Too Many R's
Question: I recently traded in my '04 Ram 2500 Hemi Automatic for a '06 Ram 2500 Cummins G56 six-speed. When I am on the freeway cruising at 75 mph the Cummins is at 2,500 rpm! That seems insanely high for an engine that redlines at 3,000 rpm. I tried to find higher gears, but I was told that with the combo of axles that I have the highest ratio available is 3:73, which is what I already have.
I thought about bigger tires, but the whole point here is that I'm trying to get better economy and the added weight of bigger tires plus the slight lift it would give the truck would just mean that I'm pushing more air and not improving economy.
I have attached pictures of the old truck's rear axle (because I can't figure out what it is) as well as shots of the new truck and axles. I heard that the Chrysler 10.5- and 11.5-inch axles look the same on the outside. Is this true, or did my old truck have the 10.5 and the new truck has the 11.5?
Chris W.
via 4wheeloffroad.com
Answer: The highest (numerically lowest) gears I could find for your truck was a 3.42. This will lower your rpm some while cruising, but it's only about an 8-percent difference from the 3.73. In the end you're looking at spending $1,500-plus for a 250-ish rpm difference. If you just drove at 70 mph instead of 75 or waited for tire-buying time and went up a size, it would probably make more of a difference. That said, I have already written some gear manufacturers about this and asked if they might want to investigate an even higher highway gear.
Your Hemi had a 10.5, and your Cummins has an 11.5. There is a slight bulge on the right side of the diff cover of the 10.5, while the 11.5 has a larger bulge on the cover's right side.
Double The Ford
Question: My buddy has a '90 F-250 (which used to be 2WD) running Dana 50 and Sterling 10.5 axles from an '03 F-350. The truck has a V-8, a C6, a custom lift, and 42-inch TSLs. It will mainly be used for the mud but he has an itch to get into the rocks. So I showed him the way of the 203/205 doubler. The problem is finding a Ford NP203. We found you can get them remanufactured at a certain auto part store, but the Chevy units are plentiful. We have found the adapter for the Chevy case to the Ford NP205. Is there a way to adapt a Chevy NP203 to the C6 or vice-versa?
Beau
via 4wheeloffroad.com
Answer: I called the doubler experts at Off Road Design (970.945.7777, www.offroad design.com) and was told that unfortunately you really need the Ford 203. The most important feature of the Ford 203 is the 31-spline input gear; the housing with the correct Ford bolt pattern is nice, but the input gear is key. If you can come up with the 31-spline input by itself you can put the gear into a GM or Dodge 203 since they interchange. From there you drill the correct bolt pattern into the 203 front face, use the appropriate doubler adapter, and you're set. But usually the 31-spline Ford input gear comes in a Ford 203.
Applications for the Ford 203 were F-100s and big Broncos up to F-350s all through the '70s. You do have to watch out for the divorced Ford 203s; they were in some of the 3/4-ton trucks and don't work for a married system. But they might have some value for your buddy since it's possible to mate the 203 and 205 and connect the whole transfer case system to the transmission with a driveshaft. This technique works well in longbed trucks.
Stupid Ford
Question: I have a '98 Ford F-250 (Light Duty) 3/4-ton 4x4 pickup. I am confused as to why my truck is only a seven-lug instead of an eight. It has a 6-inch Fabtech suspension lift on it, and I'm currently running 35-inch Buckshots on it. I'm looking to upgrade to Super Swamper LTBs and some black rockcrawler rims.
I've been saving up my money to buy a package deal, but I have a problem. I can't find wheels for a seven-lug anywhere! I've even gone to wheel shops looking for the original wheel skins and center caps, and apparently they don't even make those anymore. I haven't seen too many of these F-250s around, but the ones I do see have stock wheels on them, same as mine. My wheels are very rusty and need replacement.
James D.
Answer: This is ridiculous. Why can't there be some consistency in wheel bolt patterns?! Five lugs for Jeeps, six for Toyotas and half-tons, eight for 3/4- and 1-tons! Sorry, James, it's not your fault. All these silly car companies keep screwing things up.
Your 7-on-150mm bolt pattern is really hard to find wheels for. I did find some aluminum wheels from Ultra Wheel Co. (www. ultrawheel.com) that might work (PN 164-6876P). Otherwise my advice is to call every wheel advertiser in this magazine and ask if they have something for your crazy seven-lug truck.
Have you thought about taking off your wheels having them sandblasted and powdercoated black? That would probably be cheaper than buying new wheels, but you may need to have your truck on jackstands for a couple days until you get the wheels back.
Solidly Confused
Question: I am about 90-percent done with an SAS (spring-over swap) triangulated four-link on a '95 GMC 1500. I have the links made and installed, the axle truss done, and the steering done. The axle is a high-pinion Dana 60 out of an '88 Ford dualie.
I am curious about a Panhard bar. Do I need one with this application? The upper links go from the frame to the center of the axle, and the lowers go from inside the uppers to the axletube just inside the knuckles. I was reading in your Sept. '08 issue the story "Links, Leaves, and a Bar Named Track" (page 30). In the section headed "Links Part One, Three, and Four," I get the impression that if you have your links triangulated, a track bar may not be needed. I can see the relationship between the opposing angles of the links locating the axle side to side and can see why you would need a Panhard bar if you did not have triangulated links. I also see where a Panhard bar would help with bumpsteer.
This truck is a trailered trail rig and will be driven on the road a little bit, but never for long distances or over 60 mph.
Chris
via 4wheeloffroad.com
Answer: For your truck I think you'll be fine without a Panhard bar, but I'm not sure if you use a regular steering box or full hydraulic steering. If you have a four-link suspension where at least two of the links are triangulated, such as your uppers, you don't need a Panhard or track bar (Panhard bars and track bars are the same thing).
If you mix a triangulated four-link with a Panhard bar, you will have a binding issue, as the Panhard forces the axle to move side to side during suspension movement, whereas the four-link moves the axle straight up and down. You will need at least two radius arms or three or four individual straight links to keep the axle located when using a Panhard bar.
The problems arise when you run a triangulated four-link with a steering box, as this can cause bumpsteer, especially if you have crossover steering.
I'd recommend a three-link with Panhard if you are running a steering box with crossover steering, or full hydraulic steering if you are running a triangulated four-link. Most of the time you need your draglink to run parallel to and be as close to the same length as one of your suspension links, and this is usually easiest with the Panhard bar. I have seen it done with a four-link, but it requires mounting the steering box back on the frame near the link mounts and using a bell crank steering arm.