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February 2008 4x4 Tech Questions - Tech Line

Posted in How To: Tech Qa on February 1, 2008
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Four Wheeler
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Los Angeles, CA 90048-5515.

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Question: I have a new Nissan Titan 5.6L pickup that I think is just great. I want to get a bit more performance out of the engine and a better sound from the exhaust. I have searched the Internet and can't seem to find an after-cat exhaust system for it. I would like to go with stainless steel if possible. Do you have any idea where I can get a good sounding system for my truck?
Danny McMaster
Oak Harbor, WA

Answer: There are a number of sources for your Titan's exhaust, including Stillen (866/250-5542,, Banks Engineering (800/601-8072,, Dynomax (734/384-7806,, and Magnaflow (800/824-8664), as well as a system I found at Ultimate Truck (877/921-1531, It's made of mandrel-bent T304 stainless steel and comes with a lifetime warranty. It's a totally bolt-on system that they claim can be installed in 40 minutes or so. This is a very quality product, so expect to pay for what you get, as the system is in the $500 range.

Question: I have a brother who recently burned up a valve in his '95 Chevy 4x4 1/2-ton truck with a 305. How does that impact me, you might ask? Well, I'm the guy who gets to "help" him fix it.

Where can I find information on the feasibility of upgrading to a 350 in place of the 305? Or find out if there are some reasonable upgrades to perform to the 305? I have some compatibility concerns with regards to the existing computer and fuel-injection system. Any recommendations? This truck has always seemed underpowered when trying to tow anything.
Mike Sellek
Lansing, MI

Answer: 1995 was the last year of the throttle-body fuel injection and the last year of the 305. Luckily, the 350 was still offered and shared the same fuel-induction system. This is a super-easy swap. Take out the present motor and put in the throttle-body 350. You should change out the computer to one for a 350, but the one from the 305 will make it run OK. I am sure you could transfer the intake-manifold throttle body and distributor from the 305 to the 350 if you had to, but I'm not sure about port size on the manifold matching. I have also been told that the throttle body won't flow enough air/fuel mixture to get all the potential power

Question: I have an '00 Grand Cherokee that I bought a few months ago. I had it serviced by the dealer, and during a conversation with the service manager he said that I had to use a special power-steering fluid, not just the standard stuff that I can buy at the auto parts store. Is this true, or is he just trying to get me to buy my replacement parts and fluids from their part's department?
Lee Armensted

Answer: Actually, he is right. Grand Cherokee WJs, and their international-market counterpart WGs, do take a special p/s fluid. Most power-steering fluid is red in color, but the special fluid is amber in color. (However, both fluids will darken in color with use, and fluid color is not an indicator of fluid condition.) The correct fluid is Mopar MS5931, and the part number for a quart is 04883077. Something that I didn't do was to check and see if any of the products on the shelf of the local auto parts stores met the requirements for your vehicle. Just might be.

Now you're going to ask me why? Sorry, I don't have a clue, the only other Chrysler-built vehicle that uses this fluid is the 2004 Crossfire.

Question: I was writing in response to "Gearbox Options for '60s Suburban" ("Techline," Oct. '07). I was able to convert a '67 Chevy pickup to power steering using a p/s gearbox out of '72 Chevy pickup. Power steering was an option, I believe, in pickups from '68 on, and probably sooner in GMCs. The p/s box has the same mounting bolt pattern as the manual, although it does have a slight bulge on the frame side. On the models with power steering, the bulge is accommodated by an indent in the frame, which is not in the earlier models with manual steering. I was able to accommodate this with the use of some thick lock washers used to space the box out away from the frame. This was enough clearance to mount the box and had little if any effect on the steering geometry. Just about any GM pump and hoses should work on the other end, and depending on the motor, the brackets could be the hardest part. The Suburban may be a little different than the pickup, but shouldn't be much.
Les Enlow
Hopkinsville, KY

Answer: Yes, the Chevys built in the '60s did have power steering options, but they were a ram style. Several people have written to tell me that the later box will just bolt up, by either using a spacer or not using the fourth bolt. My information on the subject was flawed, so thanks for setting me straight.

Question: My concern is the locking differential (G80) that GM has on its '05 pickup trucks. I am told this is based on an Eaton Locker and is very rugged. However, there is no external engagement mechanism, meaning you have to spin one wheel over 70 rpm for it to engage, I am told. It would automatically disengage when both wheels are speed matched, forcing a repeat of the engagement process at the next "stuck." I would rather engage my driving wheels to prevent getting stuck. And what if I tried doing a few donuts on dry pavement? I would appreciate your comment on this unit. Also, what do you think of adding a mechanism to manually engage/disengage the unit? Has any "kit" been developed for this purpose?
David Boutin
Brunswick, Maine

Answer: I couldn't agree more with your assessment of the GM locking differential. I have a Chevy pickup with the optional differential and was convinced by a couple of GM engineers that the new model would work great. Well, my opinion is that I totally wasted my money on this option. Oh, wouldn't it be nice if there was some aftermarket kit that allowed us to modify the present rearend and just pull a cable for a positive lockup?

For a replacement, it depends on what rearend you have in your truck, as you didn't say which model you had. If it is the big AAM rearend, then you are pretty much out of luck. That is, until some time next summer when Tractech will release its Truetrac limited-slip unit for it.

Now from my understanding, there has been a shortage of the AAM axles, so your truck may have what is referred to as a 14-bolt. Or, if you have a 1/2-ton pickup, you may even have a 10-bolt rearend. If this is the case, then there is both a Truetrac and a Detroit Locker available. For a selectable locker, there are ARB Air Lockers also available for these last two rearends.

Question: My current (and first) project involves an '82 K-20. It came from the factory with a 6.2L diesel, a TH400, an NP208, and 10- and 14-bolt axles. To me, that's the perfect drivetrain with the exception of the engine, front axle, and transfer case. I have an NP205 and a Dana 60 to put under it. Now, for the good stuff-the 454 bored 0.040 over with a few more modifications. It came out of a '90 C-3500 (which is in my backyard), so I have everything I need. The motor is computer controlled with TBI and so on, so would I have to use the same-type distributor, or could I use one with a vacuum advance?

I'm gonna make this work because I know I can do it, but my dad says it's not possible and it's a dumb idea. The truck is not gonna be street-driven so I don't have to worry about inspection. All I need is for you guys to tell me it can be done, and that would make me feel so cool because you guys are the coolest.

Answer: What a great project for a 19-year-old. I am impressed with what you have planned and getting a complete donor truck was a great idea, one I always suggest when doing a project such as this. Keep in mind that you will need a different adapter between the transmission and transfer case, as the one from the 208 will not work.

My suggestion is that you take your time and do everything right the first time. If in doubt about something, ask questions, lots of questions, and most likely you will get different answers. Not that any of them are wrong, but consider the source and the application before you do the same thing to your truck. But also don't think that you have to have all the trick parts and pieces right away. Pay attention to the safety features and make sure they are right. Don't overcam or overcarb! This is one of the biggest mistakes most people make.

I am a bit confused as to your question about the distributor, but this is an answer to what I think that you're asking. You must use the electronic distributor with the throttle-body injection. The control box (computer) advances and retards the timing as needed. No, you cannot use a vacuum-can-type distributor with the EFI system, and no, you cannot use the electronic distributor with a carburetor fuel system. Either one is interchangeable within the engine blocks when using the matching intake manifold.

Hey, make it street legal! Half the fun of owning something like that is being able to cruise with it and show it off. Be sure to control the urge to display "the speed and power" part. Tickets are tough at your age-well, actually, tough on anyone when it comes to insurance rates. You will know what it is capable of, so you really don't have to prove it. Besides, big-block power can even break Dana 60s and 14-bolt axles. Most important of all: Have fun building it.

Question: A buddy and I have a disagreement regarding how often one should repack front wheel bearings. He says that his Cherokee uses a wheel hub that comes factory-sealed and can't be repacked, and is good for, like, forever; therefore there is no reason to have to repack the wheel bearings on my Jeep that has locking hubs.
Jim Hoffman
Bend, OR

Answer: Well, your buddy is partly right. His Jeep Cherokee, as well as the rest of the pack of newer Jeep vehicles, uses a sealed unit bearing. While not "good forever," they do last a long time mainly due to the design of the seal and the fact that there is no locking mechanism that can allow water and dirt to enter, no matter how well the hub manufacturer tried to prevent it. On a vehicle with locking hubs, it is imperative that you periodically do check the wheel bearings.

Part of my yearly maintenance procedures on my trail Jeep is to repack the wheel bearings. OK, maybe it's a little excessive compared to the relatively low miles that are put on it each year, but I figure that it's just good insurance if nothing more than to check things out. It's a good thing I do this, as this year I discovered that a seal had leaked, water had intruded and, well, the wheel bearings were trash. Repacking them is not a pleasant chore, nor is adjusting the preload and locking the nuts in place, especially when you have to fight with either of two styles of retaining nuts. If you have the double-nut, bend-over flat washer style, then you know that you can only bend it over so many times before it breaks and has to be replaced. If your hub nuts are of the type that use the little locking pin that has to line up perfectly with the proper hole in the locking ring-plus the tab on the ring must fit properly into the slot in the spindle-you know what a pain that can be.

I came across a new interesting locking mechanism this last year from Stage 8 (800/843-7836, Yep, the same people who make the neat locking bolts. Instead of the locking pin that never seems to line up properly, the new XLock system uses specially designed components that make installation a lot easier than before. XLock is made from 4130 chromoly steel, through-hardened. Originally designed for the U.S. Military, the patented locking spindle nut has been modified to fit Dana 44 and Dana 60 front spindles. The engineer I spoke with at Stage 8 told me that the XLock will withstand 450 lb-ft of reverse torque without failing or loosening. No, that does not mean it will withstand 450 pounds of torque when the vehicle is backing up. It means that if the locking retainer is not removed, it would take in excess of 450 pounds of torque with a wrench to loosen or break the locking system.

I just happened to get one of the early prototypes to try out. And guess what? There was a design flaw. Not in the overall design, as that was great, but in the thickness of the grooved spindle nut. Seems that the Scout-style Dana 44 front hub/spindle combination that I was using is a bit different than those of the GM variety; the spindle nut was too thick and would not allow the Warn hubs that I was using to fit properly. I was able to machine the thickness down on the spindle nut so it worked as it was originally intended. As a result of my finding, Stage 8 has now incorporated a thinner-designed spindle nut in the kit.

How it all works is that first you install a thrust washer over the spindle against the wheel bearing. Next comes a washer that is notched on the outside and has a tang on the inside that follows the machined groove in the spindle a lot tighter that the original setup ever did. The spindle nut, besides having the notches for the hub wrench to fit into, also has a shallow groove around its circumference. Once the proper adjustment is made to the wheel bearings, you slide over the locking retainer so that it engages both the notches on the spindle nut and those of the notched washer behind it. A pair of pin-style snap-ring pliers work here for getting it into place. You have eight different positions that it could fit into, so rotate it around until it fully engages. Then install the large snap ring into the groove on the spindle nut to hold the locking retainer in place.

Oh, and you can buy them directly from Stage 8 if your friendly off-road shop doesn't have them.

Question: My Chevy pickup has ABS brakes that are acting strange. When I apply the brakes for a normal stop, the pedal kind of pulsates like it would if I was doing a panic stop. It only does this at slow speeds.

I took it to one shop where they replaced, I believe, something called a "dump valve," but it didn't make any difference. Another shop wants to replace the pump and ECM, both of which were quite expensive. Is this what I have to do to make my brakes right, or do I just live with the problem if it's not a safety issue?
Mary Peterson
Ann Arbor, MI

Answer: You failed to tell me the year of your truck, but I'm going to make an educated guess that it's a few years old, and another guess as to the cause of the problem is based on where you live. Michigan winters and road salt mean rust and corrosion.

At each front wheel is a thing called a speed sensor, which does just what its name implies. Actually, it's part of the front hub assembly. Without going into a lot of detail, here is how it works: A tone wheel inside the hub sends a signal to the speed sensor, which relays information to the ECM (electronic control module), which in turn sends a message to the ABS pump and its components to regulate brake pressure.

Now if the tone wheel fails to send the proper signal, then the total ABS doesn't work properly. My guess is that there is a corrosion buildup either on (or under) the pickup sensor that has changed the distance between the sensor and the tone wheel. Sounds like a minor problem, but the clearance here is quite important.

Have your shop remove the sensor and clean it thoroughly before reinstallation. While they're at it, have them use a scope to monitor the wheel speed sensor output where it is hooked up to the ECM connector. This way, any wiring or connector problems will also show up. When you show this to them and they just say, "Duh!," be sure to find another shop!

Question: I have a '72 GMC 3/4-ton 4x4. I recently put in a locked-up 4.56:1 GM 14-bolt rearend, but my stock Dana 44 front is a 4.09:1. This seems to work fine off-road but not on the street. I am getting two new tires, Q/78-16s. There is about a 1-inch difference in height between the new and old tires. Should I put the new tires on the front or back to cut down on the bind?
Mr. Conyn
Rathdrum, ID

Answer: Change out the gearing to match! You're going to break all sorts of parts, if you haven't already. Different tire size is not the answer. What if you get a flat on the trail? Are you going to carry two different-size spares? Also, you should not be using four-wheel drive on the highway. Use it only on a loose surface.

Even with the matching gears, there is some variation in tire size and axle speed while turning, and even going down the highway, in a straight line. When turning the vehicle, the front axle will turn at a different rate than the rear due to the radius of the front circle that the tires turn on is different than that of the rear. Some slippage must take place to compensate for this. In a loose surface, this can take place, but on the highway it's a different story. The tires must skid a bit, which wears them out quite fast, and in fact with this much gear ratio difference, they have to skid a lot. Besides that, it puts a great amount of strain on all drivetrain components.

Question: I have a '71 Chevy K-5 Blazer and I heard about a problem that they have with the steering, i.e., that when you would turn the wheel, it would somehow bend the frame. Is this true, and if it is, where or what can I do to fix this?
Jason O'Leary

Answer: This generation of Chevy trucks, be it a Blazer or a pickup, have a tendency to crack the frame around the steering-box mounting holes and eventually, in a worst-case scenario, actually tear out a piece of the frame at this mounting point. It's not real common with stock vehicles unless they have been used really hard, but it sometimes shows up. When larger tires and a lift kit are installed, it becomes much more prevalent.

The majority of the problem is caused when a poorly designed or low-cost suspension lift kit is installed. When the vehicle's ride height is changed, what happens is that the axle and related drag-link mounting point are now at a greater distance, height-wise, from the steering box than they were originally. Unless some method of compensation-like a modification to the pitman arm, drag link, or raised steering knuckle-is used, you end up with the steering-box gear off-center. This limits the steering box's turning sweep to the right. In a sharp right-hand turn, there is still more angle for the steering knuckles to turn than there is movement in the steering box. This puts more pressure onto the steering box, and its mounting location, than it was ever designed for and eventually damage occurs.

There are quite a few different companies that make reinforcement kits. RJR Off Road (800/632-9192, offers a weld-in brace that will not only repair any damage but strengthen the frame in this area. Off Road Design (970/945-7777, tackles the problem in a bit different way with not only a repair plate but brackets that triangulate the mounting area to stiffen it up before it breaks. Rough Country Suspension (800/222-7023, makes a new steering arm with the proper geometry.

Question: I just got an '87 Toyota 4x4, four-banger, Thorley header, recent rebuild on motor, Weber carb, aluminum intake, and 33x12.50 BFG muds. Is there anything else to help with power, or is it just gears left? The truck will only be driven 30 miles at a time on the highway.
Adam Filger

Answer: Sounds to me like you have a really good start on building a nice four-wheeler. I noticed that you didn't mention anything about changing the camshaft out for a "competition grind" of any kind. I think that this was a wise choice. Too many people think that a camshaft change is the way to more power. Yes, it can do wonders to wake up an engine. However, the power gain is in the upper rpm bracket, and you generally end up losing both torque and horsepower at the bottom end of the rpm range. With your small engine, you need all the torque you can get it to put out.

Yes, I know that lower gearing will up the operational rpm, but also more rpm means more wear on the motor. Let's talk about lower gearing. My choice would be to first change out the axle gearing to something in the 4.88:1 range. Yes, I am aware of the fact that they make gearing in the 5.29:1 and 5.71:1 range, but I think that is way too low as it makes for a much-too-small pinion gear. This small size lacks the necessary strength for serious use, with always worrying if it is going to break-or should I say, when it is going to break.

Yeah, I know you said that you only plan on driving it 30 miles on the highway. Well, plans have a way of changing over time. This way you're not going to be working the clutch too hard (you did or are planning to go to a stronger aftermarket clutch, right?) and you will be able to use Fifth gear on the highway if so needed.

My next step would be either one of the various "doubler" transfer-case combinations that are available, or a lower gearset for your present transfer case. I wouldn't get too carried away with super-low gearing unless your thing is to get out and walk beside your vehicle. How low for overall gearing? Sorry, I don't have an answer, as everyone's driving style is a bit different, and vehicle use is a bit different. That's why I suggested you start out with just the lower axle gears, then check with the locals that you run with as to what their gearing is and how it works out for them.

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