Originally Posted By: abs
I'm reviving this thread because Ford appears to be having some issues with its synthetic 75w-140 gear oil (described earlier in the thread)when used in the PTUs. Apparently a significant percentage of these PTUs are failing, at least in part due to the oil severely thickening to the point that it looks like grease. Here are links to photos of what I'm talking about from two different Ford vehicles, both equipped with a Ford PTU, both failed and both had the Motorcraft 75w-140 lube in them:
Ford Edge Failed PTU
Taurus X Failed PTU
As previously discussed, Ford considers their 75W-140 Motorcraft lube to be a lifetime fluid. Based on these photos it would seem the truth may be far different.
I personally replaced the PTU fluid in my Ford Flex Ecoboost last weekend at 60k miles and discovered that the fluid was very black but also notably thicker than the brand new Motorcraft 75W-140 fluid in the bottle. It had not reached the point where I was unable to suction it out of the PTU (there is no drain plug) but there is no question that it had begun to thicken.
So the questions are many:
1) What could cause a 75W-140 Synthetic gear lube to thicken up like this? Ford has had some issues with the PTU air vent clogging on some vehicles - could that affect this situation? Does gear lube thicken due to overheating, due to water/moisture accumulation in the oil, due to running out of additive pack, or for other reasons?
2) What fluids, if any, would be more likely to withstand the tough conditions in these PTUs and help folks like me avoid a failure? Obviously more frequent changes (or any fluid changes) should be mandatory and I wouldn't be surprised to see Ford issue a TSB on that eventually. In the meantime, what are some great oil options?
As previously noted, I prefer products that are fully tested to meet industry accepted specs. As an example, I am about to switch my rear differential to Mobil Delvac 75w-90 which has a very long list of approvals . . . What is available with a similar list of approvals in the 70W-140 viscosity?
Regards,
Andrew
Regarding #2: The PTU sits about 2-3 inches or less from the exhaust manifold just after it makes its bend to travel to the tail. The silly little heat shield does nothing to dissipate the heat cooking the PTU fluid. Combine that with the design flaw of no drain plug and maintenance spec of "lifetime" fluid and the result speaks for itself in the pics. I also think thr PTU was under engineered for the task at hand.Ford would have done well to tear a page from the Euros and the Haldex design. Or Subarus AWD design....both far more robust than the POS that they settled on.
