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Discussion Starter #1
I'm looking for a 4 speed transfer case. I know that Atlas has it but they do not recommend it for heavy duty application. My vehicle is going to weight about 10,000 lb (455/70 R 24 wheels).
 

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I'm building vehicle for heavy off-road application. The project aims to develop assemblies as well as a whole new multi-purpose vehicle adapted for operation in extremely hard terrain conditions (military training ground, places, rail and air accidents).
 

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Gotcha. Well that being said ORD has an adapter and gear kit that couples the range box from an np203 to the np205 assembly giving you a full gear to gear set up that is easy to operate and very reliable while still being cost effective. Since I'm assuming you will be running a diesel the 3 ranges should be more than plenty with there super low kit. Coupled with super low gearing like the rockwells have and you have a very capable simple and reliable platform. For extreme heavy duty there are 2 spd cases used in 2.5 ton trucks and bigger with the same principle high torque and low axle gearing. If you want a true hd you'll have to go full custom $$$ any particular reason you want to go with a 4spd? Also a few particulars on your concept would make helping you a lot easier ex weight flexability speed ground clearance tire size etc
 

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Initially planned to use the 6.5L Peninsular Military engine but it can only run with GM 4L-85E. I need a diesel engine which can run other with manual or automatic transmission. The second problem was the 4L-85E has a "narrow" gear ratios. From my calculations I need 4 speed transfer case (our client wants to have a minimum driving speed less than 2 miles per hour). Then Atlas said for Heavy Duty application they recommend only 2 speed transfer case. Then became interested in the Duramax engines running with the ZF S6-650 manual gear box (for that application Atlas 2 speed transfer case is ok). I understand that no company has 4 speed transfer for heavy Duty application (my vehicle is going to weight about 10,000 lb)? Are there similar companies to Peninsular offering engines for military application (working with a different transmission than GM 4L-85e)?
 

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if its reliabilty your after and not speed then honestly imo the old 6.2 diesels are great for reliability and mileage and when geared properly have plenty of torque. the 203 should bolt right up to the back of the tranny you want to use with the 6.5. its all about gearing. current ratio on a stock 203/205 doubler is around 3.96:1 couple that with your first gear ratio and say a 5.13 axle ratio and you have a crawler. throw on instead a set of portal axles with say a 2:1 ratio at the hub as well and your looking at ft per hr and not miles per hr. the gear kit that ord has for the conversion lowers it more keeping things simpler on your end so you can use the eng/trans you origanally wanted a 3 spd case and a good set of axles. any idea what kind of suspension you want to use? solid or ifs?
 

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will you be using the 3.08 or 2.48 first gear ratio transmission? if you tell me that and the tire size they want to use i can give you your 1st gear speed
 

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bedtime for me but fyi if you use the 3.08 trans 5.33case and a 5.13 ratio with a 37 inch tire commonly used by the military your looking at 0.91 mph at idle and roughly 70mph top speed and with the 3.96 case your looking at 1.23 mph at idle.
 

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any idea what kind of suspension you want to use? solid or ifs?
i can only say that it is going to have Independent suspension with Hub portal (reductions).
what is the top speed they want to run
About 80 mph
will you be using the 3.08 or 2.48 first gear ratio transmission?
Peninsular recommends 2.48 (4L-85E)
if you tell me that and the tire size they want to use i can give you your 1st gear speed
455/70 R 24

You say not to give up the 6.5L Peninsular Military engine?
 

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sounds like a hmmwv suspension with unimog tires. if so the portals are reserve rotation and you will have to have some custom stuff made. im not sure of how to calculate in the portals but assuming that your close the the 5:1 ratio at the axles your looking at roughly 1.98mph at idle with the 5.33 case. as long as you stay with the "1ton" style setup like the hmmwvs have you should be fine under 10k lbs using the ord case and 6.5 with 4l85e. i would however talk to an engineer and see about getting the planetary hubs regeared and switched to a forward rotation if your using a standard hmmwv planetary in order to be compatible with off the shelf parts for the primary drivetrain
 

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Here is another thought :thinkingto get low gearing. Could you put in a second manual 4 or 5 speed transmission between your transmission behind the engine and your transfer case. You would need a divorced transfer case at least from the first transmission. I have done that in some farm equipment in the past to get my gearing down. You would need to determine how heavy duty the second trans and transfer case would need to be to handle the torgue multiplication you would get. Or how about a 4 speed auxilary trans used in some trucks for the 2nd trans. then you wouldn't need to worry about making a bearing support for the input shaft that normally uses the pilot bearing in the fly wheel. Not sure of there ratios but I have seen a low-low gear. underdrive gear, direct and overdrive ratios in these auxillary trans.

Just a thought since don't know all your details and how much space you have to work with. :goodluck
 

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He's going to go with a custom 2 speed case. Basically to meet requirements for what he wants it has to drive like a normal vehicle but be able to do a single super slow crawl speed and being the nature that it is has to be able to be operated by people who probably shouldn't be driving in the first place lol. Add too many levers or buttons and bad things happen. I was just trying to point him in an off the shelf direction but from the details he gave me custom is his only option
 

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He's going to go with a custom 2 speed case. Basically to meet requirements for what he wants it has to drive like a normal vehicle but be able to do a single super slow crawl speed and being the nature that it is has to be able to be operated by people who probably shouldn't be driving in the first place lol. Add too many levers or buttons and bad things happen. I was just trying to point him in an off the shelf direction but from the details he gave me custom is his only option
Yea I know to many sticks would/can be confusing for some people. I was was just giving another option to get low gearing for crawling speeds which I have done in some shop built farm equipment. I like to use the KISS principle when ever possible.
 
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