Wondering About "Questionable" Jeep V-6
Question: I was reading Willie's Workbench in the January issue ("Jeep Engines De-Mystified") and it seemed like a nice solid article about the engines until it got towards the end. I don't understand how an engine can be questionably 210 horsepower? Is it advertised as more powerful than it is? Less powerful? Isn't it against the law to falsely advertise something like that? I just didn't like how it was considered questionable without posting any facts or anything. (It was even called questionable twice in the article.) I would love to know more as I am on my third Jeep now, an '07 JK with this "questionable" engine in it. Thanks in advance.
Answer: Perhaps questionable was not the proper word to use. Most people, especially those with automatic transmissions, feel that the motor lacks the power of the 4.0-liter, which was rated at 190 horsepower. Yes, vehicle manufacturers have to adhere to certain guidelines when posting horsepower and torque figures, but I suppose likeeverything in the real world, there are some "fudge factors" involved. (Go check with your local tire dealer and ask him how many tires advertised as 35x12.50-15s actually measure a true 35 inches tall.)
Perhaps it's the higher weight of the JK versus the TJ, or the fact that the V-6 makes its horsepower and torque at a much higher rpm--the vehicle just seems to lack the power that it should have. There wasnothing derogatory being applied to the motor. The last "questionable" was because the motor has not proven itself to be as reliable as the 4.0L as of yet.
Just as a side note, I have driven and/or owned vehicles with every one of these engines that I listed over the years, so I have a pretty good handle on how they feel "rated," horsepower-wise, as well as their dependability.
Transfer Case for GM 5.3L Wrangler?
Question: I have a question about which transfer case I should use. I have an '88 Jeep Wrangler with a 6-inch lift and 35-inch tires. I bought a wrecked '07 Tahoe 4x4 with a 5.3 and auto trans. I'm going to put the 5.3 and auto trans in my Jeep, but am not sure which transfer case to use. The Tahoe transfer case also has the on-dash switch which I was thinking would be cool to have--a Jeep with no shifters in the floor at all. My stock transfer case is a NP231 with a 2.72 ratio. The Tahoe has a NP246 with a 2.72 ratio.
What are my options or what should I do? Do I get an adapter and use my NP231? Does the NP231 need to be "beefed" up? Is the NP246 stronger and ready to go? Do I need to get a second job and save for an Atlas II?
Answer: At first thought it just might be cool to have an electric-shifted 246 transfer case in your Jeep. This large heavy-duty transfer case was used by GM since about 1998 and is found in everything from Tahoes to Escalades. However, I could give you a million reasons why you don't want to use it in your Jeep. I don't have anywhere near that much time or space so I will just pass on some highlights.
To start out with, it uses an electric speedometer drive, while your Jeep uses a mechanical speedo. It's an active transfer case, which means that it has the ability to alter the amount of torque sent to the front axle when the computer senses wheel slippage. To do this, it has an internal clutch pack that relies on speed sensors that monitor the speed of each axle as well as that of the driveshaft, which feeds this information to a computer. This in turn locks up the clutch packs to provide the needed amount of power to the proper axle. The computer also tells the front axle when to engage the front axle shift motor to lock the axleshafts together. One of the big problems with this system is that all the tires must be the exact same height or it will trigger a trouble code. To say the least, it is a very complex operating system that requires a special scan tool to troubleshoot and quite a bit of experience using it. Sure it could be done, but the wiring would be truly a nightmare.
By all means stay with the 231 transfer case. It's simple, and surprisingly quite strong. If you're worried a bit about its overall strength, there are several modifications that can be made, such as replacing the planetary gears with the strong six-pinion system and wider chain from the 241 case, and using an aftermarket 32-spline output shaft. Rockland Standard Gear (877/774-4327, www.rocklandstandard.com) has some already built up that way or you can order the parts and do it yourself.
Now with that said, you still may have a problem with the automatic transmission control module trying to send some strange signals to the trans because the 246 transfer case is not wired into the system. You may have to end up using a 2WD ATC for things to function properly. Bet Mike Weinberg at Rockland could give you the proper information to make it all work together.
As to the engine swap, well that is pretty straight forward and there are several kits on the market to make the installation quite easy.
Letter Of The Month
"Low" vs. "High" Gear Ratios
Question: Here is a question that has always bugged me. When I read about changing ring and pinion ratios in a differential, I understand how you divide the number of teeth on the ring gear by the pinion gear to get the gear ratio. What I don't understand is why a lower gear ratio is not as strong as a higher gear ratio. Oh, and why is a 5:1 ratio considered a "lower" gear ratio while 3:1 is considered a "high" gear ratio?
Answer: The first question is pretty easy to answer. The ring gear is a given size in diameter. For instance, a Ford 9-inch rearend actually refers to the ring gear being nine inches in diameter, regardless of gear ratio. With the 3:1 ratio, for every three turns of the driveshaft (as it's connected directly to the pinion gear) the ring gear will turn one complete revolution. In this example, the ring gear will have 39 teeth and the pinion gear will have 13. Let's go to the extreme just to make it more dramatic, and pick a 6.50:1 gear ratio. The ring gear would still have 39 teeth on it, but the pinion gear will have less than half that many with only 6 teeth. What this also means is that to get a proper mesh of the gear teeth, the pinion has to be considerably smaller, which also means that there are not only fewer teeth but also a lot less contact area on the ring gear teeth, which also relates to less strength.
As to the second part of your question. When the driving gear has fewer teeth than the driven gear, then the driven gear will turn at a lower speed than the driving gear. So a 6.50:1 gear ratio turns at a lower speed than a 3:1 gear ratio, hence the term "lower" gear ratio. Think of a cement mixer. The electric motor has a very small pulley on it, while the pulley that turns the drum is quite large. The drum turns at a much lower speed than the electric motor does. Hopefully that clears it up for you.