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Metallurgy + the Laws of Physics = Buyer Beware

The car sat on the lot for about a month, until a salesman noticed a collection of white/gray powder under the middle of the vehicle. Curious as to what was going on the salesman went to move the Hummer, put it in gear and promptly blew the rear driveshaft out of the vehicle. They then removed the BW 4484 transfer case from the vehicle. By looking at the photos provided here, you can see what happens when a transfer case with a magnesium case is filled with seawater for more than a month. The case is now paper thin and riddled with holes as if attacked by metal-eating moths. The used-car lot bought a new BW 4484 and fixed the problem. The core was sent to us, and it makes a good basis for this article.

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Metallurgy + the Laws of Physics = Buyer Beware

Up to Standards

Author: Mike Weinberg, Contributing Editor
Subject Matter: Transfer case
Unit: BW 4484
Vehicle Application: Hummer G3
Issue: Salt-water infiltration

Up to Standards

  • Author: Mike Weinberg, Contributing Editor
  • Subject Matter: Transfer case
  • Unit: BW 4484
  • Vehicle Application: Hummer G3
  • Issue: Salt-water infiltration

The old cliché “What you don’t know can’t hurt you” describes emotional stress but nothing else. What you don’t know can definitely hurt you, cause large financial losses and be downright dangerous to your personal safety. The country has been inundated of late with severe weather conditions, most of which seem to be caused by a change in the jet stream. Tornadoes, heavy rains and large storms seem to crop up everywhere. The aftermath of these occasions will have severe effects on people for a long time. After the dust settles and the rebuilding starts there is always collateral damage that shows up long after the event. Some of this hidden damage finds its way into our shops.

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Everyone knows about the horrendous damage in the Northeast caused by Hurricane Sandy, which was called a “super storm.” Onshore winds coupled with a 15-foot tide surge caused massive flooding that resulted in loss of life and terrible property damage. Not all this damage was immediately apparent to the naked eye. It was clear that salt water had damaged huge amounts of the infrastructure as well as personal property. This means that a huge number of vehicles sustained salt-water flood damage.

Then there was damage that is showing up now as a result of people driving vehicles through salt water that was deep enough to get into parts of the driveline but went unnoticed until catastrophic failures showed up. One such story concerns a late-model Hummer G3 that was traded in to a new-car dealership on Long Island, N.Y. The vehicle apparently did not suffer complete submersion but was involved in travel through pretty deep water. The dealer who took the car in trade sold it to a used-car dealer, who took it to his lot, detailed it and placed it on the lot for sale.

The car sat on the lot for about a month, until a salesman noticed a collection of white/gray powder under the middle of the vehicle. Curious as to what was going on the salesman went to move the Hummer, put it in gear and promptly blew the rear driveshaft out of the vehicle. They then removed the BW 4484 transfer case from the vehicle. By looking at the photos provided here, you can see what happens when a transfer case with a magnesium case is filled with seawater for more than a month. The case is now paper thin and riddled with holes as if attacked by metal-eating moths. The used-car lot bought a new BW 4484 and fixed the problem. The core was sent to us, and it makes a good basis for this article.

People use their vehicles for much more than getting from point A to point B. This means that you need to be aware of some of the places that these cars and trucks visit routinely. Does the truck have a trailer hitch? Does it get backed down a ramp into water more than hub deep to put a boat in? Does the owner like to off-road through streams, mud bogs, swamps etc.?

Any of these should be a warning to you to check the vehicle for extreme-duty usage; something like mud on the roof may give you a hint. Have there been heavy rains or other adverse weather conditions that influenced the vehicle and the customer never bothered to check the differentials, transmission and transfer case for water infiltration?

We showed an example of what seawater is capable of when mixed with magnesium, but fresh-water contamination plays hell with bearings, rusted internal parts, and transfer-case clutch packs and other driveline components. After severe weather that causes any local flooding you should work up a program to get your regular customers in for service and safety checks, which will generate income for the shop and probably generate some strong repair orders.

For many years manufacturers used magnesium cases on transfer cases because of the metal’s stiffness and light weight. However, magnesium has some other qualities you need to be aware of. Magnesium is very susceptible to damage from galvanic corrosion, which is caused by contact between dissimilar metals. Magnesium and aluminum get along relatively well, but steel is the arch enemy of magnesium.

Certain designs create further problems, such as the New Venture 246 transfer case, which has both cases made from magnesium. One problem with the 246 is the oil pump, which is driven by the output shaft and is made from aluminum alloy. The alloy is tougher than the magnesium and over time beats a hole in the case, causing a fatal drip that never gets found until it is too late to save the internal parts. The second issue is the pressure applied to the mainshaft during application of the clutch pack, which makes the galvanic corrosion from the steel bearings worse and results in the bearing bores getting wallowed out, necessitating replacement of both cases.

The third issue with magnesium is “creep” due to high operating temperatures. Magnesium will begin to creep when operating temperatures reach 125°C (257°F). Creep causes leakage and increases bearing displacement. We manufacture a U.S.-made aluminum replacement rear case for the NV 246, 261 and 263 under our Tranzilla brand. There are aftermarket aluminum cases available that are knockoffs of the magnesium OEM case but do not have the strength of the original magnesium case because they are made to the exact same dimensions with aluminum, which does not have the strength and stiffness of magnesium. Our case, which was voted a Transmission Digest Top 10 Products winner, was redesigned with stronger webbing and is five pounds heavier than the OEM and other aftermarket cases. It is guaranteed for life against oil-pump “beat-through,” without any case-saver plates, and will never experience bearing creep or bore wear.

Times are changing, and the weather cycles are becoming more pronounced. We cannot change Mother Nature, but we can be prepared for the forecast, and by being aware of the problems that can be created we can be prepared for the aftermath. As this quote from the film “Mechanic” says, “Victory loves preparation.”

Mike Weinberg is president of Rockland Standard Gear.

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