| ryandinan |
Hello!
I have an 02 MDX touring with about 81,000 miles on it. We bought it used, and before purchasing, I had asked if it had all the transmission recall work performed on it (I came to this forum first!). They told me it did.
Anyway - I may or may not have a problem, because I can't find any mention of this on the forum, but I find the behavior a bit odd.
On one particular road I travel each day, there is a relatively tight curve that leads immediately to a steep downhill run. I normally end up braking slightly before the turn, just as it starts going downhill (slowing to about 45mph).
Now here's what I find strange...
The MDX responds by downshifting from 5th to 3rd gear to help slow the vehicle as I round this corner/hill (normal). As I finish the turn, and proceed to coast down the hill, (my foot is off the brake) I start to pick up a lot of speed again - however - the vehicle does not immediately shift back up to 4th/5th gear. It will stay in 3rd all the way down the hill, at 60+ mph, with the rpms "screaming" over 3500.
Normally by the time I reach the bottom of the hill, it will finally wake up and shift back into 5th. During this time, there is nothing I can do to force the MDX to get back into a higher gear - using the accelerator does nothing but force the vehicle to go faster in 3rd gear, and thus, increasing rpms higher... It's almost like it forgets what it's doing.
I was just wondering if this was "normal" behavior for the transmission, or if I should be concerned that something could be wrong?
Thanks!
-Ryan |
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| phecda |
| ryan, this does not sound like normal tranny behavior in any automatic trans vehicle. Sounds like a transmission problem to me. Have it checked out. Downhill in 3rd gear??!! Don't think so. |
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| ryandinan |
Thanks for the reply!
Darn, I was not wanting to hear that!
Like I mentioned before, it only happens when decelerating from a fairly decent speed, down a hill. It's almost like it knows you're on a hill, and uses the transmission to assist in the braking... I have noticed this in other Hondas (my friend had a 2000 Civic, and it would gear down when going down a hill while breaking).
The only difference here, is that it stays in 3rd gear for quite some time after (3-5 seconds) - it doesn't quickly return to 4th/5th after letting off the break and coasting the rest of the way...
It's done this since we've owned it (coming up on two years now).
Thanks - I'll ask to have them check it out.
-Ryan |
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| phecda |
| If this is normal tranny behavior for the vehicle, that would really bug me. I don't want vehicles & their manufacturers trying to guess my intentions while driving, and trying to be my nanny. If I'm going downhill I certainly don't want the thing in 3rd gear unless I put it there. This is akin to putting a governor on the accelerator. Don't babysit me. |
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| JL_SS |
| Acura's and Honda's have grade logic control which keeps the tranny in a lower gear going up or down a hill to keep the tranny from hunting on uphills and/or add engine breaking assist on descents. Check Acura.com for a description. It is not actually grade based but it measures a number of variables like throttle position to judge what you are doing. |
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| ryandinan |
Thanks for the info!
I assumed there was something like this - the only thing is, it doesn't seem like the "logic" is being all that logical :)
There really shouldn't be any reason why the thing stays in 3rd gear as long as it does, especially when Im accelerating and the rpm's are racing... it's almost like it has a time limit built in before it will shift....
-Ryan |
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| phecda |
| Wow, that is interesting. I like the idea of a little smart work on uphills, but not at all sure I like the idea of automated engine braking that leaves me out of the decision loop. Can this be programmed out of the computer? |
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| phecda |
I found the blurb in acura.com under MDX about Grade Logic Control & Shift Hold Control. It reads:
...when encountering a steep uphill or downhill grade, Grade Logic Control will instruct the transmission to hold a lower gear for better climbing or increased downhill engine braking. When accelerating through a curve, Shift Hold Control will delay upshifting for as long as possible to avoid disrupting the chassis or power delivery until you have exited the curve. |
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| phecda |
| ryan, have you tried the manual mode (M) on that downhill situation? That blurb about Grade Shift Control said it operates when transmission is in automatic mode. This suggests that M mode might let you upshift as you wish. |
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| ryandinan |
:confused:
How do I use the manual mode? Do you mean "manually" shifting down into 3rd during the hill, then shifting back into 5th?
If so, yes I have tried that, and the same thing happens. It will stay in 3rd for quite some time before it finally goes back to 5th.
At lunch today, I tried some experiments, based on the new knowledge of the "grade logic". I figured the computer would need to know several things; your speed, the current gear, throttle position, and how much pressure you apply on the brakes.
Sure enough, I could get the vehicle to demonstrate the same behavior on several smaller hills, if I simply braked harder (I would see the tach jump up from 1500 or so, to 2500, indicating that it had changed gears to assist in braking). Immediately after getting the gear to change, I would accelerate back up, and sure enough, it would "stick" in that lower gear for 5-6 seconds. I suppose it is just more noticeable at higher speeds, as the rpms are higher.
I suppose the next question is, is this typical for 02 MDX's to stay in the lower gear for a bit of time, even after accelerating back up?
Thanks again!
-Ryan |
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