To understand this, let's first look at what happens when you drive on slippery roads with open differentials. With an open differential, the tire with the least traction will receive most of the engine's torque, resulting in one spinning tire and one coasting tire that can keep the vehicle anchored directionally. You may not be able to get forward motion, but the vehicle will handle more predictably and will not fishtail as much as with a locker. Take the same driving conditions and install a rear locker, and now whenever one tire spins and loses traction, both tires spin and lose traction. With both tires spinning, your directional stability goes to almost zero and the vehicle could fishtail or even spin around. Why? Well, as we've been taught, "When you lose traction in one direction, you lose traction in all directions." Add a locker to the front and you lose most of the steering control as well.
Now having said all this, we know that lots of people out there run lockers in the rear of their 4x4s even in regions that get a lot of snow because they are willing to make the trade-off of stability for true four-wheel drive. These types of vehicles should not be lent out to drivers who do not have experience with locker-equipped 4x4s, as their handling dynamics are entirely different than production 4x4s. The best choice for snow and ice driving is a selectable locker that could be left in the open mode until the vehicle got stuck, then engaged as needed.
Heavy Chevy
I own a '79 Chevy pickup with a 350 engine, a TH350 tranny, and an NP203 transfer case. I've broken the transmission housing twice in the last two years, and the local shops tell me the transfer case is just too heavy for the transmission. I see many vehicles with this combo in your magazine and want to finish my restoration, but not if I can't solve this problem.Bill CaverDeetrail, Colorado
You didn't mention where the transmission housing keeps breaking, but we bet it's on the front where the engine block bolts to it. The NP203 transfer case is indeed a heavy piece of machinery, but more important, the distance from the front engine mounts to the rear mount on the adapter is too long for maximum strength, which causes a lot of trans-case breakage. CRC Transmissions (Dept. 4WOR, 3139 Los Feliz Dr., Thousand Oaks, CA 91362, 805/497-0399) informs us that in normal service, most trucks didn't have a problem, but playing Dukes of Hazzard caused plenty of breakage of the early Chevy transmissions like yours.
Around 1979 or 1980, GM introduced reinforced cases for its pickups, including the S-10s. This "K" case (named for the cast-in capital K on the unit) was stronger and featured a cast-aluminum lower cover instead of the sheet-steel version. This allowed for reinforcing struts from the bottom of the transmission to a plate under the engine mounts for more strength. Switch your case to the later style with the associated struts and half your problems may be solved.
But wait, there's more! If your case is cracking in the rear or breaking the adapter itself, you might need a torque-reaction bracket on the passenger side of the transfer case to limit movement. If the bolts that attach the adapter to the transmission are loose, this can also allow movement that will eventually break a casting. Back in the mid-'70s, a kit was available from 4Wheel Parts Wholesalers which included safety wire and bolts drilled for it, but it was discontinued. You could drill your bolts to accept wire or just use liquid thread-locker.
Domestic Pathfinder PartsI own a '92 Ford E-350 van equipped with a Pathfinder Equipment Company 4x4 conversion. When the Dana 60 frontend needed alignment, my local shop couldn't find tie-rod ends because Pathfinder is out of business. I called Dana Spicer Technical Service and found out Advanced 4 Wheel