Archives >> Power Strokes 1999-Up (11/99-12/99)

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DU302
Member
Member # 3389
Reged: 10/19/99
Posts: 29
Loc: Pittsburgh, PA
Downshifting an automatic
#159138 - 12/19/99 12:12 AM

I need some help to settle an argument. Is it harmful to downshift an auto tranny in such a situation as cruising down a steep grade in an attempt to go easier on the brakes? I don't see why it would be harmful, except to gas mileage maybe, but can it be bad otherwise?

Thanks,
Mike

Diesel Don
Member
Member # 3793
Reged: 11/14/99
Posts: 275
Loc: Vancouver Island BC Canada
Re: Downshifting an automatic new
#159139 - 12/19/99 12:34 AM

Du302 It is only harmful to downshift your auto trans if it over revs your motor. The governor protects the motor from over revs
if you have your foot into the throttle but when you downshift, you must make sure your speed is not too high for the gear you are dropping into. Educate yourself on this by watching your tac while keeping the truck in
first and second gears.

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Y2K F-350 XLT 4X4 CC SRW short box,PSD. Wedgewood blue and silver & most of the bells and whistles



Richard T Rasmussen
Member
Member # 1274
Reged: 05/12/99
Posts: 568
Loc: Castle Rock Co USA
Re: Downshifting an automatic new
#159140 - 12/19/99 02:50 AM

I've been down shifting automatic transmissions on Ford products since my '73 Bronco-never have seen a reason not to.I down shift every down hill(pass)when towing.
Rich

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'99 F-350 Crew DRW PSD Auto Manual-hub 4x4 Lariat BrightAmber Two tone(Prairie Tan), Leather ,Loaded
Ultimate bed liner,Warn Trans4mer,catless with ATS 4" cat back,A-pillar w/pyro-engine,trans temp,boost in dash,Pac Brake,Adopted in Colorado,June '98 **ATS chipped 10/99**




Wayne B
Member
Member # 103
Reged: 04/01/99
Posts: 3489
Loc: Ashburn, Va. USA
Re: Downshifting an automatic new
#159141 - 12/19/99 11:44 AM

The basic rule is go down in the gear you came up in. Do not down shift just to slow down like you would in a manual. Down shift to hold speed. Replacing brakes is cheaper than replacing trans.

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2000 F-250SD XLT PSD 4X4 ESOF Auto, SC, LB, Camper Pkg,Tow Pkg,LSD,4 Wheel ABS
Cab Lights, Pwr Seat, Pwr TT Mirrors, Cab Steps, 265X75X16, PTO Provision, Idle Control, 40/20/40 Seat.
Bright Clear Coat Red, Graphit Int.
Born 7-30 Delivered to dealer 8-16, Then to me on Aug. 17th.
Wayne Bradish
Ashburn, Va.
Home To Redskins Park!




DU302
Member
Member # 3389
Reged: 10/19/99
Posts: 29
Loc: Pittsburgh, PA
Re: Downshifting an automatic new
#159142 - 12/19/99 11:52 AM

So it can be hard on the tranny? I don't drive an automatic and never will unless I have to, but my buddy tells me that doing this will kill the tranny and drivetrain in general. Neither of us are anything close to mechanics, but we know some stuff. So what you're saying is that it is not good to downshift on a steep grade, with no load or trailer, in order to use the brakes less?? I really never thought it was harmful.

Thanks for the help!
Mike

gefaell
Member
Member # 3570
Reged: 10/31/99
Posts: 50
Loc: Silicon Valley, California. USA
Re: Downshifting an automatic new
#159143 - 12/20/99 12:08 AM

Consider RTFM. Reading The Ford Manual.

Seriously, in the owners guide/manual it is all spelled out clearly and explicitly with an accompanying chart to make it even less confusing.

In short, as mentioned earlier there are limits where you can shift. Brake to within those limits and shift.

Also we learned here (ford-diesel.com) that the cruise control locks (unlocks?) the TC and provides additional braking. Certainly does work.

After learning these things and using them I don't think I'll ever need an exhaust brake.


Glenn
Member
Member # 739
Reged: 04/15/99
Posts: 144
Loc: Harpers Ferry, WV, USA
Re: Downshifting an automatic new
#159144 - 12/19/99 06:56 PM

I have never actually used the shift selector in my automatic (4R100) to downshift but there have been times when I've kicked the O/D OFF to drop down a gear. I usually only do it when I know that there is a definite stop awaiting me at the bottom of the hill.

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See my truck FOR SALE at : http://www.classifieds2000.com/cgi-cls/ad.exe?P61+C15+R138956
*************************
Glenn Smith
99.5 F-250XLT,4WD,RC,Auto, 3.73 LS
Deep Wedgewood Blue W/Blue Denim Interior




Eric Shaunfield
Member
Member # 4214
Reged: 12/09/99
Posts: 287
Loc: Reagan, TX
Re: Downshifting an automatic new
#159145 - 12/20/99 05:05 PM

Downshifting an automatic is becoming a complicated thing. Older transmissions that were not computer controlled use a valve body to control gear shifting, newer transmissions usually use a computerized valve body. This means the shifters on most newer cars just relay info to the computer, they don't actually select the gears. I don't know if this is the case with the new ford PSD. If it is then you can downshift as long as you aren't going to over-rev your engine and the comp. will do the rest. If you do this in with an older transmission you can burn up the front pump or wear the pressure plates or clutch packs. Read the manual and follow its instructions, that way if you burn up a transmission you can tell ford to fix it. Whaterver the situation try to downshift as little as possible, if you are in a hilly area leave it in third, less "hunting" by the transmission and better engine braking.


JBird
Member
Member # 356
Reged: 04/04/99
Posts: 112
Loc: Northfield, MI USA
Re: Downshifting an automatic new
#159146 - 12/20/99 09:52 PM

Downshifting manually will have absolutely no ill effect on the powertrain. The transmission is fully capable of downshifting as well as it upshifts, that's what the gear selector positions are for. You can't overrev the engine by manually downshifting. Try it. In a safe area, go about 50mph and throw it down into "manual 1." The trans will shift into second, then at a safe speed, first (hang on, there's lots of compression braking ) This does no more damage to the trans than an upshift. And while it's true that these transmissions are electronically controlled, they still have plenty of springs and valves in their valve bodies to provide redundant, manual shifting. This allows for a "failure mode" in the event of an electronics malfunction.

Bob Riley
Sponsor
Member # 4125
Reged: 12/03/99
Posts: 7400
Loc: Sebring, Florida
Re: Downshifting an automatic new
#159147 - 12/20/99 10:25 PM

Jbird is correct, they will not over rev. Like he said, hang on, the truck will lock the tires to keep rpm's from over reving. I tow thru mountains sveral times a year. If you do not practice engine breaking , you will not have trailer brakes at the bottom of the hill. Electric trailer brakes overheat, it has nothing to do with cost of pads. I have learned this the hard way one time and almost lost the rig when I couldn't stop at about65mph down a 30 degree grade. The trailer had no brakes till several hours from then.
Bob

2106
Member
Member # 1945
Reged: 07/01/99
Posts: 361
Loc: Maryland - USA
Re: Downshifting an automatic new
#159148 - 12/21/99 11:41 AM

Gefaell,
So, if as I top the hill, I slow down to 40mph and set the cruise control to 40 mph It will hold me there if I don't touch the brakes with trailer in tow?

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99.5 F250 PSD XLT CC SB 2WD 3.73TL 4R100 Camper/Trailer Pkgs. Tires-265 Build 5-20-99



spepin
Member
Member # 8991
Reged: 10/23/00
Posts: 1489
Loc: Castaic, Ca.
Re: Downshifting an automatic new
#159149 - 12/22/99 12:24 AM

Glenn, you say you turn O/D off to drop down a gear when approaching a stop. In my 99.5, turning O/D off unlocks the TC thereby eliminating most of the engine braking. I must leave O/D on to get any kind of braking effect. Does your TC stay locked while out of O/D?

K1VVT
Member
Member # 3189
Reged: 10/04/99
Posts: 438
Loc: Hope, ME, USA
Re: Downshifting an automatic new
#159150 - 12/22/99 12:37 AM

In a 1988 auto HD 250 I hauled a 8K+ 5th since '92 and used the transmission for braking most of the time, also with a tractor in tow other times, no ill effects at all.

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00 SD250 LB 4X4 7.3 ,3.73,auto, ext cab, Harvest Gold/Black Lariet, TT
ordered 9/14 build 10/18
on Rail 10/20, on the road 11/05



TEX
Member
Member # 3799
Reged: 11/14/99
Posts: 101
Loc: Frankfort, Ky.,USA
Re: Downshifting an automatic new
#159151 - 12/21/99 01:09 PM

Only tried once to downshift my rig while towing my 5th wheel and it certainly did pass the red line don't know how long it would have stayed there as i put it back in 4th. Since then I know I can downshift, within limits,and plan to do it when I can.

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99.5 F250 SD XLT 4x2 PSD SC LB, Auto, 3.73LS, Dark Toreador Red.


johnmModerator
Administrator
Member # 199
Reged: 04/02/99
Posts: 2110
Loc: Las Vegas, Nevada
Re: Downshifting an automatic new
#159152 - 12/21/99 01:26 PM

spepin
If you're sending someone some styrofoam, what do you pack it in? A box, of course.

Now to the subject. The transmission is supposed to provide some engine braking. That is what I had mine into the shop for. When it was taken out of O/D, the engine used to drop to idle RPM. If yours is doind that, the trans has a broken or wrong pump in it. Mine was replaced and the trans now shifts properly. I take it out of O/D at 65+ and it slows down to about 50 and then I pull it into second and it will slow to about 25-30 before the converter unlocks. If I pull it into first, (not over 35 MPH) it will slow to about 15 before the converter unlocks. I do this on a regular basis with my travel trailer in tow. According to the trans and engine tech at the dealer that repaired it properly, that is the norm. Again, caution and prudence are in order. If you are going 85 downhill with a 20K trailer behind and you pull it into second, expect a loud noise and a few expensive problems.

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John Morrissey johnm@me.unlv.edu
99.5 White F250 XLT SuperCab, PSD, 20,500 miles, LWB, 2WD, 4R100, 3.73-LS, 4W-ABS, TT & CMPR Pkg, pillar Boost and Pyro, 265/75-16's, Born 02/11/99, Above Cab Topper, FMC Cab Steps & Mud Flaps.
http://albums.photopoint.com/j/AlbumList?u=167679

wms
Member
Member # 504
Reged: 04/07/99
Posts: 185
Re: Downshifting an automatic new
#159153 - 12/21/99 01:49 PM

gefaell states: "Also we learned here (thedieselstop.com) that the cruise control locks (unlocks?) the TC and provides additional braking. Certainly does work." gefaell, Can you please run this past us again?

Am I understanding that if you, for example set the cruse control to maintain say 20MPH, then when you want to slow down from say 60,
push (set) the cruise control button, and the TC stays locked up, slowing you down with the engine? My 2K seems to unlock and sort of freewheels.



gefaell
Member
Member # 3570
Reged: 10/31/99
Posts: 50
Loc: Silicon Valley, California. USA
Re: Downshifting an automatic new
#159154 - 12/21/99 02:25 PM

No No!

What I've been doing is that I START the downhill in Cruise Control, say at 60MPH. The truck pretty much doesn't go faster than 65MPH.

From what I've read here, having the CC on locks (or unlocks?) the TC. This is what keeps the speed down.

Also, downshifting to an appropriate gear for the speed range you desire is part of this.

PRIOR to exceeding the speed, not after. i.e. this seems to keep my speed from going up, I don't use it to slow down.


wms
Member
Member # 504
Reged: 04/07/99
Posts: 185
Re: Downshifting an automatic new
#159155 - 12/21/99 02:45 PM

Thanks gefaell, this is sort of complicated to describe in words. By having the cc "on" do you mean the steering wheel button engaged? When the brake peddle is hit the CC disengages, but the master cc button is still on. Does this master cc button when on
delay the unlocking of the cc? This is an important topic, as I am looking for a way to assist the truck when slowing down with my 11K fifth wheel. Please don't anyone mention an exaust brake!

bj
Member
Member # 443
Reged: 04/06/99
Posts: 121
Loc: Mesa Az 85202
Re: Downshifting an automatic new
#159156 - 12/24/99 12:59 AM

Gefaell,
is seems to me what you're saying is that:

having the cruise control engaged somehow makes the truck maintain a slower speed downhill more effectively that if the cuise control is off, even in OD...

Is this what you're saying?

If so, I don't recall this conclusion being stated before. I'll do some searching but I don't have the time right now. I don't know the answer but this doesn't sound correct to me. Does everyone else agree with this?

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99.5 F350 SC Lariat, LWB/SRW, 4x4, Man hubs, ABS, auto, CD,3 guage A pillar
Trailer/camper/off road, Ltd. slip, Ord 1/99, Built&Delivered 4/99
Pulling '99 Sunnybrook 30RLFS(7100 lbs. dry), Inyati liner, Donated 2/99


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