Info on Allison transmission please

[needbigtruck]

This is a quote I found while researching the Allison: "The range selection feature holds the gear pre-selected by the driver and electronic safeguards prevent the transmission from being shifted in a manner that could cause engine damage or loss of vehicle control" So to be clear I can select 6th gear and the transmission will not shift out of 6th (even if vehicle slows a little going up big grade) until engine RPM's drop to a point the engine would stall (like down to 1000 RPM or so). I own a VW Jetta TDI with a DSG transmission that once 6th is selected will stay in 6th until I get to about 30 MPH (around 900 RPM) or I floor it. I love this feature on the Jetta, and don't regret not getting a stick. Point is I currently own 2001 with the 6 speed manual, which Chevy does not offer any more. My only option of the big three is to go with a Dodge. They still offer a stick. If I can truly shift the Allison with the paddle shifter then I could be persuaded to stick with Chevy. I have few complaints with my current truck, leaking fuel lines rotted brake lines and the awful emergency brake setup, is about all I have to complain about, but these, or other comparable problems are common to all 3 manufacture's. I'm in the market for a new truck and really like driving a diesel with a stick shift. Like I said if the quote really means what is says and I have control then I could stay a Chevy man.

[DmaxMaverick]

It means what it says. It's no more complicated than that.

[needbigtruck]

OK let me be more specific. Let's say I'm cruising along at 60, with the transmission selected to 6th gear, and the light ahead turns red, so I kick off the cruise and I drift down in speed to lets say 45 MPH. The light turns green so I hit resume on the cruise. Will the truck accelerate back to 60 without automatically shifting down a gear or 2.

[DmaxMaverick]

It will stay in the selected gear until the engine RPM falls below the range for that gear. If it does fall below, it will downshift to the next lower gear within that range. Meaning, if you just drift (coast), it will downshift according to the engine RPM and range for the next lower gear. If you accelerate from that point, it won't downshift any further (no "passing gear" affect). You can then manually upshift once the next higher selected range becomes available again. In the same situation, but you brake, the speed will decrease more rapidly, and may downshift more gears, more quickly. In any case, it will not downshift if the current selected gear is within the acceptable RPM range. It would likely "feel" like it will downshift where you would normally, if it were a manual transmission, and your intention is to not lug the engine below what the MFG considers unsafe for you or the powertrain. If under power, it won't upshift at all. Unless you are on compression (downhill) and overspeed, it will just ride the governor. If under power and the speed falls (climbing a grade), it will downshift, as it should, and as you should if it were a manual, to prevent the lugging condition.

In other words, the computer will let you drive in whatever gear you want, as long as it doesn't (potentially) cause powertrain damage or an unsafe condition.

[Kennedy]

The Allison is going to shift to the proper gear to keep the RPM within the proper range. It will not hold your gear "up" but will hold the gear "down" so think of it more as a shift range inhibitor.

That said, the LML trucks will run at lower RPM than previous models. It will run 1200-1500 much more readily than previous models. It also tends to maintain converter lock through the shifts.

[More Power]

GM and Ford went to automatics primarily because the manual transmissions suitable for a pickup truck couldn't reliably handle the input torque of current diesels. For example, the ZF-650 6-speed manual that GM used in their earlier Duramax trucks was rated for a maximum of 650 lb-ft of input torque. As you know, the current Duramax produces nearly 800. And... the flywheel, pressure plate and clutch disc have unique challenges behind a diesel that produce some maintenance inevitabilities over the long term.

Secondarily, meeting current emissions requirements is made more difficult when the computer can't manage gear selection.

Thirdly, the Allison has proven itself.

[JWM]

Stay with Chevy. I also wanted the manual trans. like the one in my 2001 Chevy. [I] bought a 2012 Ram 6.7 with manual tran. The Ram was gutless when towing our toy hauler and only got 6 mpg. It only got 14 mpg empty at hwy. speed. I traded it in on a 2015 GMC w/Duramax Allison. First tank of fuel, 18.02 mpg. Still getting use to the auto but the tap feature will hold the gear you choose until the RPMs drop. The other feature is if you have the trans in 4th it will not up shift beyond that gear. DO NOT BUY THE DODGE. After owning the Duramax you will not like the Ram with standard trans.