donkiboy

2006 TL / auto

Whenever I go up an incline (at approximately 30 - 45 mph) the automatic would downshift into 3rd from 4th.
Is this some sort of fail safe to prevent too much load on 4th gear?

I do know that 4th gear is extra long. I'm just worried that this is a sign failing pressure switches.

truonghthe

the AT know when to down shift depend on road speed and input on the acceleration pedal all of this is autonomous in your case it require more power to climb the hill. your car is doing what it suppose to do, If the car keep in 4th gear then you will have problem since your car won't have enough power for the climb and the torque converter will heating up the fluid.

LeVeL

Why would you want it to stay in 4th at 30mph uphill?

shownfu

It does it because it's an automatic - so it automatically chooses the best gear for you.

csmeance

Under 2500 or 2100 RPMS the torque converter is unlocked meaning the wheels can spin at a different speed than the engine. After that point they are directly connected though the transmission. When it's unlocked, the difference in RPM is what causes heat to build up. If you are going uphill in to low of a gear, the car engine will be lugging, the transmission will be generating excess heat and you'll essentially be damaging your car. It's designed to shift into 3rd to keep the difference in speeds to a minimum to generate less heat and to prevent engine lugging. You should be replacing the 3rd and 4th gear switches as preventative maintenace to ensure a good long life for the transmission.

NoTLoud

I asked a similar question the other week. Car is equipped with Grade Logic. I never really notice the downshifts going uphill, mainly downhill. Same premise. Do you notice the car downshifting harder going down hill under similar speeds? Mine seems to downshift rather hard occasionally. I was initially quite worried thinking the torque converter was going, but I believe it's just how the car performs. Only had it for a couple months, so I'm still getting used to things and hyper sensitive to anything transmission related.

truonghthe

The Grade Logic only available in the 07-08 TL. OP TL is a 06 model, as far as the harsh down shift just change the ATF and pressure switches then the problem will goes away.

NoTLoud

Ah, did not know that.

Now I am a little concerned about my car's transmission, mainly the torque converter. It'll kick down gears pretty hard occasionally going down hills. I've done the 3x3 and pressure switches <5k miles ago.

donkiboy

That explains what I've noticed for months now. If I left off accelerator (in 3rd gear) it feels as if car is in neutral and coasting. Upon getting back on accelerator, the wheels would engage.
I'm baffled as to why the trans was designed to engage / disengage the wheels. I'm guessing this only applies to 04-06 TL, which are prone to failure.

YeuEmMaiMai

that is a big fat NEGATIVE

Honda has been using grade logic since 1994 in the Honda accord and it has been carried forward in the Accord, CL, TL and every other car that uses an at since then...

Acura's Advert for 2002 TL

http://news.honda.com/newsandviews/a...aspx?id=159-en
5-Speed Automatic Transmission

• Quick-response, 5-speed Sequential SportShift allows semi-manual operation
• Wide-ratio, 5-speed design helps improve performance and fuel economy
• Direct-control, automatic transmission managed by Powertrain Control Module (PCM) for enhanced shifting smoothness
• Grade Logic Control for reduced gear "hunting" when driving in hilly country

https://www.edmunds.com/honda/accord/history/
notice in 1994 they introduced it

NoTLoud

So to confirm: The 06 TL DOES have Grade Logic?

I want to confirm that the harder/harsher downshifts are within normal operations when going up/down hills.

It's the only issue/concern I have with the transmission right now. I notice they are harsher the colder the outside temperature is and the colder the engine is. I know when I will experience them in my daily commute.

However, sometimes, I can feel the car wants to downshift, but it will hold its current gear, kinda get a little jerky, and then downshift. I DON'T feel that this is normal. This makes me worry the torque converter is going bad.

Again, I've done the 3x3 with Honda DW-1 and pressure switches within the last 5k miles. The only other issue is lag in accelerator response, which I also notice more in colder weather. Looking at APP sensor replacement for this.

EDIT: Just did some further reading on what csmeance described above. Is the jerkiness I am experiencing before the downshift engine lugging? So once the engine starts to lug, the car will downshift to get the engine and wheels spinning at similar speeds to prevent the excess heat build up? If anyone can confirm this is the case, then I believe I can stop worrying about the torque converter.

alexb92

Yes, the '06 TL DOES have Grade Logic. Check your motor and transmission mounts if you feel your shifts being jerky even after a 3x3 and pressure switch replacement.

NoTLoud

Thanks for the confirmation. I am feeling more confident that the car is operating as expected. I've only had it for 4 months, so I'm still learning its quirks.

I am fairly sure the dealer replaced the front and side engine mounts before I bought the car from them. I was told they replaced "a couple," the sales guy didn't really seem to know. I may head there and try and get the paperwork to have on record. At least from inspection, they look brand new. Rubber still has the new film look to it. I haven't got a chance to look at the rear. I was just reading up on the tranny mounts and it looks like they could be a potential source of some of my issues. I will inspect them either this weekend or next. It does not look like they are too much of a hassle to replace or inspect. They also look like around $100 to replace all 3, which I would do if one was shot. I want my car to drive properly and last for a long time, so any preventative maintenance is a solid investment to me. Plus, the car being 10 years old, stuff is bound to start popping up, so I want to stay on top of things as much as possible.

YeuEmMaiMai

yes sir it does... also remember when you are going down a hill and the car is downshifting it will feel more pronounced as the transmission is taking up more of the car's weight (gravity pulling it down the hill)

alexb92

It is usually the upper transmission mount that cracks.

MyGuti

As others have stated, the car is performing as it should. I just wanted to clear something up......if your going downhill, the car will not downshift. Instead it will stay in current gear and rpms will rise until the car has sensed it has completed the downhill or rpms hit 3-3.5k mark and shifts into a higher gear. This will depend on speed and obviously how lengthy the downhill is. So again, if your going downhill, your car should not downshift, it should remain in gear and rpms will rise.

Second, it will take time to get used to the cars automatic downshifting.....ive gotten so used to my car's "shift behaviour" that I often can coast without applying the brake as I know the engine will downshift itself and I wont need to apply the brakes (on a straight road).

And finally if your experiencing excessive vibration or rough shifts, look at the engine mounts as mentioned earlier. Sometimes its just the one mount, I had that issue and once I swapped it out the vibration disappeared. For the rough shifts try the pressure switches.

alexb92

This is somewhat incorrect. If you apply the brakes while going down a steep hill, the car will downshift to apply engine braking.
See the below info that I screen shot from the 04-06 service manual.

MyGuti

well yes, I thought that was just common sense.....if you brake...car slows down and engine shifts to a lower gear...because your braking and going slower.
I don't brake on downhills a whole lot lol