would be guarding a apocalypse proof 3500 diesel dually with my life.

I am following you guys posts and listening and learning but am ready to order the switches is why I interrupt and ask.
 
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