Feeling Tired
Question: I own an '83 Dodge with a Dana 60 front and a Dana 70 rear axle. I have recently purchased a set of 395/85R20 Michelin XMLs (46 inches tall). I had not anticipated that these tires would be significantly heavier than a typical set of 44s. I now have concerns that the axles will not hold up to the added mass, particularly the front Dana 60.
I am now weighing my options. While Rockwells are cool and Dynatrac now offers a massive front Dana 80, I cannot afford the large lump sum of cash I'll need to purchase them. I'd like to keep the axles I already have and build them up. At least I know they fit the truck, and I own them. Some years ago, there was a four-part article "Ultimate Super Duty" in your magazine [beginning Aug. '02]. The truck in this article had a Dynatrac ProRock 60 front axle and the same size and brand of tires I plan to use. According to the article, the truck did bust a 35-spline stub shaft, which was attributed to a steering failure. Did that Dana 60 really hold up well? Or was the truck prone to more axle-/stub shaft failures after the story ended?
Ed R.
via 4wheeloffroad.com
Answer: 4-Wheel & Off-Road magazine still owns the Ultimate Super Duty but we rarely run the 46-inch Michelins on it even though they made the truck look awesome. After it broke a steering box and a stub shaft on the 2002 Ultimate Adventure, it was followed with two more broken front axleshafts. In the rear we broke one axleshaft, the ARB locker, and spun a tube in the Sterling housing. Nowadays there are chromoly shafts available from CTM racing (760.450.0006), Superior Axle and Gear (888.522.2953), Alloy USA (866.35.ALLOY), and Yukon (www.yukongear.com). Also, there are 300M U-joints from CTM available which are extremely strong compared to the factory parts we had in the Ultimate Super Duty. Dealing with the broken housing could be done with a substantial bridge/gusset if you can weld. However, you are then moving the weak point elsewhere such as to the ring-and-pinion, and the front low-pinion 60 will be the first failure I'd expect. I know you are on a budget and I understand that the Michelins can be had cheap from military surplus yards and Internet auction sites, but I would advise against using them in extreme terrain with anything less than Dynatrac's Pro-Series Dana 80, Rockwell 2 1/2-ton axles, or some of the larger Mercedes Unimog portal axles, like the U-1300 variant. I see three real options: more axle, less tire, or gentle driving. In the tire category you could also consider grooving the tires to remove weight. In fact I have seen these Michelins grooved not only on the tread but also on the sidewall, though I'm sure they were never designed for sidewall trimming. You could go with the lighter, yet probably more expensive, 46-inch Mickey Thompson Baja Claws (330.928.9092), or 44-, 47-, 49-, or 53-inch tires from Interco (www.intercotire.com), but I fear unless you get down to 44s you'll still be breaking stuff in your 1-tons. If your axles are unlocked, they might live a while longer, but performance will be greatly hindered. I hate to say it, but I think you should go bigger for axles or smaller for tires, neither option being cheap.
Mr. Soggy-Foot
Question: I have a '71 Chevy 3/4-ton 4x4 pickup (350-350 205 NP). The truck has a lot of miles and the history of the running gear is unknown, but it seems solid. The problem is that the gear lube from the transfer case is being pushed through the speedometer cable and leaking on the driver-side floorboard. I have checked and cleaned the transfer case vent several times. I have blown through the vent, and it is free. I also removed the steel cap from the vent and attached a rubber hose and routed it up to the firewall, but still no help. The lube in the transfer case is a good-quality 80/90 with 1 quart of Lucas additive. Could the transfer case be building up too much pressure for the vent to work correctly? If so, how do I fix it? Please help before my wife kicks my ass for tracking gear lube in the house.
David
via 4wheeloffroad.com
Answer: I spoke to the guys at Performance Automotive and Transmission Center (888.877.1008), and they said that the plastic speedometer gear can either get a small groove worn into it or the small lip seal can start to leak around it, and the next thing you know there's some gear lube in your speedometer cable. Then it's like a small-grain auger or drill bit just grinding around and pumping the lube up into your cab and out onto your foot. PATC can supply the parts to repair the leak, but be sure to clean or replace your speedo cable as well.
Another thing to check, if you have an aftermarket manual oil pressure gauge that actually uses a long plastic tube running from the engine, is that it hasn't sprung a leak. You may be getting oil behind the dash as well, and it could be dripping down onto your floor. Make sure the oil is gear oil or engine oil to verify.