Ok, i was trying to figure out why when i first brought my car, i was getting 16 MPG or so in the city. and now im getting 13 MPG. and i remembered that i reset the TV cable sometime after i got it, i actualy adjusted it quite a few times since then. but i do know the shift points are higher. it usualy shifts around 3000 rpms or so. But i remember hearing that if u set the TV cable for lower\softer shifts, then it can cause excess heat and wear on the tranny.

 

But if the engine's shift points are too low, the engine will lug and consume more gas because it's struggling.

 

Not true. The engine shift points may be low, but will not consumer more gas. Its called your foot. Sure your engine is struggling, but it is your foot that adds more gas to the equation. If you don't move your foot, engine will struggle, but more gas won't be consumed.

...Hmmm however you do need more gas in a higher gear to keep it moving, if shifting too early. Like starting off in second instead of first, you need more gas to get it moving.

So its give and take. Just shift when it is naturally time to, and when staying in one gear, like driving 30mph in 3rd, go into 4th instead, just one gear higher. Shift normally, but when staying in one gear choose the next higher one.

Whatever man, get fuel injector cleaner or something.

 

sorry but I have to agree with Iroc22 on this. you do not need more gas in a higher gear. That is why they have gears. They control the speed of the car. The engine does not. If it did, we would not need a transmission.

Engine speed and gas consumption are relative to each other. If the motor shifts too low, you are not in any power range for the engine to work effectively. Hence, bad milage.

and yes, if you shift too low you will add wear and heat to your tranny. Because it is trying to make power you are not letting your engine create. Therefore it works harder creating heat and wear.

you have to find the "happy medium." let the engine create the power and let the transmission transfer the power to make the car move. too high=rough shifts and poor milage......too low=excessive wear and heat and poor milage.

 

The V-8 models won't lug if they are running right. I too modified my TV cable for a firmer shift. In reality unless your driving habits changed it should not cause a loss of 3 mpg. TV cable adjustment controls what is referred to as overlap. Overlap occurs when the engaging and releasing gear are applied at the same time. This provides a smooth transition but generates a little more heat in the process. The cable controls the line pressure hence the shift point and firmness. A feel in your pants shift may be nice, but one drawback is drivetrain stress. I experminted a lot, driving around and playing with it as the adjustment is very fine. I finally just used the book method and left it alone. With proper care and maint the later 4L60(700r-4) boxes are averaging close to 100k depending on driving habits. It's up to you what you like, guess I am just getting old- don't want to spill the morning coffee when she shifts.

 

Higher RPM=more gas being dumped in=more gas being consumed (unless you find some magical way around this)=lower mpg.
Keep your foot out of the pedal, shift around 3500 or so and you'll naturally get better mpg than if you were to redline every gear. It's common sense...really.

 

Whoaaa , STOP.

You do not adjust the TV cable but only one way, correctly. Any other way causes improper line pressure which will destroy a tranny in time.

The only way you adjust shift points is with the governor.

 

Actually I'm sure that's quite true. I'm sure if you have a tranny shifting at 1k rpms compared to it shifting at 2500 rpms, it will be better for gas shifting at 2500 rpms. Cause like mentioned the motor hasn't reached it's powerband thus putting more of a load on the engine.

Think of it this way, say you're cruising up a mountain at 1500 rpms and you have your foot real far on the gas just to make it up. But if you put it in drive and the motor is around 2000 rpms then the motor is closer to it's peak power thus making it less of a load on the engine.

This is just an example though.

 

That's why an automatic has a torque converter and the stock eproms don' t lock it until 40 mph - to prevent lugging so you can stay in hgher gear (than if it was a standard).

For standards, you are correct. But automatics are different because of the torque converer and the locking speeds.

 

True, but not all of us have stock parts. My tranny for instance will stay in OD at full throttle, so I have to shift into D so it won't struggle when I go up to college in the mountains.

Or am I still missing the point of the convertor. I was told by transfixleo, if going up a steep incline below like 2k rpms or so to shift into D so the tranny won't have a strain on it.

 

what I rmemeber hearing is shifting low is good.. as long as you are not lugging the motor

but also it is better to use about 3/4 throttle rathen ***** foot it

only reason I can understand that is when the throttle is open there is less pumping loss in the motor. the throttle plates cause a restriction

not sure if that is the best explanation but I know on my car

shifting around 2500rpms at 3/4 throttle I gained about 3-4 mpg city driving then if I just ease the throttle

 

Mark, I would strongly disagree with that statement. Any transmission technician familiar with the 4L60 will "fine tune" the TV cable for shifting depending on customer request. The method of depressing the pedal until it self adjusts results in a very smooth shift with a fair amount of overlap in the first-second change. The governor acts in conjunction with line pressure to control shifting point and firmness. Fine tuning of the TV cable will result in a nice 1-2 shift with a minimum of overlap which in and of itself will shorten transmission life. If you want to see it in print I would refer you to a Haynes manual #10360, chapter 3 which refers to the act of fine tuning the TV cable. We are not talking about large changes, in reality the adjustment is a very fine one and takes a little driving around to get it right. The governor itself only provides the range at which a shift occurs, not the exact point. The shift point is altered by the TV cable position which also controls line pressure. Fact is that line pressure is constantly changing in an auto trans, much more radically than the hair or so change in the TV's base setting. For more info check www.technicalevolution.com/tv.htm

 

wow, i didn't expect this many replies for this!! Thanks Danno for all ur info. And of course mark, and everone else.. I think i'll go with the transfixleos method.. that is if i can get my tv cable to adjust properly..

 

I'm in the lower shift points = better mileage camp. Let me explain my reasoning:

(This applies to a carburated stick-shift, but I imagine that other configurations will be similar).

There are only three ways that fuel can enter the engine:
-When the throttle is depressed and the squirter fires
-At idle through the idle circuit
-Through the main venturis

In the case of the second two, the amount of fuel drawn increase as (manifold/venturi) vacuum increases. Both vacuum's increase as engine rpm increases. It follows that this engine will always use less fuel per time at a lower rpm. If you can maintain the same vehicle speed at a lower rpm, you will use less fuel per mile.

As far as I know, when the engine is lugging it is not using more fuel per revolution; it is however under a lot more stress.

 

Lower shift points won't always equal better mileage, just like a lower cruise rpm down the highway doesn't mean you will get better mileage. It's all about efficiency. Purely as an example, an engine 80+ % efficient from 1000rpm to 4000rpm. Below that mileage will suffer as well as above that. The best rpm to be at for mileage will be the lowest rpm the engine will operate at efficiently. Some of the cam companies advertise rpm powerband and suggested 'cruise' rpm. Below that cruise rpm the engine becomes inefficient(valve overlap can cause this) and the engine will run poorly(poor mileage). It a stock engine the lowest efficient rpm is very low, you probably don't have to worry much about going below it unless you really, really lug the engine. But, cruising down the highway at the low rpm to get the mileage is wasted, if you must kick down a gear or unlock the converter to pass someone or when pulling hills. As far as shift points changing mileage, you would have to severly change the shift points to alter mileage a noticeable amount.

 

NO, any real tranny mechanic will only adjust the TV but ONE way, and that is the correct way. Just PM transfixleo or probuiltautomatics. Go ahead and destroy your tranny, I'm not payin for the rebuild.

 

You don't think there are tolerances to be considered. The cable doesn't change with time. I don't want to get into a pissing contest with the experts, but any expert will concur that the best shift is the one that provides the minimum overlap with least strain on the drivetrain. If that requires a hair or two adjustment that is beneficial. I agree one should not use it to compensate for a properly installed shift kit. By the way, nobody here is asking for you to buy a box but I'll send you a book on automatics free of charge.

 

i'm sorry but like u guys are all kinda getting sidetracked. the only way to get better gas mileage in these cars is to not drive them. at all. i think the f-body is one of maybe 4 or 5 cars in the world where the fuel gauge drop : speedometer climb is the same ratio as your engine's compression - 10.5:1

no disrespect guys i;m just kidding around. i would say try and let your car idle itself along down the road and shift @ about 3000-3500 ... my l98 would keep me rolling down the highway at 75 with almost no pressure on the pedal in OD and it'd only be rolling 2700-3000 rpm's

 

The key factor is not how efficiently the engine is using the fuel that is put through it, but rather how much fuel enters the engine. Unless an engine is sucking in more fuel at lower RPM's, a lower RPM will always yield a lower rate of fuel usage.

An engine may run more efficiently (in terms of energy output per gallon of fuel) but if you can't use that energy than it will be wasted. Suppose your engine when running most efficiently is at 3500 rpm and producing 180 hp. If you only need 80 hp to keep your car moving, you're probably not getting the best fuel mileage.