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March 2013 Nuts & Bolts

131 1303 01 March 2013 Nuts And Bolts Vacuum Boost Brake System
Fred Williams
| Brand Manager, Petersen’s 4Wheel & Off Road
Posted March 1, 2013

Your Tech Questions Answered

No Steer, No Brakes
Q I recently got my hands on a ’72 International Travelall 1110 for what I thought was not so bad a deal. It needs a new steering gearbox and power steering pump. Can the brakes be messed up by my steering pump going out like on the military HMMWV? I am in the Army; that is why I am asking. The brakes are acting like the HMMWV’s when the pump goes out.

A I doubt the brake problem with your Travelall is related to steering, unless it has been outfitted with a hydroboost system. The hydroboost brake system uses hydraulic pressure from the power steering pump to boost the brake pressure, resulting in an easier pedal. If the power steering pump goes out, you’ll feel a very weak brake pedal.

I think your problem may be a faulty brake booster, or a vacuum leak. The standard brake booster is run off of a vacuum hose from the engine and has nothing to do with the steering pump. I have included two photos: one of a vacuum brake booster, the other of a power-steering-pump-fed hydroboost. If you have the hydroboost then, yes, the power steering pump is part of your problem. If you have the vacuum booster then you may have another problem with the brake system, be it a vacuum hose leak, booster failure, or something between the master cylinder and each wheel cylinder. Take some time and search for leaks. Remember, you are dealing with a 40-year-old system so it may be time for some repairs and upgrades.

Sonoma Up
Q I have an ’03 GMC Sonoma and I’ve been looking for upgrade suspension parts for it and can’t seem to find anything. You know of any place that might sell parts for my truck?
Casey W.

A BDS ( offers 5-inch suspension lift kits for both the ’95-’05 S-10/Sonoma and the ZR2 versions. The S-10 and Sonoma suspension will clear 31-inch tires; the ZR2 version will clear 32-inch tall tires.

Doubled 300
Q I’m stationed in Germany, but on a recent trip home to Washington, I picked up a ’75 Cherokee Chief for $800. It sports an AMC 401, a TH400, and a BorgWarner Quadratrac. I don’t like the idea of relying on a chain-driven transfer case (not to mention the low range doesn’t work) and was thinking of switching to either a Dana 20 or 300 doubled with an NP203. I’d read an article on a forum where a guy had doubled the Dana 20 with an NP203, but I haven’t been able to find anyone that makes a doubler for it. A few companies seem to make doublers for the 300. That in itself kind of narrows it down to the 300 for me. In your opinion, which would be the better choice for use on trails and mild rockcrawling? If you think the Dana 20 would be better, do you know who make a doubler for it?
Bryan S.

A In my opinion the Dana 300 is a better transfer case than the Dana 20; however, you must realize that either case will see a massive torque increase by doubling them with a 203 low-range box. The doubler idea makes sense, but the second transfer case in the double (in your case the 20 or 300) is taking a larger torque load because of the 203 low range upstream. The torque is multiplied by each gearbox, first through the transmission, then through the 203, and then through whatever case is behind that.

I would recommend an NP205 behind the 203 box since they are massive compared to the Dana 300, which is larger still than the Dana 20. The Dana 300 is lighter weight and lower geared than the 205, but since your Chief has the big, torquey 401 and is pretty much a fullsize wheeling rig, I’d lean toward the 205 if you are going to get into some rockcrawling scenarios.

The other problem you’ll run into is that all of these transfer cases—the 20, 300, and 205—have a centered rear output. The rear axle behind the Quadratrac is offset a bit to the passenger side. If you run a centered transfer case to the offset rear axle you may be prone to driveshaft vibration. I’d suggest looking for a new centered rear axle; another Dana 44 would be fine unless you are planning big tires, then probably something heavier duty like a Dana 60 or a 14-bolt.

Tall Hauler
Q I have an ’08 F-350 with a leveling kit and 35-inch tires. I will be hauling a heavy slide-in camper, so I want to ditch the leveling kit and go with a 4- to 5-inch suspension lift. I was wondering whether the lift blocks for the rear (in any given kit) would hold up to the added weight, or should I look at new springs instead?

A I don’t understand why you want to ditch the leveling kit for a lift kit just because you are adding a camper. In my view, adding a camper means you want easy access to the bed of the truck to get in your camper, and lifting it 4 to 5 inches won’t make this any easier. Plus, by raising the truck and then adding a camper you are making it less stable with a higher center of gravity. I’m not saying don’t do it, but it seems counterproductive. I’d rather you put a set of airbags on the rear if you really need help supporting the camper.

Now maybe you just want the truck to be taller than the leveling kit offers. If so, then I understand the lift kit, and I agree that a kit with new rear leaf springs offers a more stable suspension than one with rear lift blocks. The lift blocks will work, but the lift springs in addition to a taller, heavier load like a camper will be less prone to axlewrap. You may also want to look into the new airbag mounting cups from Daystar and BDS. These support the airbags, allow the axle to droop out without stretching the airbags, and allow you to compensate for the added lift height with spacers under the airbag cups.

One More Time
Q You tell everyone you can’t flip a low-pinion axle to get a high-pinion rear axle, but what about flipping a high-pinion to get a low-pinion rear? You wouldn’t have a problem with oil starvation, would you? If I’m crazy, tell me why I’m crazy so I understand. I have a couple of high-pinion 44s that I want to put in a ’92 XJ.

A Flipping a low-pinion axle over will not make it high-pinion, and flipping a high-pinion axle over will not make it low-pinion. Flipping either axle over will make it turn backwards. It all has to do with the gear cut. The high-pinion axle is cut different than the low-pinion one; they are not the same and not interchangeable. The rotation of the pinion is the same, but if you flip the axle over you are in effect putting the ring gear on the opposite side of the pinion and this will make the wheels turn the wrong way. If it starts as a high-pinion front axle then it can be turned around to be used as a high-pinion rear axle, but it cannot be flipped upside-down to be used as a low-pinion axle, and the same goes for a low-pinion axle.

The only time you would ever flip an axle upside-down is if you turn the direction of the engine around, like if you point the front of the engine towards the back of the vehicle (say, in a custom buggy), but 99.9 percent of four-wheelers never build anything like that. When the back of the transmission and transfer case point towards the front of the vehicle, then you would want the axle flipped upside-down so it makes the vehicle go in the right direction.

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