Transmission Questions...???
Hi, This is somewhat of a followup to my post about towing in the mountains with a gasser. In that post I saw a lot of talk about different transmission designs, how they have changed over rec...
Forum Discussion
Reality is any of the big 3 make solid transmissions that can tow a lot. They will all last a very long time if not abused. For the most part they are similar in design but often use copywrite marketing terms to describe features making it difficult for a non-technical buyer to understand the differences.
Locking out is more towing slang than technical term. It basically means selecting the highest gear that the transmission can use. If you put the lever so it points to "2", the transmission generally won't go into a gear higher than second gear (there are exceptions).
Some of the confusion may come from a similar term of locking up the torque converter. In this case the two halves of the torque converter are locked together eliminating the inherent slippage and wasted power of a torque converter. In early versions the torque converter would only lock up in the highest gear. More recent transmissions can lock up lower gears.
- This is mostly about fuel efficency as the slippage wastes fuel but slippage is neccessary when the vehicle is stopped.
- There can be a side benefit regarding overheating the transmission fluid. That slippage creates friction within the transmission fuild and heats it up. While towing up a steep hill, it can create a lot of heat but once the torque converter locks up the slippage goes away and you impart very little heat to the fluid. Of course this assume the engine is capable of maintaining speed in a gear that locks up. (this also explains why tow vehicles often have transmission coolers added)
- It can also play into engine braking. That same slippage makes engine braking with an automatic transmission less effective as the slippage allows the transmission to spin faster than the engine. By locking the torque converter, the transmission can't spin faster than the engine, so for a given speed the engine braking is increased. (this is also where an exceeption to locking out a gear comes into play. If the RPM gets to the point where the engine could be damaged, the transmission may decide to bump up to 3rd gear even if you have 3rd gear locked out)
Google "how an automatic transmission works" and you will find a page that provides a great deal more information including pictures an animations of how they work.
Locking out is more towing slang than technical term. It basically means selecting the highest gear that the transmission can use. If you put the lever so it points to "2", the transmission generally won't go into a gear higher than second gear (there are exceptions).
Some of the confusion may come from a similar term of locking up the torque converter. In this case the two halves of the torque converter are locked together eliminating the inherent slippage and wasted power of a torque converter. In early versions the torque converter would only lock up in the highest gear. More recent transmissions can lock up lower gears.
- This is mostly about fuel efficency as the slippage wastes fuel but slippage is neccessary when the vehicle is stopped.
- There can be a side benefit regarding overheating the transmission fluid. That slippage creates friction within the transmission fuild and heats it up. While towing up a steep hill, it can create a lot of heat but once the torque converter locks up the slippage goes away and you impart very little heat to the fluid. Of course this assume the engine is capable of maintaining speed in a gear that locks up. (this also explains why tow vehicles often have transmission coolers added)
- It can also play into engine braking. That same slippage makes engine braking with an automatic transmission less effective as the slippage allows the transmission to spin faster than the engine. By locking the torque converter, the transmission can't spin faster than the engine, so for a given speed the engine braking is increased. (this is also where an exceeption to locking out a gear comes into play. If the RPM gets to the point where the engine could be damaged, the transmission may decide to bump up to 3rd gear even if you have 3rd gear locked out)
Google "how an automatic transmission works" and you will find a page that provides a great deal more information including pictures an animations of how they work.
