Click for Coverage
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

January 2008 4x4 Tech Questions - Techline

Posted in How To: Tech Qa on January 1, 2006
Share this

Address your correspondence to:
Four Wheeler
6420 Wilshire Blvd.
Los Angeles, CA 90048-5515.

All letters become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department also can be reached through the Web site at Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

Question: I am in the process of swapping a pair of '79 Dana 60 axles into my '79 Bronco. With 9 inches of lift, I need to correct the pinion angles. I bought Dedenbear Cs to correct the front, and heavy-duty spring perches for out back.

What is the maximum pinion angle I can run on each axle before starving the pinion bearings? I've been told 18 degrees is the number, but have heard 12 and 25 degrees also. With everything mocked up, with Cage radius arms and the pinion pointing straight at the double cardan (plus or minus a degree), it's at 19 degrees.

I was also told of a modification that can be made to a washer of some sort involving some well-placed cuts and bending it to act like an impeller. Have you heard of this and know if it works?

Also what's your opinion on relocating the fill hole to add more fluid?
Chris Howland
Lebanon, CT

Answer: This is a really good question. I always figured, or read some place, that about 8 degrees was maximum. Maybe it was from a conversation with a Spicer engineer where he mentioned it. Then again, this can vary with the design of the rear end. So out of real curiosity I made some inquiries: Chris at Code 4x4 (970/625-8998, ) has custom-built a lot of rear ends and says that he has gone as much as 20 degrees, even on street-driven vehicles, without a problem, but he doesn't recommend going that high. Terry at Randy's Ring & Pinion (866/246-4897, says 15 degrees is the maximum. Steve at Dynatrac (714/596-4461, says 9 degrees is the maximum. However, Dynatrac also offers on its rear end, or through selected dealers only, a special option of what the company calls "dual high-sump oiling system." There is some custom work involved when installing this kit, and it is not for the do-it-yourselfer. With the kit installed (by one of their dealers), they say it can work up to 18 degrees, and they've even heard of some going as high as 24 degrees.

Some people recommend using a big flat thin washer, sometimes referred to as a "slinger," between the pinion gear and the bearing to sort of act like a dam and hold the oil in the bearing. I believe it was originally designed to prevent too much oil from going forward and overloading the pinion seal. Maybe I am wrong. Some Dana 60s have them, while others do not. Just keep in mind that it will act as a shim and definitely affect the pinion depth setting. I tried to find some information on making the slinger into an impeller without much luck.

Now, keep in mind that there is a big difference between a trailer queen that only sees limited highway use and a street-driven rig. When off the highway, the ups and downs move the oil around and usually lube things quite well. Going down the highway at speed, it could be quite easy to starve the pinion bearings of oil.

All three of those folks I talked to (as well as myself), agree that you definitely need to overfill the housing. How much? Tough question to answer. Most likely to the point where oil doesn't start coming out the vent tube when driving down the highway at speed. Probably the easiest way to do this is back the vehicle up a very steep ramp, or to jack the rear of the vehicle up to the point where the pinion is nearly level. Then fill the rear end up to the fill plug. Some vehicles with high-pinion housings have differential covers with a much higher fill plug, while several aftermarket covers have the fill plug in a higher location.

The subject of synthetic lubes-versus-non-synthetics is a very debatable question, with several builders of custom housings saying that the synthetics don't offer enough resistance to pressure during shock load in an off-highway operation. However, my choice is still synthetic due to the superior lubrication, especially to the pinion bearings, in a marginal situation.

On your Bronco, 20 degrees sounds pretty darn high. Keep in mind that you actually want to run the pinion at a downward angle about 111/42 to 211/42 degrees to allow for pinion climb.

And I do hope that you're talking about the rear end. That much pinion angle on the front without cutting and turning the steering knuckles will put them at a negative caster angle and make the vehicle undriveable.

Question: I have a '93 YJ that had a 2.5-cylinder/five-speed manual combo. I swapped in an AMC 401/Turbo 400/Dana 20 with 12 inches of lift, 38.5-inch Boggers, and Dana 60s front and rear with a Detroit and an ARB. After my Holley Truck Avenger carb was stolen off the Jeep, I installed a Holley TBI system and got it up and running without ever really being able to fine-tune it before I had this problem. One morning, I went out to start it and the starter solenoid clicked really fast a couple of times. From then on, the light on the dash cluster that comes on when you first turn your key to the "on" position did not engage, and the starter solenoid no longer clicked. The fuel pump does not receive power, and nothing happens when I try to start it.

After months of ripping apart the electrical system, I found a couple of burnt-out grounds and fixed them. I plugged everything back in and went to start the Jeep. Hurray! The light came on again when I went to start it. The solenoid clicked again, so then, I thought, the battery was a little dead. I tried and started it again, and the light goes out with no power going to the ignition system again. I checked all the ignition and starter fuses, and checked all grounds.

I am running out of ideas and am thinking of just selling it as is, but it is the Jeep that I have always wanted, and anything I buy would be built like this again.
Tyler Estler
Plainsboro, NJ

Answer: Problems like this can be really hard to diagnose, especially without seeing the vehicle first-hand. I am sure lots of changes have been made during the course of the various modifications, especially to the wiring. Here is my best shot.

OK, you've checked all the grounds. But have you? There should be a ground between the body and the frame, and between the engine and the frame. This is where people really screw up, not using a large-enough ground wire. I believe that both of these places should have a ground the same size as what you're using for the battery cables, and they must be making a good contact. Be sure there is a good clean connection between the steering column and the dash, as this is the ground for the ignition switch.

But I don't think that is your problem. Usually, when the solenoid just clicks, it's an indicator that the battery is not producing enough current to maintain the contacts within the solenoid. The battery is fully charged, right? The post connections are clean and tight? I have seen just enough corrosion buildup on the posts where low-amp-draw equipment such as the headlights will work, but not enough amps will get to the starter solenoid to make it work. It also could be a bad starter solenoid, but I doubt it.

My guess is that you're not getting a good current flow from the battery to the ignition switch or from the switch to the starter solenoid. A big clue to the problem is the fact that the electric fuel pump is not working. Usually, it gets its power from the power distribution center (mounted to the left of the steering column) or from the fuel-injection control box (computer). A lot depends on how many factory wires were bypassed during the engine and EFI swaps.

So, the first thing to check is whether there is power to the ignition switch. Seems to me the easiest way to find this out is if the signal lights and heater work with the key in the "on" position. Next step would be to check the voltage at the wire that activates the solenoid when the key is turned to and held at the "start" position. There shouldn't be more than about a 0.5-volt drop between the end of this wire and the voltage measured at the battery. If there is no current here, then I would unplug the connector at the steering column and check the voltage there. At the bottom of the plug are three prongs all in a line; the outer left one with the 18-gauge yellow wire labeled "A41" is the one to check.

Still no voltage? Then you have a bad ignition switch. I suggest that you consult a factory service manual on the proper way to replace this switch. OK, so you have voltage here but not at the solenoid. I believe that this wire doesn't go directly to the solenoid but to the power distribution box. In it are a bunch of fuses and relays. Three things that you most likely haven't checked are: the fuel-pump relay (second on top row), automatic-shutdown relay (fifth one, top row) and the starter relay (sixth on top row). There should be a sheet on the inside cover of the box that shows the location of each one. About the only way, and perhaps the best way, to test these would be to replace one at a time with a known good relay. (OK, you could take a bunch of time figuring out which post was ground, feed, trigger, and output, then hook up a bunch of wires and bench-test it.)

I'm not really sure what red light you're referring to that now does not come on. With the original engine and PCM (computer) there is a red lamp that would illuminate when the Powertrain Control Module (PCM) detects an open or shorted circuit, or absence of current flow in an output device such as when the key is first turned on. However, it was only designed to illuminate when the ignition key is turned to the "on" position, and it stays lit for three seconds as a bulb test. Signals that can set the malfunction indicator lamp are low battery voltage input. However, without the original PCM, it should not work unless someone has wired it somehow into the Holley EFI system.

So what it all comes down to is that you spend some time with a test light and volt meter.

Question: If I have a Dana 30 and put in 4340 chromoly shafts with 27-spline inners and outers, and large 297X or 760X U-joints, will it make it as strong as a Dana 44 or strong enough to run 37-inch-tall tires?
Longview, TX

Answer: I can answer both questions with a No and a No. OK, so let's now go into a bit more detail. First, the housing and axletubes on a 44 are a lot stronger and beefier than those on a Dana 30, which results in less flex. Flex within the housing can actually pull the ring gear away from the pinion gear to the point where not full contact is made and gear breakage will occur. Next is the fact that the ring gear on a Dana 44 is 811/42 inches, while the ring gear on a Dana 30 is only 711/48 inches in diameter. This is also true with a lot smaller pinion as well as the pinion shaft. This all relates to fewer teeth in contact between the ring and pinion.

Now if you compare a high-pinion Dana 30 to a standard-rotation Dana 44, as most vehicles use up front, then the strength factor gets a bit closer-maybe somewhere in the middle between the two, maybe a bit less. This is because a standard-rotation 44 is driving on the back side of the gear teeth while a high-pinion unit is driving on the correct side.

OK, now we can get to axleshafts. Dana 30s use a 27-spline axle of 1.13 inches in diameter, while most Dana 44s use a 30-spline, 1.31-inch axle. While this doesn't seem like a really big difference, when engineers work it out with their magic math, there is a major difference in strength. OK, but what about using the chromoly axles? Well, they come close, but still not quite as close as one would think.

There is another option. Use a special ARB Air Locker that takes the 30-spline axle. Now we are up to the 44 in strength, and in fact better than a stock 44 axleshaft. But remember, we are still using that small Dana 30 ring-and-pinion and a housing with not nearly as much strength in it.

Will it handle 37-inch tires? Sure, but for how long is anyone's guess. If you drove the vehicle only on easy trails, maybe a long time. But put a tire up against a big rock and stand on the skinny pedal, and most likely you're going to clean the teeth right off those gears. Is it worth taking the chance? I don't think so. In fact, depending on the weight of the vehicle, gearing, torque available, and driver's state of mind, a 37-inch tire just may be too big for a Dana 44, even with chromoly axleshafts.

Question: I have an '01 Chevy HD Crew Cab shortbed with an 8.1L and an automatic. I have a 6-inch lift with 35s and I do a lot of towing. The truck has almost 130,000 miles on it and runs great, but of course, the mileage really sucks. How big a deal would it be to put a Duramax in it, or maybe even a Cummins? I know I can come by a Cummins a lot cheaper than a Duramax, but would the adapting process be too costly?
Karl Anderson
Mendon, IL

Answer: If you think that the diesel swap is going to save you money, well, think again. My guess is that the payback time after all the work is done will be about another 130,000 miles, and that is not counting all the time and labor you're going to have in the truck, as well as getting it smog-legal if you live in a state with inspections.

The easiest motor of the two to fit into the engine compartment would be the Duramax, naturally, as it was first offered in 2001 in your truck. Where the big problem comes is that there are two separate computer systems-one for the engine and one for the transmission-and they "talk" to each other. Jim Brightly, founder of the Diesel Page ( has made this conversion on his street-rod truck, an '89 Chevy 11/42-ton. Needless to say, it was not an easy task, and he ended up grafting the diesel's dash to his cab to get everything to work right and proper. In the end, it came out looking nicer than factory. I am not sure if the gas motor's dash on your truck is comparable to the wiring of the diesel engine's, so it's something that you would have to check out. There are lots and lots of electrical components to make this diesel run. My guess is that you would also have to swap over to the Allison transmission.

The 12-valve Dodge/Cummins diesel in some ways may be the easier swap, wiring-wise. I believe motor mounts are available from There seem to be some clearance issues with the taller and longer inline motor. This is solved in two ways: modifying the frame to sit the engine down lower, or raising the body a couple of inches with a body-lift kit. There may even be some clearance issues with the A/C pump bracket. I have been told that Cummins offers an A/C compressor bracket that mounts the compressor up high next to the alternator (PN 3930888), which cures the problem.

You could use your present transmission with an aftermarket stand-alone computer system and a performance rebuild, as adapters are available to mate the engine to it through a Cummins dealer. I think that it would be easier to just use the complete matching transmission and transfer case from a Dodge truck. Steve Rumore at Avalanche Engineering ( has done several conversions but these have been on earlier trucks.

Question: I have an '05 Dodge Durango 4x4, and I have gone up in tire size from 30.5-inch stock tires to 34-inch new tires. I have 3.55:1 axle gears and I'm swapping to 3.92:1s to compensate. I used an online calculator to find the new gear size, so I'm good there. Do I need to replace anything other than the ring-and-pinion in this swap, or am I able to reuse the rest of the shims and bearings? How difficult is this task?
James E. Westerfield
Friendwood, TX

Answer: You're going to have to change out the front differential carrier for one that will accept the lower gears as 3.54:1/3.73:1 is the breaking point for the Dana 30 front.

The rear, I believe, is an 8.25 Chrysler and will accept the lower gearing. If you're going to do any even semi-serious four wheeling with this vehicle, I would recommend going to a much lower gear ratio than the optional factory 3.92:1 gearing. You're going to notice a real lack of performance with that tall of a tire.

I just recently did a swap from 3.73:1s and 31s to 4.10:1s and 33s on my wife's V-8 Grand Cherokee and now I sure wish I had gone to the 4.56:1 ratio as I really noticed a lack of power. I'm sure it's due partly to the added wind resistance from the higher stance and from more rolling resistance.

How difficult is this task? Well you're going to need a foot-pound torque wrench, beam-type inch/pound torque wrench, common automotive handtools, a dial indicator, a caliper or micrometer, a good service manual, and a bit of mechanical skills to accomplish the gear swap. If the gears are not set up properly, and that means perfectly, then they will quickly wear out and/or break.

Question: I have a '99 Ford diesel Super Duty 4x4 with an automatic transmission that was replaced by Ford on an earlier recall program. The replacement transmission occasionally leaks fluid-but only when the truck is in four-wheel drive! Sometimes the volume of lost fluid is so great, the transmission will start slipping. If I replace the lost fluid, normally about 5 to 6 quarts, and drive in two-wheel drive, this stops all further leakage. I can drive thousands of miles in two-wheel drive pulling heavy loads and in hot temperatures-and it never has leaked a drop.

The repair shop has suggested pulling the automatic transmission and replacing the seals on the automatic transmission fluid pump. However, I suspect the pump seals are not bad-not if the automatic transmission doesn't leak fluid in two-wheel drive.

What repairs or action would you suggest to remedy this problem? Could this be an overheating problem related to use of four-wheel drive, which puts a heavier load on the transmission and causes the fluid to be lost?
Ronald Mahan
Florence, AL

Answer: Five or six quarts is a lot of transmission fluid. The whole underside of the truck would be covered with it. My first step would be to clean the underside of the truck completely, then drive the truck in only two-wheel drive for a while just to confirm that there are no leaks, both by visual inspection of the underside and with the transmission dipstick. ATF, being red in color, stands out pretty good.

Next, find a loose-surface dirt road and drive the truck in four-wheel drive until you detect a leak and then try to trace where the leak is coming from. My guess is that there is a bad seal between the transmission and the transfer case, and the transfer case is filling up with ATF, so in four-wheel drive, the excessive fluid is being pushed out the vent tube of the transfer case.

Please let me know what you come up with-perhaps this is an ongoing problem with Ford, and in the future I will be able to help someone else with the same problem.

Question: What is the difference between a four-wheel-drive SM465 transmission and a two-wheel-drive unit? What I see, from what few pictures I can scrape up, is that there is a yoke on the end of the two-wheel-drive unit. Is there something I am missing, and if there is, what is it?
Shaun Murphy
Oshkosh, WI

Answer: I checked with Bob Hutchins of All Trans in Portland, Oregon, and he says that the output shaft is a different length and different spline count on the two-wheel-drive as compared to the four-wheel-drive version. So, if you want to hook it up to a transfer case like the NP205 or NP208, you must have the matching shaft, which can easily be changed.

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results