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December 2002 4x4 Truck Repair Questions - Tech Line

Posted in How To: Tech Qa on December 1, 2002
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Address your correspondence to:
Techline,
Four Wheeler,
6420 Wilshire Blvd.,
Los Angeles, CA 90048-5515.

All letters become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department also can be reached through the Web site at www.fourwheeler.com. Due to the volume of mail, electronic or otherwise, we cannot respond to every reader, but we do read everything.

Chevy Questions
Question: I own a '69 Chevy K-10 shortbed 4x4 equipped with a 350ci V-8 that currently is under construction. The truck also has a granny-low four-speed, stock transfer case, stock 12-bolt axles, and a 6-inch suspension lift. Is the transfer case an NP208? If not, how do I tell what it is? The front axle is of the closed-knuckle design. Is this good, or bad?

Will the disc brakes from a '76 4x4 Blazer bolt onto my axle? I was thinking about putting power brakes on it, too. Is this as easy as bolting on a power-brake booster from a '70-'72 truck?

I'm experiencing angle problems in the front driveshaft. The ears on the driveshaft are hitting the inside of the yoke on the differential. I'm not currently using a constant-velocity joint. Should I be? Are wedges on the front axle a good and easy solution?
Tom Foster
Otwell, Indiana

Answer: We like the early Chevy pickups so it's great to hear of your efforts to keep one alive. The year your truck was built, 1969, was the first year that the very stout NP205 transfer case was used. But there also is the chance that you have an NP200 or NP201 (the 201 has a PTO plate on the side). If you have a 200 or 201 T-case, you'll find the numbers 196 cast into the top of the case. You can bet it's hard to see with the T-case installed in the rig. By the way, this number also happens to be the low-range gear ratio-1.96:1. This is also the same low-range ratio in the 205. The 205 should have a data plate riveted to the front side of the T-case. Again, it's in a difficult position to read. These cases are made from cast iron.

The NP208 transfer case is quite easy to distinguish from the others because it's made out of aluminum, with lots of strength ribbing along its sides. There's a red-and-silver data plate riveted to the left-rear of the case. The advantage of this transfer case over the 205 is the fact that the low-range ratio is a cool 2.61:1. However, this T-case wasn't built until 1980 and saw usage until 1991. So unless someone swapped it into your 1969, most likely you have a 205.

Yes, the disc brakes are a basic bolt-on after perhaps a slight amount of grinding on the steering knuckle. You will need a disc-brake master cylinder and a proportioner valve to balance the system. It appears that the power brake booster also should bolt into place. Master Power (888/251-2353, www.mpbrakes.com) is a good source for these parts.

As to your front driveshaft problem, this is pretty common with vehicles lifted as high as yours is. No, a CV joint won't help the clearance problem and in fact most likely will make it worse. The front axle in your truck is a Dana/Spicer 44 and has been used by a lot of vehicle manufacturers. What this means is that there are lots of different styles of pinion yokes available. Some have more clearance than others. I spoke with Paul Carey of Randy's Ring & Pinion Service (800/347-1188) and he suggested using Spicer yoke PN 2-4-8091-1X. This yoke uses the same 1310 series U-joint that you presently have. The one negative factor is that it is of strap design other than the full U-bolt design. These straps have a tendency to stretch after miles of hard usage, so it is a good idea to replace them every few years. Randy's has this yoke in stock at less than $30.

Mud Madness
Question: I'm 15 and want to build a hard-core mudding truck to drive to school and take mudding on the weekends. I have a 1970 Ford F-250 with the 360 and five-speed transmission. I want to swap out axles from a four-wheel-drive truck to mine. I would also like to swap a 460 for the 360. Can I beef up the stock four-wheel-drive axles to take the Kansas mud? If so, where can I get the parts? I have only found a four-inch suspension lift for it and I want to run 44-inch tires. Where can I find a lift that will give me the clearance I need? What tires can take the mud but don't wear excessively on the highway?
Justin Allen
Peck, Kansas

Answer: It's very difficult to build a hard-core anything, be it a desert racer or a mud machine, and still keep it streetable as a daily driver. If you play hard, you're going to break things, and when you do, there goes your transportation. Next, I have said it before, and I will say it many times more: You are money, time, and frustration ahead to sell what you have and buy a factory-built 4x4 than try to make a two-wheel-drive truck into four-wheel drive. This is especially true with Fords, thanks in part to the way that their frames are made, with a large front crossmember that must be removed from the two-wheel-drive trucks for front-axle clearance.

If you plan to use 44-inch tires, then you definitely need a custom-built suspension that will handle the traction needs of these tires. You're also going to need a Dana 60 front axle out of an F-350 to handle the load.

As to a good mud tire that works equally well on the street, well, there just ain't no such critter. Sure, the Super Swamper Boggers and the Ground Hawgs are great mud tires, but neither is the most practical choice for street usage. I recommend you get out to a few mud events, see what the locals are using, look around for the parts that you need, then make a master plan for the construction, keeping in mind just what every part is going to cost.

Chevy Buildup
Question: I'm building a 1978 Chevy 1/2-ton 4x4. I have a 350ci truck-engine block with four-bolt main bearings that has been bored 0.40-over and I also have a fresh set of 76cc truck heads. I'm running a Turbo 350 and for now an NP203. I plan on replacing the dished pistons with a set of flat tops. I think that should boost the compression up to 9:1. I also plan on running an Edelbrock Performer manifold. I'm not sure what cam I should run and what gear ratio. I drive the truck on-road more than off. It has a four-inch lift and I plan on running 33- or 35-inch tires. I've been told to use 4.11 or 4.27s if I run 33s, and 4.56 or 4.88 for 35s. Do you agree?
Patrick Doyle
Nashua, New Hampshire

Answer: Depending on the block deck height, how much is taken off the cylinder head to square it up, and the gasket used, the compression ratio will come out between 9.O:1 and 9.2:1. With the Edelbrock Performer manifold I suggest you also use a matching Edelbrock Performer cam. The company has spent a lot of dyno time to match the cam to the flow pattern of the manifold.

The gear ratio you choose will depend upon how serious you are about your off-highway travels versus how much time the truck spends on the street. If it sees mainly freeway miles, then perhaps the stock 3.73 ratio will be just fine with 33-inch tires. I suggest that you buy the tires first before making any gear ratio changes and see if you're happy with the performance and whether you need the lower gears. Naturally, lower gears will raise the engine rpm at highway speed. If you plan to spend a lot of time off the highway, then the lower gearing is the way to go; 4.10 for the 33s and 4.56 for the 35s would be good combinations.

Electric Fans For More Power
Question: I wish to add more horsepower to my rig's engine by using electric engine fans. My truck is a '97 Chevy Z71, powered by the 5.0L V-8 with EFI, A/C, and automatic transmission. Which fan size would be best, how many are to be installed, and whose product should I use?
Erv Hartung
Las Vegas, Nevada

Answer: While I am sure that there are several fans available that would work just fine, one company that comes to mind that produces quality products is Flex-a-Lite. It offers, under part number 280, a dual 15-inch fan setup that pulls a nearly unbelievable 5,500-cubic-feet of air per minute. This is a huge amount of air and compares favorably with the factory fan. While it's a direct bolt-in replacement for your truck, it's not without its drawbacks. The biggie here is that it takes a full 28 amps to keep it running. However, being thermostatically controlled, it will only run when needed. The company's dyno indicates a 12hp gain and a fuel efficiency increase of 2 mpg with this fan replacing the OEM mechanical unit. Several of the mail order stores such as Summit Racing Equipment (800/230-3030, www.summitracing.com) have this fan available.

The Torsion Lift Question
Question: I have been told that I can gain an inch of lift on my 2000 GMC by simply adjusting my torsion bars. Is this true? If so, how do I do it? What are the negative effects?
Craig Breckenridge
via fourwheeler.com

Answer: You can, but making this adjustment requires a special tool (Chevy #J-36202) which will hold the tension on the torsion bar as you adjust it. If you do raise it the one inch, you will have to have a frontend alignment done.

The downside is that you will have limited your suspension's droop, or down-travel, by the amount that you gain in compression travel and the ride quality will suffer. We don't recommend doing this.

'Cruiser Question
Question: I was wondering if you can direct me to a site where I can find the factory specs for the 1976 Toyota Land Cruiser FJ-40. I checked your site but found no archived articles. I also have tried checking all over the Web, with no luck. I would appreciate any help.
Matthew J. Lutz
via fourwheeler.com

Answer: I suggest that you contact Cool Cruisers of Texas (214/707-8993). This shop restores '76-'83 FJ-40s. If anyone would have this information, they should.

See Our Website!
Want your tech questions answered on the Internet? Is so, just log onto www.fourwheeler.com and click on "Text Exchange" to get the scoop from readers with the same problems you have. It won't cost you a nickel.

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