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Discussion Starter · #1 ·
Hello guys.... I am wondering what the damage (or extra wear) that might occur to the transmission if I use Georgia Overdrive in my heavily loaded Van or when I have a trailer hooked up? I don't think it's only a manual transmission that this is relevant to. I keep thinking about it but cant figure what is still spinning & what is not (especially between manual & automatic).
I'm ZERO knowledge on transmissions. So I have quite a hard time to try to imagine where the (disconnect) is when you got her in neutral (between the two different types Manual & auto). And if it really makes a big difference between the two with regards to being in GO.
I only ask this because (aside from all the other issues/risks), I read something about how it could damage the transmission. So I was just hoping for more details of what is spinning, being cooled, or lubricated (or what is not) when it's in GO. I guess I should mention that for MY situation I have an automatic. So there is no problems with governed engine speed and not being able to get it back in gear. Guess there could be over speed issues if I got er' up to 150 MPH and put er' back in drive. Just don't see that happening LOL.
Just wondering if there is some sort of major slow down of trans fluid flow & thus cooling issues. Is that really all that can go wrong?? ASIDE from all the OTHER obvious issues. Control ability, going to fast for conditions, Hot Brakes at the bottom & brake fade... I hear a LOT of talk about ways to use your Scan Gauge and other speed control methods to save on MPG. But not much about popping it in N on the big slides down. There's LOT'S of places where all that idle time would be saving fuel wouldn't it? OR is our fuel cut down so much when you let off the pedal it only amounts to speed & no engine brakeing? Either way I would wonder the advantages vs. disadvantages/damage to Trans.......Any comments? DDT
 

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My comment is what is Georgia Overdrive?
 

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I know - I know!

Georgia Overdrive is when you put your transmission in neutral at the top of a hill then coast down the hill. Basically, using gravity to maintain speed until you make it to the bottom of the hill.

Guess what he is asking is will there be enough lubrication coursing through the veins of the transmission going 70 MPH in neutral to prevent issues. Or any other damage that might occur.
 

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I was kicked off a form because of my stance on the idea......... not a good one while yes there might be fuel savings the danger of not having control over the engine braking and who really knows what would happen when putting the auto trans back into drive at that kind of speed.. would not chance it.
One should read up on the Scangauge form web site, some on there are not real bright.
 

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Discussion Starter · #5 ·
Well here's a few things I got to say at this point with some amount of humor.
First off, I guess Mark has the same type of computer as I do....One of those that does not have access to GOOGLE....LOL
Now RT's "I know, I know" (kinda) gets a small part of the reason I didn't bother to explain just what a Georgia OD was. Sort of wanted to see who knew or at least would look it up & then (pretend) they knew. Any "REAL" trucker (should) know what it means. I figured a big diesel site like this might have a few or more guys that knew what I meant.
As for Alaskapsdvan:...Any site that would kick you out for your opinion one way or another on the subject ain't worth spit on a stick! You should be glad not to be on such a site.
Personally, I have not felt any big loss of control issues from doing this in my van. There's a BIG difference between doing this in your van & doing it in 40,000 or 80,000 lbs. of Tractor Trailer. But that's sort of what I was hoping for some information on. The big rigs are Manual Transmissions (for the most part). I got an automatic as you know.
RT summed it up perfectly in his second paragraph.
"Guess what he is asking is will there be enough lubrication coursing through the veins of the transmission going 70 MPH in neutral to prevent issues. Or any other damage that might occur. "
That's what I want to know???? Forget any ideas of teaching me Highway Safety.
Your not a Cop & I am not an IDIOT! (usually). I got a straight through exhaust and no, guaranteed to work, seat belt restraint system to speak of. I'm not carrying passengers or selling it so it's not hurting anyone but me. So as I said....RT asked the question for me in the most straight forward way....... What's happening in there (if) I use Georgia Overdrive practices on long downgrades?
I starting to think this might be related to how these vans are supposed to be towed as well. REAR off the ground OR Flatbed'[ed. So there has got to be some part of the transmission that is either still spinning or engaged through the rear wheels via the axle & into the Trans. Can Anyone give me any details about this. DDT
 

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First off, I guess Mark has the same type of computer as I do....One of those that does not have access to GOOGLE....LOL
That's what I thought it was, but I wanted you to tell me.
"Guess what he is asking is will there be enough lubrication coursing through the veins of the transmission going 70 MPH in neutral to prevent issues. Or any other damage that might occur. "
As long as the engine is running there will be lubrication flow to the entire transmission. Will it be enough to lube the rear of the trans (which is spinning at it's normal RPM for 70 MPH?) I don't know. I don't know that we looked at lube flow in neutral, engine idling, vehicle at 70 MPH.
I'm not carrying passengers or selling it so it's not hurting anyone but me.
Unless you run into someone.
I starting to think this might be related to how these vans are supposed to be towed as well. REAR off the ground OR Flatbed'
I believe the owner's manual states if the rear wheels are on the ground it can be towed at a maximum of 35 MPH, and it was a fairly short distance, too. If it will be faster than that and more than a mile or so the rear wheels must be off the ground.
 

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Discussion Starter · #7 ·
Thanks Mark:.....Those answers start to tell the story of just why it might be bad for an automatic Trans. vehicle to do this. I didn't know the specifics of how fast or how long you could tow with the rears on the ground. That's good info to know. Myself, I wouldn't feel good trusting any two job unless it's rears off or flatbed. BUT in so much as there IS this requirement or limitation in towing & I can see there are similarities in towing & coasting in neutral. Even though the engine is on & at idle, I have to imagine there must be large losses of pressure or fluid flow through the Transmission & if there are still parts in the rear section of the Trans. spinning at axle speed for 70 or 85 MPH,
and not getting the full flow of cooling bath as they would if engine RPM is kept up high as would be if left in drive... That could cause problems. But what would make it different for/with a manual? Even a Big Tractor Manual transmission? But lets stick with a small engine (van)....Are not those rear of transmission parts still connected via the spline gear to the drive shaft (woops, I have been calling it the axle). And still spinning at drive shaft/differential/axle/wheel speeds? This is a well known technique of big rig drivers to do while descending long grades (hopefully one's they are very well acquainted with). That's why it actually has a name given to it. If you Google or WiKi it you might find it's origins interesting (or not). I certainly understand that in your years in the business , testing for things like this never came up. Obviously it's not recommended. I just wonder if maybe someone on here that lives in big hill country maybe does this all the time and could report never having a transmission problem related to doing it (that he knows of). Now just for fun you should all go listen to the song (Six days on the road) by Dave Dudley
and you can all enjoy better the lyrics that refer to his 10 forward gears and a Georgia Overdrive!
Does this site frown on links posted to stuff like this????????? DDT
 

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Hopefully someone will chime in with first hand experience.

There's not a hill in sight (pun) big enough for me to coast down and maintain speed, but I routinely throw mine into neutral and coast into town. I know the exact spot to do it and let my truck slow down gradually enough to be going the right speed as the speed limit decreases on the way to our one stoplight... I do a lot of coasting. I'm over 200K on my original brake pads. (and transmission!)

As to why standards, axles, and the like can do this - most are lubricated passively - by some portion of the spinning mass being submerged in gear oil - no matter whether they were loaded or not.
 

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But what would make it different for/with a manual? Even a Big Tractor Manual transmission?
Manuals don't rely on pressure fed lubrication. They are splash lubed - oil is splashed around by the moving gears.

Are not those rear of transmission parts still connected via the spline gear to the drive shaft (woops, I have been calling it the axle). And still spinning at drive shaft/differential/axle/wheel speeds?
Yes they are. The rear half of the trans always spins at driveshaft speed no matter what gear the trans is in.
 

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Plenty of hydraulic pumps make full pressure at relatively low speed. Your power steering pump, for instance. You don't need it on the highway, you need it when you're at idle. Same with your HPOP. The injectors need the same amount of pressure at idle that they need at 2200 rpm.

I don't know if this is the case in the transmission, but it wouldn't surprise me......
 

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Discussion Starter · #11 ·
O.K. Guys.....First off, thanks for getting into it with me. Now....What XRACER brings up was going to be my next question......What drives the Transmission pump? If it's connected or related to engine RPM that a problem. If as he suggests it is separated (in some manner) and develops (good) pressure no matter what the engine RPM, Then it would seem O.K. to pop into N & coast no matter what the speed. With the towing you have the engine OFF so that would explain the issue there with rears off over 35 MPH or 1 mile or more distance.
I don't think RT experience counts (fully) for what I am asking about here, BUT is is worth knowing it seems to be O.K. for the small hills or flat coasting to slow downs or stops. I can't think of any other components or reasons this procedure would hurt.
Radiator fan stops turning faster and doesn't cool radiator as good? I don't think so.
Shift lever components wearing out faster because of more use? Seems unlikely.
Any other thoughts on any of this....Especially what drives the Trans. pump.
Not wanting to beat a dead cat here. Just get as much information as I can before I keep on with what might be a bad habit. DDT
 

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The transmission pump is driven by the engine. If the engine is off when you're in Georgia Overdrive there is ZERO fluid flow in the transmission.

This pump does not develop full pressure at idle speed. It's output is quite limited at idle speed.
 

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I'll tell ya right now, you start playin' around w/ "Georgia Overdrive" in that van w/ a trailer behind your lookin' for a disaster~!! Just for starters the last thing you want is a trailer pushin' that thing down a hill~! When ya look out the side window wonderin' who is passin' ya and you realize that it's YOU it'll prob'ly be the LAST thing you see~!! I just hope that I ain't anywhere near YOU on the hill~!! If yer askin' questions like this you really haven't a clue what your doin'!! Just a few things..do you know what your tongue weight is? What the trailer gross weight is?? Does the trailer track straight behind you, or does it "wag" at higher speeds or when you change lanes~?? "Tag-a long" trailers are much harder to handle than a semi, with the pivot point BEHIND the axle it makes turning, lane changes, backing up etc. much more tricky than a tractor-trailer "rig"~! Seriously, DON'T try to play with "Georgia Overdrive" in that thing, it WILL get you sooner or later and the time you might save ain't gonna add up to anything remotely worth the risk you're taking not only with yourself but with other vehicles and people on the road I got more than a few yrs. and miles in a lot of different trucks & trailers,- doubles, triples, oversize & overweight etc. You also risk overheating your brakes from excessive use tryin' to hold the speed down or maybe not being able to get it back in gear. When you overheat your brakes you risk losing them , by cracking disc rotors, pads actually coming right off the backing plates, drum brakes just splitting into pieces, and a nice fire can start pretty easily~! Take it easy-drive safe, trust me, you'll be glad you did. I've seen some real horror shows out there, don't be the next one~??
 
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