Overdrive FYI

[Kevin2050]

I came across the following.....is this accurate?


Dont drive constantly in overdrive (OD).
The premise behind OD is that it lets your engine spin at lower RPM's, reducing drag and increasing gas mileage. If you drive in town a lot, and the car shifts constantly between OD and third gear, you're not saving gas, reducing drag, or saving the OD band--in fact, just the opposite occurs. This greatly weakens the OD band, which is already a fairly weak piece to begin with. As a general rule, if you'll be driving under 45 MPH for under 10 minutes at a time, lock out OD and shift into D. The OD gear should ONLY be used for highway use, or extended driving over 45 MPH.

[OVERTONE]

All that is very true, even on the highway if you are doing a lot of hill climbing and the tansmission is constantly shifting in and out of OD it is a good idea to drive without it until the road flattens out.
What did Jeep have in mind by puting the OD lockout on the dash instead of on the shifter? The guy who approved that probably has never driven a car!
Ed

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Totally Stock 98 ZJ 2WD
Stone White,Moon Roof
Dunlop Radial Rover 255/70R15 tires
Chrome plated valve stem caps
_ _____________________ _
79 Toyota SR5 Pickup

[BluJeep]

I know, that was a pain when I had my ZJ. On the WJ is has been relocated to the shifter. So I guess they woke up!

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'99 WJ Laredo 4x4, Patriot Blue/Taupe, 4.0L, SelecTrac, leather, CD, sunroof, rear air-deflector, K&N drop-in, Gibson CatBack, Edelbrock IAS shocks, rear TrueTrac, 1" rear Addco bar & Energy bushings, Amsoil synth throughout , "deer alerts", "4.0 Litre High Output" badge from an XJ on the liftgate, American Flag on the antenna! :-)...

Next mod:
- WarpSpeed Cold Air Injection Kit (A-n-n-n-y-y year now...)

[AviatorJud]

Well, it's obviously not THAT bad for it or MANY more people would be in for transmission problems all the time! I'd say 95% of people who drive them around town dont lock out OD...hell, most people have no clue what that even means!!! I dont doubt that its easier on the band, but I dont think its such a critical thing must be done to prevent problems. I've never had a problem with my OD band (yet) and neither have most people. Besides, it will still save some gas...if engine RPMs are lower, you're using less gas- especially if you drive around town at 40-50 MPH in most places. The ONLY place I think you should really lock it out is in lots and lots of stop n go downtown driving where you never get above 20MPH.

Just my opinion.

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Judson K. Mulherin
1996 ZJ Limited 5.2L V8 Quadra-Trac, Chargold
*Mobil 1 Synthetic oil
*Rusty's air tube w/ K&N & custom heat shield
*Adjustable IAT sensor
*Clear corners
*Mopar 'Jeep' splash guards
JeepsUnlimited.com sticker in rear window

[Taz]

I keep mine locked out when I get into the stop and go part of town. It constantly shifts out of OD if I'm driving slow and speed up.

[BluJeep]

<font face="Verdana, Arial" size="2">Originally posted by SpeedingZJV8:
...The ONLY place I think you should really lock it out is in lots and lots of stop n go downtown driving where you never get above 20MPH.
Just my opinion.
</font>

But if you're going that slow in traffic, it wouldn't even shift into OD in the 1st place, would it? If that's the case how can it cause a problem?



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'99 WJ Laredo 4x4, Patriot Blue/Taupe, 4.0L, SelecTrac, leather, CD, sunroof, rear air-deflector, K&N drop-in, Gibson CatBack, Edelbrock IAS shocks, rear TrueTrac, 1" rear Addco bar & Energy bushings, Amsoil synth throughout , "deer alerts", "4.0 Litre High Output" badge from an XJ on the liftgate, American Flag on the antenna! :-)...

Next mod:
- WarpSpeed Cold Air Injection Kit (A-n-n-n-y-y year now...)

[razorbackME]

These transmissions are known as not extremely reliable (my brother, tstalcup, just had the tranny in his 93 ZJ rebuilt for the 2nd time, and it has 140,000 miles). That being said, any amount of excessive shifting increases wear on the clutches and band of a tranny. The devices work on friction, and smooth shifting is a result of these parts slipping. Slipping creates wear, so the more it happens, the quicker these parts will fail.

Generally, an automatic transmission is a simple device. The vast majoroty of complexity involved is for shift smoothness and applying shifts at the right time.

You can build a really simple AT without all this logic, but you would have a severe case of whiplash from brutally hard shifts.

[This message has been edited by razorbackME (edited 11-28-2001).]

[8898]

<font face="Verdana, Arial" size="2">Originally posted by BluJeep:
But if you're going that slow in traffic, it wouldn't even shift into OD in the 1st place, would it? If that's the case how can it cause a problem?

</font>

It does not shift into OD until over 30 mph.

[Jeep2Relax]

The overdrive is the weakest gear of the trans. And for long trans life should only be used in highway driving. The default position has to be overdrive on for gas mileage (CAFE) reasons. The Auto makers (All of them) figure that the trans will last long enough to ge beyond the factory warrenty. After that repair is on the customer or some paid for extended warrenty.
We have alot of heavy duty pickups and other work vehicles that come with auto trans w/overdrive, trannnys were going out all the time until they started turning off the od. When I start my ZJ I turn the od off and only turn it on for freeway driving. I am at 132,000 miles on the original trans. and I tow a 6,300 lb trailer.
Save some gas or burn up the trans. your choice. Is it worth the risk?
My .02

[EricE]

"Save some gas or burn up the trans."

Over the life of the vehicle I would spend a LOT more on gas than on a new tranny!

Of course I am thinking of at least 200k out of the tranny!

EricE

[louc]

I've heard this, I too turn off my O/D unless going on the highway. I heard that the problem is that at lo revs in od, the trans pump doesn't turn fast enough to adequately lubricate the od unit in the rear of the trans--anyone know if that is really true?? Also heard they improved the oiling of the O/D unit in the later trannies.
Also not running in OD saves your brakes to an extent, you get more engine braking.

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Lou C

98 ZJ Laredo 4.0 Selectrac Mopar skids tow hooks, tow hitch, Painless Wiring headlight bypass harness, Hella 450 fogs

[Jeep2Relax]

The other variable in this is where you drive. Hilly roads or flat. everything around here is either up or down.
Any way with my budget I usally have the extra buck or two for gas, its the new tranny all of a sudden that bothers me.
Engine braking is also a good point. Besides i don't like the sluggish acceleration and all the down shifting when in od.

[This message has been edited by Jeep2Relax (edited 11-29-2001).]

[MoparMadman]

Mine is rock solid reliable. And I rarely lock out the OD.

Can't speak to the tranny reliability thing either except that I've never had a problem with mine. I've never heard of these trannies being any better or worse than other domestics.

Some of the mopar guys have actually adapted the A518 tranny to their B/E bodied big block cars. The internals are usually replaced with better materials. Haven't heard anything from them about reliability issues and OD.

[justin2002]

So, I live in Florida as you might have expected. Anyways, I do little highway driving unless I want to get around town instead of through. My question is, if I spend most of my driving around 50 or so because of little traffic, should I have overdrive on or off? I can pay more for gas if need be and I would like acceleration too, its amazing now, but just wondering if it can be better?

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1996 5.2L V8 4x4 Grand Cherokee Limited Rosewood
**Current**
-Flowmaster 40 series
-Gold exhuast tip
-Pioneer CD player
-Infinity Kappa 652.3i speakers
-K&N FIPK
-PIAA Superwhites headlights
**Soon**
-Driving lights
-Ventvisors
-New bug deflector
-Rock rails
-Some nice decals
-Firestik antenna
-some sweet subs...

[doanlaw]

I have a 99 wj with the 45fre or whatever and i can tell you this, when you lock out the overdrive gear, the only way to get to the 2nd second gear is by stomping on it, have it kick down to the low second, and then upshift to the high second, at which point it will probably kick you right back into 3rd again. Ive noticed with the overdrive on, it will kick straight down to that second high gear and hold it there much easier.

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99 WJ 4.7, Carsound/Dynomax exhaust, tereflex bb, 265/70 x-terrains on 16x8 terrons, bilsteins, self modified air intake.