Overdrive?

Discussion in 'Tow Vehicles, Hitch & Towing' started by frolin, Aug 26, 2014.

  1. Unstable_Tripod

    Unstable_Tripod Well, there's your problem!

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    I added the bold for emphasis of this point. Based on comments made in some of the RAM forums, I believe the change in the way Tow/Haul operates took place in 2009.
     
  2. Phranc

    Phranc New Member

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    The whole idea of not using OD if it's hunting is because most transmissions, when in OD, will not lock the torque converter when the transmission shifts to the next lower gear. Running in Direct, with the torque converter unlocked builds a tremendous amount of heat. Manually shifting to 3rd, or direct allows the torque converter to lock up, thereby reducing the slippage and heat buildup.
     
  3. fix_it

    fix_it Member

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    I generally agree with this. In regards to the OP's vehicle, I have the same year and model. Mine is Chevy. His is GMC. Same truck. Same manual. My manual, as well as his, says "You should tow in overdrive". It also says that you may choose to select 3rd or even 2nd gear if the conditions warrant. So, while the manual encourages using OD when appropriate, it also acknowledges that there are times that it is not appropriate.

    My real world experience with a vehicle identical to the OP says that towing in overdrive will cause reduced gas mileage and make the transmission run hotter. I would never advise someone to make their transmission run hotter.

    Also the issue of the stripped sun shell in the 4L60E is very real and applies to all vehicles with that trans (or the 700R4, which uses the same geartrain) all the way back to 1982.
     
  4. Dubbya

    Dubbya Wherever you go, there you are...

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    I have a factory installed transmission cooler in my '97 F-150 (6 cyl auto trans) but I turn off the OD when towing in town and when I'm going to be driving under 60mph.

    If it's not too windy or I'm pulling on the flats, once I get to 60, I turn it back on for increased fuel economy. If the transmission is upshifting/downshifting constantly at highway speeds, I disable OD. Every time I stop, I disable OD until I'm back up to highway speeds. I wouldn't be able to do this with a heavier load like a TT but the pup is just over 2000 lbs loaded and the pickup handles it well.

    I've been doing this since we bought our pup three years ago but to be honest, our biggest camping trip was 4 hours away. This summer, we took a 3000 km round trip this summer and our average speed was 60-65 mph. I disabled/enabled OD as stated above and still haven't had any problems. The transmission has over 268, 000 km's on it and the trans fluid and filter were replaced last summer.

    It's always best to follow the manufacturer's instructions but they do tend to err on the side of caution assuming that the average Joe doesn't have any idea what they're doing behind the wheel. That's all fine and good but the manual's recommendations don't factor in those of us who apply a little common sense and Ford isn't paying for my gas.
     
  5. fix_it

    fix_it Member

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    http://popupportal.com/index.php?topic=66796

    Here is a link to a tread I started a couple of years ago after I blew the front seal out of my 700R4 towing in overdrive. I overheated the transmission bad enough that the front seal came out of the pump. Then I was stranded an night on the side of the road 700 miles from home. Whatever you do, keep the transmission cool and the torque converter locked. That is the key, regardless of anything else, keep it cool. You can have a gauge added for the trans temp quite easily if you so desire.

    This was my old tow vehicle. I still have it but it has been replaced by my recently purchased 98 Tahoe for long road trips. Although I would still take that Suburban cross country today if I needed to.
     
  6. Yak

    Yak Well-Known Member

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    OD off and tow/haul mode are 2 different animals, READ YOUR MANUAL!!
     
  7. 96Rockwood

    96Rockwood Member

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    Not true in most cases....certainly not true for GM's OD does not disable TCC operation in 3rd gear.
     
  8. Phranc

    Phranc New Member

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    How about come tell my GMC that. 2008 Canyon and when the TC unlocks, then downshifts, the TC never locks back up until it shifts back into OD.

    If I manually shift the transmission to 3rd gear, the TC will lock. As a matter of fact, in OD when you are coasting, i.e. going down hill, the TC unlocks, but stays in 4th gear.
     
  9. Dubbya

    Dubbya Wherever you go, there you are...

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    The TC in my F-150 does the same thing Phrank's truck does.
     
  10. yetavon

    yetavon everything is better around a campfire.

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    To the OP, our 97 Silverado pulls a 3500 Lb HTT around in OD unless we start hitting hills and before it begins hunting gears. The problem with this transmission is the amount of clutch material being used while in OD and overheating it is a quick kill. make sure you have a trans cooler and a temp gage is a good idea...
     
  11. 96Rockwood

    96Rockwood Member

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    Has the been confirmed with a scan tool? The reason I ask is the TCC will remain off after the 4-3 downshift till you have backed out of the throttle some. I will not come on right after the downshift, however it will not to long after.
     
  12. tconroy

    tconroy Active Member

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    I have always used the tow mode ( or 3rd gear) when towing with my Ford. i have 183 g's on it and it is much happier when doing this. I have always done this in every truck I have owned. I tow boats all the time with a toyota ( brand new 2015) and it struggles big time unless I use the tow haul mod.
     
  13. Old_Geezer

    Old_Geezer Well-Known Member

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    Seriously? And to think I was doing what I read in a forum somewhere about towing in M-1 all the time. Man it makes one hell of a noise and really sucks the gas, not to mention it takes an awful long time to get to the campground. I was wondering about all of it.

    Go figure [:O] [:D]
     
  14. Phranc

    Phranc New Member

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    No, the shift when you let up on the throttle is the shift back to OD, then TC lockup. Confirmed by tach readings and a scanner. The only transmission I never had that would lock up in third gear was the one on my F350 Powerstroke 7.3L diesel. But those are programmed differently than the gas model.

    It's not necessary, or prudent to lock the TC until you have reached the top gear in the range selected. Even when you have pulled the shifter out of overdrive in to drive, and TC has locked, as soon as you put it in OD, the TC will momentarily unlock until the Transmission has shifted into 4th, or what ever your next gear is after Direct.
     
  15. fix_it

    fix_it Member

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    Lets say you have the selector in OD and are cruising at a steady 30 MPH at a light throttle. You may be traveling too slow for high gear so the computer commands 3rd. Then it locks the TCC because you are driving at a steady speed and light load.

    Also, I should point out that this may not apply to older non computerized transmissions. For example the 700R4, the predecessor to the 4L60E that the OP has, was a stand alone transmission. It was shifted hydraulically. The only connection it needed was one 12 volt wire to turn on the lockup solenoid. However, this wire was internally routed through a switch to engage the TCC only in 4th gear. Some were wired to engage in either 3rd or 4th. So, some of these vehicles will only lock in 4th regardless of the selector position.

    Now lets say you have the selector in OD and traveling 60 MPH. The computer will command 4th gear and lock the TCC. As you approach a steep hill, the throttle will begin to open more as the load increases. The computer sees this through the TPS, MAF, and MAP readings. The computer will first unlock the TCC in an attempt to gain some torque multiplication in the converter. Then, if needed it will command 3rd gear. There would be no need to lock back up in 3rd as the torque multiplication of the converter is desired to get over the hill and back into 4th and lockup as quickly as possible.

    Yes the TCC can and will lock up in a lower gear than is currently selected. But it's not likely to do so under a heavy load or high speed, as doing so would hurt performance.
     
  16. tenttrailer

    tenttrailer Art & Joyce - Columbus, O

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    I use OD, but when I come to hills, I disengage at the start of the hill so the lock up TC does not disengage. Once I start up the hills I turn the OD back on and it automatically shift back into OD once the grade changes. Some times it will be a mile or so before the grade changes.
     
  17. Heritage

    Heritage New Member

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    I only use OD on flat ground.
     
  18. FarmerDave

    FarmerDave Active Member

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    I'm glad I have a manual trans. I tow in OD all the time. In fact once I am up to cruising speed I am normally in OD until I have to stop.

    Manual takes the guess work out of if the trans is going to cook itself whether to use the "Super Magic Towing Switch" or having the selector in the right spot.

    OD just another gear, I agree with all the posts saying know what your vehicle needs to do to preserve itself rather than blindly following "Grampy said never tow in OD no matter what" cause he cooked his AOD in his F-150 back in the day etc.

    Be interesting to see how the newer 8 and 9 speed autos cope with towing, enough gears to have the engine in the sweet spot, but probably lots of shifting.
     
  19. skeetercampsintexas

    skeetercampsintexas Active Member

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    FarmerDave, I too would like to see how these new trannys perform. I'd be willing to be the torque converter clutches have some super space age rocket scientist material in them to keep temps down. Personally I wouldn't buy one until they've been out for 5 or 6 years, I'm not a fan of being a guinea pig
     
  20. turborich

    turborich Active Member

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    I tow in OD until I start to climb, then OD is off until I reach flat land again. If you've been driving/towing with a 3 speed + OD transmission then you should know when to turn it off. The newer trucks with the tow/haul mode should take all of the guess work away.
     

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