Question about overdrive transmissions..

MacLeod

I still wouldnt tow in overdrive mainly because if youre tugging a 6000 pound trailer behind you chances are youre rig's going to be shifting in and out of OD everytime you encounter even the slightest grade and this constant shifting in and out aint good for the tranny.

I tried it the last time I moved from Texas. I had my beloved Dodge loaded way down and had a big computer desk that stuck up 4 feet over the top of the truck to catch all kinds of wind. Needless to say she was in and out of OD constantly so I finally droped it out of OD and drove the rest of the way in 3rd running 62 mph.

HiPerf360

Do as you wish...

I have done very little towing with a 1/2 ton truck.

But with my one ton trucks i dont do a lot of downshifting until there is over 10-12,000 pounds behind it.

I pulled my boat a few miles with my wife's Denali and it was a little too much for it. (345hp)

Red230SX

FWIW,

My Hemi (345) yanks my boat around no sweat.. But that's only 5200Lbs (It's rated
for a max of 9200).

And I take it out of OD that is what the manufacturer says to do. I am not arguing
with them.. At least not on an automatic tranny powered by pixie dust...

VR3

If you were driving in the City, would is be better to put the truck in the regular drive instead of overdrive and when you plan to drive on the interstate, put it in overdrive?

audiobliss

Nah, I don't think so. In the city, it probably wouldn't even engage all that often; should be ok, I'd think...but I don't know for sure.

audiobliss

HiPerf360 wrote:

As you can see this gets very technical quite quickly so I could type all night.

I wish you would whenever you have the time. I really enjoy raeding about this sstuff and don't know much about it, so the more you tell the more I'd appreciate it.

neomagus00

audiobliss wrote:

I wish you would whenever you have the time. I really enjoy raeding about this sstuff and don't know much about it, so the more you tell the more I'd appreciate it.

ditto... i like knowing techical stuff...

if you don't want to type, a link would be cool, too...

MacLeod

Vr3MxStyler2k3 wrote:

If you were driving in the City, would is be better to put the truck in the regular drive instead of overdrive and when you plan to drive on the interstate, put it in overdrive?

Well it couldnt hurt. Switching out of OD keeps the tranny from shifting that extra time which saves wear and tear on the tranny, although I cant say how much. However, while driving around town you may not get up enough speed to hit OD anyway.

VR3

Actually...

I more so meant the highway more than the city... since the speed limit is 45 - but there are alot of stop lights...

So... Hmm...

Can you switch into OD from regular D while driving or do you have to stop?

Same question for the front and rear tank - while driving or do you have to stop to switch..?

Thanks..

MacLeod

You can switch OD on or off while driving.

I would leave it on for highway driving as 45 is plenty fast enough for OD to be used.

VR3

What about the tanks? Can i switch between tanks while driving if need be?

Thanks - sorry for all the questions.

audiobliss

I don't see why in the world you couldn't.

HiPerf360

Put your transmission in OD, let it do the shifting for you.

Why try to out smart something if you don’t completely understand how it works?

VR3

Well the reason why I ask...

If putting it in overdrive and I get up to 35-40 mph, and i have to let up on the gas - it will shift into OD --- but then I am still slowing down due to the light, so now it is downshifting all over again...

Is this bad for the OD? I would personally like to use OD as it keeps the RPM down and it saves gas... but I dont want to wear out my vehicles because of it either.

neomagus00

well, you shouldn't be going from acceleration to braking anyways... driving more gently will conserve more fuel, and cause less wear and tear... just gently lift off the gas to allow maybe 3 seconds of drifting before you need to begin braking...

VR3

Thats how I drive anyways... Im just trying to figure out the whole premise...

Sounds like as long as I continue to drive the way I do - then I wouldnt have any issues...

Hmm - Thanks, again, as always hehe

PoweredByDodge

Jesus H. Christ...

I go away for like, what, a day, and you people get in trouble. God, I need a backup me to fill in when I'm drunk or chasin girls.

Sid, welcome to automotive hell. Have a set, you're gonna be here a while. Probably for the rest of your life. No matter what vehicle you own, it's going to suck at something... it's just a matter of at "what", and how much it bugs you.

First, lets dispell some myths...

---

1- The poster who stated "do not disengage your lockup feature" (for the torque converter) is absolutely 100% CORRECT. Some older trannies did not have lockup torqueconverters, namely my favorite A-727 torqueflite and the rest of the load-flite family did not get lockups until later in life. However, their life expectancies were markedly shorter back then (a torqueflite will outlast anything, including the Ford C4 which is another adaptation of hte same Simpson gear set, but even it could be killed evenutally).

Lockup TQ's prevent slippage at high speeds and under high torque/stress. They're "good stuff". There's only one time to disable that feature, but you're tranny isn't dead just yet and you dont' need to shift 1 / 2 / 3 / R manually so that you can drive it to a repair shop -- so leave it alone.

And FYI - I believe - i'm not sure, but i believe - that hydraulic valve body trannies don't have lockup torque converters, because the lockup is an electrical circuit only present on electronic valve body trannies... dont' take that to the bank though.

2 - Everybody (not you guys, just some hack mechanics in general - i'm no pro, but i hate hacks that pretend to be pro's) think that you can "outfox" an OD tranny by leaving it in D instead of OD. Well news flash - I'd rather have a 508 (overdrive 727) than a 727 any day... but they're more money. Overdrive is good stuff -- final gear ratio of 0.65 to 1 versus 1 to 1 gives you greatly improved fuel economy. If you have to put the truck in D to stop "bad noises" or keep it from jumping into OD, then all you're doing is stopping it from jumping from the 3rd gear to the 4th... which would be a temporary solution if 4th gear was stripped or otherwise jacked up. That's not the case here, or at least it doesn't seem to be.

3- 20 year old automatics are nothing like today's automatics. Hard shifting and "noises" from transmissions were common. You don't have the sound deadening that modern cars do. You also don't have the **** **** problems that modern cars do either. One of the finest transmissions ever made, albeit a stick, was the Mucie Rock Crusher... and no not every muncie was a rock crusher, so leave that one alone... the Rock Crusher (circa 1960's) had a gear set that lined up almost straight, with no angle to the teeth, this created one HELL of a CHATTER going down the road. It sounded like you were - literally - crushing rocks... hence the name. If operated properly... there was no difference in wear between a rock crusher and standard muncie... and while I'd kill to have one fall in my lap, there are a lot of ppl who would hear a muncie chatter at a car show and say under their breath, "did you hear that guy's piece of **** tranny?".

And onto the show.

---

1- How a tranny shifts (automatics): Shifting is hydraulically regulated (hydraulic valve body - wink wink) or electronically assited hydraulic shifting (electronic valve body on NEWER cars). You're dealing with the former, and easier to deal with of the 2.

With an electronic deal... you've got speed sensors, the computer, tach monitor, blah blah blah, my left ****... and then the computer decides shift points... but, all its doing is mimicing a straight up hydraulic valve body tranny which is just this.......

You've got an input shaft... from the motor to the tranny. Then you have an output shaft from the tranny to the drive shaft... When you're driving on level ground, like an old lady, the RPM of the input shaft (engine) is close to the RPM of the output shaft (wheels) with respect to the gear reduction of whatever gear you're in. So what happens? Light hydraulic pressure (speaking relatively... it's enough to jack up a bus, but compared to what it is under other conditions, its light) ... the valve body interprets this and you get smooth easy shifting at LOW speeds. For example... 1 to 2 happens at say 15 mph... and 2 to 3 at 25 mph... and 3 to 4 (OD) at 35 mph.

But you stab that **** pedal and you've got a high rpm at the input shaft(motor) compared to a very low rpm (possibly even zero when you first hit it) at the output shaft (wheels), and this results in very high hydraulic pressure inside the valve body and tranny itself. This pressure keeps the individual gears locked in place longer... or i should say until the gear can overcome the force of the high pressure to kick itself out and allow the next gear to be activated.

This is the only way it can be... you've got a stick lets say -- and you want to take off real quick... well you throw it in first, stab the gas, and VROOM till you're at 25 miles an hour and 4,000 rpm... then you drop it in second and you're at 40 mph and 5000 rpm before you shift to third.... well you eat gas, eat tires, and go fast... you wanna be conservative - you shift at 10 mph out of first, at just arount 1500 rpm... then you shift outa second at 20 and 1500 -1700 rpm.... etc etc...

The automatic is just trying to do what you would be doing... when you are on the gas and going 35 mph, it's going to stay in 3rd.

It thinks you want to speed up.

It's not psychic ... it's a piece of machinery --- it may love you back some day, but it won't read your mind.

My 99 ram was a piece of work... you could chirp the tires while driving if you nailed the gas at the right time between 2nd and 3rd. normally that doesn't happen with automatics, but it was exceptionally stiff (in a good way). Most people don't know this, but an automatic that engages and shifts very hard and crisp is actually healthier for the vehicle and hte tranny... thats why TransGo makes those shift kits for automatics. Manufacturers sometimes make their trannies "extra loose" or soft shifting not because its better but only because the customer says that they want a smooth ride and the customer has complained in the past that the tranny "is making funny noises and jerking me around a bit so i thinkits broken" --- its not **** broken... its fine... leave it alone... go get a moped with a fat chick on the back.

So, what do you do?

Well... you are getting going and you want to get to 40 mph... so you pass that 35 sweet spot and ease off the throttle a little and she'll slip on into 4th gear just like she'll slip on into any other gear after the previous gear's sweet spot... OD is just another gear dude...

But lets say you want to go at specifically 35... and you're sweet spot is 35 (i had to deal with this myself)... well if you get to 35 and stay at 35, it may "fake stick" in 3rd... by fake stick i mean that its not sticking, there's nothing wrong with it, it just hasn't crossed the threshhold yet... you deal with that by gassing up to 37 and then letting off... that extra mile an hour or two isn't gonna get you a ticket, and after you're in 4th gear you can let it ease down to even as low as 30 (generally) and still be in 4th.


Is [insert anything] bad for the Overdrive ??

The answer is neither yes or no -- rather, it's another question... "Is that activity or whatever you wanna call it something that would hurt any other gear? If it would, then ya, it'll hurt 4th gear, OD. If no... then no it won't hurt OD..." -- OD's just 4th gear dude. On a 5 speed automatic... 0.85 is the 4th gear --- and 0.65 (just fer example) is the second....

all OD means is this...

Gear

---

name

1

---

first drive @ lets say 2.5 ratio
2

---

second drive @ lets say 1.5 ratio
3

---

third drive @ 1 to 1 ratio
4

---

fourth gear -- but its at 0.65 to 1... which is "over" 1 to 1... so its "OVER" drive. get it?

Try the whole 35 mph sweet spot deal and let me know how it turns out for you.. also try accelerating like an old lady - then like a normal person - then like a bat out of hell... and write back with your description of the shift speed and shift rpm for each (just ballpark it - dont go lookin at the gauge and crashin your truck). Do this on flat road under dry conditions... It'll shift different on a hill going up or down to compensate for load and what not -- but that's just operating off of the pressure idea i talked about earlier.

As far as the previous owner stating it shifted funny or didn't or whatever --- many drivers never get used to the shift to OD. When you shift from 1 to 2, you're engine rpm's drop momentarily, but its only a little... then 2 to 3.. . they drop but still not a lot... you're still revvin like a **** to keep movin quick... 3 to 4 or 4 to 5 and you start to get this real soft shift and the rpms go way down and it almost feels like the truck is losing power... well ya... that's what its supposed to do... conservation of energy... you wanna use less gas by using a higher gear... cool... well the only way to use less gas it to put out less power by revving hte engine slower. I can go 45 mph with my 2003 in 5th gear and it's just a hair above 1,000 rpm... you'd think it was gonna stall.... and it feels like a pig on wheels.... but i pinch an assload of fuel economy outa it --- until i get nuts and decide to do burnouts.

I wanna know more about your situatioin dude... I don't think you have a problem... honestly I don't, but I would like some more info to be more sure... I've given you some tidbits to go by - use it when judging how your truck shifts and get back to me.

audiobliss

^^ Awesome post.

neomagus00

very much ditto ^^