Auto Musings - For The Bored Only!

[Sam]

Posting this here as opposed to the 120 forum because It's probably relevant to all autos. And to set the context, I'm told that an auto should never be towed. Don't really understand why by I'll take it as good advice.

So the question is... if towing is a bad idea, then is the same true of coasting?

When braking down hill, in "D" as opposed to "3" (early 120 auto box), there is no engine braking. But when you get below a certain speed it starts to feel like the "D" element is pushing against the braking... so I tend to knock it into neutral to stop with less resistance (no engine braking to lose anyway).

Now of course, even without engine breaking it's safer to be in "D" than neutral in case you need to floor it - but I'm just wondering if this little bad habit is potentially damaging to the box?

I only do it because the fight between the braking and drive makes it feel like the discs are warped and I dont want to think about that - so I knock it into neutral - bit like turning the stereo up to [strike:34k7fz08]stop[/strike:34k7fz08] [strike:34k7fz08]fix[/strike:34k7fz08] hide a rattle.

So apart from daft and potentially dangerous... harmful to the box?

 

[sae70]

I think that the not towing an auto thing comes from the fact that you can't get them out of P when the engine is off or the key out until they are in P and they want start until in P and want shift till the brake is applied and and........... Not sure about all of those combinations to be fair but I'm sure you could tow our auto Subaru Forester so long as you lifted the flap next to the shifter and inserted some thing to allow you to shift it out of P without the engine running or something.....

 

[LandCruiser1978]

I've heard this before .. my advice read the manual !

If it doesn't say don't do it then don't worry ...

I do know you can tow an auto as long as the engine is running and the box is in neutral somthing to do with oil being pumped round the box

Engine off no oil being pumped around Hence the chance of damage

Thats my view ..

All the auto's i've owned / own i always slip in to neutral and coast . I've never had a problem yet .

I've also heard you can actually bump start an auto tow along in D and app it will start . (This is one im NOT willing to test ) please don't take my word on this

 

[Crispin]

It's because there is no pump working and not pumping the ATF around into the places it needs to be.
Someone clever will come and answer soon...

 

[LandCruiser1978]

I do know you can tow an auto as long as the engine is running and the box is in neutral somthing to do with oil being pumped round the box
Engine off no oil being pumped around Hence the chance of damage

It's because there is no pump working and not pumping the ATF around into the places it needs to be.
Someone clever will come and answer soon...

Does that mean i'm clever Crispin because i was first to get it right

 

[Crispin]

You get a star

 

[joinerman]

Yeh you can bump an auto, years ago i had an old rover P5 & it siezed through lack of the black stuff in the sump, anyway sump off & a set of oversized shells but it was to tight to turn over with the starter, towed it in N up to 40mph & dropped it into D & hey ho up it fired, left it running for about three hours, after that it would start normally.
Stuck it exchange & mart next day, sold a couple of days later, never had any comebacks, LUCKILY. lol

 

[silvercruiser]

What if you knock the transfer box into neutral when being towed then surely your not engaging/damaging the auto box.

I dont know why we are having this conversation as we drive landcruisers and we all know that WE tow others


Joe

 

[Gary Stockton]

Sort of on the same thought - what are the options when winching an auto? In neutral or drive? Thinking more of self-recovery here. And what about lowering out? In neutral or reverse??

 

[karl webster]

If i remember right you are ok towing a auto at a top speed of 30kmh up to 20 miles or so the handbooks say. Obviously You could exceed that in my opinion.

The best option if towing a cruiser auto any distance would be take the props off
Not alot of hassle and saves any damage.

Joinerman.... I have ALWAYS been under the impression that a auto cannot be bumped. The reason being is that the engine spinning the torque converter makes the blades come out to make oil pressure that then is converted to drive.Somehowish

Maybe the vehicle that you did it with was different than Cruisers. I may be wrong,if i am you learn something new every day. It would be far easier for me to bump my auto down my hill at my house when the batteries are flat next time

karl

 

[Chris]

When you tow an auto, the wheels turn the diffs, the diffs drive the props, the props turn parts in the transfer box including the viscous coupling. That generates heat. Putting it in neutral does not disengage everything. You can tow an auto, but if you wanted to be truly safe, taking the props off would be the best option. This has been covered before at some length and some very learned people contributed. I thought it was nonsense before that and that towing an auto was fine. Now in an emergency, I'd tow one. For a short distance. If I had to. But I wouldn't use it to haul one a long way, at speed. I don't think that coasting in one s a problem at all.

Most cruisers aren't locked in P. If they are, then you simply press the shift lock button and move the lever. That's not really part of the issue.


Chris

 

[Scott]

You are not advised to tow an auto for any distance or speed, as the without the engine driving through the autobox the oil pump is not driven, and the box suffers damage through lack of oil pressure.

You are unlikely to be able to bump or tow start most of the auto boxes that you are likely to come across these days, as for this to work the auto box in question needs to have a oil pump on the output of the box. This oil pump would be driven by the prop shaft as the vehicle was being towed pumping the oil around the box, and enabling it to build up the pressure to operate, and turn the engine.

I asked an auto transmission specialist friend of mine the "is there any way I can tow start this if the starter failed?" question and he said "no, it needs to have a rear oil pump, like some of the old Mercs had".

To tow an auto, as Karl said removing the props is the safest option. But putting the transfer box into neutral, as Silver cruiser mentioned, has the same effect as the auto box isn't being turned and has no idea that the car is being towed. Just make sure that it doesn't slip into gear when being towed.

With regard to winching, the speed and distances involved shouldn't be large enough to upset the auto box. In most winching situations the auto box is more helpful, in that it's easy to drive assist with the wheels going at the same speed as the winch, this can be difficult to acheive in a manual.

I do get fairly reasonable engine braking from the auto box in my 80. Down hill on the road you can feel the difference/improvement as you disengage the overdrive, and the engine braking is pretty effective when you knock it down into second or first, you just need to know at what speed the box likes to change down into that gear. I find that manually controlling the auto box on descents can be very helpful to slow a heavy or towing vehicle, and when driving in mountainous areas so as to avoid over using the brakes.

Edit - Chris has posted similar comments whist I was waffling on. (Note to self, type faster!).

 

[Sam]

This has been covered before at some length and some very learned people contributed.

Yeah had a feeling the thread might go this way again...
Soaking up all the comments though... I can feel my brain filling up by the day

And to set the context, I'm told that an auto should never be towed.... ...so the question is if towing is a bad idea, then is the same true of coasting?

So... all ok then? - 'Cos the engine's powering the box?

 

[uHu]

Back to the OP:
As long as the engine is running, you can put the gearshift into any forward gear, or N, whatever your speed is. If you want max engine brake, just shift to L or 2 and the box will change to the lowest allowable gear according to the vehicle speed.
And as said here, as long as the engine is running, the input shaft of the box is running, and the atf-pump is running. And that means you can then coast or tow as you please.

 

[Crushers]

exactly the same as a manual, assisted or unassisted. depending on the requirement at the time.

towing an auto, stick the t/case in neutral, unlock the hubs and away you go.
if 80/100 etc then lift the front and dolly the back wheels, do not tow in neutral.

Sort of on the same thought - what are the options when winching an auto? In neutral or drive? Thinking more of self-recovery here. And what about lowering out? In neutral or reverse??