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The latest PWA (and probably others) with its Hercules re-power article mentions a Dennan (sp?) overdrive. Where did it come from? What are the ratios? Google won't bring anything up on it for me except its mention in (these) forums. What other auxiliaries are out there besides Gear Vendor and US Gear in this genre? Also, I can't seem to find the low gear ratio on a Dodge NP 271-D transfer case. Anyone know?
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The Dennan is made by Dennis Gronan. They are British Laycock units he prepares/modifies for use in the Power Wagons.
He has not made any for a few years, and there is a waiting list for the next production run. I believe they are about $1100 but am not sure. I am on the list to get one for my '52 power wagon.
I am not sure about the ratio. Everyone that has one seems to like them. The only caveats I have heard is that 1, they are not made for extreme off road use or high torque situations, and 2, if you forget and shift into reverse with the ovedrive engaged it will severely damage/destroy it. -
overdrive unit
Thanks for the information on the Dennan. Does your comment on the torque mean that it should not be put behind a Cummins engine? I'm about convinced to use a US Gear overdrive unit on a Cummins 4x4 because it fits behind the tranny and in front of the transfer case. That process requires a considerable lengthening of the front drive shaft and corresponding shortening of the rear. Then today I read the current PWA and thus my original question. Gear Vender advertizes an in-between unit also, but is very tight-lipped about it both on the phone and with e-mail. It is supposedly only for racing. They seem to think an overdrive in 2wd is all one needs. That also limits gear splitting to 2wd operation. The truck in question has the G-56 which has a beautiful deep-under in first (6.29:1) but the overdrive is only .79. An extra 20% would really help especially with $3 fuel and lots of freeway driving, taking RPMs from 2400 down to 1920 roughly. Any further advice? Again thanks.Comment
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I am not qualified to give you advice on the questions you ask. A man named Cabell Garbee, however, is someone who probably knows many of the answers. He often posts under the military truck section of this forum. He drives a M-37 with a diesel repower.
I would suggest a post there.Comment
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use a STAK transfer case
it will fit in the stock location with mods to the bracketry and can do the following. it will provide three ranges of reduction. deep reduction for crawling, a higher range of 4wd and an overdrive. you accomlish a lot with the case as you save on driveshaft mods, you gain overdrive in all driving combos and you improve your low range. the cases are modular and they build them to your truck's needs. i will eventually do a cummins repower in a ffpw and im planning on using one. you could also just change the transmission to a nv4500 with a married 205. thats a pretty good combo too. mannycComment
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stak is cool, i WAS going that route, but changed my mind
3.73 low
1 mid
.69 high
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4.33 low
1 mid
.75 high
(i may be a little off on the ratios, but that should be close)
about $3000!Comment
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the STaK
The people at STaK said that their case with OD should not go behing a tranny with OD such as the G-56. They said it made the gears spin too fast in that transfer case. It would be OK behind 1:1. He also said that one couldn't split gears with their unit. But you're right that would be an ideal solution. He thought that it would stand the torque of a diesel. If they told you something different it would be interesting to know what to believe. Also, evidently New Process and New Venture Gear are the same thing. The same source indicated the ratio of the 271 as 2.72:1 in low range. The Duramax uses a 261 which is 40 pounds lighter but the same ratios. A 263 or 273 is the same case with solenoid shifting.Comment
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its non synchro. you MAY be able to double clutch (for gear splitting), but not in any kind of hurryComment
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STaK
The double clutching should be no problem. The unit is obviously built for stout. Has anyone in Dodge-land actually tried it behind an overdrive transmission? Your comments are helpful.Comment
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iirc they specifically do NOT want you to run it in conjunction with an OD tranny, or tow heavy loads.Originally posted by leekathy@atcjet View PostComment
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Just installed a Stak4x4/Nv4500 combo in a friendīs Ramcharger itīs the 5.44:1/3.05:1/1:1 version.
Thatīs heavy duty my friends. With 5.13s in the pumpkins and 37" tires you have a real lo-lo there, we are looking forward to try it on the rocks.
In the case of the OD unit the lever location is critical. It has to be very close to the gear selector to be usable, and the other two levers must be locked to avoid an accidental shift into low.
IMHO the OD should be in the tranny for ease of use and the t-case have to make the underdrives.
Can you imagine reaching under the dash, pass the gear lever to select the OD while you are at highway speeds. Scary.Comment
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