Car guru's-Automatic transmission
 

So I was wondering if this habit i'v developed is helping or hurting the transmission on my vehicle.

I'v started this thing where when I accelerate I pretend I have a manual. I'll be at a stoplight, and as when it goes green I start to accelerate, and just as the rpms reach the point when my transmission switches gears, I let up on the gas and then back down to simulate a "manual" gear shift. I'v noticed that I have it timed pretty well where when I let off the gas, the rpms don't drop me back into a lower gear after switching, thus causing the transmission to have to shift up again as I continue to accelerate. I'v also noticed that this is more for gears 1-3, as 4-5 don't make much difference at those speeds.

Is this bad for my transmission??http://www.discussworldissues.com/fo...ies/blush1.gif It is fun though!

Your auto will have a torque converter so I can't see how you would be doing any harm at all. Someone might know better than me though...

it can overheat and fail if "mistreated"

Yeh, but what he's saying is he is letting off the gas and then going back on it. I can't see how that would do any harm with a torque converter in the middle unless he tied it to a tree first?

well torque converters work on a hydrodynamic principal (although similar to but differs slightly from a hydrostatic transmission), so if his constantly stalling and accelerating the vanes hes putting extra stress into it before it can attain coupling, obviously oil has a high sink rate (heat soak),but equally once its absorbed heat it doesn't easily dissipate it which is known as pumping loss which in agricultural/plant machines is dealt with by water cooling.

OHP is right, in that what you are doing will generate extra heat. But its no more so than say stop and go traffic during rush hour. So thats not the main killer here.

The biggest issue is that when you let off the gas before the shift the transmission reduces line pressure and you get a softer shift. traditional auto transmissions start applying the next gear before the previous gear is fully released. This gives the illusion of a butter smooth shift, but in reality goes against any criteria for long life and good performance. Example, for an upshift to 3rd gear the 3rd gear clutch packs will begin to apply before 2nd gear's packs have released. This results in an overlap where the 2 gears are fighting each other, which induces extra wear and tear on the clutch packs. Since you are letting off the throttle at the shift point, the transmission see's the reduced throttle % and reduces line pressure. Slowing the shift down and inducing extra wear because 2nd and 3rd gear are engaged at the same time for a longer period of time. Performance automatic transmissions as found in drag cars minimize this overlap as much as possible while increasing the rate at which the clutch packs are applied. When done right there is no banging into next gear, just a sudden increase in acceleration because the shift happens faster than a person can really detect it.

Letting off between shifts is akin to riding the clutch in a manual car. Resting your foot on the clutch is a bad idea. The extra slippage wears the clutch disc out faster.

What sort of 'auto' is it, conventional with a torque converter and epicyclic gears or an 'automatic' that is a 'manual' gearbox with one or two clutches which is electronically controlled?
As Fruity said, the additional shifts will increase the wear on the clutches and brakes in the transmission. I'd disagree about the backing off being bad, in principle, as the transmission will have a lot less torque to handle, reducing the high load slippage and wear, but that's just an opinion.
Personally, I hate transmissions which are 'over keen' to hold or drop a gear, regardless of it being potentially more efficient for economy, and will also ease off to encourage it to change up before gently applying a bit more throttle but short of causing it to drop back down again.
Most (all?) newer (last couple of decades) auto's use lock up torque converters which remove slippage as the 'normal' operating slippage is inefficient and hurts fuel economy.

I would remind you that, like all other parts of a vehicle, automatic transmissions also need regular checking and servicing, something that many people seem to ignore to their later regret - repairs can be damned expensive!

I honestly don't know what kind of transmission it is, or what it has http://www.discussworldissues.com/fo...ies/blush1.gif
It's an 05 wrangler TJ, does that help?

So basically it would be better when accelerating to keep constant and allow the shifts to happen continuously? It always felt as if there was a lot less strain if I backed off, maybe it's a sign I need to have it looked at.

I don't know jack **** about engines/vehicles so i'm wanting to learn. Thanks for the replies!

BTW who drives an automatic jeep?! I do, that's why I got in this "manual" mode, especially if I pull up next to another jeep http://www.discussworldissues.com/fo...es/tongue1.gif

05' Jeep would be a traditional slushbox.

Just hold the throttle steady state. It'll shift like its supposed to.

From my previous post I didn't mean to imply that lifting off prior to the shift is a catastrophic thing. Just that it generates more wear/tear on the transmission.

Personally, when I think of an Automatic, I think of a slushbox transmission. I have a DSG in my car which is, as you describe, an electronically controlled manual transmission. But I consider a DSG to be a DSG (neither automatic or manual). And I know quite a few people on the car forum I'm on to have similar opinion.

But that's just my opinion.

I would remind you that, like all other parts of a vehicle, automatic transmissions also need regular checking and servicing, something that many people seem to ignore to their later regret - repairs can be damned expensive! This. Although it can be expensive to service some transmissions. I paid about $130 just in fluid and filters for my transmission, and that's needed every 40k miles. But at least I do my own servicing. I've seen quotes of as little as $350 and as high as $500 just to service a DSG.

And it never hurts to service a manual tranny as well. I know a lot of manuals state they have lifetime fluid and don't need servicing, but there are way to many components on vehicles these days that state the same thing that end up still having service schedules or require servicing anyways. I just had to add water to my supposed "Non Serviceable Battery" just a couple of days ago.

I would be more concerned about dicking around with your car, paying attention to playing with the shifting rather than paying attention to the road.

I'm not convinced that lifting his foot counts as dicking around, but feel free to prove me wrong.

80K is classed a life time for transmission oils (well for BMW anyway) I replace mine every 50k,that's including my Diff oil.

Ive done two transmission oil changes, and it makes all the difference,if your gear box feels notchy that means the oil is due a change.

that's a good point, I haven't changed the tranny oil since i'v bought it, and I just passed the 80k mi mark, maybe I should have it changed.

And really, dicking around?http://www.discussworldissues.com/fo.../rolleyes1.gif

I don't know man... I have found the 42RLE doesn't like having its fluid changed. http://www.discussworldissues.com/fo...es/unsure1.gif It likes its old, smelly, used-up tranny fluid.http://www.discussworldissues.com/fo...ies/blink1.gif

If its a traditional slushbox then it is a bad idea to do a fluid flush on one if it hasn't been serviced regularly. This is because as the fluid gets old, debris and sludge forms from the wear and tear of the hard parts. Normally with regular service this is flushed out before it becomes a problem. But if its not maintained the buildup becomes so big that the next time the fluid is flushed all of that sludge and debris gets shoved into the valvebody of the transmission and can clog it badly resulting in a swift spiral of death as the valvebody ceases to act properly and actually starts to cause wear/tear at an increased rate.

I've seen some transmissions with the blackest, foulest smelling fluid out there that worked fine fail exceedingly shortly after a fluid flush because all that gunk got shoved around the valve body and started to damage valves. And a normally slushbox lives and dies by its valvebody.

So get it serviced regularly...except if it's a stubborn slushbox?http://www.discussworldissues.com/fo...es/tongue1.gifhttp://www.discussworldissues.com/fo...ies/wacko1.gif

Shoulda got an autostick.

Speaking of tranny fluid changes for the first time in history I decided to follow the manual and have the fluid changed out as suggested. It now shifts funny. *sigh* On the bright side if it breaks I'll have an excuse to have a few upgrades done when I get it rebuilt to support the bigger turbo I'm throwing on when the stock one dies.

Tranny Fluid is the sort of thing you google with safe search on strict AND DONT IMAGE SEARCH http://www.discussworldissues.com/fo...es/unsure1.gif

/googles

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hmmmmmm