April 2009 4x4 Truck Tech Questions - Tech LinePosted in How To: Tech Qa on March 1, 2009
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V-8 Swap and 44s on a Budget?
Question: I am trying to build my '91 Chevy shortbed with a 4.3L TBI V-6, five-speed, and four-wheel drive. I want to swap in a solid axle and try to keep the five-speed. I'm on a very tight budget, but I want to try to use a GM axle and change out transfer cases. Can I get an NP205 easy with a GM axle? Where do I start?
I'd also like to do an engine swap to a 350. I want a solid drivetrain on a budget. I want to run 44-inch tires. What year of GM truck should I look at for 1-ton axles? If not those, what axles would be the next best?
I plan on using the truck for mud races and rockcrawling, but at the same time want it to be driveable on the streets.
Answer: If you're looking to run 44-inch tires, you can't expect to do this on a tight budget. Dana 60 axles are not all that cheap-even salvage-yard units. Most of the conversion kits on the market are designed to use the Ford high-pinion model of the Dana 60. Then you're going to need to change the steering to a crossover type, which will set you back about $600 to $800 dollars to do it right. Most likely you're going to need a hydraulic-assist ram to turn the tires. Put away $800 to $1,000 for this. Stock axleshafts and axle joints will work for a while but will eventually break with 44-inchers, so this means more money.
Then you have to decide on what you want to do for suspension: coilover or leaf springs? Just the brackets necessary to do a leaf-spring suspension are close to $1,000, and then you need the proper lift springs. Besides that, you're going to have to do quite a bit of fender trimming to clear the 44s, as most of the kits are designed to work with only up to a 40-inch tire. Now if you want to do a coilover front suspension, just about double the cost of the total leaf-spring package. Don't forget that you're also going to need a new rear axle, with the most common being a GM 14-bolt at a minimum.
Engine swap? The V-6 to V-8 swap is not all that hard, but you will need a new computer as well as the wiring harness to complete it. Don't forget the bigger radiator too. Your present transmission and transfer case are not up to the job, so they are also going to have to be replaced as well. Also, don't forget to add in the cost of new front and rear driveshafts, which could run close to another $800 or more.
Your "tight budget" better be close to $8,000 to $10,000 by the time it is all done. And that is doing it on the cheap side. If you plan to update brakes and other components, use a new custom-built front end and such, you could easily double or triple the cost. A couple of websites to take a look at are Off Road Unlimited (www.offroadunlimited.com) and Off Road Design (www.offroaddesign.com); they have the parts and pieces that you will need to make the conversion.
NP203/205 Doubler Strength
Question: I am considering going to one of those "doubler" setups where the gears of a 203 transfer case are used in front of a 205 transfer case in order to achieve a 4:1 low-range ratio. I am in the well pump-installing business, and my truck, a 1-ton Chevrolet, is pretty well loaded. The motor is a big-block 502. Will the doubler transfer case be strong enough to handle the weight and engine power? What is your opinion?
Answer: I would think that the transfer-case combination should handle the torque without a problem as long as it is reasonably applied. You might want to give the guys at Off Road Design a call for their opinion. Advance Adapters (970/945-7777, www.advanceadapters.com) has recently come out with a new super-strong output shaft kit for the NP205. It's reported to be made from an alloy similar to 300M, which is really tough stuff.