Q What is a crawl ratio? How can you figure it out? What’s the best ratio? I’m trying to build an S10, so I want to do it right.
A Your crawl ratio is the transmission First gear ratio times your transfer case low-range ratio times your axle ring-and-pinion gear ratio. I have no idea what your factory parts are, so I’ll guess that your S-10 has a 700R4 automatic transmission with a 3.06 First gear. Behind that it may have an NP231 with a 2.72 low range. And your axle gears may be 3.50 for argument’s sake:
3.06 x 2.72 x 3.50 = 29.13
Your crawl ratio is 29.13:1. Not very good if you’re looking for slow crawling control and torque multiplication for big tires off-road. That said, the automatic uses a torque converter so it can make up for the dismal number, but lower would be better. If you have a small engine then you’ll definitely want a lower crawl ratio.
My Toyota has a four-cylinder engine and 39-inch-tall tires, but by using a R151F transmission with a 4.31 First gear, dual Toyota cases with two 2.28 low-range options in series, and Dana axles with 7.17 ring-and-pinion ratios, I have a megalow 160.64:1 crawl ratio (4.31 x 2.28 x 2.28 x 7.17). Plenty low for big tires and a small engine.
Without knowing your current drivetrain it is difficult to know what ratio to send you toward. Bigger engines with more torque don’t need as low a crawl ratio; smaller engines do. Let’s say you have a 4.3L and a 700R4 auto and want a lower crawl ratio. You can go to a 4:1 low range in an NP231 if that is the transfer case you currently have. Multiply that with an axle ratios around 4.88 and you’re now at 59.73, twice your current crawl ratio. If you have a 4.3L Vortec V-6 and 33- to 35-inch tires I think you’d be pretty good for off-roading and still daily driving.
The first step is identifying what you have for transmission, transfer case, and axle gearing. Then determine how big a tire you want to go to and what type of terrain you want to wheel (rocks will want a lower crawl ratio, sand and mud not so much). An automatic will make up for a higher crawl ratio to a point with the torque converter, while a manual is best with as low a ratio as you can get. Remember, you can always shift up if the crawl ratio is extremely low.
Q I have an ’90 GMC Stepside z71, mostly stock. I have had this truck since 1993. The truck is in good condition, except northeast Pennsylvania has been pretty tough on the frame. I have had it patched a few times, but I am waiting for the inspection station to finally say no some year. I can’t seem to part with her. What is the easiest way to fix rust?
A Wow! How quickly I forget the dreaded Pennsylvania rust. I am a native Pennsylvanian who now lives in California, where I could find a truck like yours but rust-free for $2,000-$5,000 all day long in the classifieds. Fixing frame rust isn’t going to be easy other than sandblasting, grinding, and welding in new patch panels (see “Costly Corrosion,” May ’12). If your frame is rotten then I assume all the fasteners and body panels are not far behind, so doing a frame swap isn’t a great option either; the work wouldn’t be worth it. You could do these repairs, but rust doesn’t rest and eventually you’ll be repairing more and more of the frame than is worth fixing.
My best advice: Keep driving it until the frame fails or the inspector gives you the thumbs-down, and then search Craigslist or eBay Motors for a similar truck to yours but from the Southwest. Buy it, fly out here, and drive it home. You’ll get to see America, have an adventure, have a new rust-free truck, and save yourself the time and expense of replacing your frame and all the other rotten parts.
Nuts, I’m Confused
Flipped & Lifted?
Q I have a ’79 Chevy Blazer that has 4.56 gears, a 360-horse 350 V-8, TH350 transmission, and a 205 transfer case. It has a 21⁄2-inch Rancho suspension lift and a 3-inch body lift. I have the steering problems narrowed down and taken care of. I want to know what the benefit of a rear shackle flip kit is, and if it would affect the drivability of the truck. If I put this kit on, would I be able to get rid of the rear blocks? I was also wondering how I would go about getting rid of the 3-inch body lift on the truck. It is not cool on a windy day!
A Your Blazer sounds like it needs a quick suspension revamp. How about replacing your 21⁄2-inch lift and a 3-inch body lift with a 4-inch front spring and an Offroad Design (ORD) rear shackle flip? The shackle flip allows you to delete the lift block, keep the smooth-riding stock leaf pack, and gain enough clearance for a 37-inch tire with slight trimming. It works just fine for street driving and off-road use. ORD also has a 21⁄2-inch shackle flip, but the 4-inch seems to work best on Blazers that are often tail-low.
ORD offers various front leaf springs for a 4-inch lift, or you could keep your Rancho 21⁄2 and run the lower 21⁄2 flip kit. You could remove the 3-inch body lift (not a bad idea in my view), but without knowing your tire diameter it is hard to determine between the 21⁄2- and 4-inch. I’d say go up to the 4-inch leaf pack and 4-inch shackle flip, and ditch the 3-inch body lift if you’re running tires 35 inches or taller tires.
Since you’re looking into proper suspension upgrades and away from extremely tall body lifts (I don’t care for body lifts over 2 inches) I think you deserve this month’s Nuts, I’m Confused prize. I spoke to the crew at ORD and they’d like to send you a set of sway bar disconnects, perfect for an on-road GM 4x4 that also likes to twist it up off-road. These bolt on easily and not only allow more movement when disconnected, but also correct the geometry of your sway bar to still control your axle movement without overly binding the suspension. The ORD guys are experts on your square-body Chevy trucks and Blazers. They offer everything from bumpers and steering components to suspension and gearing modifications. Find out more at www.offroaddesign.com or 970.945.7777.
Q I scored a great deal on an ’87 Suzuki Samurai and have been in the process of undoing the previous owner’s hack and booger work. It’s almost time for the “fun” stuff (tires, bumpers, lockers, winch). But before the bigger tires can go on, I know I need to change the gearing. I have talked with several “experts,” and some say to change the gearing in the transfer case. Others say to change the gearing in the differentials. Others say to change both. Where should I change the gearing?
A Adding lower gears is important for off-road performance because it helps the engine compensate for larger tires, and it helps motivate the vehicle over off-road obstacles with less strain. Putting lower gearing in the transfer case is a good idea because it offers a gearing reduction in low range when you want it, but it also compounds the torque applied to your driveshafts and driveshaft U-joints. Putting lower gearing in your axles is good because it protects the driveshafts, but it also means you cannot shift out of that lower range because those gears are always on, and it cost more to change axle gears than transfer case gears because you have to change two sets versus one.
The Suzuki Samurai has a unique benefit in that you can purchase transfer case gears that lower both the high- and low-range gearing. This is good because you’ll want some lower gearing in high range to make up for the bigger tires for street driving. Plus, depending on the size tires you spend money on, the Suzuki axles may be a waste of time (they are good to about a 33-inch-tall tire before components start snapping with severe use).
My vote for a Suzuki is to always do the transfer case gears first. This will get you lower for both street and trail and can compensate for quite a few jumps in tire size. Many companies offer transfer case gearsets. Examples of these are a 4.16:1 low range with a 12.2 percent high-range reduction, a 5.14:1 low range with an 18.3 percent high-range reduction, and a 6.5:1 low range with a 20.2 percent high-range reduction. A few of the companies: Trail Tough (877.789.8547, www.trailtough.com), Calmini (800.345.3305, www.puresuzuki.com), Rocky Road Outfitters (888.801.7271, www.rocky-road.com), Petroworks (800.952.8915, www.petroworks.com), Trail Gear (559.252.4950, www.trail-gear.com), and Low Range Off Road (801.805.6644, www.lowrangeoffroad.com).
What’s With That?
Q My friend Todd got his Jeep in your magazine, and even on the cover [“Powered-Wagon,” Mar ’12]! My Jeep is way cooler than his. How come you didn’t feature mine?
A We look for a lot of things in a feature truck. Is it unique and different? Is it a high-dollar shop-built vehicle or a low-buck garage project? Does it have cool parts, or is it a recipe for a buildup that works but which we’ve seen time and time again? There is a magazine issue for each of these. Take this month for example. We have a cover section about axles, and the truck on the cover has some very cool axles. It is an oddball one-off concept, but we think it’s cool enough that it will sell magazines. Next month we concentrate on our Cheap Truck Challenge, so we may choose a feature truck that’s also cheap, or we’ll flip it and feature a high-dollar 4x4 just to contrast against CTC.
Dark paint and a bunch of sponsor stickers are less appealing to the eye and photographer than bright paint without stickers, but that photo of your Jeep (above) does make it look cool nonetheless.
The most important thing is we are out there at events looking for trucks that actually work. The best way to get in the magazine is actually pretty simple: Paint it a bright color, send it in to our Readers’ Rides department (we peruse those submissions for feature trucks), and get out there wheeling. Don’t be afraid to invite us to your local trail rides and 4x4 events. We can’t attend every event, but we definitely can’t go if we don’t know about it! Maybe we’ll see you on the trail, Brian.
Old But Available
Q I have a ’58 Chevy Napco 4x4 truck, and I can’t find an input seal for the old Spicer 23 divorced transfer case. Any idea where I can find one?
A You can get the seal or completely rebuilt transfer cases from Lugo Parts & Restoration in Loomis, California (916.652.0840, www.lugoparts.com).
Confused? Email your questions about trucks, 4x4s, and off-roading tech using “Nuts, I’m confused” as the subject and include a picture (if it’s applicable). Digital photos must measure no less than 1600 x 1200 pixels (or two megapixels) and be saved as a TIFF, an EPS, or a maximum-quality JPEG file. Also, I’ll be checking the forums on our website (www.4wheeloffroad.com), and if I see a question that I think more of you might want to have answered, I’ll print that as well. Otherwise drop it old-school style with the envelope addressed to the address below. Letters published in this magazine reflect the opinions of the writers, and we reserve the right to edit letters for clarity, brevity, or other purposes. Write to: Nuts & Bolts, 4-Wheel & Off-Road, 831 S. Douglas St., El Segundo, CA 90245 fax to: 310.531.9368 Email to: firstname.lastname@example.org