Turning off your car at 55 mph


#141

Theres nothing more to research, this is how transmissions have been working for more years than I have been working on them. Unless the laws of physics change, you are just S.O.L. Earl.

transman


#142

Your arguement was that a converter could never push (or turn) an engine and that is just not true. I have proved it several times.


#143

Here are just some of the posts about this subject. It seems that I am not the only one who dissagrees with transman!!
An automatic transmission will never “reverse drive” an engine. When you shut your engine off in an automatic transmission, thats it, the engine stops spining which in effect takes away all hydraulic pressure to the transmission releasing friction elements which are engaged. This is because the trans pump is no longer turning. The internals of the transmission are still spinning due to the driveshaft/s still spinning. These parts are being damaged because there is no atf lubricating them.

transman
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Not true. There are even patents to look up on this. Nearly all modern cars shut off all fuel to the engine while decelerating. They can do this because automatics now can and do in fact “reverse drive the engine.” Also note that if they couldn’t do this, using a low gear to do engine braking going down a hill wouldn’t work.

The AT will indeed “reverse drive” the engine…and it doesn’t even have to be a terribly “modern” car.

Tried it last night in my '88 Dakota. Once at 30MPH (in 2nd gear) and at 40MPH (in “D”…i.e. 3rd).

SO if you hit the brakes more than say 3x…the next time you do it will be unassisted…so it would be harder to stop than you are used to. No pwer steering either…
Actually, if you leave it in gear, you won’t lose power steering until you are going fairly slow. This is because the transmission (even an automatic) will keep turning the engine.
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An automatic will NOT keep turning the engine. Read my post above explaining it.

transmanTransman618,

You are incorrect. Tried it last night in my '88 Dakota. Engine keeps turning, PS,PB keep working, engine fires up (w/o starter) when turned to ON.

Like I said in an earlier post, when the clutches bleed down your 88 dakota’s engine will not keep turning. When they bleed down, thats it, you can push it, pull it, drop it from the sky if you feel the need, the clutches will not re-apply.

Try reading ALL the posts before you go pointing fingers.

transman
Pretty much what happens with an automatic is the engine will stay
coupled with the drive train for a short while, depending on how fast you’re going

A VERY short time, (seconds) until the clutches bleed down, unless you have one of those old iron Torqueflites with the rear pump. (If you can find one anymore) I havnt seen one in years.

transman
Updated: 03/04/2011 06:36:08 PMFlag comment as inappropriate

by: tardis 03/04/2011 6:49:41 PM
Top 250 Contributor

And this was exactly the case for my 91. However, my 2006 will go until the speed drops to about 25 MPH. Starting from 80, that was well over a few seconds. Vehicle speed is the factor now, not time. The clutches don’t bleed down because the pump is still turning and pumping.

Theres nothing more to research, this is how transmissions have been working for more years than I have been working on them. Unless the laws of physics change, you are just S.O.L. Earl.

transman

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Mine does, as do many others. My specific case is a Lincoln LS if you want to look it up. The computer turns off all fuel when coasting. Unfortunately I also verified that the transmission will keep turning the engine when the fuel system failed one day out on the interstate.

You’re driving along and the engine is going and the torque converter is in full lockup. If the engine shuts down, the transmission keeps turning, front and back, so the transmission pump keeps going and all the hydraulics continue to function. Of course, when your speed gets pretty low, the front part of the transmission is no longer turning fast enough for the hydraulics to keep going.

Seems to me, as long as the transmission stays in gear and there is no “free wheeling” feature, the front pump is still being driven providing pressure so it STAYS in gear spinning the inert engine. Since the engine is turning over, there will be power to the accessories like brakes and steering…The car will simply coast to a stop, a non-event…

I couldnt resist.

Ellis said: Technicly the engine braking comes from the engine thru the converter to the tranny to the driveshaft to the differential to the axles to the wheels to the tires. oblivion is CORRECT. Good Grief!!!

Engine braking DOES NOT come from the engine, it STARTS in the transmission
transman

Can I find anyone out there who will stand with me?


#144

Here is another situation I had years ago with my 71 ford pick-up with a 1979 302 and a C-4 cruise-o-matic tranny.

I had some dirt in the fuel tank so had another fuel filter installed at the fuel tank which was behind the drivers seat so I could easily change it out on the road.

Was driving down the interstate about 50 mph when I noticed a loss of power, pumping the gas just gave it a few small jolts until the accelerator pump went dry, then a dead engine.

I did have a tach and even with a dead engine tach was still reading 2000 rpm. I then dropped the tranny into “2” trying to make it off the road, and tach did go up some.

When I got to about 20 mph dropped it into “1” and it did engage…I was desperate and did manage to pull over. I think when I hit about 10 MPH thats when the engine stopped spinning and all dash lights lit up. So the tranny did stay engaged. This was a front pump only transmission as Ford had removed all rear pumps by 1965.

This got me curious as maybe someone changed the tranny to an earlier year so one day doing about 40 mph I dropped it in neutral shut engine off then tried to bump start it…

No go tried D,2, and 1 and nothing. had to use the starter.

Now my 59 t-bird does have front and rear pumps and can be bump started as I tried this.
Get it up to 20mph, turn on ignition and drop it into “L” and it will fire.

What gets me here is why my 1987 Marquis is puzzling. As I said in a earlier post, I did try this by going about 55 or 60, shut key off and within 5 or 7 seconds lost power steering. Turned ignition back on and nothing…a dead engine…I just did this a 2nd time yesterday with same results on the Marquis.

One other thing…if the tranny does not reverse drive the engine to some extent, then why when going down the highway say at 3000 rpm and you take your foot off the gas pedal, how come the tach does not drop down to idle speed ??

SO GO FIGURE…STRANGE.


#145

Most of the old trannys could be bump started, most newer ones cannot. My engine will hold back the van until it reaches a slow speed. I don’t know how slow that is.


#146

My parts guy drove up today in his 97 Dodge Ram pickup with the 518 Chrysler transmission in it (The same as yours Earl) I just couldnt resist taking his truck out for a ride. Took that ride of his up to 60mph and cut off the ignition. Wouldnt you know, I lost all braking and PS after 4 seconds!!! The truck did not start back up and coasted like it was in neutral to a slow stop. I do have to say I’m in awe. You are one of a kind Earl. You know, you dont contribute too much here but you ARE entertaining.

transman


#147

Well, mine is a '96 and it doesn’t lose power steering or brakes and WILL start up when you turn the key ON. It’s hard to believe that a '97 would be different. Was it a V8?, with 4 speed auto? Maybe the pickup has a different tranny than the Van?
why don’t you try a '96 or older before you make out that I am an idiot? Surely there will be one in your shop soon.
If you think I’m an idiot, what about the guys who agreed with me, or had the same results as I??


#148

My manual says my transmission is a 46FE. is that much different than the 518 you mentioned?

I got to wondering, if the transmission is what does the braking, does it also power the vehicle forward??


#149

Theres no 46FE. It would be a 46RE. The 518 series Chrysler covers the 46RE and 46RH. The RE is the electronic version started in 96 where the RH version is all hydraulic with electronic overdrive. The 518 series was put in the 1500-2500 trucks and vans (Gasoline Only) The 2500-3500 series trucks and vans (Diesel and V-10) used the 618 series transmission also known as 47RH and 47RE which is a heavier duty version of the 518’s (46RE and RH). The 518-618 series transmissions are the same transmission except for a thicker case and heavier duty hard parts in the 618’s. The all suffer from the same internal leakage problems. I’m very surprised yours hasnt had any issues with the front clutch leaking. This was very common in these. A manufacturer defect in the front clutch drum where the inner piston seal groove was cut too deep during machining caused the front clutch to leak. This causes delays in reverse engagement and an extended 2-3 upshift. You state that you have never had any transmission problems in any of your vehicles. If this transmission has never given you any problems, I am very surprised.

transman


#150

It is a 46RE I didn’t have my glasses on.


#151

Well, just for hoots I dropped by the transmission shop a friend of mine runs and floated this scenario by him. Like Transman, he specializes in this area and he’s as good as it gets. The following is a bit about him and his operation.

Started out at about 12 years old after school and weekends in his dad’s transmission shop and took it over back in the 80s after putting up a brand new building.
Has 6 bays for in-car service and R and R, several very large rebuild rooms, office and front counter, and even a pretty decent sized parts department where he actually stocks just about everything for most transmissions.
He’s got several employees to do the R and R, handle the office, etc. and at this point he has going on 40 years in the transmission field only.

He’s considered the “go to guy” around here on automatics and even some of the new car dealers send some of their problem child transmissions to him. As odd as it sounds some of them even send some warranty work to him. (Paper shuffling at work somehow.)

Anyhoo, I posed this to him and in a nutshell he says crap. He echoed everything Transman said without my even saying a word about what was or was not said.
As to whether there’s something with a Chrysler trans that would make it a bit off the wall, he says it’s no different than anything else.

He has no idea where this is coming from and like me (I’m still waiting for a decent technical explanation of how this can occur) he’d like to hear it too, just as I would.


#152

Evidently you and transman think I and several others here are lying or are so stupid that we don’t know what is happening when we try it.
transman said that a converter would never push an engine. That would be with the ignition on or off. What happens when you downshift going downhill? Something holds the vehicle back. (slows it down). I have a stop sign and a downhill 2 blocks to my house, I shift into 2nd before I leave the stop sign and don’t have to use the brakes. Now all this is with the ignition ON. We have been talking about with the ignition OFF.
I and others on here believe that when you turn off the ignition, everything is turning and will because the pump is turning and there is pressure until you slow down to some point that the engine stops turning. Much more than 4 seconds in my van. Evidently this doesn’t work on Ford or some others.


#153

Where do you think those engine rpm’s are coming from?? With your foot off the accelerator, coasting in gear, your tach will drop as the vehicle speed drops. This is the TRANSMISSION causing the engine rpm’s to be anywhere above idle speed with 0% throttle. Like I said before, cruise your van at 60 mph, let your foot off the accelerator. Your tach will probably be in the neighborhood of 2700 rpm’s and will slowly drop as your vehicle speed drops. With your foot off the accelerator, the engine is no longer pushing the vehicle, it is the TRANSMISSION controlling the engine speed. The amount of rpm’s depends on what gear the transmission is in. The fact that the vehicle is slowing is because the engine is no longer contributing to pushing it and is now just another force working against speed. While cruising at 60mph, take your foot off the accelerator and place the gear selector in “N”, feels like you can cruise forever, huh?? Look at your tach, its at idle, Now drop it back down into “D”, tach rises again and your vehicle slows. Drop it into L2, trans downshifts and rpm’s rise even more. This is engine braking and it comes from and starts in the TRANSMISSION.

This is so simple, why are you not getting it??

transman


#154

Regardless of the expertise of those that have commented that this “shouldn’t happen”, I can indeed verify that it does happen with my car. The transmission will stay engaged for quite a bit longer than a ‘few seconds’, and the motor will resume normal operation by simply turning the ignition back to ‘run’, as long as I don’t let it coast long enough for the transmission to disengage.

All the other arguments against the empirical evidence provided by myself and others are like people looking at the ocean from the beach and saying “it’s not as big as I expected”

I do understand how a transmission and TC function, but verifying this does not require an in-depth understanding of torque transmission or fluid dynamics, it simply requires a person to try it and use their eyes and ears.


#155

Thamks, oblivion, I need someone to agree with me. Can you understand why transman insists that it all depends on the transmission. OF COURSE an engine and torque converter cannot hold back a vehicle without the transmission. Neither can a transmission hold back one without the torque converter. Nor can any of this happen without drive asles or wheels.
The statement that “a torque converter can never push or turn an engine” Is ABLOLUTELY FALSE.


#156
 I just don't know if I believe it.  Your reasoning is sound, but going down the Rockies, my Chevy Corsica kept the fuel shut off for so long that my radiator cooled off and I lost heat. I did not have the transmission disengage.  I also have ran out of gas at speed, and did not have the revs drop (until I stuck it in neutral to try to restart).  I really think this could depend on the transmission design rather than being universal.

 But, anyway.. what happens when the engine is shut off?
 0) Make damn sure you find out what conditions lock the steering column (and how to unlock it with the key) BEFORE you try this!!  Remember, it's not like the steering wheel will lock dead ahead, it'll turn SOME then lock, so you'd for instance turn the wheel to pull onto the shoulder, THEN it'd lock and you'd steer right into the ditch!  Obviously, don't do this on a busy road either.  Even if you have no problems, you'll be slowing down, speeding up, the car might turn off your lights when you crank, etc., which will be pretty rude and confusing to any traffic around you.

 1) If your engine RPM stay up, nothing happens.  Your power steering still operates, you still have full braking.  On a few GM cars I've had, if you put the car back to "run" (no cranking or anything), the fuel injection system sees the engine is turning over at a good speed already, and just resumes spark and fuel like nothing happened.  I'm sure transman is right for some models, though, you should be prepared to have the tranny go out of gear on you.

 2) If you put it in neutral, your engine RPM will drop to zero.  You will lose power steering (you should still be able to steer but the steering will be stiff to very stiff.)  Your power brakes have a vacuum chamber so you should have a few full pumps of the brakes (somewhere between 2 and 5) but if you "ride" the brakes it could use it up.  The brakes will still work too, just stiffer.  BUT, if you feel inclined to try giving the engine a few cranks, it must be in neutral or park (and obviously you can only put it in park when you are stopped.)

 3) Other possible computer-related odd effects.  When I ran out of gas in my Chevy Corsica* (at about 75MPH), I tried putting the key to "off" then back to run -- nothing.  So I put it in neutral to try to restart (since I didn't know it was out of fuel.)  There was virtually no traffic on the road so I just coasted as far as I could.  After around 30 seconds, the speedometer dropped from ~55 to 0 (along with every other gauge) -- the computer had decided since the engine wasn't running to shut off the dashboard!

*I didn’t make it a habit of trying to run on fumes… the gauge showed about 1/8th of a tank, and I was only a mile or two from the gas station I intended to fuel up at. Obviously the gauge fibbed a bit.


#157

I’m still curious about the extent, if any, of Elly’s mechanical experience. Where do you get your knowledge from on automotive problems?

That being said, there is one thing I’m going to be doing a lot of and that’s performing this test on any vehicle I get a chance to perform it on; especially Chrysler products.

By your logic this abnormality is to be considered normal. In turn this means that any Chrysler I do this test on will provide the same results as your test did.


#158

What’s located between the tranny and engine>>


#159

there may be some Chryslers of different years or models that will not operate like mine, but I am sure mine is not the only one.
I understand your questions about my experience, and after reading some of your posts, I question yours.


#160

Well, with 2 old pros like transman and ok4450 telling me I am wrong, I guess i will go stand in a corner and repeat, several times, “I was wrong, a torque converter cannot “reverse drive” an engine!!” “I was wrong, a torque converter cannot “reverse drive” an engine!!” “I was wrong, a torque converter cannot “reverse drive” an engine!!” “I was wrong, a torque converter cannot “reverse drive” an engine!!”

Shall we start another Thread? Like “A V8 engine cannot propell a car, it is done by the transmission”