I was checking out Allison's website, and found a very interesting PDF...

I was really surprised that you could actually control EVERY gear like in a manual transmission. That is way cool...

I wonder when Ford is going to introduce something like manu-matic type auto in their trucks?! That's the whole reason I bought a manual because of the "control"...

Anyhow here it is for your reading...

http://www.allisontransmission.com/s...t=SA5521EN.pdf

 

Isn't that a fancy way of replacing the original PRND321?

Chevy has PRNM X where X is the gear you select with the +/- button. It still shifts automatically from 1-3 if you select 3rd gear.

It looks like you can manually select 4th and 5th gears though which would be nice I guess, still not sure how useful that would even be when towing heavy at highway speeds though.

 

I would like to stay in 4th or 5th as a "forced" gear to save fuel... There a lot of times when even the most sophisticated automatics still search go in and out of the drive and over drive modes... which wastes gas. I dunno how many times, I've driven an automatic where I knew there was plenty of torque and hp being applied, but still dropped a gear or sometimes two wasting gas for no reason.

So technically it really isn't like a replacement to PRND321, because you can only "force" the truck to stay in 3rd, 2nd, and 1st... where as on the Allison you can "force" it to stay in 4th and 5th as well.

I don't know how many times people have told me that they hate their auto because they know that it doesn't have to drop a gear to go up a very slight incline which resultes in a waste of fuel.

Which I do have a real life experience, to get home there is this one very long hill on the highway and I generally need only 4th if I don't get a good running start, but I can usually stay in 5th the entire way up. Most F150's drop into 3rd, but mostly 2nd and the engine is doing nothing but racing to keep up with me while I'm pushing at 2000 rpms..

 

ManualF150 - Do you tow anything? If you did, I doubt seriously you would even think that by forcing the transmission to stay in any particular gear would give you better fuel economy. The automatics down shift because the PCM/TCM is doing it's part in attempting to keep your engine in it's peak efficiency range.

Don't get me wrong, I like standard transmissions as much as the next guy (I grew up with them and severly bad-mouthed automatic as a young-en), but my preference in towing is with the automatic. That said, I can understand in some circumstances the need to lock the transmission is a particular gear, but saying it can be done to inprove fuel efficiency is not one of them. Fuel economy is a result of engine efficiency - do you know the RPM range that your engine is most efficient at? How about engine loading (you know, the point at which it develops is best HP/Torque)? I don't and don't pretend to know either. That is the job of the PCM and TCM. Between the 2, they are more efficient and a whole lot faster than I am at figuring it out.

 

Yes, I do tow. Yes, I know the engine "sweet-spots"... Yes, I know if keep it in a tall gear while bogging the engine down, you could potentially be using more fuel.

With that being said, a person who knows what they are driving can save a lot more fuel if they were driving stick... not to mention wear and tear on transmission components. However, a person that has no clue what they are doing behind the wheel will more than likely waste a lot more fuel... and that is with any automatic or manual.

Edit:

However, I am not pointing fingers at towing and that you should try locking it in 5th while going up a hill... that is just dumb... but what I am trying to get at is the fact that the transmission is not smart enough to understand what the engine's sweet spots are... that takes a human being in control.

 

my grandpa has the transmission you spoke of. He pulls a 29 foot TT from here in wisconsin down to florida every year. He started out the trip using the manual shift mode but found it to actually work better just letting the truck do it and leave it in automatic. It is a neat feature though.

 

Sounds like fun...


Yeah, I'm not saying it's totally bad or anything to let the PCM/TCM decide... but if you want the best bang for the buck out of gas mileage, some human control doesn't hurt.

I would probably mess around with this on straight stretches of highway... where there are small inclines... other than that I'd let the truck do its thing.

 

If its like our motorhome with the Allison and I think it is, if you selected 4th gear it wouldn't stay in fourth. That only makes it so it won't go into any higher gear than 4th. So it will still downshift but it won't upshift past 4th gear.