| Author |
Message |
Ben Richardson
Tinkerer
NSW
V8 UZZ31 GT-L
Posts: 55
Reg: 03-2007
|
Ok ive done a bit of searching here and else where but im specifically asking about the soarer auto.
Is it detrimental to the gearbox shifting into neutral on downhills and then back into drive while driving?
Can a mechanic or auto transmission expert reply, from what i found you have people saying it will kill your transmission, others saying they have done it for 20 years without a single gearbox failure.
Why am i asking this? I work in the mountains and on the way home i can coast in neutral in many places and couple i can coast for 5kms or so, this has been giving me approximately 50km extra out of a tank of fuel. Im just curious if the saving in fuel is at the expense of the gearbox thereby making it pointless. |
Joshua Rao
Goo Roo
WA
JZZ30 vvti GT-L
Posts: 1169
Reg: 09-2006
|
While I am no expert, I fall into the been doing for a few years and no transmission failure group. There is a thread from a while back on this somewhere |
David Vaughan
Goo Roo
ACT
V8 Ltd manual
Posts: 3965
Reg: 07-2005
|
My vague recollection is that the previous thread was more about the road safety of doing it rather than mechanical safety of the gearbox. My limited knowledge of auto boxes says there is no mechanical problem arising. On the contrary, it will generate less heat in the box for what it is worth (stuff all really  ). On the other hand, it is considered a poor driving practice, leaving you unable to accelerate promptly and of course wearing your brake pads and calipers more to make up for the petrol saved. 
I am not going to condemn it but I would not do it myself and advise against it.
Of course, you asked a mechanic or auto transmission expert to reply, and you got me and Joshua anyway   |
Michael Fabian
Tinkerer
queensland
soarer JZZ31
Posts: 32
Reg: 07-2008
|
In my manual it says that you shouldn't do it because it damages the transmission |
David Vaughan
Goo Roo
ACT
V8 Ltd manual
Posts: 3966
Reg: 07-2005
|
Why, though? I really would like to know. |
Ben Lipman
DieHard
NSW
Soarer TT manual
Posts: 951
Reg: 04-2006
|
Maybe due to the fact that in neutral the oil is not flowing through the normal path and lubricating all those automaticcy bits inside, even though the output shaft is rotating(being driven from the wrong end no less!)
I'm no expert. I just know we have to disconnect the propshaft on some of the heavy gear at work before towing over 30kmh, or further than 800m. There must be some sort of reason, cos it aint an easy job. |
Michael Keen
DieHard
nsw
Soarer TT
Posts: 910
Reg: 10-2007
|
just dont do it, in case you accidently put it into reverese gear or park... ouch.. in a manual the gears are all turning, on the shaft, by friction, it is when you select a gear does it postive engage it. to get drive, so i cant see how it hurt a manual.. or auto for that matter, i know and have seen some auto damaged by not taking tail shaft out. while towing. and this is cause i reckon the engine aint turning so no oil is flowing through the box, cause i pretty sure the oil pump on the input to tranny, on most boxes, but if you engine was running, i could not see a problem..
just by a hybrid to save fuel |
Ben Lipman
DieHard
NSW
Soarer TT manual
Posts: 954
Reg: 04-2006
|
Yeah I hadn't thought about the engine running bit. When we tow it usually means she's broke. Better leave it to an expert to say if you are damaging the box in angel gear. |
Matthew Sharpe
Goo Roo
North Island
JZZ31
Posts: 3832
Reg: 10-2005
|
What Michael said - should be OK as long as the engine is running. |
David Vaughan
Goo Roo
ACT
V8 Ltd manual
Posts: 3967
Reg: 07-2005
|
If the engine were not running then safety is really shot to bits. That idea killed two women near Thredbo a long time ago. The steering lock engaged, and they did not wiggle it free before going off the road. |
Ben Richardson
Tinkerer
NSW
V8 UZZ31 GT-L
Posts: 56
Reg: 03-2007
|
Ok some good arguements, i know about towing autos being an issue but with engine running i guess its not.
Slipping into reverse would only happen if you pressed the button in so im not worried about that.
Until there is an electric soarer on the market ill stick to coasting , currently im getting around the 830ks per tank mark at the moment, the majority of ks are highway though. |
Ben Lipman
DieHard
NSW
Soarer TT manual
Posts: 956
Reg: 04-2006
|
Ben Richardson wrote on Friday, October 17, 2008 - 03:07 pm:830ks per tank
Holy crap Batman!
That's bloody good. |
Mike Bradberry
Goo Roo
Queensland
V8 UnLimited
Posts: 1068
Reg: 07-2005
|
My fuel consumption worsens on downhill runs because I have it in a lower gear. |
David Vaughan
Goo Roo
ACT
V8 Ltd manual
Posts: 3970
Reg: 07-2005
|
Actually, putting the car in neutral would have bugger all to do with that. A petrol engine (unlike a diesel) uses the throttle basically as a "petrol pump". If you close the throttle, there is no demand for fuel except to keep the motor running. Therefore, if you are idling (as in coasting in neutral) then only modest fuel is required. If you have the gears engaged in a manual, then zero fuel is required so long as the car keeps moving. That is, coasting in gear would be more economical than coasting in neutral.
In an automatic, it depends... but I expect that coasting in neutral would be negligibly different from coasting in gear.
That level of economy has far, far more to do with flat running at steady speeds than coasting down a hill, unless coasting has replaced accelerating between downhill corners (which I myself do when I want to lose someone (not that I would ever try to do that)).
I think this coasting in neutral idea is rubbish. Still, like I said in my first post here, I do not condemn it ... |
Stuart Smith
TryHard
NEW SOUTH WALES
SC400 V8 GT LIMITED Proper Prior Preparation Prevents Piss Poor Performance
Posts: 220
Reg: 06-2008
|
Coasting in neutral has no detrimental effect on the transmission, the oil pump is driven off the torque converter, so, as long as the engine is running, there will be sufficient oil supplied to the working parts, I can regularly get 140 plus on Mt ousley between Bulli tops and Wollongong.
The problem I see is when you engage drive at the bottom of the hills, it is hard to match the engine revs with the road speed and the engagement is harsh (dont have this problem with my other vehicles, just my Soarer) |
Ben Kelly
TryHard
Wentworthville
v8
Posts: 407
Reg: 08-2005
|
Holy cow! i travel to wollongong regularly...im a bit worried by people coasting down mt ousley trying to save money. I would prefer if all you soarer owners were engaging the full capacities of your vehicles..sheesh. Oh and i stick overdrive on when going down mt ousley and sometimes gear back to 2nd...don't want to boil my brake fluid! |
Ben Richardson
Tinkerer
NSW
V8 UZZ31 GT-L
Posts: 57
Reg: 03-2007
|
Next time your going downhill in 4th check your revs, then slip into Neutral, your revs will drop about a grand, less revs means less bangs which means less fuel used When you slip it back into drive make sure to get the revs up to road speed so it slips in smoothly.
Around town ill be lucky to get 700 out of a tank, but highway driving 750, coasting down the mountains will take it above 800. I hardly ever give it a boot full either which makes a huge difference.
Yes it is a little bit more dangerous coasting, but you just need to be aware and be ready to slip it back into drive, not hard really. |
David Vaughan
Goo Roo
ACT
V8 Ltd manual
Posts: 3971
Reg: 07-2005
|
I suspect that fewer RPM does not mean fewer bangs, not when you can be banging on empty. It depends on how much fuel is needed to turn the engine, and if you are dragging it around by the wheels then you need zero fuel at the time, whereas idle needs some to keep it moving.
The more I consider this proposition the more I think it is
A. Wrong.
B. Silly. |
Ben Richardson
Tinkerer
NSW
V8 UZZ31 GT-L
Posts: 58
Reg: 03-2007
|
im not sure what your trying to say regarding rpm to fuel usage, i wasnt looking for agreement on this, i know for a fact its saving fuel, just wanted to know if i was killing my auto in the process. |
Spencer Cameron
Newbie
NSW
JZZ30 (converted Manual)
Posts: 4
Reg: 04-2008
|
Ben Richardson wrote on Friday, October 17, 2008 - 11:14 pm:Around town ill be lucky to get 700 out of a tank, but highway driving 750
Sweet jesus.. ive never got more than 450 from a tank...
As for the subject at hand, im inclined to side with Stuart on this. While the auto oil pump may not be supplying alot of oil flow relative to the tailshaft speed, the box is also under almost no load so it wouldnt be much of a problem.
And as for Mt Ousley, i go down there in 3rd (manual)
No braking for me! XD |
Michael Keen
DieHard
nsw
Soarer TT
Posts: 934
Reg: 10-2007
|
gee while your at it just switch it off to, it is bad pratice to coast in netural, you want to save fuel buy a prius.. |
Stuart Smith
TryHard
NEW SOUTH WALES
SC400 V8 GT LIMITED Proper Prior Preparation Prevents Piss Poor Performance
Posts: 225
Reg: 06-2008
|
Ben Lipman wrote on Thursday, October 16, 2008 - 07:40 pm:There must be some sort of reason
The reason that we need to remove the tail shaft when towing with the drive wheels on the road is because the oil pump is driven by the torque converter, which is obviously driven by the motor.
By towing more than a nominated distance, the residual oil is not enough to lubricate/cool the guts of the auto, which will be driven by the wheels turning down the road, result- smoked auto trans. |
Stuart Smith
TryHard
NEW SOUTH WALES
SC400 V8 GT LIMITED Proper Prior Preparation Prevents Piss Poor Performance
Posts: 226
Reg: 06-2008
|
Ben Kelly wrote on Friday, October 17, 2008 - 10:36 pm:a bit worried by people coasting down mt ousley
I would be more worried by the new speed camera they have just installed at the Southern end of the Wankers camp (where the gravel stopping bed is), right next to the siamesed point to point cameras, where they time you to the speed camera at the TAFE/Uni area.
This baby takes an image of driver (digital face recognition), Number plate (expired rego, warrants), and start time to next camera (smile penalty is in the mail) all within 0.2 seconds, it also has a decibel meter for noisy vehicles (mainly trucks using jake brakes, I think) |
Ben Kelly
TryHard
Wentworthville
v8
Posts: 416
Reg: 08-2005
|
Thats pretty crap Stuart, tell me is it before the earliest possible turn off into wollongong (which is the one i take), ie the one with the give way signs?
Don't know much about wollongong but a mate of mine reckons he ran out of petrol at the top of mt ousley and made it all the way to a car parking space in the uni.hmm anyone? |
Michael Crimp
Tinkerer
QUEENSLAND
V8 UZZ32
Posts: 92
Reg: 06-2008
|
Ok,
According to my RACQ bloke towing in neutral under 60kph for less than about 50km with the motor turning over for steering and Brakes is OK.
Until he told me that I would have never towed an auto or would have disengaged the tailshaft which on a 32 with 4ws etc would take about as long as waiting for a flatbed lift tow truck. |
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