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Discussion Starter #1
Just wondering what everyone is driving their trans in and shift speed/rpm, ive been using 3 for just about all city driving until i hit 80 then shifting im running the 4l80e with 3.73's and 265/75/16. i use the same shift habits for gravel/dirt driving. just trying to get more fuel millage because i cant fill my slip tank up at work right now
 

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mine tows cooler in OD than in 3rd. If I'm pulling an obnoxious amount of weight, then I use 3rd (really obnoxious, though).

SnowDrift
 

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I always us OD, only time i hold it back is if i'm pulling a trailer in the mountains or really hauling @ss!
 

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Always OD
 

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Well,

For my shift habits, pretty simple - it's "OD" to go ahead, and "R" to back up,
 

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No matter what a diesel engine gets best mileage at the lower RPM,even with a load on it, exactly opposite of a gas engine, I run mine in OD all the time as well. I would think you will burn more fuel running 3rd, vice OD
 

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Discussion Starter #8
i was just thinking about possisbly causing the tranny to shift gears to much at lower speeds causing heat build up/ premature tranny failure
just a thought.
 

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Always overdrive. I even plow snow in overdrive.
 

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Holy ****, you must be flying!!:eek: :muahaha:
LOL! Well, it only shifts into overdrive when it wants to!:)
With the amount of going forward, then backing up, then going forward I do, it's just easier to drop it into OD than finding D.
 

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I thought the manual said you are supose to tow in 3rd gear? I have to pickup a boat in FL and trailer back to CT.. I can't see doing that trip in 3rd gear.. Problem I'm having is that if I use D then around 50mph or so my truck goes into Safe mode.. dropping down what seems like 1.5 gears.. Have to stop, count to 20 and then restart.. Dammed if I do, Dammed if I don't...
 

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I've always towed in OD with a diesel. Gassers seem to do better with heavy loads in drive, but diesels make lots of power down low.
 

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If you're just picking up a boat, maybe less that 6000 lbs or so i'd just us OD and not even worry about it unless your tranny is weak and on the way out already, just pull it into 3rd on the steep hills if you like.
 

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I believe the reason that the manual advises you to tow in 3rd is because in that gear the transmission ratio is 1:1 moving parts are at a minimum and the torque load is on the main bearing in the front and back of the transmission. In OD, you're putting power through an offset shaft to generate reduction and, in general, those bearings aren't as stout - to what degree I don't know but I lived next door to a guy who complained about replacing three transmissions on his Dodge (he was a brick layer and really loaded up a 20' flatbed) until he listened to me and left in in 3rd.

If you're willing to operate at say 65mph or less, I think the best answer is 3rd with the transmission wired per Heath's guidance to lock the torque converter in third and I'd do just that if I could identify the proper brown wire at the ECM and splice it.
 

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I believe the reason that the manual advises you to tow in 3rd is because in that gear the transmission ratio is 1:1 moving parts are at a minimum and the torque load is on the main bearing in the front and back of the transmission. In OD, you're putting power through an offset shaft to generate reduction and, in general, those bearings aren't as stout - to what degree I don't know but I lived next door to a guy who complained about replacing three transmissions on his Dodge (he was a brick layer and really loaded up a 20' flatbed) until he listened to me and left in in 3rd.

If you're willing to operate at say 65mph or less, I think the best answer is 3rd with the transmission wired per Heath's guidance to lock the torque converter in third and I'd do just that if I could identify the proper brown wire at the ECM and splice it.
OD does not require an offset shaft. the 4l80e a planetary gearset transmission and there are no offset shafts at all.

The 3rd gear requirement in the manual is that you NEED to keep the input shaft speeds up above 2000-2200 for proper operation of the oil pump.

That old wives tale about 'burnin up a transmisison if you use OD in town' is a myth. OD is just a 4th gear, where the input turnes a lower rpm than the output, which is to say, the output is overdriven, hince the term overdrive.

I have seen near fist-fights over the "OD-dont OD" in town thing. I just laugh

Tim
 

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OD does not require an offset shaft. the 4l80e a planetary gearset transmission and there are no offset shafts at all.

The 3rd gear requirement in the manual is that you NEED to keep the input shaft speeds up above 2000-2200 for proper operation of the oil pump.

That old wives tale about 'burnin up a transmisison if you use OD in town' is a myth. OD is just a 4th gear, where the input turnes a lower rpm than the output, which is to say, the output is overdriven, hince the term overdrive.

I have seen near fist-fights over the "OD-dont OD" in town thing. I just laugh

Tim
Is it true that the pump doesn't pump as much when in OD or is it that the RPM's are too low to pump efficiently? This is a catch 22.. Burn more fuel or over heat the tranny.. One tranny guy told me that if I tow all that way in 3rd that I would burn out the pump since it wasn't designed to pump like that for long periods of time.
 

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I've always said dxxn the war & towed in overdrive Unless I was in the mountains & the vehicle started to downshift. That only happened pulling the 26' camper. Our boat is a 16' Crestliner 140 merc cruiser IO. So it's not like I was pulling anything heavy. I use Amsoil ATF. I have quite a few miles logged on my vehicles & no tranny problems yet. Does anybody have any synthetic trans fluid stories. Pros & cons of using synthetic trans fluid? I have run synthetics in everything for quite some time now & haven't any major problems.
 

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Is it true that the pump doesn't pump as much when in OD or is it that the RPM's are too low to pump efficiently? This is a catch 22.. Burn more fuel or over heat the tranny.. One tranny guy told me that if I tow all that way in 3rd that I would burn out the pump since it wasn't designed to pump like that for long periods of time.
Its the RPM. As long as the input shaft (and the engine attached to it) is turning over 2 grand or so, the pump will be doing its job ok. The engineers were worried about grandpa trolling down the superslab at 52 mph and 1700 rpm towing an 10k pound 5'er.

As far as buring out the pump. With my gears (4.10) and my propensity for cruising in the upper 70's I am usually a tad over 3 grand on the tach. And my tranny is going on 201K miles.

Tim
 
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