Timthetoolman

If TL AT is shifted manually to minimize use of 3rd gear will this extend transmission life? I have been shifting manually from 3 to 4th well before shudder starts in third gear for the last 5,000 miles. I am hoping that this reduces 3rd gear clutch wear. To reduce number of shifts I shift manually.

Background: I have been following the general procedures mentioned much on this site including regular Redline ATF mix fluid changes, multiple 3 and 4th gear pressure switch changes (over time/miles) and add on Magnefine filter changed once (old one looked pretty clean)--Started all this at about 87,000 miles after feeling shudder and now at 156,000. I see third gear shutter not to many miles after fluid change (works for awhile but nowhere as long as years ago, pressure switch changes now not making a noticeable difference...).

I had the transmission fluid tested by a lab and it was fine (also looked pretty good), right before a fluid change. Otherwise the transmission still shifts and works great.

Superunknown

When you say shudder, are we talking genuine transmission shuddering, or just a really hard, hesitant or "bucking" shift? I thought shuddering indicates the damage is done, so that would be something if you nearly doubled your mileage after that. My transmission shuddered for a brief moment on a Tuesday, and it was dead by Thursday.

I've read different theories about what causes transmission failure in the 5AT, but if there's a consensus on a singular root cause, I haven't stumbled across it yet. There's all the ATF discussion on this board, which probably doesn't need to be dredged up. This article fingers a pressure relief valve in the torque converter lube circuit, which leads to a roasted TC. This one blames the 3rd and 4th gear pressure switches, which cause mayhem if they drift even slightly out of spec. It also touches on the lube circuit issue. Then there's case bore walkout, which may explain why so many 5ATs do jet turbine impressions in lower gears.

In any event, fluid and switches (and maybe that filter Acura forgot to tell its dealers about) seem to be all you can really do until a rebuild opens up the opportunity to modify the lube circuit. I don't know that judicious use of sport shift accomplishes anything. I used to do it to reduce the laggy 2->3 upshift after letting off the throttle at low speeds... Wouldn't say I got anything out of it as the transmission failed anyway.

Timthetoolman

The shudder feels just like the shudder felt around 2500-3000 rpm, while in third gear, when the pressure switches need to be changed or possibly a little more pronounced. Thanks for the links.

losiglow

iTrader: (1)

I think you've got it right with the manual mode. I micromanage my shifts using manual mode 99% of the time. It's partially because I'm used to a manual, and prefer to decide what gear I want to be in. The other reason is because I believe it extends transmission life due to reducing the number of times it's having to shift. For example, on a hill, the normal AT is going to up and down shift a bunch of times simply due to the need for more torque (downshift) followed by letting up on the throttle when you get to a certain speed (upshift). We have about a 3 mile hill up to my neighborhood and if I leave it to the ECU, I'll probably see at least 4 up/down shift cycles. If I attempt to give it enough throttle to keep it in 5th (without it deciding to upshift to 6th), I'll end up 20mph over the speed limit when I reach the top. Instead, I keep it in 5th with a constant throttle which is still in a reasonable RPM but without all the shifting. I have a 4G BTW. Same principle though.

Another example would be if you're downtown or in an urban area with a lot of lights. In only a quarter mile, the car will want to shift all the way to 4th gear, even if you're only getting to 20-25mph before getting to the next light. Keep in mind, the ECU is programmed for fuel economy, not for transmission longevity. In cases like those, I don't bother shifting past 3rd. Or even 2nd if I won't even be reaching 3K rpm before slowing down. Accelerating while cruising is another. You might want to pull ahead of another car on the freeway. If you give it enough throttle it will downshift. But if you don't need that much power, just putting the throttle down in a higher gear is plenty of power to pass without a downshift.

For most people, that all seems a bit overkill but I'm convinced it helps significantly in the long run. If you think about it, a mechanical device has a certain number of times it can function before wearing out, even if it's maintained to a tee. By reducing the number of times it has to function (shift in the case), it's simply going to last longer. The exception with a transmission might be the scenario when you're giving it throttle in a lower gear and the TQ unlocks (or never locks in the first place) in which you're shearing the ATF and creating heat. But the 4G locks at a very low RPM. About 1500. I'm not certain about the 3G. Proof is in the pudding I suppose. I bought my 4G at 58K and now have 183K. Transmission works as well as the day I bought it.

Timthetoolman

losiglow--well put and totally agree including that most people will not be interested in going to the extra effort.

Diomaiuti

I do much the same, but with less focus on 3rd specifically.

Several ways I've chosen:

In parking-lot maneuvering, I put the trans in low b/c otherwise it'll go to 2nd, then back to 1st repeatedly as I speed up or slow. Then I just adjust road speed to keep rpms at 2k or less. When I finally get a straight shot to the exit, I'll take it from Low to manual and let it upshift to 2nd if I think there'll be no stop required (or if I get impatient).

In stop & go traffic, I put it in 2nd manually, so there's no shifting needed until & unless traffic opens up enough to justify 3rd. This might be a little problematic (anybody with an opinion, please chime in), but I do have an OBD scanner in the car and I'll plug it in and keep an eye on trans fluid temp (in the summer anyway). It seems to take a pretty long time to get the trans up to near 100 C just cruising, so if I haven't been driving for long, I assume the temp is probably ok.

A series of closely-spaced traffic lights is just more stop & go, but usually there aren't enough for me force 2nd, so I usually allow 1-2-1 shifts to happen. But I don't let it get to 3rd unless there's a decent distance before the next red or if traffic requires it.

My drive to work includes about 10 miles of straight but hilly road. If the road is clear I'll anticipate the next hill and keep my speed high enough that I can get over the crest in 5th without seeing the TC unlock. That takes me a little over the posted limit. Oops.

If there's slower traffic ahead, I stick it in 4th and try to run around 45-50 mph. The TC seems quicker to unlock in 4th, and I'll see the rpm jump a couple of times, on the steeper parts. Haven't figured out how best to handle this situation.

I did a pretty much complete changeover to Red Line ATF (racing/D4 in varying proportions but probably averaging about 2/3 Racing) in 2011 at around 110k and since then, an annual 1x3 refresh. I have changed the pressure switches twice now. I have no external filter or cooler, but I did get the internal filter changed a couple years ago. It looked fine to me.

I currently have just over 250k, and no obvious problems so far.

Diomaiuti

Scottwax

Most transmission shift with higher line pressure manually than they do in automatic mode. Higher line pressure means firmer, faster shifts which reduces the slippage on upshifts most manufacturers program into the transmission (via the valve body, ATF shift modifiers) to give the soft smooth shift most people like. Common mod among transmission rebuilders of GM transmissions like the TH350/400 was to add a shift kit to the rebuild to quicken shifts to extend transmission life.

I know in my own car, manual shifts are quicker and firmer, especially the upshifts. But in the real world, the difference in transmission life between automatic and manual shifting isn't very large because typically someone who manually shifts an automatic is someone who also drives their car harder than the average person.