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Re: 42RH overdrive transmission upgrades and install
[Re: roadrunninMark]
#1175830
09/02/12 10:02 AM
09/02/12 10:02 AM
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Joined: Jun 2008
Posts: 10,958
Oakdale CT
gdonovan
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Quote:
Excellent 
If that makes you happy, this should really thrill you!
Some notes-
1) Only one *hobbs adjustable* pressure switch is required for this setup, they generally tend to be the most expensive items and you should be using relays anyways since I have seen pressure switches fail from handling the amp load of solenoids.
2) Time delay relays are used for two reasons- Reason one is that pressure switches tend to flutter around the set point and can cause the transmission to rapidly shift back and forth between forth and third, not good. This way once the PSI switch settles down the relay will finally time out (5 to 10 seconds in my case) and you get a solid shift. Note that each time the switch flutters, the timer on the relay restarts! So you will not get a shift till you time out which is a good thing.
You can also extend the mph at which the trans shifts by simply extending the time of the relay- Instead of 5 seconds make it 10 or even 15. I may make it 10 in my case since we get a lot of traffic in this area which floats back and forth in the 45-55 mph range. I could set the pressure switch higher raising the mph point or just set the relay to come on a touch later. I would rather have the relay come on later since my Duster is happy to cruise on the backroads with OD and LU active at 55-60 mph while turning 1700 rpm. The 5.9 has more than enough grunt at this low rpm to pull away without using very much pedal. A 5.2/318 might be want a bit more road speed and a higher mph set point to make up for the less available torque. Your engine, rear end ratio and tire size will determine what works best for you in regards to mph PSI setting and time delay on the relay.
The second reason is it does away with having to have two pressure switches, the lockup time delay relay is keyed into the first relay and makes the car feel like it has a five speed trans (I can hear and feel lockup when it happens) plus it also protects lockup from the same flutter condition that can happen in overdrive. Remember, the timer for the LU relay does not start till the OD relay has timed out and made the shift into OD!
By time delaying the shift it gets you further out of the zone when flutter can happen.
Even if you do get in this zone then you have to just deal with just OD going back and forth and not both at the same time.
For less complexity you could do away with one relay and just have OD and LU come on at the same time, I ran the car for several weeks that way. The relays are dirt cheap though, I picked up three 0-30 second relays shipped with bases for less than what you would pay for a single pressure switch and they even have LED's that show when they are powered up and have timed out.
The dash switch kills everything of course, just a regular 904 at that point Mine is disguised as a map light switch in the factory location.
I really don't like the vacuum based switch for WOT- If you are undercarbed then at WOT you will draw a vacuum at higher rpm's and overdrive will trip back in! I'll be swapping to a mechanical switch off the carb for this reason since I'm only running a 625 cfm Carter.
Any questions feel free to fire away!! Diagram is in handy 8 x 11 printing format. Red lines indicated 12V+ circuits, black indicate ground side of circuit.
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Re: 42RH overdrive transmission upgrades and install
[Re: roadrunninMark]
#1175834
09/02/12 01:21 PM
09/02/12 01:21 PM
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Joined: Jun 2008
Posts: 10,958
Oakdale CT
gdonovan
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Quote:
What do you estimate the total cost you have in this trans? This trans is exactly what I am looking for. I want to put in my 71 behind a new hemi. Car is in bodywork stage right now but I am hoping to have done and painted by end of year. What convertor would you recommend for me? Hemi will be either 6.1 or very low possibility of a 6.4 Right now I have the stock open 2.76 rear gears in the 8 3/4. Car would be same as yours, a "warm" cruiser.
$150 transmission core
$230 Mopar Performance converter
$24 Shift kit
$195 Driveshaft shorten and balance
$123 Trans rebuild kit
$40 Five clutch front drum
$15 New aluminum accumulator
$40 4.2 ratio kickdown lever
$29 Longer speedo cable
$6 Trans mount
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$852
Yes, aside from the driveshaft I did all the fabrication and transmission building.
My advice to you would be to go with the A-518/46RH (727 based) for use with the more powerful engine, use a trans with lockup so how loose the converter is doesn't matter at cruise (though if using a stock 6.1 or 6.4 camshaft I doubt you need a very loose converter)
As for brand I'd suggest doing some research as to whom can make you a lockup unit. I tried both a MP unit (which filled my trans with debris in a few miles!) or currently a Hughes unit (which I have to send back this winter as they neglected to make loose enough)
A Viper converter has been mentioned by the Dakota/Durango guys and there are a few other companies that can handle the work as well.
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Re: 42RH overdrive transmission upgrades and install
[Re: roadrunninMark]
#1175837
09/02/12 03:30 PM
09/02/12 03:30 PM
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Joined: Jun 2008
Posts: 10,958
Oakdale CT
gdonovan
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Quote:
Gary, you think the stock convertor that would come with the trans work? (518)
Nothing to lose by trying it, at worst you would have to pull after and swap for another. The factory converters are pretty good, I ran the factory 904 one with great success in the Duster before swapping over to the 42RH.
Quote:
Also, would I need the 4.2 lever, aluminum accumulator?
Check the archive section on the lever selection (under 727) and most late model trans come with a plastic piston which is why I replaced mine.
904/727 units will swap right in if you have a used one kicking about.
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I assume I won't need the front 5 clutch drum (as the 518 has it already?).
I'd have to bust the books out but safe not to assume anything and verify everything! I'd not be surprised if some 518 came with some 4 clutches. You could in that case get a different drum or run thin clutches OR thin steels.
Quote:
Last question, as I never have rebuilt a trans before, how difficult would it be to do so? (I don't think I will need to remove the OD section?)?
Thanks
Very time consuming and you will need some special tools and manuals to do the job and the overdrive section should be gone though too. For a novice its not a trans I'd start off on as it can really try ones patience at times.
I've done piles of 413's 904's and 727's and really had to take an extra level of care doing this one, extensive valve body mods didn't help.
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Re: 42RH overdrive transmission upgrades and install
[Re: BigBlockMopar]
#1175838
09/02/12 03:34 PM
09/02/12 03:34 PM
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Joined: Jun 2008
Posts: 10,958
Oakdale CT
gdonovan
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Quote:
I think I want to finetune the activation speed based on my combo..
Hence the suggestion of using a hobbs adjustable pressure switch and the delay relay, between the two you can really tune when the OD is activated.
I could adjust the switch with an allen wrench as low as 35 or as high as 75.
Like this one-
http://www.ebay.com/itm/Honeywell-Hobbs-...=item3f163d523a
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