Overdrive OSS and TSS
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Joined: Jan 2007
Posts: 23
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From: BC, Canada
Overdrive OSS and TSS
Shouldn't OSS and TSS should be the same if there is no tranny slippage? In overdrive I have OSS about 500 less than TSS, when overdrive is turned off both equal out. It seems the change is in 4th and 5th gear only. Does this sound right....has anyone ever checked this out?
Last edited by skwr; Feb 25, 2007 at 02:03 PM.
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Joined: Sep 2003
Posts: 57
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From: Calgary, Alberta
Hey skwr,
No the oss and the tss should not read the same in od. The oss is the output shaft speed sensor which will go up and down in relation to vehicle speed. The tss is turbine speed shaft sensor which is measuring input(turbine) shaft speed and will go up and down with engine rpm in neutral, park and while going down the road. It will not match engine rpm exactly because of the slip in the torque con until the convertor clutch locks up. If you watched tss with the engine running in neutral it would be close to engine rpm, put the trans in drive and the fwd clutch comes on and stops the input shaft so it would read zero and then increase as you start to move. It will go up and down as the trans shifts into the next gear.
So when you cancel od you are in 3rd gear which is 1:1 ratio, so both tss and oss should read close to the same provided the torque convertor clutch is locked. In 4th gear, you are overdriving the gearset so the tss should read slower than the oss, just like engine rpm is lower at higher speeds. Your reading are saying that oss is lower than tss which doesn't sound right but I am not sure what you are using to get your readings. The IDS we use has readings for some sensors in Hz and rpm and that can cause readings to look wierd.
The pinpoint tests in the shop manual don't give specs for what the oss and tss should read. Basically they ask if the oss goes up with vehicle speed it is ok and if the tss goes up with engine/vehicle speed it is ok. The PCED manual gives some numbers at idle,55mph etc but they warn that those numbers are not exact.
Also you know that you trans is a 4speed not a 5speed right?
So in the long run, your trans is operating normally, if there was something wrong with the oss/tss, codes would be set and trans shift concerns would be evident.
Clear as mud?
No the oss and the tss should not read the same in od. The oss is the output shaft speed sensor which will go up and down in relation to vehicle speed. The tss is turbine speed shaft sensor which is measuring input(turbine) shaft speed and will go up and down with engine rpm in neutral, park and while going down the road. It will not match engine rpm exactly because of the slip in the torque con until the convertor clutch locks up. If you watched tss with the engine running in neutral it would be close to engine rpm, put the trans in drive and the fwd clutch comes on and stops the input shaft so it would read zero and then increase as you start to move. It will go up and down as the trans shifts into the next gear.
So when you cancel od you are in 3rd gear which is 1:1 ratio, so both tss and oss should read close to the same provided the torque convertor clutch is locked. In 4th gear, you are overdriving the gearset so the tss should read slower than the oss, just like engine rpm is lower at higher speeds. Your reading are saying that oss is lower than tss which doesn't sound right but I am not sure what you are using to get your readings. The IDS we use has readings for some sensors in Hz and rpm and that can cause readings to look wierd.
The pinpoint tests in the shop manual don't give specs for what the oss and tss should read. Basically they ask if the oss goes up with vehicle speed it is ok and if the tss goes up with engine/vehicle speed it is ok. The PCED manual gives some numbers at idle,55mph etc but they warn that those numbers are not exact.
Also you know that you trans is a 4speed not a 5speed right?
So in the long run, your trans is operating normally, if there was something wrong with the oss/tss, codes would be set and trans shift concerns would be evident.
Clear as mud?
