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.
Over time, the transfer-case...
Over time, the transfer-case chain will stretch. Sometimes, chains will stretch so much that they can actually slap the inside of the transfer-case housing. Because of this, it's important to check for excess slop in the chain. Ours was in great condition, so we reused it.
Insufficient lubrication can...
Insufficient lubrication can mean a quick and expensive end to your transfer case, so Heady highly recommends a new oil pump and filter. He notes that it's important to make sure that the hose connections are tight and the unit is installed properly.
Grit can get between internal...
Grit can get between internal surfaces like the output shaft and the drive sprocket. Here, Heady inspects the inside of the drive sprocket right after he removed it from the case. He says that most of the time, the output shaft will take the brunt of the damage from foreign matter. Both of ours were in good shape, so we cleaned them up and reused them.
It's always a good idea to...
It's always a good idea to replace all bearings and seals. Most rebuild kits come with all of the required components to complete a rebuild.
Reinstallation of the transfer...
Reinstallation of the transfer case begins by placing the new gasket on the transmission. Make sure you clock the gasket so that it is lined up with the six mounting boltholes.
Lift the transfer case into...
Lift the transfer case into position and slide it onto the transmission output shaft until it mates with the transmission housing. Install and tighten the six mounting bolts, reconnect the shift linkage, vent hose, 4WD indicator switch wire and driveshafts. Finally, fill the unit with ATF fluid and check for proper operation.