1998 LS400 Overdrive
08-22-15, 11:45 PM
#1
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1998 LS400 Overdrive
Hey guys. New to Club Lexus but I think making this account will be the best thing I could ever do being a Lexus owner. I have a question... Today, I have a 91 LS400, and they obviously have overdrive (button on the shifter). Tomorrow, I'm buying a 98 and I'm curious if they had OD. My friend has a 96 and he doesn't have an OD button on his shifter like the UCF10s, and I was wondering if he has OD or not, and if he does, is it on all the time or is the button to turn it off hidden in some weird other location? Because his car did seem a little slower. Thanks in advance!
08-24-15, 08:05 AM
#2
Lexus Champion
The first overdrive was a separate 2-speed transmission bolted on the rear of a RWD car's normal (automatic) transmission, much like a transfer case is bolted on to provide 4WD functionality on RWD cars and trucks. It had to be controlled as a separate transmission, engaged and disgaged with its own gearshift lever, unless it was electro-hydraulically controlled, in which case it could be controlled by a button.
It worked in the following fashion, operated by the separate lever or button:
A separate transmission, of course, adds complexity and cost (2 separate transmissions) to the car and if operated too often and especially if operated when the normal transmission was not already in its highest gear, would put a lot of strain (and therefore heat) on the driveshaft and rear differential (driveshaft would be spinning faster than the output from the normal transmission). It would be the same as trying to ride a bicycle uphill while keeping it in a high gear, rather than downshifting.
In new cars, however, overdrive is not typically a separate transmission but merely extra gear ratio(s) that would provide tall, overdrive ratio(s) of less than 1:1 (0.9:1, 0.8:1, 0.7:1, 0.6:1 or even close to 0.5:1 in the new 8-speed transmissions). In these modern, electronically controlled transmissions (from the late 1980s onward), 4-speed and 5-speed overdrive transmissions provided an overdrive gear ratio in the top gear (4th or 5th depending on the total number of gear ratios in the transmission). The latest 6-, 7-, 8-, 9- and 10-speed transmissions provide overdrive gear ratios not only in the top gear but in lower gears as well (the 2 or 3 highest gears and higher in these transmissions could be overdrive ratios).
While I am not aware of the design of the Toyota/Lexus RWD automatic transmissions of the late-1980s and early-1990s, I do not believe that they had separate overdrive transmissions; I believe that those 4-speed and 5-speed were modern electronically-controlled transmissions with overdrive gear ratios in the highest gears already in the normal transmission. The overdrive button would have been a holdover from the days of the separate overdrive transmissions. In these modern Toyota transmissions, the button merely allowed you to shift out of the top (overdrive) gear; I am familiar with the Toyota FWD 4-speed automatic transmission of that era and the button allowed you to manually shift from 4th-gear to 3rd-gear, and to shift from 3rd to 2nd required you to move the normal gearshift lever.
All Toyota/Lexus transmissions since those early 4-speed transmissions (in the 1st Generation 1989 to 1994 Lexus LS) and 5-speed transmissions (in the 2nd Generation 1995 to 2000 Lexus LS) have had overdrive gear ratios within the normal transmission. The 6-speed transmissions (in the 3rd Generation LS) had overdrive gear ratios in both 4th- and 5th-gear. The 8-speed transmissions (in the 4th Generation LS) have overdrive gear ratios in both 7th- and 8th- gear. In these latest transmissions, there are still overdrive gear ratios but no longer controlled by the button. To manually shift, regardless of the gear you are in, you use the transmission lever or paddle shifter -- you sequentially shift down (8-7-6-5-4-...) or up, and into or out of the overdrive gear ratio(s).
In these new transmissions, you no longer know (unless an idiot light in the instrument panel indicates) if you are in an overdrive ratio or not, but then, you do not have to, since it is all electronically (computer) controlled.
It worked in the following fashion, operated by the separate lever or button:
- In overdrive unit 1st gear, the separate overdrive transmission provided no gearing change (i.e. gear ratio was a straight pass-through ratio of 1:1).
- In overdrive unit 2nd gear, the separate transmission provided a taller gear so that the speed of the driveshaft (which would be the output of the overdrive transmission) was faster than the speed of the input (which would be the output from the normal transmission), providing a gear ratio of perhaps 0.8:1 or 0.7:1.
A separate transmission, of course, adds complexity and cost (2 separate transmissions) to the car and if operated too often and especially if operated when the normal transmission was not already in its highest gear, would put a lot of strain (and therefore heat) on the driveshaft and rear differential (driveshaft would be spinning faster than the output from the normal transmission). It would be the same as trying to ride a bicycle uphill while keeping it in a high gear, rather than downshifting.
In new cars, however, overdrive is not typically a separate transmission but merely extra gear ratio(s) that would provide tall, overdrive ratio(s) of less than 1:1 (0.9:1, 0.8:1, 0.7:1, 0.6:1 or even close to 0.5:1 in the new 8-speed transmissions). In these modern, electronically controlled transmissions (from the late 1980s onward), 4-speed and 5-speed overdrive transmissions provided an overdrive gear ratio in the top gear (4th or 5th depending on the total number of gear ratios in the transmission). The latest 6-, 7-, 8-, 9- and 10-speed transmissions provide overdrive gear ratios not only in the top gear but in lower gears as well (the 2 or 3 highest gears and higher in these transmissions could be overdrive ratios).
While I am not aware of the design of the Toyota/Lexus RWD automatic transmissions of the late-1980s and early-1990s, I do not believe that they had separate overdrive transmissions; I believe that those 4-speed and 5-speed were modern electronically-controlled transmissions with overdrive gear ratios in the highest gears already in the normal transmission. The overdrive button would have been a holdover from the days of the separate overdrive transmissions. In these modern Toyota transmissions, the button merely allowed you to shift out of the top (overdrive) gear; I am familiar with the Toyota FWD 4-speed automatic transmission of that era and the button allowed you to manually shift from 4th-gear to 3rd-gear, and to shift from 3rd to 2nd required you to move the normal gearshift lever.
All Toyota/Lexus transmissions since those early 4-speed transmissions (in the 1st Generation 1989 to 1994 Lexus LS) and 5-speed transmissions (in the 2nd Generation 1995 to 2000 Lexus LS) have had overdrive gear ratios within the normal transmission. The 6-speed transmissions (in the 3rd Generation LS) had overdrive gear ratios in both 4th- and 5th-gear. The 8-speed transmissions (in the 4th Generation LS) have overdrive gear ratios in both 7th- and 8th- gear. In these latest transmissions, there are still overdrive gear ratios but no longer controlled by the button. To manually shift, regardless of the gear you are in, you use the transmission lever or paddle shifter -- you sequentially shift down (8-7-6-5-4-...) or up, and into or out of the overdrive gear ratio(s).
In these new transmissions, you no longer know (unless an idiot light in the instrument panel indicates) if you are in an overdrive ratio or not, but then, you do not have to, since it is all electronically (computer) controlled.
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Mythicalni (02-13-20)
08-24-15, 10:56 AM
#3
Driver School Candidate
It doesn't have a button to engage/disengage OD but 5th is a over drive ratio. Dunno why your friend's car felt slower. But you'll be getting 98 with more power so win-win.
08-24-15, 04:35 PM
#4
The first overdrive was a separate 2-speed transmission bolted on the rear of a RWD car's normal (automatic) transmission, much like a transfer case is bolted on to provide 4WD functionality on RWD cars and trucks. It had to be controlled as a separate transmission, engaged and disgaged with its own gearshift lever, unless it was electro-hydraulically controlled, in which case it could be controlled by a button.
It worked in the following fashion, operated by the separate lever or button:
A separate transmission, of course, adds complexity and cost (2 separate transmissions) to the car and if operated too often and especially if operated when the normal transmission was not already in its highest gear, would put a lot of strain (and therefore heat) on the driveshaft and rear differential (driveshaft would be spinning faster than the output from the normal transmission). It would be the same as trying to ride a bicycle uphill while keeping it in a high gear, rather than downshifting.
In new cars, however, overdrive is not typically a separate transmission but merely extra gear ratio(s) that would provide tall, overdrive ratio(s) of less than 1:1 (0.9:1, 0.8:1, 0.7:1, 0.6:1 or even close to 0.5:1 in the new 8-speed transmissions). In these modern, electronically controlled transmissions (from the late 1980s onward), 4-speed and 5-speed overdrive transmissions provided an overdrive gear ratio in the top gear (4th or 5th depending on the total number of gear ratios in the transmission). The latest 6-, 7-, 8-, 9- and 10-speed transmissions provide overdrive gear ratios not only in the top gear but in lower gears as well (the 2 or 3 highest gears and higher in these transmissions could be overdrive ratios).
While I am not aware of the design of the Toyota/Lexus RWD automatic transmissions of the late-1980s and early-1990s, I do not believe that they had separate overdrive transmissions; I believe that those 4-speed and 5-speed were modern electronically-controlled transmissions with overdrive gear ratios in the highest gears already in the normal transmission. The overdrive button would have been a holdover from the days of the separate overdrive transmissions. In these modern Toyota transmissions, the button merely allowed you to shift out of the top (overdrive) gear; I am familiar with the Toyota FWD 4-speed automatic transmission of that era and the button allowed you to manually shift from 4th-gear to 3rd-gear, and to shift from 3rd to 2nd required you to move the normal gearshift lever.
All Toyota/Lexus transmissions since those early 4-speed transmissions (in the 1st Generation 1989 to 1994 Lexus LS) and 5-speed transmissions (in the 2nd Generation 1995 to 2000 Lexus LS) have had overdrive gear ratios within the normal transmission. The 6-speed transmissions (in the 3rd Generation LS) had overdrive gear ratios in both 4th- and 5th-gear. The 8-speed transmissions (in the 4th Generation LS) have overdrive gear ratios in both 7th- and 8th- gear. In these latest transmissions, there are still overdrive gear ratios but no longer controlled by the button. To manually shift, regardless of the gear you are in, you use the transmission lever or paddle shifter -- you sequentially shift down (8-7-6-5-4-...) or up, and into or out of the overdrive gear ratio(s).
In these new transmissions, you no longer know (unless an idiot light in the instrument panel indicates) if you are in an overdrive ratio or not, but then, you do not have to, since it is all electronically (computer) controlled.
It worked in the following fashion, operated by the separate lever or button:
- In overdrive unit 1st gear, the separate overdrive transmission provided no gearing change (i.e. gear ratio was a straight pass-through ratio of 1:1).
- In overdrive unit 2nd gear, the separate transmission provided a taller gear so that the speed of the driveshaft (which would be the output of the overdrive transmission) was faster than the speed of the input (which would be the output from the normal transmission), providing a gear ratio of perhaps 0.8:1 or 0.7:1.
A separate transmission, of course, adds complexity and cost (2 separate transmissions) to the car and if operated too often and especially if operated when the normal transmission was not already in its highest gear, would put a lot of strain (and therefore heat) on the driveshaft and rear differential (driveshaft would be spinning faster than the output from the normal transmission). It would be the same as trying to ride a bicycle uphill while keeping it in a high gear, rather than downshifting.
In new cars, however, overdrive is not typically a separate transmission but merely extra gear ratio(s) that would provide tall, overdrive ratio(s) of less than 1:1 (0.9:1, 0.8:1, 0.7:1, 0.6:1 or even close to 0.5:1 in the new 8-speed transmissions). In these modern, electronically controlled transmissions (from the late 1980s onward), 4-speed and 5-speed overdrive transmissions provided an overdrive gear ratio in the top gear (4th or 5th depending on the total number of gear ratios in the transmission). The latest 6-, 7-, 8-, 9- and 10-speed transmissions provide overdrive gear ratios not only in the top gear but in lower gears as well (the 2 or 3 highest gears and higher in these transmissions could be overdrive ratios).
While I am not aware of the design of the Toyota/Lexus RWD automatic transmissions of the late-1980s and early-1990s, I do not believe that they had separate overdrive transmissions; I believe that those 4-speed and 5-speed were modern electronically-controlled transmissions with overdrive gear ratios in the highest gears already in the normal transmission. The overdrive button would have been a holdover from the days of the separate overdrive transmissions. In these modern Toyota transmissions, the button merely allowed you to shift out of the top (overdrive) gear; I am familiar with the Toyota FWD 4-speed automatic transmission of that era and the button allowed you to manually shift from 4th-gear to 3rd-gear, and to shift from 3rd to 2nd required you to move the normal gearshift lever.
All Toyota/Lexus transmissions since those early 4-speed transmissions (in the 1st Generation 1989 to 1994 Lexus LS) and 5-speed transmissions (in the 2nd Generation 1995 to 2000 Lexus LS) have had overdrive gear ratios within the normal transmission. The 6-speed transmissions (in the 3rd Generation LS) had overdrive gear ratios in both 4th- and 5th-gear. The 8-speed transmissions (in the 4th Generation LS) have overdrive gear ratios in both 7th- and 8th- gear. In these latest transmissions, there are still overdrive gear ratios but no longer controlled by the button. To manually shift, regardless of the gear you are in, you use the transmission lever or paddle shifter -- you sequentially shift down (8-7-6-5-4-...) or up, and into or out of the overdrive gear ratio(s).
In these new transmissions, you no longer know (unless an idiot light in the instrument panel indicates) if you are in an overdrive ratio or not, but then, you do not have to, since it is all electronically (computer) controlled.
08-25-15, 08:49 AM
#5
Lead Lap
yes there is an overdrive in the 98-00 cars, just no physical button to turn it on or off. moving the shifter to the "4" position from the "D" position effectively turns on and off overdrive. although i'm not sure if this would technically be considered an "overdrive" because top speed is actually reached in 5th gear
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