Do NOT let it hunt if you can avoid it. This is one of the main reasons transmissions fail in vehicles like these.
Vehicles like what?
Continued shifting and torque converter slipping cause heat to build up relatively quickly especially under a heavy load, like towing at highway speeds.
On the Ridgeline, the ECU will monitor transmission temperature and lock the torque converter to prevent overheating. See
http://www.ridgelineownersclub.com/forums/showpost.php?p=245541&postcount=220 .
Stick it in D3 or D4, which ever causes the vehicle to minimize shifting.
Welcome to the ROC... now, are you sure that you are on the forum for the correct vehicle? The Ridgeline does not have a way to limit it to D4. It can only limit to D3, and the OM specifically says to not use that as a towing mode. As the lead engineer says in the above link, "Just tow in drive and plant your foot into the accelerator."
The engine will handle the higher revs just fine an will not cause any significant additional wear.
Correct. The warning in the OM is specifically about risk to the transmission by sustained locking to D3.
Your fuel mileage will suffer, but a few extras bucks on gas is a lot better than buying a new trans.
Avoiding routine use of D3 is apparently all about protecting the transmission.
Unfortunately the trans in 1st gen MDXs is the weakest link...so baby it when you can.
Early prototypes of the Ridgeline were based on the MDX, but the final product is not an MDX.
You couldn't be more correct! Let's continue to look at this.
Okay!
I was taught to not let an automatic trans "hunt''. I don't know if that is right or wrong.
It might be right for most automatic transmissions, which use a planetary gearing system. The Ridgeline doesn't have one of those (nor do any Honda AT's that I know of).
Engines seem to be the same except the Pilot has VCM, RL doesn't.
Why do you say that? Is it because they have the same displacement?
Transmission is the same except for 5th gear. Pilot=0.612, RL=0.538. Transfer assembly is the same. Final drive ratio is different. Pilot=4.312, RL=4.533. There may be other differences that don't show on the Honda website. ECM programs may be different, etc. About the only significant difference is the gearing.
Again, there is no reason to conclude from reading certain spec sheets that the differences that you can find there are the only differences.
You might want to see the series of four videos from the Ridgeline's car show introduction, done in a very dry and engineering-oriented style by the head of engineering for the Ridgeline. Here is Part 3, talking about the engine and transmission:
The specs did change slightly from what was given there to when it shipped. Most worth hearing: "It is NOT the same engine that's in a Pilot. This transmission was also specifically developed for this vehicle. It's a vehicle that is designed to tow and work as a truck from the ground up."
That would allow the RL to pull more weight.
That and other stuff, yes.
Others have posted more details in the past on the ROC. Sorry, but I just don't have all of the references saved. Hopefully they'll chime in again.
But that doesn't address the question off allowing "hunting" or not.
Two other things that haven't been repeated in this thread:
1. The 2009 model year had engine and transmission changes that may lead to less hunting at highway speeds.
2. Use premium fuel for towing. It may also reduce hunting.
Must be some Honda transmission experts out there.
Gary Flint is the expert, and I have cited him twice above (in the video and the post about TC lockup).
Differences in the wording in the manuals may be due to recent revisions in the Pilot OM.
I don't have an explanation for the Pilot OM's wording. Maybe it's wrong, or maybe other engineers who have worked on the new model did things differently than with the Ridgeline.
Someone must have a 2011 or 2012 RL OM.
Tom
I don't think that it's changed since 2009, and this particular piece of advice (about NOT using D3 as a towing mode) has not changed since the original 2006 model.
"Just tow in drive and plant your foot into the accelerator."