What's the difference between a 6-speed AT vs. a 6-speed overdrive AT?

Question

AT = Automatic Transmission.

Answer 1

As far as I know (and I do know a lot) all 6-speed automatics will have at least one overdrive gear. Often 5th gear is an overdrive too. This means that for each full revolution of the engine, the output shaft of the transmission will turn more than one full revolution.

This allows the engine to turn more slowly for a given speed of the car, supposedly saving gas (but sacrificing the power at the wheels to accelerate without down shifting).

Answer 2

Overdrive is a technique wherein the drive wheels of the car are driven more than once per engine revolution. This reduces engine speed and thus fuel consumption.

Currently most tranmissions that have 5 speeds or more provide an overdrive gear.

While in general usage there is probably no difference between a 6-speed AT and 6-spend overdrive AT, if you are buying a specialized or limited production vehicle there is more likely to be a difference in the features supported by transmissions that are so differentiated. For example, a RV with a 6-speed tranmission and overdrive could implement overdrive with an additional transfer case which provides selection of overdrive/underdrive.

I could provide more examples, but most are probably not that interested.

Answer 3

OD changes the gear ratio in the higher gears to reduce idle and save mileage and reduce engine wear/noise.Its known as the cruising gear. In the good 'ol days you had to manually put the transmission in OD however today its electronic. You may have a button to shut it off although unless you are towing or climbing a steep grade there is no reason too.

The above post is as wrong as it is accurate.

Some makes will claim to be a six speed when truthfully its a 5 speed not a 6. However you didnt state the make/model so I cant tell you. There are True 6 speed AT's with overdrive.

If you really want to get confused although the 2000+ v8 Grand Cherokee's are listed as a 4spd electronic trans with OD they do have a 5th gear and are capable of 6th. '99 models had to have a software update so the TCM would use the 5th gear. Neither models were ever given an update to enable use of 6th. Rumor had it in 98 the Plymouth Prowler would recieve the 4.7V8 wich explains the building of the transmission to have 6 speeds but when the plan was scraped the design of the tranny stayed the same but the software was written never to use 6th!!!

Answer 4

A standard 6 speed automatic transmission the 6th gear is overdrive. A 6 speed transmission with overdrive is the same thing, just worded different to confuse people.