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Unread 12-23-2004, 07:48 AM   #1
canuckJGC
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RPM increase of 300-400 at 50mph
Hi folks - '98 JGC I6, 100k - Between 50-60mph, the RPM's will jump 300 or 400 for a split second then drop down to normal (as if you might punch the throttle a little). It is pretty 'rythmic' as well -- happens every few seconds like clockwork. The speed stays relatively steady. I don't think it is the tranny. I'm a bit baffled -- speed sensor maybe? Anyone have an idea here?

Thanks!

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Unread 12-23-2004, 07:58 AM   #2
canuckJGC
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I should mention that the engine surges -- not just the tach. If it is an EGR problem, will that throw a code?
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Unread 12-23-2004, 08:04 AM   #3
spr
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has it kicked out of overdrive yet? What you describe was the beginning symptom of what mine did before a long drive it kicked itself out of overdrive and never went back in, then started slipping in all shifts but 1,2. End result remanny tranny-
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Unread 12-23-2004, 08:17 AM   #4
canuckJGC
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No it has not kicked out of overdrive. I just had the tranny serviced a few months ago and all looked good.
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Unread 12-23-2004, 08:32 AM   #5
greasefingers
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If the vehicle surges than I would not think that it is the tranny.
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Unread 12-23-2004, 08:59 AM   #6
njrealtor55
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sounds like tranny. make sure to use atf+3 only. other atf fluid will produce that slipping.

i'd drop the pan, change the filter, and refill with atf+3.
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Unread 12-23-2004, 02:46 PM   #7
b1pig
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Ditto on fluid check of the tranny. In all seriousness, sounds like the tranny is momentarily unlocking the torque converter.

May be an electrical issue... TPS maybe... that would be my next test if a fluid/filter change on the tranny doesn't fix it.
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