02LibertyLimitedChick
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I do ALOT of around the town driving. Stop and go, stop and go. Is it ok to leave the truck in o/d? Or should I just turn it off unless I'm on the highway? Opinions?
O/D on or off???
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tjkj2002
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Just leave it in OD,it's not going to hurt anything.Actually you will get better mpg then locking out OD.Since you have the 45RFE when you lock out OD you also lock out the 2nd "2nd" gear.
02LibertyLimitedChick
Full Access Member
tjkj2002 said:
oooooh ok. Thank you! I was wondering if it was helping or hurting.
FirstJeep
New Member
I have to disagree, my best frineds dad is a transmission mechanic for ford and actually is one of the top they have. Anywyas I asked him about O/D in the city and he said it should not be used unless you are doing 80km/hr or higher. Driving stop and go traffic is ******* some of the O/D parts and just makes your trans shift more often. I drive highway for 20 mins each day and they city for another 20 to get to work and as soon as the speed limit drops from 100 to 60 i turn off the overdrive.
I'm sure everyone will have an opinion on this but this is what i do and I trust my source to be correct.
I'm sure everyone will have an opinion on this but this is what i do and I trust my source to be correct.
2003KJ
Member
If i'm running alot of city driving, less than 50mph, i'll usually leave the OD off. To me, it's less shifting. And especially at those low speeds, the way the KJ is geared, the OD gets "confused" a lot, and ends up going in and out and in and out....and it gets really annoying...lol.
tjkj2002
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Well I can't say for the '03 and above "weaker" trannies but my ****** will go into OD at 35mph so I'm running 1200rpm instead of 1900rpm,and at 50mph I'm turning 1900rpm instead of 2600rpm.Getting better mileage also,and less stress on the engine.Also I have 4.10's so that makes a huge difference.Keep up with the fluild/filter changes and you will have no problems.Now you shouldn't use OD when towing as that can hurt your ****** but no towing let that ****** do it's thing.
JeepJeepster
Full Access Member
If youre not going to be getting over 55mph for some time, its best to turn O/D OFF. I always turn mine off until I get over 55mph. O
What all of you are saying is correct.
But the key is that you do not want your ****** to continually search for gears as when it does this (you can feel it) continually shifting up and down, the fluid gets hot - hot - hot - right away and it is the excessive heat that will destroy the ******. Every vehicle will be different. Different ****** and shift points, etc. Your rear end gear will even make a difference if it's 4:10 as opposed to 3:73 or whatever. You don't need to even know what you have - just feel it shifting. For instance, around here there is a lot of mountain driving and if I feel the trany starting to search for gears I immediately lock out O/D. When I'm towing I always lock it out to keep it from shifting back and forth from O/D to D and back. You might use an extra $5.00 in gas but this is better than trashing a $2,000 ******. Sometimes while towing, I've had to go to 2nd gear even though I had O/D locked out as it was shifting between 2nd and drive back and forth. This will kick your rpm's up (watch your tach) and be easier on the ****** and actually the entire drivetrain. I have done a lot of towing with different vehicles. My last tow vehicle is still running the original ****** with 190,000 miles on it. It all depends on how you treat it.
Dave
But the key is that you do not want your ****** to continually search for gears as when it does this (you can feel it) continually shifting up and down, the fluid gets hot - hot - hot - right away and it is the excessive heat that will destroy the ******. Every vehicle will be different. Different ****** and shift points, etc. Your rear end gear will even make a difference if it's 4:10 as opposed to 3:73 or whatever. You don't need to even know what you have - just feel it shifting. For instance, around here there is a lot of mountain driving and if I feel the trany starting to search for gears I immediately lock out O/D. When I'm towing I always lock it out to keep it from shifting back and forth from O/D to D and back. You might use an extra $5.00 in gas but this is better than trashing a $2,000 ******. Sometimes while towing, I've had to go to 2nd gear even though I had O/D locked out as it was shifting between 2nd and drive back and forth. This will kick your rpm's up (watch your tach) and be easier on the ****** and actually the entire drivetrain. I have done a lot of towing with different vehicles. My last tow vehicle is still running the original ****** with 190,000 miles on it. It all depends on how you treat it.
Dave
I live in the country on gravel roads. I usually will lock out the OD until I make it to the highway. Same for running around in town. I lock out the OD. Searching for gears and constant shifting is not a good thing for any auto ******.
Maybe not necessary, but I guess it's the semi driver in me that like the extra control over the ******. (lol)
Maybe not necessary, but I guess it's the semi driver in me that like the extra control over the ******. (lol)
02LibertyLimitedChick
Full Access Member
Wow great info! So....when I am driving during the week to work and school, like I said, I'm usually in bumper to bumper traffic, so I rarely hit over 50mph. So after reading all this, I'm thinkin I may keep the o/d off during that time......
JeepJeepster
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Ive made it a habit to hit the button as soon as I get in the Jeep. I dont even know that I do it anymore... O
KJ02Ltd
Full Access Member
tjkj2002 said:
So, you're saying it starts out in 1st, then goes to 3rd?
I'm not saying your wrong, but what would be the point in that?
If that's true, then why isn't the button labeled 2nd/4th off?
jpm
thecause17
Full Access Member
I'm not sure about that either...only thing I've ever heard like that is when you put a vehicle in "L" or sometimes it says "2", they start in 2nd gear....
tjkj2002
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The 45RFE has two 2nd gears,one for normal use and the 2nd on is a slightly higher ratio for passing at highway speeds.
kjpilot
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KJ02Ltd said:
This transmission is a 5 speed that runs as a 4 speed. the 2nd 2nd gear is not the regular 2nd gear, it is used as the kick-down passing gear. Meaning, the only time you get to use it, is when you really stomp on it.
indieaz
Full Access Member
If you are staying out of overdirve at 40-50mph all you're doing is wasting gas.
Everytime you accelerate from a stop your transmission goes through a 1>2 and 2>3 shift. Why do you want to keep it from performing an equal number of 3>4 shifts? I'm confused by all the posts - is the logic here that he overdirve will wear out faster than 1>2 and 2>3? That makes no sense especially considering the amount of torque the transmission has to ahndle in the 1>2 shift (the way most poeple drive anyways) is much highe than the 3>4 shift. Knowing this mos ttransmissions allow a LOT of slipapge from 1>2 so that the shift is soft giving the allusion of a smooth ride. The reality is your 1>2 and 2>3 bands are going to wear out long before your 3>4.
Everytime you accelerate from a stop your transmission goes through a 1>2 and 2>3 shift. Why do you want to keep it from performing an equal number of 3>4 shifts? I'm confused by all the posts - is the logic here that he overdirve will wear out faster than 1>2 and 2>3? That makes no sense especially considering the amount of torque the transmission has to ahndle in the 1>2 shift (the way most poeple drive anyways) is much highe than the 3>4 shift. Knowing this mos ttransmissions allow a LOT of slipapge from 1>2 so that the shift is soft giving the allusion of a smooth ride. The reality is your 1>2 and 2>3 bands are going to wear out long before your 3>4.
Jeger
Full Access Member
04Liberty said:
I agree with this theory as well, even though you may be in bumper to bumper traffic..if that traffic is moving at a range of speeds that doesnt make you ****** constantly kick in and out of OD then it wont hurt a thing. Just be conscious of what your ****** is doing and lock out OD if you notice it hunting.
JeepJeepster
Full Access Member
indieaz said:
No.. The only thing that O/D does is shift way to early. So, then it must unlock the torque to get up to speed b/c it locked to early. Keeping O/D off until you get to 50-55mph will keep the ****** cooler, keep down wear and tare, and probably save gas since it locks the torque earlier in 3rd gear which makes the rpms lower. O
indieaz
Full Access Member
Right, converter lockup is what heats upt he transmission - but being in 4th gear. The two are not directly corrolated. In GM 4-speed transmissions (4l80e 4l60e et. al) for example converter will lockup in 3rd gear as well...so long as you are going 50mph+.
I haven't tested this recently in my jeep - but i'm quite sure converter lockup does not happen until at least 45mph. The actual act of locking the converter up does not warm up your transmission...the converter being locked up does. So locking/unlocking during acceleration will have little impact on transmission longevity. The converter being locked up during 50mph+ cruising also will have little impact. During times when converter lockup would cause excessive heat buildup (anytime more than x% throttle is needed - oprobably around 25-30%) the converter will unlock to save the transmission from heating up. The other reason being is the unlocking of the converter will move the engine closer to it's powerband (which is still more efficient than a 1:1 input/output ratio).
I haven't tested this recently in my jeep - but i'm quite sure converter lockup does not happen until at least 45mph. The actual act of locking the converter up does not warm up your transmission...the converter being locked up does. So locking/unlocking during acceleration will have little impact on transmission longevity. The converter being locked up during 50mph+ cruising also will have little impact. During times when converter lockup would cause excessive heat buildup (anytime more than x% throttle is needed - oprobably around 25-30%) the converter will unlock to save the transmission from heating up. The other reason being is the unlocking of the converter will move the engine closer to it's powerband (which is still more efficient than a 1:1 input/output ratio).
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