Wear on an automatic transmission?

As most of you are no doubt aware, you can force an automatic transmission to hold a gear by downshifting, however most of the time on a 4-speed auto you are supposed to just select D4 and let the auto do its job. That's what it's made for.

I've heard from friends and other sources that 'rowing through the gears' on an automatic transmission (AT) will induce unexpected wear and tear and other side effects on the AT. By this I mean driving an AT just like a manual transmission stick shift, shifting to 1, moving off, shifting to 2, 3, and 4 stepping up through the gears. This way you can drag a lower gear a little bit longer before shifting, for slightly more performance, or forcibly drop a gear to take advantage of engine/compression braking without having to hit the service brakes. I'm aware that the compression braking effect translates into more slippage in the torque converter and thus more heating of the automatic transmission fluid, but otherwise should be no different from a stick shift.

Technically, I can't think of any reason why this would induce any more wear on an automatic transmission. Shifting the AT gear lever to hold a lower gear, letting you drag a little bit more before shifting up should not stress the AT any more than a stick shift. Is there something I'm missing?

Regular downshifting, to slow down, with any tranny is likely to wear the friction surfaces (clutch plates or cluster bands) instead of the brakes. Brakes are much cheaper to replace.

Descending long, downhill, stretches is proper use of a lower gear to take advantage of engine braking, and will keep the brakes from over heating and, subsequently, fading.

Manually holding an AT in gear, longer, before upshifting should be no problem. IIRC some transmissions will upshift at higher pressure when shifted manually and thus wear the AT even less because it doesn't slip into gear.

Technically, I can't think of any reason why this would induce any more wear on an automatic transmission. Shifting the AT gear lever to hold a lower gear, letting you drag a little bit more before shifting up should not stress the AT any more than a stick shift. Is there something I'm missing?



Hey kevin. The only thing your missing without getting to deep into the subject is that 95% of your auto transmisions dont have any actual gears (as you would see in a manual trans) For simplicitys sake we'll say each 'selected gear' has a set of clutches called clutch packs. In your lower gears there is whats called a 'planetary gear set' ...While a manual trans has gears that may be 3" in diameter or larger, these platetary gears are very tiny. Theres a sun gear (the drive gear in the center) and the planets around the perimeter of the case. These gears are typically only an inch and a half in diameter and secured by a little axle pin. This planetary set is what gives an auto trans its gear reduction. They can't handle the shock loads of abrupt throttle changes and are very comonly the cause of trans failure. Also these are one way cluthes called 'sprags' they consist of a flimsy metal (sometimes plastic) collar and very small roller bearings. There are alot of parts in there, and they call it a slushbox for a reason. If when you shift your trans manually and you feel a harsher or firmer shift chances are the trans is saying ouch !!!. It shouldn't make a diference but when you shift manually, the trans obviously isn't shifting within it's preset perameters and possibly being forced to handle more load than its design intentions...
A honda and saturn among a few others are basically a manual trans with actual gears that are electronically controlled with the aid of cluthes to smooth shifting and of course the torque converter as they all have to take the place of a manual tran's clutch. This style is pretty much bullet proof as they dont have the sprag/planetery failures that are pretty common with a typical auto unit...Also the gm 4L80e (basically a 4 speed electronic version of the bullet proof turbo 400 of yesteryear) is also quite hardy, as is the top of the line of most manufactures...The most important thing to avoid is excessive fluid temp or a low fluid condition, which happens to be the leading cause of failure.

jayflash, tequilathursday, great explanations! /ubbthreads/images/graemlins/thanks.gif

I've experimented a few times, when I'm going pretty fast I shift down manually to a lower gear and the shift is a lot harsher, you can almost hear the thing yelp. Good point about brakes being cheaper. Now I understand why they say you'll trash an AT by forcing it to shift down.

Also, as I suspected, holding it in gear longer does not adversely affect it since it is merely delaying the shift. The manual indicates as long as I do not exceed the max speed for each gear (65kmh/40mph for first, 120/75 for second, unlimited for rest because it won't go fast enough to exceed design limits /ubbthreads/images/graemlins/smile.gif), I should be ok.

i've been wondering about the same thing.

every once in a while while at a stoplight or other i'll shift into 1, and manually shift foward (as going faster), to 2, then to drive, (not sure if this is called upshifting or downshifting /ubbthreads/images/graemlins/icon15.gif), to utilize more power while accelerating. i was wondering if this might be bad for it, so i hardly ever do it, but it's sure a lot more fun that way...

rev matching downshifts on m/t will make your downshift a LOT smoother, and it can also be done on a/t when you're feeling spirited but takes some practicing. also, i've found a/t's to offer very little engine compression unless in 1st gear (meaning you're going R E A L slow) compared to manuals, because the of the torque convertor in the way.

holding gears while accelerating (as roth mentioned) will let you rev higher (generally, the trans shifts up well short of redline in most cars, with few exceptions; sometimes engaging a sport or power mode will hold upshifts longer, again depends on your car).

I use my 4x4 with the A4OD trans and I just trashed my tranny but it took 140,000 miles of towing my bass boat and the hills of Tn took their toll. I leave it in drive (3rd gear) while towing to reduce the tranny searching for the right gear and that helps to reduce those hard shifts. I suspect if I hadn't flushed the fluid occasionally the trannys life would have ended earlier.

HI Smokinbasser, That's pretty good milage. It's also a decent trans. I don't know what your plans are or for how long you intend to keep your truck, but a good aftermarket trans cooler is worth its weight in gold. Especially for towing. (not to mention the hills) /ubbthreads/images/graemlins/smile.gif Heeping it out of OD while towing or heavily loaded is the best thing you can do. I've seen countless Dodge truck transmissions eat themselves way before the factory warranty is expired. Not mine though (5speed baby!!!). /ubbthreads/images/graemlins/buttrock.gif
Your Ford's a keeper

Manually shifting an auto trans is better for it. Reason is auto transmissions of today are designed for smooth shifting and therefore will shift real slow into the next gear to keep from causing any bump. This slow shift causes more wear on the clutches (think riding the clutch in a manual transmission). There are a lot of shift kits out there to increase pressure to make a faster shift and letting the engine rev higher and then shift quickly into the next gear you wear the clutches less.
The reason you feel a harsh shift KevinL then downshifting is because you didn't match the speed of the engine and transmission. If you have ever driven a manual transmission you will know you have to rev the engine higher before downshifting so the speed into and out of the transmission matches. Next time you want to downshift your auto, get on the gas a bit, downshift and then slowly let off the gas. If timed right you can make the shift smooth enough that you can't feel it.
jayflash, downshifting will not wear transmission clutches, slipping clutches it what wears them. Your much better off to downshift on a gear than risk overheating the brakes and not being able to stop. I made the mistake of buying a minivan a few years ago. Driving it down a mountain road I downshifted and was doing ok, until the transmission went back into OD all by its self. I had to ride the brakes and got to the bottom and went back up the other side and into town and had to stand booth feet on the brake pedal to stop. I had to drive that hill often since its on the way to my parents home and each time I went down there and back I had to replace the brake pads and turn or replace the rotors. The owners manual of the van said the transmission will override the selector to avoid over-reving the engine so it made that van very dangerous for mountain driving

eugene, re. the auto trans going up on it's own accord to prevent over-revving, i've had that happen only when shifting down to 1 (2nd didnt provide enough engine braking, and the car was still gaining speed). however, 2 still provided some (but not enough) braking.

Eugene, I agree and pretty much stated everything you indicated - maybe not as completely, however. I'm still of the opinion that it's, generally, better to use the brakes instead of CONSTANTLY downshifting. I'm not an expert and will be interested to know more about this subject.

ok then, can someone give some tips for manually shifting?

about when should i shift? i usually wait until around 5 (6 starts redline), and it does it right before 6. i proceed through 1, then 2, then to drive, or shouldn't i go all the way to drive?

is it bad to shift at lower rpms?
can i shiftd down from 2 to 1, etc?

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iddibhai said:
eugene, re. the auto trans going up on it's own accord to prevent over-revving, i've had that happen only when shifting down to 1 (2nd didnt provide enough engine braking, and the car was still gaining speed). however, 2 still provided some (but not enough) braking.

[/ QUOTE ]

That's when you shift into "R" for "real slow".

i hate driveing cars with auto,s so boreing to me.plus ive been unlucky with auto trannys matter fact that is what always seems to go out on cars i had.but i always have like 500 dollors cars sometimes less sometimes more

Roth, I'm not sure I understand everything you are asking, but let me try. First off, if you've got the pedal to the metal, most trannys will upshift at the maximum RPM that's safe for the engine and will also give you the fastest acceleration. So for most ATs, manually upshifting, at full throttle, doesn't gain much. However, some ATs aren't programmed for best acceleration and may upshift too soon. If that's your case then holding it in gear until the R's are near redline will gain you some acceleration. Another consideration is the peak HP and torque RPMs. Over revving will actually decrease your acceleration so you've got to shift in the sweet spot for max performance.

Another advantage of holding the trans in, say, 2nd or 3rd gear when driving in town and heavy traffic, is the engine is closer to max torque and will respond more crisply. Manually upshifing, in some ATs, actually wears out the clutch packs and bands LESS, because they engage more quickly, but less smoothly.

It's good to anticipate downshifting during long, downhill, streatches - get into a lower gear before you pick up too much speed. I don't believe it's good for an AT to downshift at high RPMs, at least not on a regular basis. Downshifting into 1st is ok at lower speeds, say under about 25-30 MPH. A 3rd to 2nd downshift should be ok in the 50-60 MPH range - it all depends upon your gearing.

Sometimes I downshift into 2nd gear when I need a little engine braking or know I'll be quickly accelerating soon. That way it's already in the lower gear and will respond more quickly.

Every engine/transmission combination is unique and you will have to determine your best upshift/downshift points. Upshift before the acceleration flattens out and downshift at an appropriate speed for each gear to minimize mechanical stresses.

BTW, I've owned two Ford Escorts, both 1900cid SEFIs, one with an AT and my present one has a five speed manual. There is no comparison - the stick shift blows away the AT completely. This isn't always the case though; there's not much difference in some cars.

Hope this helps a little.

my step mom had a rx7 with a auto dat crazy car shifted was to early rotary engine dont make much power at low rpms

Hello Roth,

I was taught to shift (automatic or manual) based on the engine's performance.

My current gas engine reaches peak torque at 3800 RPM, but is pretty flat above 2500 RPM. My peak horsepower is at 5000 RPM, and the whole thing blows up at 6000 RPM (Red Line is 5700).

For the best performance (which may not be the best gas mileage), I shift to keep the engine RPM's in the 2500 - 4000 range. At 3200 RPM, everything is very snappy.

Please note that Your Mileage May Vary. /ubbthreads/images/graemlins/smile.gif

Tom

My 1989 Toyota 4WD ext cab pickup w/3.0L V6 (yep, 31x10.50's too /ubbthreads/images/graemlins/wink.gif ) has over 300,000 miles on its auto tranny. It's still running pretty good IMO.

Last night a guy with a manual 1996/1997 Chevy standard cab 2WD S-10 w/4.3L V6 started messing with me and we ended up doing two runs. /ubbthreads/images/graemlins/grin.gif From a dead stop, I was side by side him the whole time up until around 50 mph. That's when he was a bit into third and started pulling away from me. We had the same exact results both runs. I'd say not bad for a fifteen year old auto tranny with over 300,000 miles on it.

The fluid's been changed only two (or is it three /ubbthreads/images/graemlins/confused.gif ) times within the last 180,000 miles though. /ubbthreads/images/graemlins/crazy.gif Baaaad me. /ubbthreads/images/graemlins/ohgeez.gif

I have tried the manual shifting on my auto tranny but I prefer it shifting by itself. If I needed it to go to redline before shifting, I just press the "ECT Power" button on my truck and it does just that when floored.

You should try an automatic transmission in a car with throttle-by-wire and a sport switch some time. {Often} In that case, the sport switch isn't just changing the shift points, it's advancing the throttle timing too /ubbthreads/images/graemlins/naughty.gif

for most driving, you should just leave the car in D and allow the transmission to change gears for you.

For Longevity's sake to make your tranny last as long as possible as an automatic, you need to do two of two things, 1, install an oversized transmission oil cooler, these will look like miniature radiators about 6" x 9" long and wide, about an inch thick. Use this to by-pass the original transmission oil cooler that's locatedin your radiator. By using this, you ensure that your transmission will never overheat, which can cause things such as the inability to neutralize the tranmission at a stop, or the sticking in a certain gear for longer than necessary.

The second important thing is to change your transmission fluid once every 30,000 miles, they say 60,000 miles, but for most youngin's this is too late, changing the transmission fluid now to a better grade such as Amsoil's ATF, your tranny will last decades longer. A flush is good to go with the tranny while you're at it.

Neutral drops into gear to burn out, extended usage in a certain gear will cause excessive heat buildup and teeth damage. So take care of your transmission, and it'll take care of you!