I know that generally, manual transmissions come in 9, 10, 13 & 18 speeds/gears. The most common are 10 & 13. I see many threads on automatic transmissions but I don't see any that discuss the number of speeds or gears. Just curious, what are the different automatic transmissions & what are the most common for 18 wheeler 80,000 lb class 8 trucks? I had some experience with residential & front-end load garbage trucks when I worked for Waste Management up to 2004. I dont know that I ever specifically knew or asked but I think/assumed these were 6 speed automatics. I think they were Allison transmissions. Ofcourse these were straight trucks. Thanks in advance for any relevant info.
The difference is Allison is a full automatic, the transmissions in a class 8 are auto shift, the have the same gears as manual tranny but are shifted with a computer.
Automatics (Allison) are generally 5 or 6 speeds. Automated Manuals are generally 10,(DT12), 13 or 18 speed manual transmission that are electronically controlled.
Allison is starting to make in-roads into the over the road market. They have had a ten speed out for a few years now, but I have seen the six speed used by a fleet for highway tractors. The driver seemed to like it. I have an 18 speed auto-shift in mine. I haul 140,000 lbs.
The place I work at has 6spd Allisons in the newer dumps and they have been working great. Some of them are paired up with pups so they do haul bigger loads and they move the truck along just fine. These trucks have DD13 engines in them.
If you have a 13 or 18 speed automatic and you leave it in auto mode, when you come to a hill will the transmission drop just a half a gear like a manual or a full gear ? How bout if you have it in manual mode then drop a gear, half or full gear ?
I have 18 spd UltraShift. Depends on hill and how hard you are pressing on the accelerator . It will do both a half or full shift. Manual I can do pretty much what ever I want, as long as it is within rpm limits.
