Send your Gearhead questions to: Off-Road Adventures, Gearhead Dept., 801 West Artesia Blvd. Compton, CA 90220 info@oramagazine.com
You’ve Got Questions? He’s Got Answers!
DURAMAX DREAMS
I have a 1982 Chevy Silverado 3/4- ton which currently has a 383 stroker and TH 400 trans. I am leaning towards putting a 6.6 Duramax diesel engine in it. Does anyone sell a kit to allow me to install this engine in my truck? Will the 6.6 bolt up to my TH400? It’s built to hold 500hp or so but do you think this trans would hold up? Are there any complications I’m not seeing?
Justin
Las Vegas, Nevada
A buddy of mine installed a Duramax into an ’89 Chevy and it was a big job. First off, as good as the TH- 400 is, the Duramax would eat it for a snack. The other element is that the Duramax engine and Allison trans are so integrated electronically, I’m not sure how you’d separate them. So, step one of this mental exercise is to figure on installing a complete engine, trans and t-case as an assembly. Next is the electronics. Gotta have them. The engine is pure electronics. What my buddy did was transfer the majority of the wiring from the late model Chevy into the old truck. This was a very big job! Because he wanted the late model message center, he ended up installing the dash out of a late model Duramax truck into his old truck. It’s very sharp but lots of work! The engine will fit under the hood, but your drivetrain may need some help if you have a 10-bolt front axle. The 14- bolt rear is also actually a little light for a Duramax in some cases, but is likely to be OK. Anyway, there are a bazillion details to this job. The best thing you can do is go to www.62-65-dieselpage. com and read about the conversion there.
STOVEBOLTS: ALERT READER UPDATE
I saw the question from reader Donald Weston in the November 2006 issue about putting a later automatic behind the 235 six in his ’58 Chevy. He can get the adapter kit he needs from Langdon’s Stovebolt Engine Company (586-739-9601, www.stoveboltengineco.com). The kit allows the use of 200-4R, TH- 350, TH-400 and 700-R4 transmissions with ’62 and earlier Chevy six cylinder engines.
Lonny
Via e-mail
Weston, if you’re still out there, hereyago. Lonny, you get the Gearhead’s steely-eyed missile man award for passing this along. Thanks!
HOLY, SHUDDERING YODAS, GEARHEAD
I have a 1980 Toyota 4x4 with 33x12.50 tires and a 3-inch lift. When I engage 4-wheel drive, the truck shudders and vibrates unless in loose material. As far as I know, the diffs are matching I have replaced the front ujoints in the front shaft. When shifting out of four-wheel drive, the shift lever binds. My question is whether it’s a simple driveshaft problem or a scary transfer case problem.
M. Wozniack
Oklahoma, Via e-mail
Something you wrote set off bells. “As far as I know, the diffs are matching.” Does that mean there’s a chance they are not? Is it a recently purchased truck? The symptoms you describe sound a lot like mismatched gearing. If the truck does not have lockers or limited slips, you can get an idea of the ratios in the following way: T-case in neutral, wheels blocked. Make a mark on the pinion yoke and on the snout of the diff. Jack one tire off the ground and spin it exactly two revolutions while counting the number of times the mark on the yoke rotates past the mark on the diff. If it goes past four times and a skosh, then you have 4.10s, four and a quarter turns is 4.30:1, etc. Up front, it’s the same, but you need to lock both hubs. If you have lockers or limited slips, this won’t work. It’s also possible you could have a problem with your front diff, such as blown spiders that are locked up into a wad of broken metal and essentially giving you a spool. That will show up in the ratio test mentioned above. You won’t be able to spin the lifted front tire. Anyway, there’s some ideas to get you started on tracking this down.
TRULY NEUTRAL
I have a ’93 Jeep Wrangler 4-cylinder with a five speed manual. I’ve been told different ways to tow it: 1- disconnect driveshafts, 2- put everything in neutral, 3- put transfer case in neutral and transmission in first but not to go beyond 300 miles. Are any of these correct?
Jack LaFargue
Hayward, California
Every manufacturer has different recommendations for flat towing, and some just flat recommend against it period. The Jeeps in your era (pre ’95 Wranglers with the NP-231 transfer case) did not have a “true” neutral position for the t-case. While the neutral position does uncouple the t-case from the trans input, it actually couples the front and rear outputs together. You get horrendous backlash from that, which can literally grenade the transfer case. Common knowledge has been that if the CAD (Center Axle Disconnect) on the front axle is disengaged, the backlash is eliminated. The problem is that the vacuum operated CAD stays in the last position it was put in... But what happens if you start the engine and shift to neutral? The CAD engages and stays that way. If you make the shift with the engine off or with the vacuum line to the CAD disconnected, you are safe in theory, assuming the Cad is already disengaged. Another option would be to use a Posi-Lok. This device converts the vacuum servo to a cable operated device so you would know the axle is disengaged. Also in theory, a locking hub conversion up front would allow you to disengage the axle. The way I see it, all these items leave a bit to chance and human error. If you tow a lot, the foolproof method would be a 2-low kit. These kits allow you to operate in low-range 2-wheel drive but also include a true neutral position. This isolates the rear output, which, incidentally drives the t-case oil pump so you are then totally safe to flat tow. Check out 4- Wheel Drive hardware (www.4wd.com/800-333-5535) for all your Jeep needs.
SPLINEY EXPLANATION
I have a stupid question, so please don’t laugh. Why does a higher spline count mean a stronger axle shaft? You’d think that a thick spline, like a 10- spline would be stronger than the little teeth on a 30-spline.
John Walker
Hollywood, California
John, the only stupid question is the one you didn’t ask. Well, except for asking women their age and that sorta stuff. Anyway, it’s all about something called Minor Spline Diameter. Let’s use your 10/30 spline example. The weakest part of any axle shaft is the part with the smallest diameter. Where is the smallest diameter on most axle shafts? Usually, its at the base of the splines. This part is called the minor spline diameter. On a Jeep 10-spline axle, the splines are deeper so the minor diameter is smaller. The 30-spline shaft has many more, much shallower splines, so the minor diameter is larger. The shaft diameter of a Jeep 10-spline is approximately 1.12 inches. The minor diameter is 0.94 inches, about a 16 percent difference. A 30-spline has a major diameter of about 1.31 inches and has a minor diameter of 1.18, about a 10 percent difference. A 27-spline Dana 30 shaft, nearly the same major diameter as the 10-spline, has a major diameter of about 1.17 inches and a minor of 1.11, about a 5 percent difference. There are other factors at play also, but this should help you to understand a bit better.
POWER WAGON COG QUERY
I’m the proud owner of a 2005 Dodge Power Wagon. I love this truck and my wife for letting me get it! I’m trying to find out what axles are under the truck. I know it’s running 4.56 gears I’m also wondering about the electronic locking front and rear diffs. Who makes them and how strong are they? The only problem I have is the size of the vehicle trying to fit up the Jeep and old wagon trails around Colorado
John Harrold
Aurora, Colorado
Both the axles in your Power Wagon are made by American Axle. The AAM 9.25, which is a descendant of the Saginaw 9.5 inch until known as the metric 14-bolt or semi-float 14-bolt. In terms of strength, it’s in the ballpark with a Dana 60. The rear axle is the AAM 10.50, which is an evolution of the legendary Saginaw 14-bolt and is a very stout unit. The lockers, also from AAM, are called the TracRite GTL. They use a gear type limited slip (similar to the Detroit TruTrac combined with an electrically actuated locker. I haven’t heard much bad about them, other than the wiring that locks them out in high range. I had the opportunity to test a PW in ’05 and loved the truck. The drivetrain’s mighty stout for a stock 4x4, especially if you keep the stock 33 inch tire size. You’re safe to 37s by most estimates, maybe bigger, though the election of gear ratios for these AAM axles isn’t huge yet.
THE RANGER SPARK-KNOCK BLUES
I have a 2000 Ford Ranger with the 3.0L engine. It knocks a lot when I go up hills and even on the flats. When I shift down, it goes away. The dealer said it’s just spark knock and I was just wondering if this was common on these engines.
Doug
Pennsylvania, Via e-mail
Well pinging is a common problem for 3.0L but I wouldn’t be so dismissive about it. Long term, it can eat up your engine. I hope your dealer did you right and checked out TSB 00-24- 08, and several others on the topic. It outlines some things they can do to help. There are many levels to this problem, one of the most common being carbon buildup. Carbon can be cleaned from the engine using a decarbonizing fluid, like Motorcraft PM-3 or Seafoam (both available at many auto parts stores). Basically, you run the engine at idle and spray the stuff into the engine a bit at a time though a vacuum hose. After, you go out and give it a good “Italian Tune- Up”, an analogy to the high revving Italian sports car engines that used to load up when driven at low speeds. A few full power runs where you get the rpms up to 3500-4000 rpms a few times will blow out most of the carbon. This works for preventative maintenance too. Most people agree that the problem is more prevalent with city driven rigs than those run often at high speeds or driven hard. There are also products you can put in the tank that decarbonizes the engine as you drive. One I have used for years is BG Products 44K (www.bgprod.com). For more stubborn 3.0Ls, owners have had success by replacing the 195 degree thermostat with a 180 degree. It lowers combustion temps a skosh, lets the engine run a little richer and that can be enough to reduce or eliminate pinging. Others have installed colder spark plugs, the Autolite 764 in particular, and had success. It may take all three things, but first try the decarbonizing. According to my Ford contact, a crusty MAF sensor wire can also be a possible cause. He cautions that there is no need to run anything more than 87 octane in this engine and that most higher octane fuels will actually tend to make the engine carbon up more.