Auto slippage.
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Senior User
Joined: Nov 2003
Posts: 283
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From: Wynne, Arkansas
Auto slippage.
This is, like most of my posts, probably a stupid question. I'm just trying to learn how things work.
If you have an auto, shifted in second gear, and you are at a stop, and the engine is idling, then the auto has already completed the shift into second, right?
And if you hit the gas, and take off, the slippage you feel is entirely in the torque converter and not in the bands of the transmission?
Also, the bands only slip between shifts, and the slippage is only to complete the shift?
If the above is true, how does the transmission oil go bad or get to the point the oil has a burnt smell? The torque converter isn't going to alter the viscosity of the fluid, right? Any burning has to be from the bands slipping, right?
A pal of mine was pulling a boat out the other day with his F250 and he did it in second. He told me he uses second because the truck won't roll back. I wasn't in the cab but it sounded like a lot of slipping was going on somewhere.
Again, just wondering.
If you have an auto, shifted in second gear, and you are at a stop, and the engine is idling, then the auto has already completed the shift into second, right?
And if you hit the gas, and take off, the slippage you feel is entirely in the torque converter and not in the bands of the transmission?
Also, the bands only slip between shifts, and the slippage is only to complete the shift?
If the above is true, how does the transmission oil go bad or get to the point the oil has a burnt smell? The torque converter isn't going to alter the viscosity of the fluid, right? Any burning has to be from the bands slipping, right?
A pal of mine was pulling a boat out the other day with his F250 and he did it in second. He told me he uses second because the truck won't roll back. I wasn't in the cab but it sounded like a lot of slipping was going on somewhere.
Again, just wondering.
Posting Guru
Joined: May 2003
Posts: 1,525
Likes: 3
The torque converter is the main heat generator in an automatic transmission. If a band or clutch is slipping it isn't long for this world. Friction material is only .020-.040 thick and won't survive much slippage.
Postmaster
Joined: Mar 2001
Posts: 4,968
Likes: 3
From: So Cal
Depending on the tranny, when you are at a stop, the tranny may or may NOT be in the gear you have selected. Usually the tranny will be in 1st if you have the selector in D. Then depending on tranny(computer really) if you are in 2, 3, 4 whatever, the tranny may or may not be in 2,3,4 whatever. Usually most trannies will stay in 2 if selected, but some computers will not allow this and default to 1st at a stop. Most people like to use 2nd in slippery start conditions like snow and ice.
In a tranny in good condition, the main heat generator is the Torque converter. Normall this is not a problem. However, if your lockout clutches in the converter are slipping then you have a lot of heat generated. Alternatively slipping internal clutches or bands also cause a lot of heat. Lastly some computers are set up to give a smooth shift, what happens is they slip between gears which essentailly is the clutches/bands slipping to make for a smooth feel.
Too much heat is what makes fluid smell burned. Also heat can cause seals to become brittle which makes fluid dark. Old clutch/band material also causes fluid to become dark.
Most tranny modifications seak to decrease the slip time between shifts and increase the pressure on the converter clutch. This decreases the likelihood of generating too much heat.
Just my layman's interpretation of what I have read and what tranny shop owners have told me over the years.
If fluid smells burned or is anything but red, you have a problem developing or if you are lucky, it is just past time for a fluid change.
Good Luck,
Jim Henderson
In a tranny in good condition, the main heat generator is the Torque converter. Normall this is not a problem. However, if your lockout clutches in the converter are slipping then you have a lot of heat generated. Alternatively slipping internal clutches or bands also cause a lot of heat. Lastly some computers are set up to give a smooth shift, what happens is they slip between gears which essentailly is the clutches/bands slipping to make for a smooth feel.
Too much heat is what makes fluid smell burned. Also heat can cause seals to become brittle which makes fluid dark. Old clutch/band material also causes fluid to become dark.
Most tranny modifications seak to decrease the slip time between shifts and increase the pressure on the converter clutch. This decreases the likelihood of generating too much heat.
Just my layman's interpretation of what I have read and what tranny shop owners have told me over the years.
If fluid smells burned or is anything but red, you have a problem developing or if you are lucky, it is just past time for a fluid change.
Good Luck,
Jim Henderson
