Over-riding auto transmissions...

There are certainly various chips and programmers that can adjust the programmed shift points. I've not looked at automatics extensively since I don't have one and generally hate them, but I know there are various manual valve body kits for racing that give you something similar to a clutchless manual.

I suspect the current autos are largely solenoid valves to operate the hydraulic apply bands and of course the torque converter clutch solenoid for TCC lockup. Probably still a little hydraulic pressure related stuff in the lower gears, since the manual race kits include a new valve body this makes sense.

Pete C.

So it would seem that if I could find these wires, I could manually select gears in an automatic transmission. Would a workshop/svc manual show these? Would the dealer know? I have found that dealers either don't know, or are not willing to tell.

---------------------------- Mr. P.V.'d formerly Droll Troll

How exactly is that gonna work? Wouldn't you still need a front pump to 'power' the apply devices within the trans?

If so, doesn't that tend to eliminate the whole advantage of a manual transmission? I.E. the manual trans is a direct gear interface, as opposed to planetary gearsets (which require apply devices to make different gear ranges, )

-LMB

Probably I have missed the point of the question but with an auto transmission you can manually select the gear with the shift lever.

electrically

Never going to work that way. It will fry the transmission and the computer really fast. Plus as soon as that trans tries to make a shift and cannot it is going to set a LOT of codes and probably default to first gear and limp mode.

I can 100% guarantee you will NOT fry the computer by taking away it's control of the transmission valves. It may not be happy, but it's not going to damage it in any way (unless you short something when you make the mod).

It's pretty unlikely that the computer would put the engine in "limp" mode for what it thinks is a transmission problem. Trouble codes would be set certainly. As for defaulting to first gear, the computer might try to put the transmission in first, but if you've taken control of the transmission from it then the transmission will be in whatever gear you put it in.

As for frying the transmission that would depend on how you are driving it. As long as you keep the RPM/speed in an appropriate range for the gear you put the transmission in there is very little chance of doing any damage.

As I mentioned earlier, I don't think most current transmissions are

100% computer control, the few that I've seen in the manuals seem to have computer control on the upper gears, but seem to have the older hydraulic stuff for the lower gears. I say thins based on the fact that the ones I've looked at still seem to have a fair amount of the maze of passages with check balls which would not be needed in a 100% computer controlled design.

Pete C.

Not the ones I've seen. On some you can lock out overdrive, which seems to work, but the 1, 2 type selections may delay the shift points, but every auto I've tried them on will still shift to a higher gear if you push it hard.

Pete C.

Rather sounds like the hydraulic shuttle transmissions on backhoes and whatnot. And yes, it would defeat nearly all of the benefits of a conventional manual such as lighter weight and higher reliability.

Pete C.

My experience is a heavy right foot is the major contributor to poor(er) mileage.

Most automatics shift up fairly soon under light throttle. I'd be surprised if you could get significantly better MPG by controlling the shift points (as opposed to using light throttle)

At constant speed vehicles get their best MPG.

It's under acceleration that the most gas gets swilled.

• Jumping off the line

• roaring to the next red light (in town that would be a stop light; on the highway that would be stopped/slowed traffic)

• going fast as long as possible then jamming on the breaks (ie: not coasting whenever possible) (yeah you get there sooner but just to wait at idle longer)

On the freeway wind drag from racks, etc. lower the MPG.

Carrying excess weight requires more power to accelerate.

Using cruise control on the highway increases MPG.

Oh yeah, besides saving gas driving gently saves brakes, tires, the engine, the drive train. All this and it doesn't require any installation or up front money.

It really just requires a change of mindset.

Good luck.

extensively

similar to

manually

Happens all the time on Chryslers. The PCM decides that the computer and transmission info doesn't match and puts the vehicle into limp mode.

driving

Try it sometime. The OP is asking about locking the trans in a higher gear as well as OD. Then he plans on lugging it to get better mileage. Ever seen how hot a trans gets when it is in OD and is lugged? Ask people who tow what happens to a trans when you don't kick it out of OD with a load. Fried trans is common.

Those are required even with computer control. They just put selenoids in places to control fluid flow instead of mechanical linkage.

Most automatics let you limit the highest gear that they will shift into (e.g. to get engine braking down a hill), but not force an upshift.

The simplest solution for the original poster may be to sell the vehicle and buy one with a manual transmission.

Very difficult to do I would think since the transmission is on many cars tied into the ECU.

Well, you can do that to a point with your car right now...D-3-2 or whatever sequence your car has will hold gears. If you really feel the need to be able to push the car into gear at will then get a car with one of the geartronic or tiptronic shifter interfaces. In my experience they are fun for a little while, but todays automatic transmissions are pretty darned smart when it comes to extracting the best milage.

Most new cars are programmed to maximize milage, or they have selectable modes like economy, sport and racing that bring different shift curves into play. I doubt that forcing upshifts will improve much on what your car is capable of. In-fact my experience is that most people who drive using the tiptronic shifters or a full manual transmission don't really know how to maximize milage. They hold speeds in lower gears way too long.

Try the simple solution first...slow down and treat the gas pedal as though there was an egg under it.

People drive Chryslers? Well, I suppose if you drive an automatic...

I don't have anything with an automatic, I rather hate automatics. Part a control thing, part reliability and part their piss poor performance compared to a decent manual.

As for toasting the trans, again if you're not abusing it by overloading or operating at unsuitable RPMs it should do just fine. I don't recall the OP mentioning towing with it locked in OD. If the appropriate apply bands are activated with proper hydraulic pressure (so they don't slip) and the TCC clutch is locked then there should be no excessive heat generation.

Definitely not. If it's 100% computer control of all gears, all that is required is the hydraulic pump, solenoid valves and the apply servos (hydraulic cylinders).

Pete C.

The last statement above can be analyzed even further as I agree totally with Brian. Any time you have built up speed and then use the brakes to slow it down(as opposed to allowing it to coast to a stop) you are directly destroying the energy(and fuel) that was required to reach that faster speed in the first place--using energy to get going and then using a different energy to 'kill' it. WASTING fuel via brakes is possibly a quite-overlooked phenomenon. Save your brakes AND save your fuel simultaneously. Over the years, a general rule showed itself in our businesses: those customers who seldom required brake replacement seemed to also obtain the better fuel mileage. s

So does this mean I *can* put a suitable switch on suitable wires?? How many switches? Do I have to de-activate/lock stuff out, as well as energize other stuff? Seems like if the shift handle can drop down a gear w/ no problem, I should be able to go up one just as easily.

My recommendation if you really want manual control is to look into one of the racing manual kits for an auto transmission. Probably look at Summit Racing for some options, I think B&M is one of the manufacturers.

As I noted, I don't think most current autos are really 100% computer control which means by just taking control of the solenoid valves you probably will only have control of the top two gears. The race kits have a new valve body, operating handle and linkages to give you full manual control. They are a solution that is guaranteed to work, assuming they are available for your particular transmission.

Pete C.

Unless you have a hybrid or electric vehicle of some sort, it doesn't matter how you reduce the speed, you are still loosing the energy. The people who seldom require brake replacement get better mileage because they watch for the traffic lights ahead and more often synchronize with them so they avoid coming to a stop.

The vast majority of the gas you use is in getting up to speed from a stop, and coasting down some distance back from the light so the light changes before you get there vs. racing up and stopping means the difference between accelerating back to cruising speed from 0 MPH or perhaps 25 MPH. Getting from 0 MPH - 50 MPH takes more energy (gas) than getting from 25 MPH - 50 MPH.

Pete C.