1992 Ford F-150 - Project Fiery Redhead: Part 4Posted in Project Vehicles on July 21, 2004
We love surprises, as long as they're the good kind. The nasty ones we can do without. You'll probably agree that an example of a nasty surprise is any sort of transfer-case failure. Since our Fiery Redhead Project F-150's odometer has twirled around to the tune of more than 150,000 miles, we felt that its transfer case could be poised for failure. We based this speculation on not only the truck's high mileage, but also on the fact that we had no idea as to how the truck's previous owner maintained it.
The T-case seemed to work fine, but we're not ones to tempt fate. So we had it professionally rebuilt. Like the transmission rebuild in last month's issue, we opted to rebuild the unit that was in the truck, as opposed to replacing it with an aftermarket unit. This gave us an opportunity to see for ourselves what kind of shape the unit was in, and we'd get to see how the new parts compared with the old.
The first thing we did was dial up the folks at Motive Gear. They're a massive wholesale supply house in Chicago that provides parts to thousands of jobbers, and they stock all the parts needed for a rebuild of this caliber. They're quite knowledgeable about transfer cases, so they immediately gave us the lowdown on what parts tend to wear in our BorgWarner 1356 T-case, and what we'd need to rebuild it correctly.
They shipped the parts directly to the shop that would be rebuilding the 'case, Big Gun Racing Automatics in Blackwell, Missouri. Big Gun owner Matt Heady is not only experienced in building heavy-duty automatic transmissions (he has built 'em for Bigfoot, Sudden Impact, Summit and Nitemare monster trucks), but he's also a master of transfer-case tech as well. He's been building transmissions and transfer cases for customers all over the U.S. for more than 18 years.
Surprisingly, our F-150's transfer-case internals were in reasonably good shape. Once unbuttoned, it was obvious that the unit had been wrenched on in its lifetime. Nonetheless, we installed all of the new parts. Now we have the peace of mind that goes with knowing that our transfer case is ready for years of service.
The following photos will give you an idea of what components tend to wear in the BorgWarner 1356 T-case and what parts are available in the aftermarket to remedy these problems. Some are normal wear items, while others are not. You'll also see how easy it is to remove and reinstall the transfer case yourself so you can save a few bucks.
The 411 on the 1356
Ford began using the BorgWarner 1356 in 1987 as a replacement for the BorgWarner 1345. The 1356 boasts a tough magnesium case, respectable 2.69:1 low-range ratio and chaindrive. When compared to the NP208, the BorgWarner 1356 has a much larger chain, and when placed side-by-side with the NP205 it measures 6 inches longer.
Tracking transfer-case temperature
The first thing we did after rebuilding our transfer case was install a Nordskog digital transfer-case temperature gauge. This neat little gauge simply snapped into our nifty Pro Pods Full Pillar Gauge Pod, and it offers us instant eye-level readout of our fluid's temperature. The sensor for the gauge is mounted in the drain-plug hole in the bottom of the 'case.
Why should we, or you, care about about your rig's transfer-case temperature? Probably the most important reason is that many T-cases use automatic-transmission fluid (ATF) to lubricate and cool the internal components. Standard ATF fluid has a recommended operating temperature of approximately 175 degrees Fahrenheit. Temperatures above that figure significantly shorten the fluid's lifespan, thus requiring more frequent oil changes.
In 1999, we published a multi-part series "Project MPG," written by Randy Thomas of Performance Unlimited in Hartford, Wisconsin. During some eye-opening testing, Thomas found that the transfer-case fluid in his '88 Ford big-block-powered, 1-ton, four-door 4x4 crew-cab dualie reached a scorching 380 degrees Fahrenheit during on-highway, trailer-less testing in the summertime. Considering that ATF fatigues at 220 degrees, he knew something had to be done; otherwise he'd have to change oil every 1,000 miles. His solution consisted of using high-temp fluid and Pro Blend additives to lower the average operating temperature to an average of 180 to 210 degrees.
This is an illustration of what was on our minds as we installed our Nordskog transfer-case temperature gauge. We just got it hooked up, so over the course of the next few months we'll be charting our transfer-case temperatures. We'll keep you informed.
One of the first things Heady checks during a rebuild is the oil-pump retaining brackets that are molded into the transfer-case housing. These are designed to hold the oil pump in place, but over time they wear out. Ours were in excellent condition, but here you can see an older case that shows significant wear. If they were to completely erode, the oil pump could spin on the output shaft, fluid pumping would end and the transfer case would fail. Heady says he can fix housings with worn-out retaining brackets by drilling through the housing and installing a bolt to act as a retaining bracket. Or the case half can be replaced with a new unit.
We replaced our old planetary unit (on right) with a new, beefier one from Motive Gear. The planetary pinions can wear out the thrust washers in these units, and this can allow the pinions to eat away at the planetary housing. The result is destructive metal shavings that circulate in the ATF fluid. These shavings can clog the oil pump's filter. Also, inside the planetary unit are teeth that engage the high/low shift hub, and these can wear, causing the transfer case to not engage correctly or to pop out of gear.