O/D off under 55mph..?

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guinnessman

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Hey guys so i've read sooo many posts and internet write ups on when to use/when not to use Overdrive etc etc. I cannot find a solid piece of info that says exactly WHY you should or should not do the following.

I always drive with o/d off when driving under 55mph-normal street stop light to stop light driving etc. I'll hit the highway, then i click the button to enable the overdrive band for MPG increases of coarse.

Driving like that, i've read so many different things, some say it is bad for the tranny, that it causes heat in the fluid because it is not shifting into O/D. I've read that your converter can balloon from heat etc. Something about torque converter lockup?

When it comes down to it, i simply would like to know what exactly happens in the transmission when you are riding 30-45mph in 3rd gear with o/d off..does it burn the fluid faster, harm the tranny in anyway?
:D
If you can please share your knowledge on this, it is greatly appreciated.
 
Well I'll tell you this much, when I got my tune from Torrie he switched it up so it never shifts into o/d until around 50-55, and I'm pretty sure he switches the lockup schedule too. I don't imagine he would do this if it was bad for anything, but maybe someone else can chime in with some more info.
 
Driving around with the OD off sure burns fuel faster... I only drive with OD off when I'm engine braking down a hill, or when I'm trying to get the car up to operating temp so I can turn the heater on. With my gears it will shift into OD at 27mph at low throttle...

It will lock the converter in 3rd gear, so I don't see how it would build more heat..

Edit: Actually I was sorta incorrect.. I went and tested this tonight. My Mark (stock 93 tune) will lock the converter in 3rd, but with the OD switch off it will not lock. With this in mind I would suggest running with OD on unless you're engine braking or wish to waste fuel. It's not going to overheat and toast your trans fluid instantly, but it can't be good.
 
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If it's in 3rd over the lockup schedule (after 30mph i believe) would the converter be constantly slipping causing more heat?
 
The only time I click off the OD is when I am going WOT...

Being able to tune your stuff yourself you can make the car shift exactly how and when you want and you can have it exactly how you want it....
 
I used to keep the od off around town until I got a tune. Mostly because the stock shift schedule will put you in overdrive to soon and lug the engine.
 
I never turn the od and t/c off unless im beating on it going WOT or at the track.

I dont see the point of causing excess wear on the engine and trans and getting worse gas mileage when its not necessary.
 
Many years ago, it was said that running with the OD cancelled by passes the cooling circuit in the trans..

I cant find the post anymore because it was on Cals board back in 99 or 2000.

It was a post made by a guy (nameless) that doesnt post on public message boards anymore... those that know, know "WHO" that person is.

dont ask as I dont speak his name in public..
if YOU KNOW.. dont post his name in this thread.

he said it was a bad idea to run around all day every day in OD cancel.
 
OD off in town. Its almost like a reflex to kill it. When I get my software I will set it to 45+.

As for lock up, I thought it was not the gear per say, but the speed that also determined lockup. And I thought it was 30MPH.
 
Oh, side note. When your trans is cold it will not lock-up at all. If you get in the highway you will notice this first thing. When the trans is up to temp you will feel the lock-up.
 
unity said:
OD off in town. Its almost like a reflex to kill it. When I get my software I will set it to 45+.

As for lock up, I thought it was not the gear per say, but the speed that also determined lockup. And I thought it was 30MPH.
Click to expand...

I found that setting to to 43 was almost too high.

you'll find that there are "load based" tables you can adjust.
at low loads you want it AROUND 39-43, then you can adjust the higher loads to not shift until later.

That way.. at low speeds at low loads you can still HIT OD if you desire, but IF you have ANY load at all it wont shift until 43-45-50ish depending on how much "go pedal" you have chunked at it.

I got my first gen NAILED down to where I liked it, I'm still working on the second gen... I just just copy those tables from my first gen tune and paste then into the second gen and be done with it..haha
 
Kinda related note:
On LOD, search user "ndoghouse"

He's made a plug and play module that when you start the car turns OFF TC and OD.
 
If anyone has any "technical" info, please shine in here. Does it heat up the fluid more with od off-why etc??

Also i believe it is bad to go WOT Into O/D meaning riding out 3rd gear until it hits O/D. How is is bad for the trans to floor it when you're in O/D???

Please correct me if i'm wrong (usually a daily occurrence lol)..
 
Things that you don't want to do with a 4r70w...

WOT shift from 3rd into OD... note in a 3.08 geared car this happens at 120+mph

WOT downshift from OD to 2nd

Like I said the only time I take OD off is when I'm having some WOT fun....
 
no problem..

Please dont think us saying "research" is just being lazy.
There is far too much technical data and far too many places that a typo can really screw up the information.
 
On page 6 the question "will manual shifting hurt trans" comes up.

The writer says "1996 and newer 4R70W you can do all the 1-2 shifting you want"? Somehow i think that will explode the tranny lol.
 
manual 1-2's aren't bad, manual 1-2 much above 6K are bad for a stock torque convertor tho...

trust what you read in that article as gospel.
the man the wrote it is the absolute best source of information in regards to PCM tuning and 4r70w's.

if it's written there, it can be accepted as fact.

WITH the exception of the pin out diagram for putting a later model trans in a early model car.. the image got reversed in the scanning process thus it's backwards (OOOPS)
 
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