I thought I'd post about results to date on a couple of experiments I been running over the last 2.5 years with the steering boxes in two LHD (115.01) GTV that we use as daily drivers in our family.
I rebuilt one box using instructions giving in posts to this forum. This thread
was most helpful.
It was noted that the lower oil seals that I had bought in the past from IAP then later Centerline would always start leaking after a few years in a box in a car, Those two or so years equated to maybe 14K miles of driving. This got me to wondering if maybe the seals being sold by these vendors wasn't suitable for the environment. I contacted Parker (see image) to find that they made a correct size oil seal (28 mm (id) x 40mm (bore) x 7 mm (height) high-temperature seal for this application. I bought one and installed it. Then filled it with the 90W oil that is recommended by Alfa. This box has been in the car for nearly 11K miles and the pitman arm is still dry. The Viton seal is holding tight.
The second car I didn't replace the weeping seal but instead sucked out the Pennrite Steering box grease from the box (the box I have holds 400 ml of lubricant) and replaced it with SHELL GADUS S3 V460D 2. I chose this grease because my nephew, who is heavy equipment mechanic, uses it in the gearboxes and recirculating ball steering system on the heavy equipment that he rebuilds and maintains.
Switching from oil to the grease was done with some trepidation. That is because there are more than a few post on this forum about the damage that can be done to a Burman box when grease is substituted for the recommended oil. But my nephew's 10 years of success using the grease plus a plausible explanation of how grease lubricates the ball bearings in a Burman box gave me some confidence that the damage to the moving components would be from minimal to none.
"Greases are formulated by combining a base oil with a thickening agent. They lubricate rolling bearings by bleeding a small amount of oil out of the “reservoir” of the grease thickener and into the raceway. The oil provides the elastohydrodynamic lubricating film needed to reduce friction and wear. Greases can also serve as effective seals to protect bearings from contaminants and moisture. For greater loads, especially where vibration or shock loading is likely, special anti-wear additives can improve grease performance. Likewise, special thickeners and additive packages can augment a greases natural resistance to wash-out by water or salt-water spray. Thickeners can also be processed to reduce the noise-generating characteristics of a grease. Finally, other additives can tailor a grease to specific application needs: PTFE for low-temperature torque, molybdenum disulfide for high loads, special additives to promote electrical conductivity, and specific chemistry for low vapor pressure applications."
So far, so good with this box. We can't decern any changing in the steering dynamics in the car with grease in its steering box (running on "185" 14-inch tires). And after 19K miles the pitman arm on this car has also remained dry.
Again, these results are for LHD GTVs where the lower end of the steering box is warmed to circa 70C by the exhaust pipe.