Hey,
Questions about my 2008 Corolla AT:
Bought the car with 100k miles, it now has 145k miles.
AT has been trouble free.
I have changed the AT oil twice: Once at purchase, recently at last engine oil change.
You mentioned (Some time ago), that it is not a good idea to let the AT downshift from OD or top gear while under load. (Around here that is going up grades at highway speeds.) Does that comment apply to Toyota AT’s?
Also, shortly after I bought the car, I was going down a grade at 60mph, I tapped the brakes, and the AT downshifted. When I asked the folks at my garage about this, I got blank stare, and then forgot about the downshift. Is this typical for this vintage car? Car does not have ABS.
Thanks for all the reasoned advice you have doled out!
Rog
Yes, it will do that......my 2009 MINI does, and it also has a Toyota transmichigan (Aisin)
A lot of newer transmissions will downshift if they see you riding the brakes and not really slowing down, or applying the brakes after accelerating with no throttle input. There's some complex algorithm happening there.
Thinking about what you said, or what you say Curtis said....I'm a bit confused. Wondering how do I go up a grade without downshifting if it's not good to do so under load?
Downshift manually with my foot off the throttle?
In reply to CyberEric :
Some transmissions 4L60 do not tolerate much being banged down to 3rd under load, so the polite way to deal with it is to manually shift down from overdrive before you need to.
I know that whatever trans was in the 4.7 Durango that I towed with did not tolerate downshifting under load to any gear. It did a horrifying 2nd gear internal burnout trying to go up one hill in Missouri while towing a trailer. Scary.
Added line pressure helps slippage, but there is something in the 4L60 that doesn't like a shock load either.
The paging Curtis title had me guessing what the topic would be before opening. My first guess was RVs, or maybe 15-23ft boats. Both are topics where Curtis has proven to be super knowledgeable. But, auto trans is another topic where he is deep with knowledge too.
It could have been any number of other topics. Either way, its a great reminder that Curtis is AWESOME!
Good to know, thanks Pete.
Ive got what I believe is a 4R75E in my Ford E250 with the 4.6. I've always noticed downshifts from OD feeling pretty rough.
Should I be taking my foot of the gas and downshifting to preserve this trans?
Sorry, y'all. Curtis was at camp drinking whiskey this week.
That comment mostly applies to vehicles towing heavier loads, and I think we were discussing something like and F150 or Silverado at the time. Many of the American RWD automatics are warmed-over versions of transmissions from the 60s and they added an OD. It was all good through the 80s and 90s because most of those were smog-tastic, low-power vehicles. There was a time in the 80s that the most HP you could get in a Chevy pickup was 215 hp from a big block.
In general terms, don't stress for a moment. The AT in your Corolla was designed to do exactly what it's doing. The only time I'd worry about it is if you want to tow something with it or you're constantly hauling heavy stuff.
As far as the downshifting while braking, I would dig into the owner's manual. I know several vehicles that do this now. It's like a brake assist. The computer knows if you're going downhill and will downshift to help. Not sure if your Corolla has that feature, but my GM trucks (04, 06, and 08) will do that in tow/haul mode.
The boiled-down version is that nearly all transmission wear happens during a shift. Once it's in a gear, there is very little wear. It's much like a manual transmission... the clutch gets next to zero wear when the clutch is either at the floor or fully up. What wears it is the time it spends slipping between gears. The additional damage tends to happen when you're towing, carrying really heavy weight, or otherwise abusing it. It's just that the amount of wear that happens during a shift is increased if you have a heavy trailer behind it.... which I doubt is the case with your Corolla.
Sounds like you're taking care of it. Put it in D and enjoy.
What about me Curtis?! 
Since I read this thread, I've been taking my foot off the gas when climbing a hill and downshifting. It does feel smoother than when under load. It tends to bang down into gear when under load. Should I keep doing this?
CyberEric said:
Good to know, thanks Pete.
Ive got what I believe is a 4R75E in my Ford E250 with the 4.6. I've always noticed downshifts from OD feeling pretty rough.
Should I be taking my foot of the gas and downshifting to preserve this trans?
You would likely have a 4R100 unless it's some light-duty combo I haven't heard of. I personally would ease off and manually shift. I have to be honest, though. The internet warns about it in the 4R100, but I have tried to kill four 4R100s (or the predecessor E4OD) and failed miserably. I towed 10k behind a powerstroke/E4OD for well over 100k and just put it in OD. I was hoping it would die so I could swap in a ZF manual and it never died. I had a 4R100 in another Powerstroke van that was beaten hard, and I sold it with 325k and it never missed a shift. Several other F250s and E350s that have been in my care have also proven pretty robust. I've never had one apart, but I'm told that (at least on the earlier 4R100 and the E4OD) that hitting the OD OFF button does something additional, like a mini tow/haul mode. It engages more 3rd gear clutches and ups the line pressure, but that's just what I've heard.
Long story short: Internet says they're glass in OD and we're all going to die. My personal experience with them hasn't borne that out.
Thanks Curtis! I'll keep easing off and manually shift but won't worry too much. Interesting info on the OD off thing.
Much appreciated.
