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August 2011 Techline

Posted in How To: Tech Qa on August 1, 2011 Comment (0)
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Wants Lift for Tahoe, But Not New Driveshaft
Q I have a ’99 Chevy Tahoe 4x4, and the rear end has been eating up tires, so my question is what causes that?

The second question is, I’m looking to lift my Tahoe, but I don’t want to go any higher than a 4-inch lift. Everything that I find requires me to change the front driveshaft. Does anyone make a lift for mine that doesn’t require a driveshaft swap?
Kenny Bumpus
via fourwheeler.com

A There could be several reasons for loss of rubber on the rear tires. The most common is hard acceleration, which will cause more tire wear on the rear tires. Even if you don’t actually hear the tires squeal, rubber is being worn off because there will be some deformity of the tire’s tread when they are under load, which will result in a scuffing motion. A clutch-type locking differential that has the wrong gear lubricant in it can cause the clutches to stick and not properly release when going around a corner, again scuffing off rubber. Even excessive loads over the rear axle will cause the tires to flex more, resulting in more heat that increases tire wear. There could also be an alignment problem where the rear axle is slightly cocked with one side further forward that the other. This would show up as uneven wear across the tread’s face.

As to lifting the Tahoe, you’re right that the lift kit manufacturers recommend—and with the AutoTrac system, require—a new double cardan driveshaft. There is just way too much angularity on the single U-joint involved, and without the CV joint you will experience driveshaft vibrations. Plan on adding about another 450 bucks to the price of the lift kit. I believe that you may also have to do some custom exhaust work to adjust for clearances.

Swap Tips for ’70s Tradesman Van
Q I’m 17, and finally got to buy my grandma’s ’76 Dodge B200 Tradesman van with the 318ci V-8, TF 727 transmission and Chrysler 8.25-inch rear. I want to lift it a little bit (four to five inches), and four-wheel drive is a must. My fingers are numb from researching transfer cases so much, with little to show for it, so I figured I’d ask the god of four-wheeling.

From what I’ve read, I need a transfer case with a 23-spline output shaft and an eight-hole bolt circle to match my 727. I want a driver-side drop (the Dana 300 is not), heavy-duty, part-time transfer case that will bolt right up to the rear of my 727, or have a very low-priced adapter plate. I’ve seen a lot of Dodge vans with the NP203, but really nothing else. The 205 seemed like a good choice until I found out it’s a passenger-side drop too. Would a 208 work? Basically, I just want to know what year, make, and model year to look for.
Alex Goins
Via fourwheeler.com

A You have quite an undertaking, so be sure you have the ability, the help, and the proper tools to complete this project before you even start turning a wrench. With a project like this, it’s really easy to take on more than what you can actually do.

Let’s start out with the transfer case. Instead of trying to adapt a transfer case to your present transmission, I suggest you search out the wrecking yards, Internet and newspaper ads for a complete Chrysler-style transmission and transfer case already mated together. It will most likely save you money in the long run and make just one more of the many tasks you’re going to have to do that much easier. Maybe it even would be a good time to buy a complete wrecked truck, and also use the front and rear axles from it. Not only will you have a matching drivetrain but a matching suspension too. Maybe you’re going to get lucky, and the transfer case mount/crossmember will be adaptable to your van’s frame. Otherwise, you will have to fabricate one. Yes, the Chrysler 8.25 is okay, but it would not be my choice for a van conversion.

I am not into vans, but I will assume that the van has a solid axle and leaf springs from the factory. You most likely will have to cut off the mounting pads on your new front axle and relocate them to the proper width for the current springs. Do some careful measurements before you buy the front axle, and make sure the distance between the front springs will allow the new drive axle to fit. It’s important to check this width as there may be some interference between the location where the spring has to mount and the differential housing. You might have to measure several axles to find one with the proper differential offset to allow mounting.

Keep in mind that it is important that the front and rear axle ratios match fairly close. Ratios such as 4.09:1 and 4.11:1 would be fine, while 3.92:1 and 4.11:1 would not be a proper match. Having the same wheel bolt pattern, front to rear, is also nice.

Steering may or may not be a problem. Whatever you do, don’t compromise on the steering system. Overkill on mounting the steering box and the rest of the components is the best idea.

Axle/Drivetrain Swaps for Older/Newer F-250s
Q Will a front axle off of an ’06 Ford F-250 fit my ’99 Ford F-250 Super Duty (not the light-duty)? You see, my truck is a two-wheel drive which uses coil springs and a control arm on each side to keep it all in place. The ’06 F-250 also uses a similar setup, but of course with a solid axle instead off the weird twin beam setup that mine has. Also, will the transfer case off of the ’06 F-250 fit my transmission? If not, can I adapt it, and how hard would that be? I know if anyone can get me some for-sure answers, it would be you guys.
Tony Carr, Jr.
Brownsville, TX

A I pretty much had the answer to your question, but just in case I missed something, I went to my good friend and Ford suspension fabricator Jim Cole for a complete answer, and this is what he had to say:

“While the newer coil-spring Dana 60 axle can be adapted to the 1999 chassis, it is going to be more work than just adding the front axle. Crossmembers need to be changed or modified to clear the differential, and the steering box is normally relocated too. Where you may have a problem is that your 1999 may actually still have the early-style wheel bolt pattern that will not match that of the 2006 model; some early-production SDs, made in spring 1998, had the earlier 8-on-6.5 bolt pattern instead of the latter 8-on-170mm. Of course, you could also change out the rear using the one from the donor truck, and then you would be assured of a mating axle gear ratio.

“On the transmission, if your current truck is a manual and the donor truck is a manual, then the better option is to swap the entire transmission and transfer case combination. If they are automatics, they interact with the engine via the computer as to shift points, and you may also have to change out the computer as well as the wiring harness. In some cases, it is possible to swap tailshafts on some of the transmissions to accept the four-wheel-drive tailshaft and thereby the transfer case. Another, usually cheaper, option is to source a ’60s- to mid-’70s Ford Dana 24 or New Process 205 transfer case that is remote-mounted (commonly called “divorced”). This way, the two-wheel-drive transmission is left untouched, and the transfer case is simply mounted on a separate crossmember, with an additional driveline the transmission and T-case. On pickups with a longer wheelbase, this works very well and can save money on some projects.

“Whether this whole conversion is economical or not comes down to whether or not you are looking for a semi-stock-type truck that has four-wheel drive or a lifted custom-suspension 4x4. Time and time again, I will say it is more economical in both time and money to sell the two-wheel drive and buy a factory-built 4x4, though if a custom suspension-lifted truck is the goal, then many times dollars can be saved by starting with the 4x2 version. My shop, Bloody Knuckle Garage, commonly sources the used two-wheel drive vehicles to start custom truck builds, as these vehicles are normally in better condition overall and the entire front suspension, steering system, axle, etc., are being reworked anyway, so it saves money right from the start.”

Dana 44 Full-Floater: How Strong?
Q My truck is a ’73 GMC with a 6-inch suspension lift, 3-inch body lift, and 38.5-inch tires. It has a TH 400 transmission with an NP205 transfer case (twin-stick setup). The rear axle is a large Corporate 14-bolt full-floater, with 5.13:1 gears front and rear. The front end is a Dana 44-FF. I have seen you remark that the Dana 44 is not strong enough for a rig like mine, but I was wondering if it is different if it is a full-floater?
Edward P. Tomney
Via fourwheeler.com

A My opinion? You will eventually break an axleshaft or the ring and pinion gears—hopefully, not while you’re in a bad location.

While The Dana 44-FF is a full-floating unit, and the axleshafts only have to drive the wheels, the axles are actually the same size as those found in Blazers or ½-ton trucks. You do get a stronger locking hub and spindle assembly.

Yes, we have seen people running a similar combination quite often; however, that does not make it right. It’s sure not something that I would ever run. It is time to start looking for that Dana 60. FW

->“Whether this whole conversion is economical or not comes down to whether or not you are looking for a semi-stock-type truck that has four-wheel drive or a lifted custom-suspension 4x4.”

Where To Write
Address your correspondence to: Four Wheeler, 831 S. Douglas St., El Segundo, CA 90245. All letters become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department can also be reached through the website at www.fourwheeler.com. Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

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