Manual Downshifting Harmful?

[PachoC]

In my daily commute I have to drive up and down some hills. I tend to manually downshift (to 3rd and even 2nd gear), specially going downhill, to help "hold" the car (and rely less on the brakes). The RPM stay around 2.5k to 3.0k. Is doing this on a fairly repetitive basis (daily) harmful for the transmission?

[maxnix]

Let's put it this way, brakes are a lot simpler and cheaper to maintain than engines and transmissions.

[elwesso]

Definitely.....

Brakes are easy to replace, transmission isnt... Slam on those brakes if the transmission doesnt have to shift...

Less shifting=better transmission life= more money to replace the brakes..

one transmission=10sets of brake pads (ish)

[Q451990]

I'd say a nice happy medium is to downshift into 3rd when you'll be doing sustained driving at 45mph or less. The Q feels like it's "lugging" to me sometimes at lower speeds. I think the shift points were designed more for EPA fuel economy than transmission/engine health.

Heath

[elwesso]

Definitely... At 45, my Q runs at 2200 rpm in 3rd, or 1500 in D.....

Worth it to not have the TC constant engaging and disengaging.....

[Q45tech]

YEP, 32 valve engines don't make enough torque at 1500 rpm with AC on .......lugging at 1500 shows that the engine/induction/injector cleanliness [or compression rings] is not 100% .............every single pound foot counts down there.

Very stressful to run engine below 1600 rpm in 4th gear because the engine torque is reduced by the overdrive ratio.....[0.694] and is down by 31% compared to 3rd gear.

Either turn AC off or use 3rd gear.

[AZhitman]

..or buy a 4.08.

[elwesso]

So dennis, is what your sayin its better overall (and maybe more efficient?) to run at 2000 RPM, in 3rd, going 40ish MPH??

going 40mph, in drive, with AC on and the tunes blaring has to nearly kill the engine.....

[PachoC]

If I understand the different responses correctly, there seems to be to contradicting opinions. A few favor hitting the brakes instead of using the "motor hold", while on the other hand it seems that the motor actually runs at a more efficient point when you downshift (and keep the RPM slightly higher). This is typical with a manual transmission - right before entering a curve you downshift and then accelerate... (pulling out at a higher torque than if you were to continue on the original gear, before you hit the curve).Q45 Tech, Q45 1990 - The question is still: Is the manual downshifting harmfull to the automatic transmission?

Thank you all for your responses.

[maxnix]

Q45tech's response was to Elwesso's statement immediately preceding it. Neither is Q45tech refering to downhill acceleration nor decelration.

[elwesso]

Correct, he was referring to driving in 3rd gear ALL the time, not just when decelerating...... Which is what I do if Im not going to be above 45ish for a long period of time.

[Q45tech]

Engine power and efficiency are two different things obviously creating more power via rpm will burn more gasoline.

Just that for fuel economy Q started in 2nd gear and was marginal to say the least at below 2,000 rpm in any gear.Overdrive [4th] reduces the engine torque to the wheels by [0.694=30.6%] compared to 3rd gear.

Look at what happens on the road holding 60 mph [2000 rpm] AC on and AC off when a slight uphill* is encountered.

* calculate the retarding power of gravity up even a mild incline plane.http://www.walter-fendt.de/ph14e/inclplane.htm

http://www.edinformatics.com/il/il_physics.htm

[96QQ45]

I'm curious now. Dennis, in your opinion is it harmful to downshift the transmission?

[elwesso]

(let me get in my $0.02)

While any sort of shifting will decrease its life, and downshifting (like at 35 MPH into first, but the decreased life is worth the thrill!!!) is worse, keeping the transmission COOL will help even more and add even more life.

The main thing to remember is the main killer of transmission is heat and not wear, as long as the fluid and filters are clean and fresh wear shoudl be the last thing on your mind. Its keeping it clean and cool, and it will treat you well.....