Engine RPM's
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Jed - the stock 4bts used in the vans made peak torque at about 1700 rpm. From an efficiency standpoint that is the best point to run the engine at for cruising down the highway. For max power you have to wind them up more, there is a thread on here that has dyno charts, can't remember the name of it now but I'm sure someone else knows. With a turned up pump and advanced timing the torque peak moves up some. As far where they will run reliably I'm sure they'll run fine all day at 2500, it just might wear out a little sooner than one spinning at a lower rpm.
Steve
Steve
I'm planning on a ZF S5-42 with 3.55 gears and 36" tires. It will turn about 1800 @70 but still have a 1st crawl ratio of about 55:1 with the BW 1356 transfer case in lo range. For secondary roads I can run in 4th at about 1870 @ 55 or if I want to run in 5th it will be about 1550 @ 60. I won't be doing any heavy towing or hauling so I figure this should be just about ideal.
When I bought my stepvan donor the former owner said it was good and solid. On the way home I put the pedal to the floor and held it there for 150 miles, except for a short traffic jam. Temp indicator never moved from the middle and electric fan never came on even though it was a 95*-100* day.
I now run Dana 60 4.1 rear, NV4500 with 29% O'drive, no transfer case, 31" tires, which gives 2050 rpm's @ 65 mph, spins a little higher with 29's. That gives me peak torque where it should be, say about 55, and I've had it up to almost 90 mph. I can twist it up higher once I put in the 3,200 governor spring.
http://www.4lo.com/calc/gearratio.htm
I now run Dana 60 4.1 rear, NV4500 with 29% O'drive, no transfer case, 31" tires, which gives 2050 rpm's @ 65 mph, spins a little higher with 29's. That gives me peak torque where it should be, say about 55, and I've had it up to almost 90 mph. I can twist it up higher once I put in the 3,200 governor spring.
http://www.4lo.com/calc/gearratio.htm
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4.10s and 31s and you're running 2050 at 65mph? I run 35s and 4.10s with no tach but I assumed it was a little over 2050 at that speed. I also have the ford ZF OD which is close I'm pretty sure to the NV4500.
According to that calculator I'm around 1900 RPM. That's not bad. I also run like 6psi constantly on the highway so I think my gear ratio is pretty good. MPGs are hard to calculate since my speedo is off a little bit. I need one 'o dem GPS units.
According to that calculator I'm around 1900 RPM. That's not bad. I also run like 6psi constantly on the highway so I think my gear ratio is pretty good. MPGs are hard to calculate since my speedo is off a little bit. I need one 'o dem GPS units.
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15 Posts
I'm working on my '47 WDX Power Wagon with 5.83's and the only gear swap is to 4.89's. I'm definently putting in an overdrive tranny maybe taller tires later. 35" are on it now. It's not a daily driver so the overdrive tranny might be enough for what I do with it. It would be real nice to go 50 or 55 in this thing once in a while without the engine screaming. I restored it ten years ago and I don't think I've ever gone faster than 40. 
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812 Posts
Jed;I'm working on my '47 WDX Power Wagon with 5.83's and the only gear swap is to 4.89's. I'm definently putting in an overdrive tranny maybe taller tires later. 35" are on it now. It's not a daily driver so the overdrive tranny might be enough for what I do with it. It would be real nice to go 50 or 55 in this thing once in a while without the engine screaming. I restored it ten years ago and I don't think I've ever gone faster than 40.
My 1943 Dodge WC-53 Carryall is exactly the same as a Power Wagon except for wheelbase and body style. With my 4BTA/NV-4500/NP-205 turning 4.89's and 36inch STA Tires I can run any legal posted speed. I run 60 mph at 1950 R's. There are pictures on my Image Event Site of the 4BTa in the Carryall which may or may not help you with your WDX install. My site is all Power Wagon Stuff, surf around it. Congratulations on your WDX Project, they are great trucks
http://imageevent.com/moosecreekmaple
Paul
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Hi paul, I'm very familiar with your Dodge Projects, very nice work. I wanted to ask you about the hydraulic winch set-up you went with when I get closer. The stock tranny did have a pto which ran my winch, but I think going hydraulic like you did will be very nice. I'm very excited about putting the 4bt in this truck...It's just what it needs! Where did you get the 4.89's? Vintage Power Wagons, Veteran Vehicles?
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812 Posts
Jed;
You have a Beautiful WDX, she is a head turner. I got my 4.89's from Bob Stahl at Veteran Vehicles. Email me when you ready and we can chat about the winch in detail, probably do a phone call.
Paul
You have a Beautiful WDX, she is a head turner. I got my 4.89's from Bob Stahl at Veteran Vehicles. Email me when you ready and we can chat about the winch in detail, probably do a phone call.
Paul
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