I'm not even sure where to start with this one. 2020 Expedition Max with HD tow. It just rolled over 100k on the way home from a recent 800 mile trip towing our roughly 7500lb loaded toy hauler. On the way out, I noticed the IWE grinding sound (again) coming from the left front when going uphill. On the way back, that occasional grinding turned into a full shuddering/jerking.
Since I was towing, I put it into tow mode and locked out the top two gears, sometimes more. If I wasn't paying attention and making it downshift, trying to keep up speed on inclines would increase the boost level, which is when the problem would show itself. The whole car would start shuddering, kind of like the transmission was slipping and catching, but the rpms were steady so I don't think it was the transmission. While this is happening, the boost gauge is going nuts, bouncing from zero boost to full boost.
The only thing I can think of is the IWE system. I've had issues with it in the past and replaced the firewall mounted solenoid a few months ago. Prior to the fix, I'd been able to bypass it by connecting the vacuum lines and making the hubs stay unlocked. I tried that this time but the problem persisted (not as bad, but still there). Any ideas? Could it be a failure in another part of the system? Perhaps a bad seal preventing the system from "storing" enough vacuum to keep the hubs open when boost goes up and vacuum drops?
Edit: No check engine light, error code, or other message ever came up. The engine and trans are operating at the proper temps (installed the lower temp thermostat). It drives great except for that high boost / low rpm situation.
Since I was towing, I put it into tow mode and locked out the top two gears, sometimes more. If I wasn't paying attention and making it downshift, trying to keep up speed on inclines would increase the boost level, which is when the problem would show itself. The whole car would start shuddering, kind of like the transmission was slipping and catching, but the rpms were steady so I don't think it was the transmission. While this is happening, the boost gauge is going nuts, bouncing from zero boost to full boost.
The only thing I can think of is the IWE system. I've had issues with it in the past and replaced the firewall mounted solenoid a few months ago. Prior to the fix, I'd been able to bypass it by connecting the vacuum lines and making the hubs stay unlocked. I tried that this time but the problem persisted (not as bad, but still there). Any ideas? Could it be a failure in another part of the system? Perhaps a bad seal preventing the system from "storing" enough vacuum to keep the hubs open when boost goes up and vacuum drops?
Edit: No check engine light, error code, or other message ever came up. The engine and trans are operating at the proper temps (installed the lower temp thermostat). It drives great except for that high boost / low rpm situation.
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