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Downshifting

Discussion in '80-Series Tech' started by Gauge, Feb 25, 2004.

  1. Gauge

    Gauge

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    I've driven stick shift vehicles for the past 15 years, and I've made it a matter of personal habit to routinely downshift as a way to save my brakes - especially on long downhill stretches.

    Being my Land Cruiser has an auto tranny, I find myself shifting from D to 2 to slow the vehicle down quite often. Is this bad for an automatic transmission? Are there some negative long term effects I should be aware of? Like I said I am rather new to automatic transmissions and would hate to screw it up. Does anyone else do this or has feedback on downshifting with an auto tranny?
     
  2. RavenTai

    RavenTai

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    long down hill stretches put a lot of heat in your brakes worst case possibly causing your fluid to boil, (no brakes) also more chance to warp your rotors that is a good place to down shift, for normal stops (light to light) just use your brakes that are a lot cheaper to replace also a lot easier on you drive line, with a manual you get to clutch it in, in an auto down shifting is harsher
     
  3. tomlite

    tomlite

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    Good Question. The first sign of Transmission abuse is changes which can be observed in the ATF. Usually, but not limited to, are darkening of the fluid, the change in smell to a slightly burnt smell, the inclusion of micro particulate matter which is too small to be cought by the filter and finally, the changes to the fluidic properties. particularly the kinematic viscosity. A good second indicator is noise and motion. If, when you pull the shift down to second, the shift is made with the same amount of noise and decelleration as the noise and acceleration of the normal upshift, you can feel some comfort that the level of stress is similar to normal anticipated operation. A third position that you should take is to Flush out the fluid with a High Quality Synthetic Fluid. Mobil 1 if a fairly decient choice, but better are available. Also, check the present quality of the fluid in the pan by pulling a 1 quart sample via the drain plug. Compare this sample to a container of new fluid. The bottom line is this, the better care you take of the Automatic, the longer it will last. Something tells me that you can buy 15 sets of brake pads for the cost of 1 transmission rebuild.

    Tom 1997 LX450
     
  4. TOZOVR

    TOZOVR

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    for a long time I thought using the auto transmission as a brake was a terrible idea, that it would generate too much heat. It was then explained to me that propelling a vehicle forward generates the same or more heat and stress than slowing a rig down (as long as you're not shock-loading the beast).

    I'm still rather in the middle. When I used to do SCCA and COM stuff, I was always taught that Engines are for Going and brakes are for stopping and that brakes are easier to replace than a clutch or a tranny....

    Hell, I dunno. :D I'm usless :beer:
     
  5. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    Considering the cost of a new A442 you can buy 80 sets of OEM pads. :)
     
  6. bkgiii

    bkgiii SILVER Star

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    Yeah Dan, but think of all the TIME I save not changing pads and rotors! :D
     
  7. robbie

    robbie Guest

    I would disagree with most of the posts so far. I believe the tranny is designed for down shifing and will not hurt the tranny as long as you do not overrev the engine doing it. I do think you need to use the overdrive button first and not skip a gear in down shifting.
    These are not American automatic transmission, they work so much better and designed better. The will take almost any abuse you can dish out except abuse of the fluid. These trannies need clean fluid, I drain and fill once a year.
    Yes I agree that you could buy 80 sets of pads for one tranny, but you will not need to if you take care of it. I abuse(relative term) mine alot and have over 217k miles on it and expect many more before I have to rebuild. I do think after I get more power I will get a rebuilt valve body to handle the power. later Robbie
     
  8. cruiserman

    cruiserman

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    I frequently downshift my A442F tranny, even in around town driving. On long down hills, I take it out of overdrive to slow down somewhat. I use the tranny to control speed in slipperly conditions especially.
     
  9. CDN_Cruiser

    CDN_Cruiser

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    I miss a diesel stick - now THAT"S engine compression!

    I generally only 'downshift' when I'm off road (hills, etc)

    Cheers, Hugh
     
  10. Riley

    Riley

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    I'm very glad to hear Robbie's reply. I also wondered about this as I've had standards most of my life. In my early twenties I had a delivery job and drove a econoline van. I used the auto to engine brake all the time ::)

    The tranny went on me in about 8 months in a fairly new van so I've been afraid to do this ever since.

    After reading Robbie's post I think I'll just use the engine as a brake on long hills.

    Thanks for the info Robbie. ;)

    Riley
     
  11. Sammy Jenkins

    Sammy Jenkins

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    I'll downshift as well if I need to make a short stop or anything of that sort. The only reason is, is to put less wear and on the brakes, because they are crap pads from toyota (replaced every 15-20K miles). I bet becuase the brakes are so small on the the truck that they are getting piss poor mileage on the pads. Saying that, I'm just wondering if anyone else is getting that kind of milleage on thier pads. Or is it becuase of my led foot driving.
     
  12. landtoy80

    landtoy80

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    Robbie, when you change the tranny oil, do you just drain and fill or have a full flush via a tranny oil change machine like the ones that tranny shops use?
     
  13. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    Sammy, that is a common lifespan for stock pads. A switch to 100 series front pads and a set of new rotors will get you a lot farther. I have over 20k miles on my current set of 100 series pads and I have well over 50% friction material left.
     
  14. sjcruiser

    sjcruiser

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    Dan,

    Glad to hear it's a normal lifespan; given that I've changed my front pads three times (with 100 pads & relatively new rotors the third time) within less than 3 years of ownership.

    Frank.
     
  15. Riley

    Riley

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    [quote author=Sammy Jenkins link=board=2;threadid=12059;start=msg110510#msg110510 date=1077758272]
    I'll downshift as well if I need to make a short stop or anything of that sort. The only reason is, is to put less wear and on the brakes, because they are crap pads from toyota (replaced every 15-20K miles). I bet becuase the brakes are so small on the the truck that they are getting piss poor mileage on the pads. Saying that, I'm just wondering if anyone else is getting that kind of milleage on thier pads. Or is it becuase of my led foot driving.
    [/quote]

    Sammy - I'm no expert but the pads are relativelty cheap compared to a tranny problem. I wouldn't use the tranny to help with short stops just because you want to save a few bucks over the year.

    I would use the tranny on long steep grades to reduce heating effects and increase my safety factor by preventing a brake failure.

    I guess I've never gotten over that tranny rebuild on that Ford van (and it wasn't even mine). :banana:

    Riley
     
  16. cruiserman

    cruiserman

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    Front brake pad change is an annual event for me ::).
     
  17. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    Better than a motor :flipoff2:

    I think that between the 2 of us, we could have one out in about 6 hours :eek:
     
  18. IdahoDoug

    IdahoDoug

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    I'd have to recheck my maintenance log, but I get at least 35,000 out of my pads and I tow a lot in mountainous areas. For those of you with lifts, you definitely need to adjust your rear proportioning valve if you have not already. I find the brake life on this rig quite impressive though I suspect mine is performing closer to new than nearly anyone's due to strong maintenance.

    As for braking with the tranny - don't do it routinely. You're adding a tremendous amount of wear to your tranny. Far cheaper to keep your brakes at optimum and use them for stopping.

    I'll downshift while towing down mountain grades, but since this is a safety move I'm comfortable with it. Obviously Robbie's right on with the fresh fluid comments. A clean tranny is a happy tranny.

    DougM
     
  19. yomama

    yomama

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    Cdan,

    Are those 100 pads organic or are they some sort of metallic? I have the DBA's and can only use organic pads. I should probably check them this year ::)

    Yomama
     
  20. robbie

    robbie Guest

    If you do not want to rund the 100 series pads, use the 97 model year pad. This year pad gets the longest life. As for the tranny why would you think you can not down shift? the tranny shifts and does not care what gear it is in and is only told to shift by either electronics (93- current) or by mechanical means. You are also a controling factor (that is why they left the shifter). The auto just uses a wet clutch system vs a dry clutch system(manual tranny). If leaving the tranny in drive all the time you let the truck drive you, using brakes in a corner is a no no, the truck is driving you, down shift and power through the corner for better control. Auto's are nice but create a lazy not on top of conditions drivers (pet peeve), stronger overall in design then a manual(but higher in maintance), but have gotten a bad rap over the years from poor engeerneering and driver education.
    I jsut do a drain and fill, we have a machine here at the shop that I use for customers that go the distance reccomended, it works fine. I like the ease of drain and fill my self and do it at least once a year or more If I am working my truck harder (more snow or mud runs).
    I do keep forgeting not all 80 have the big bus tranny, you later model year guys may want to take it easy and not push your truck too too hard. that small (meaning little) 343 may not hold up to the highway drive most do. catch you later Robbie