Wear in an auto transmission...

It is also against the law where you live and in most places in the world to coast down a hill in neutral.

The unloaded suspension can 'get away from you' very fast, especially if there is any wear in any parts.

In an auto, the engine turns the tranny usually. Some might not like the tranny turning the engine with a high connection speed for wear issues, but I don't know.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > Awl--

Clutches, bands, bearings, bushings, seals, O-rings, gears, pivots, valves, bores...

The clutch plates act as clutch plates.

No, they are more like the belt that holds up your pants.

Money.

Google

especially if you're incompetant to the absolute.

No, you don't have to be incompetent to lose it, just damn unlucky to have a cop spot you coasting and too honest when asked about it by said cop.

One of the 'first' rules when off roading is to always keep it in gear when descending, having it in neutral and only using the brakes can cause even the most experienced to lose control.

The physics are the same whether on or off road. Off road just exaggerates them.

There 'is' reason coasting downhill in neutral is against the law in most places in the English world.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

If you have a cop close enough to read the gear shift indicator on your transmission and you are oblivious to his presence, they you have bigger problems than complete lack of driving skills.

Well, coasting downhill at 50-70 mph is not exactly testing the limits of a vehicle or driving skill--not even my limited driving skill. Now, riding a motorcycle at 150.... :)

But Q still remains: does shifting from neutral to drive at highway speeds produce wear/tear on the tranny?

I think it puts a big sudden shock load on the automatic transmission parts,that couldn't be a good thing at all.I wonder how many automatic transmissions have blown up from doing that? cuhulin

I'd agree, except that on all cars/trucks I've done this on, it seems effortless/seamless. No jerking, very smooth. Not saying no damage is being done, just curious as to what/how, given the smoothness.

Not when you are not aware that it is illegal.

The cop said he could tell because the unloaded suspension lets the vehicle 'float' around. This is in a Very hilly city and he watches for it.

I was young and lucky and got off with a lecture.

Mike

There are a multitude of automatic transmission designs - one answer can't fit all.

Coasting in neutral, or towing with the engine off and drive wheels on the ground, can cause lubrication and overheating problems in some designs since the transmission may rely on the circulation of transmission fluid from pumps driven by the input shaft.

Revv> Awl--

Something being illegal is often merely the whim of clueless lawmakers.

The wear is that you have all the clutches freewheeling and rubbing gently against each other at a time when some of them are supposed to be locked together. That combined with the low amount of fluid circulating due to the engine being at idle speed means you can easily cook the fluid that's between the clutch plates and burn up the transmission.

In general the wear is the clutch plates and the rubber seals that keep the fluid from leaking past the pistons. If the seals leak too much the clutch pack can't build up enough pressure to lock the clutches and they slip. If the clutches wear down too much they just can't lock together anymore or you get to the point of metal on metal.

The fluid is not the clutch, it just lets the clutches slip while engaging and it carries away the heat, but it's the clutches that lock together and when they are lock the fluid is just putting pressure on the piston that pushes the clutch plates together.

You can crush a roller thrust bearing due to the high load, you can tear the ears on the clutch plates, you can over stress the cams in the over running one way clutches and cause them to fail, the high shock load might blow out an internal seal or make a snap ring jump out of the groove, in a band transmission you might snap a band.

Sounds more like you were just going too fast giving the appearance of "floating" as you went zooming over bumps. Being in neutral isn't going to do much "unloading" of the suspension at any normal speed or during a normal maneuver.

The laws of physics are the same but the forces acting on the vehicle that you need to worry about are not the same. Off roading you have issues with possibly slipping sideways, having a wheel suddenly lock if you put the brakes on while in neutral, etc. These are not issues in any legal driving on the road where you might want to coast to save a little gas. The thing that gets people in trouble coasting is that they just wind up going too fast then they get all confused when they throw it into gear and discover they need to brake too and oops, that darn guardrail is getting awfully close to them and maybe a little steering input would be a good idea too.....

Yea, there is a reason but that's not it. The reason it's illegal is a hold over from the days of lousy brakes and non-synchronized manual transmissions (and back then almost no one had automatics). There were many accidents from people who's vehicles got away from them when the brakes overheated and they could not get the transmission back in gear. In modern automatic transmissions when you are going downhill you are just about in neutral, it will usually be in Overdrive and the torque converter will be unlocked. If you throw it in neutral there isn't all that much difference.

Well said, but proly not true. It's calculated fukn revenue raising, just like the seat belt laws. Anyone really think they give a flying f*ck about our safety?

Nope, I rolled out of my driveway and down my steep street 100 yd to a stop sign before putting it in gear like I used to normally do. Cop was parked at the bottom of the hill so I saw him before I even started my car and thought nothing of it.

Ashton Crusher wrote: These are not issues

You seem to infer all the way through this that 'today's' drivers are somehow superior to the older generation and can act better in an emergency situation or that today's vehicles with their throw away non grease (use em till they fall off) suspension and steering parts don't wear out causing steering slop or something.

I don't agree.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

Some trannys don't send fluid trough the cooler in park or neutral.

He didn't tell anything from how the "suspension was loaded". Most likely he simply could tell from the way you "took off", which will look a lot different if you simply coast away then if you have it in gear and accelerate away.