Q I have an '85 Chevy army truck with a 6.2L diesel and a TH400 transmission. My problem is the truck is screaming to reach 50 mph. would I get better speed by swapping in an NV4500 five-speed? Or must I change my axle gearing? If so, what would you suggest?
A I had an '86 Chevy army truck that was stolen a year ago, Bryan. Man, I miss that truck. (To the scumbags that stole it: Hope we never find you!) I put an NV4500 in my truck and would not recommend it. The price and time needed to swap the 4500 isn't worth the effort, and the 6.2L doesn't have the power to pull the odd gear spreads of that manual transmission. Plus, the NV4500 requires special oil, resulting in $100 of lube to fill it!
These military trucks are perfect with the TH400; they just need taller tires. If you upgrade to 37s you'll be just fine for most highway jaunts. The axles are plenty strong, the rear has a Detroit Locker already, and by adding a front locker and a winch you'll be hard-pressed to come home walking. I added the Banks turbo for some more power, but the stock 6.2L isn't that bad. Well, OK, it is bad, but you can deal with it.
I miss my truck. Please keep your eye out for it. It had camo seats, a winch hidden under the front bumper, and steel rock sliders welded to the frame.
More Deadly Wobble
Q I have been helping a friend build a YJ. The stock axles have been swapped with a Dana 44 up front and a Ford 9-inch rear. Ever since the axle swap, when driving down the road at approximately 40 mph the Jeep starts to shake terribly up front! It feels almost like the front wheels are wobbling. The only way to make it stop is to slam on the brakes. The YJ hasn't been aligned since the axle swap, so I guess that could be some of the problem. However, the wheels seem to be sitting level and straight ahead. We did use a tape measure to try and make it close.
I am pretty sure the front gear ratio is 5.89 and the rear is 5.83. That may not be exact, but it is very close to what they are if it isn't. I know the ratio should be the same front to back, but the guy who installed the gears said being that close shouldn't hurt anything as long as the front hubs aren't locked in on dry pavement. I don't know if that could be causing this shake. I wouldn't think so because it's in two-wheel drive when it acts up.
Also, the tie rod bar (from tie rod end to tie rod end) is slightly bent. You know how gentle rocks are! I guess that could cause it as well.
The next upgrade is in the works: flat-top knuckles and high steer setup. We were wondering what your thoughts were as to whether these modifications would correct the shaking problem. Any input you can give us would be awesome!
A You are experiencing the elusive death wobble, Anthony, and trust me, you're not alone. I get questions like this every month. It is a phenomenon when one wheel starts to act on the opposite wheel via the tie rod, and the next thing you know there is a deadly front shake.
To start with, you need to get an alignment. Make sure the tires have the proper air pressure, check all steering and axle joints for slop or wear, and try swapping the tires front to rear because they may be unevenly worn up front. Proper toe, caster, and camber are important, and this can all be fixed with the alignment.
Fixing the tie rod would be helpful as well after you go to the high steer. Some folks use a steering stabilizer to help control death wobble, but this doesn't always eliminate the problem.
Q I'm 17 and recently bought an '02 GMC Sierra 1500 4x4. It has a five-speed manual transmission and a limited-slip differential. I'm just getting into off-roading. The only thing I don't like about my truck is its engine, a 4.3L. I can't afford to do an engine swap. So I was wondering what would be an affordable way to get more power.
A I have a truck that runs 39-inch-tall tires with a 2.7L four-cylinder engine. I can rockcrawl, play in the mud, and still run down the road. The trick is gearing. Your truck has an overdrive transmission, and the 4.3L is a hearty little engine, maybe not as powerful as a V-8, but a good start nonetheless. If you could get lower gearing in your transfer case or, better yet, your axles, you'd be surprised at how much better the engine pushes your truck around. Gearing isn't inexpensive, but it's cheaper than an engine swap.