Off Roading Crawling in Lo-Lo - non-lockup converter

["Mad Max"]

Okay peeps



Here's the project: '78 RC, 518, 203/205 doubler. Being built for camping, hauling the ATV's, and occasional rock crawling at Moab, etc.



I like the 518 because it's nice and simple. I like the 47RH because it has a lock-up converter and can be combined with an exhaust brake for 'slowing down the load'.



What I can't determine, is what kind of 'manners' a 12V will have with a 518 when in Lo-Lo crawling around. 'Going' isn't the problem - it's the 'woahing' I'm curious about.



With a gasser, ya get decent engine braking.

Without a Cummins, ya don't.



Will it really matter??? I'd love to hear some testimonials from y'all out there in 1st gen land with 518's or 727's who off road a lot.

Do you wish you had a lock-up transmission and an exhaust brake?



I hope I'm making too much of a big deal about it, but I'm going back and forth between using the 518 transmission I have now or finding a 47RH



This is my quanrdy - please lemme hear your thoughts.



Many, many thanks,

- Sam

 

[WoodChuck]

Lock up converter all the way. The transmission is essentially the same as the 518.

 

[Flexiheep]

I am guessing that you are planning to control the lockup option manually or something other than stock with a 47RH? In first gear I don't think a stock 47RH will ever lock up, at least not on throttle-off downhill stuff.

I don't think that with a 205/203 doubler you will have enough gearing to drag the motor along in low low on steep slow downhills with a 518.



Side note, I don't understand the "no compression braking" with a diesel engine thing. Even with my 518 if I down shift and let off the throttle on the road, I get a lot of slow down and the engine rpm is pulled up by the drivetrain just fine... ... I think the slushbox (compared to a manual) has a bigger effect on the comp braking than the diesel engine vs the gas engine.



Last thought, I got my 518 rebuilt a year and a half ago, it was the easiest thing to do with the time I had at hand (not much). With plenty of time to plan I would find a way to make a 47RH work if I had to do it over again. That is if I could make its control transparent to the operator during normal driving. I don't like having to give my wife complicated instructions just to drive my truck.



edit:

Just saw your explanation of comp braking problem in the other thread, What kind of a trailer are you using, did you sell your big enclosed one? My heavy trailer experience has been with my travel trailer (11. 5' tall wall, 10K lb), the added wind resistance may be what makes the big hills "easier" for me to go down.....

 

[rattle trap]

With plenty of time to plan I would find a way to make a 47RH work if I had to do it over again. That is if I could make its control transparent to the operator during normal driving. I don't like having to give my wife complicated instructions just to drive my truck.



down.....

converter lock up and over drive can be engaged with 2 pressure switches and a tee off the governor port.



for each psi = ~1mph. so you may want 2 switches rated between 40-50psi.



with a gas engine that produces vacuum you can force a downshift, converter unlock with a vacuum switch. since we arent dealing with vacuum you may have to look into the "drive by wire" nitrous oxide industry.



if 1st gens have a tps this can be accomplished. these nitrous oxide switches use voltage from ANY tps and convert it to a on/off signal for a relay.



lets say you want to force down shift at no more than 1/2 throttle and you check with your DMM and find that 1/2 throttle=2. 5volts for example. well when this nitrous switch senses 2. 5 volts it can either power or disconnect a circuit such as the one feeding the 2 pressure switches.



these pressure switches tie into the 3 prong connector on the drivers side. the middle pin is a switch hot off the ignition the 2 outer pins originally went to the pcm on 94-95 rams and are switched grounds. one leading to the lock up solenoid and one leading to the over drive solenoid.



with the pressure switches engagement is automatic. disengagement is the responsibility of the tps when speeds exceed the oil pressure switches.



reading about the "mystery switch" on 2nd gens helps to understand this a little bit.



shouldnt the 518 be a lock up unit as well? if the diesel one is not, maybe a valve body and few other parts from a gasser 46rh would work?