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Old 01-27-2007, 12:35 AM   #1
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Default engine RPM @ 70mph

I was just curious, can anybody tell me why engine RPM'* would run a little higher at 70MPH while everything'* still cold (around 2200rpm) and then it soon settles down to around 1900rpm when its up to Temp. All the while it is in high gear, because if I manually pull it into a lower gear it jumps up to 2400rpm or so.
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Old 01-27-2007, 01:20 AM   #2
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The transmission won't go into overdrive until it sees the proper temperature of the transmission fluid. I've had normal engine temps, but it still hadn't gone into overdrive. Once the tranny fluid warms up, it will go into overdrive, and the rpms will drop.
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Old 01-27-2007, 11:43 AM   #3
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Ok, I didn't realize there was a gear beyond D so to speak. It doesn't seem to actually shift, that I can feel.
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Old 01-27-2007, 12:44 PM   #4
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I seldom feel mine shift at that speed, either. You'll likely find it more noticeable when it shifts into overdrive around 46-48 mph.
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Old 01-27-2007, 01:55 PM   #5
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Quote:
Originally Posted by Archon
The transmission won't go into overdrive until it sees the proper temperature of the transmission fluid.
Our transmissions WILL and DO go into overdrive, but not lock-up. You go drive your car at 70 mph in 3rd gear and see how high your rpm'* are. You are correct about the temps though. Torque converter will not lock-up until the tranny reaches a certain temperature. What he'* experiencing is a cold tranny in 4th gear with no lock-up. Actually doesn't matter if it'* 3rd or 4th gear, lock-up won't kick in until the temps are up. Once the tranny warms up and lock-up kicks in, rpms go down and everybody is happy.
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Old 01-27-2007, 02:47 PM   #6
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Switch to a good synthetic engine oil (if you haven't already) and watch your cruising RPM'* drop another 100 or 200, reducing wear and saving fuel .
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Old 01-27-2007, 07:12 PM   #7
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I meant to check today but I thought the transmission goes into 4th instead of 3rd fairly quickly after starting out cold but it'* that torque converter lockup that'* still allowing a higher speed for the motor.

As for adding synthetic oil to the motor that is not going to have any effect on the transmission shift points.
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Old 01-27-2007, 08:11 PM   #8
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BoneZ. You're right for correcting me on the terminology. Lockup was what I was attempting to describe, rather than overdrive. I guess while we're at it, it doesn't really go into "lockup" the way the older transmissions do. There'* a precisely controlled amount of slip built in.
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Old 01-27-2007, 09:13 PM   #9
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Alot of people get overdrive and lockup confused and i was just trying to set the record striaght. No hard feelings Archon and certainly no offense.
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Old 01-27-2007, 09:49 PM   #10
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Quote:
Originally Posted by imidazol
As for adding synthetic oil to the motor that is not going to have any effect on the transmission shift points.
I didn't say it would. I said it would reduce your cruising RPM'*.
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