47rh shift logic

[Ralph Warfield]

Afternoon .. this might not exactly be protocol … I am in the middle of prepping for a trip pulling a trailer with my truck .. I have owned it for a few months and have been slowly working through the issues created by the previous owner … my latest upgrade was a new tps because of a random lock /unlock converter issue .. That issue is fixed I think … what it does now is something I can recreate consistently and it may be nature of the beast so to speak … for all intents and purposes it shifts firmly through all gears .. the lockup is what I would consider slightly slow but I don't have another auto dodge to compare it to and all the other dodges I have access to are manuals .. so not much help there … so here is the scenario … driving at 55mph approaching a hill as you start up the hill you accelerate slightly to maintain the speed and you push a little harder to maintain the speed and suddenly it unlocks and the rpms of course increase then it locks right back up … It will do the same thing if you are accelerating moderately with the t/c locked and back off the throttle a little … any thoughts or is it working properly … I have the tps and the t/v cable adjusted per the shop manual … thank you for your help … Ralph

[Mopar1973Man]

Alternator noise issue possibly.

 

Here is the fix for the 24V I'm not sure how it will pan out for the 12V.

 

[Ralph Warfield]

Maybe ... I tested out the alternator when I was troubleshooting the lock /unlock previous issue ... I will disable the alternator in a few and take a ride ... I watched the scanner during my last test drive and the pcm is definitely doing the locking and unlocking when you accelerate and back off the throttle ... and I dont mean back to idle .. I realise it unlocks when the throttle is closed ... it is consistent in od and in 3rd as far as the unlocking when you back off slightly and only I'd you are trying to accelerate... if you are cruising and back off slightly it does not unlock ... the repair manual give the sensors monitored when it locks and unlocks but doesnt exactly show the relationship in real time under driving circumstances... thanks for your thoughts ..

[Mopar1973Man]

AC noise from the alternator affects all sensors with speed. Like tachometer, output speed sensor, ABS speed sensors, etc. The bad part is the only tool that can see the noise is o-scope. 

 

 

[Ralph Warfield]

Scope is no problem... lemme go grab it 

[Ralph Warfield]

The ripple is like ... .003 volts and a swing high to low of about .006 ..you have to get below 500mv to really see a pattern ..... at 100mv its not a great pattern but this damn minuscule... the pattern looks like the bad one in the video but he has a 4+ volt swing low to high .... 

[Mopar1973Man]

Now measure at highway speed. Start watching when the TQ conv starts hunting.

[Ralph Warfield]

Lol... now you want to make it complicated... I gotta make a jumper harness for that ... I dont need to go fishing for a test lead during the ride... btw ..what did I do to deserve this kind of complication... lol ... let's see what I can work out .. almost need a co pilot... I'll be back .. 

[Mopar1973Man]

That's the whole problem to measure at the time of the problem. 

 

You could just have the alternator bench tested.

[Ralph Warfield]

I know... I actually have an alternator tester ... and older precision model ... I think it needs batteries.. gonna look into that this evening but the scope changed about 2 tenths and I suspect that was due to load ... had the lights on ... hitting the brakes make a negative spike of about .3 volts ... turning the fan on hi gives you about -1 volt and it immediately recovers.. I'm monitoring it at 10ms... I think alternator is ok ... I compared a 24v dodge I have here doin the same tests ... virtually identical...

[Mopar1973Man]

At least on the 24V the alternator charge line runs beside the ground for the PCM, ECM and VP44. Creates that issue. Being the 12V doesn't have a ECM and VP44 PSG those are out. But as for grounding of the PCM I'm not sure. 

[Ralph Warfield]

Im not sure I wish I knew where another truck with a stock set up trans was so I could compare … odd of finding another auto truck mines age that hasn't been molested in one way or another is probably nill….I was hoping someone who had one in the past would chime in and recognize my quandary and say whether its normal or odd … it is 100% repeatable .. mash halfway down on the throttle while cruising in lockup let up slightly while its accelerating and it will instantly unlock and relock … its not slipping and it has no way to monitor slippage to cause it to unlock … and the pcm is telling it to unlock and relock I can watch it on the scan tool … maybe some sort of shift logic glitch … if its normal . I might get an aftermarket controller and program it to do what it should … I know some of the programming was designed to help this trans live behind the CTD … I think the soft converter lock is part of that … hopefully one of the guys running a 47rh will know... thank you for playing sounding board today .. tough to find solid information in a lot of forums full of bad info and people who believe it ...

 

[Mopar1973Man]

@Cowboy is one member with 12V. Hmmm... If I think of other members I link them.

[Dieselfuture]

Luckily I don't know a whole lot about automatic transmissions, so I'm not much of a help. Could you possibly put @IBMobile mystery switch to control torque converter manually. 

[Ralph Warfield]

Bypassing or overriding the pcm is an option ... at the end of the day I'm not unhappy with the function and operation.. I just wanted to be sure the trans is operating correctly ... you can find normal glitches in most things but they are often things that have to be accepted or modified to improve ... but arent necessarily wrong or broken... this might be normal operation... no one so far can say ... I've eliminated the usual  causes... truck drives nice .. gets good mileage... I've driven the truck about 2k since I've had it ... fluid is still red and doesnt smell ... I'm gonna throw about 12k behind it and head on a 1500mile trip .. I wanted to be sure its behaving normal...lol... the abnormal will get you stranded every time ... 

[Ralph Warfield]

Evening guys ... this is petty and childish and I can't help myself... I posted this question on a justask site and this is the response I received... I hope you guys enjoy this as much as I did ... when I read it the first time I though the top of my head was gonna blow.... 

 

I have been searching for the torque converter lockup and unlock logic chart and evidently they dont exist so... it a 1995 47rh behind a all stock 6bt cummins .. all original no hackz.

 

 JA: Do you have the torque specs?

 

Customer: For?

 

JA: What is the make/model of your '95 transmissions?

 

Customer:47rh

 

JA: Are you fixing your vehicle yourself? What have you tried so far?

 

Customer: It works like it should with the exception of an odd unlock scenario with the converter New tps... ground verification on the pcm .. made sure the ground path for the pcm isolated ground is good... verified the alternator is not causing an ac voltage issue interfering with the pcm signal

 

william readon  Transmission Mechanic according the the service info the 47rh in trucks with a diesel DOES NOT have a lock up converter, are you setting faults for the converter clutch? what makes you think it's equipped with one

 

Omg ... are you serious .. . Please find me someone who knows something about dodge trannys... All 47rh transmissions are 4 speed with lockup converters .... not sure what you are reading but dodge hasn't used a non lockup transmission behind a cummins engine since 1993 ...

 

william readon  Transmission Mechanic no problem< however i have worked for dodge since 89 and don't remember ever seeing a lock up converter on a cummins and the service info agrees with that and here's the link to the info please note there's no mention of a lock up converter. however i will be happy to opt out for you

Edited March 6, 2019 by Ralph Warfield
Additional info

[Ralph Warfield]

Ok for what it's worth... I fixed my transmission issue ... after testing and checking and replacing... the brake switch... which is some overly convoluted 6 contact abortion ... was really sensitive and can break the signal to the lockup without actually causing the brake lights to light ... and the rod is adjustable for anyone that isn't aware ... the issue with my truck was the natural up position of the brake pedal is not the end of its travel on my truck .. so the pedal bouncing had pushed the switch rod too deep into the switch ... maybe a stop of some sort is missing on my pedal assembly or ... the master cylinder rod isnt adjusted so the pedal has full return ...  I discovered another issue yesterday ... after having a tire break a belt about 50 miles from home .. it shook the truck to death.. now I have the unlocking converter issue again ... seems the tps I replaced 2 months ago is a touch erratic... bouncing between 10 and 30% throttle while holding in one position... also seen on the voltage side as well ...  I also verified the alternator ripple to be sure it was not damaged .. I installed a new brake switch the old one had been beaten by the brake pedal till it wont hold its rid position anymore... here is what I discovered that makes little sense as maybe one of you guys have seen this on your trucks ... I did the 1000ohm resistor for the trans temp sensor as a test ... which should show up as roughly 90 degrees on the data pid...  however my solus ultra reads it as 246 degrees f... I have to believe there is a translation issue with the obd1 ... any thoughts ?... I know this was long winded but wanted to share for anyone curious ... here is another thought for the mechanically inclined and creative ... why not adapt a TPS to work on the throttle pedal and get the sensor off that electronic destroying vibration monster lol.... I know there are easier ways to make them work but not as drive and play friendly ... thanks for letting me be a part of this ... Ralph

[Ralph Warfield]

Ok last post here and maybe some of this could be tech related ... so here is my temporary solution and a viable diagnostic test ... cheap and I'll dare say accurate .... so you think your tps might be bad and you don't see anything obvious with a test meter.. hard to imitate the vibration of the engine under a load .. and you dont want to make up a bunch of test leads and have a friend watch your meter while you drive .. because I know we all use a co pilot so we can watch the road .. so here is an easy test ... virtually foolproof ... and cheap .... take a 50k ohm resistor.. mine was actually 47k so that might be a standard size it's out of a cheap 1/4 watt resistor assortment ... the 47k resistor gives you 1.60 volts or 14% throttle ... the low tps will default to 1.25v ... fold the ends and insert them between pin A and pin B .... shove it all the way down and fold over and wrap with some electrical tape to keep everything in place ... and drive it ... if the tps is the problem you will know... the truck will now drive like it should and shift like it should ... the only side effect I see is no adjustability.. the tps control the time or rpm of you prefer between the 3 and 4 shift ... with this resistor it's set for general use ... if you flog on it the 3 to 4 are kind of close... and the other result ... good or bad you decide is the torque converter no longer unlocks when you release the throttle so you have a little engine braking .. you still have double redundancies on the converter unlocking ... it unlocks when you get under 45mph and it still unlocks immediately when you use the brake pedal.... for the record... a 100k ohm resistor.. mine was 99k gives you 2.50 volts which is close to 75% and will make the 3 to 4 shift spread out further ... I think I'm going to work on a pedal actuated tps for mine ... but in the mean time it drives as good as ever with this setup ... like I said maybe not a long term fix but definitely an easy diagnostic tool ... 

[Evan]

Interesting thread.

 

[wil440]

I missed this first time round.. interesting read.. 47k resistor now in the truck as I have a few of them for my heating boiler