When I am driving in 1st or 2nd shift (slow) and.

Tiny
WUDAAL
  • MEMBER
  • 1999 JEEP GRAND CHEROKEE
  • 178,000 MILES
When I am driving in 1st or 2nd shift (slow) and take my foot off the gas pedal, say at a difference of a sec or less after releasing the pedal, it jerks (makes a sound like two heavy metals collide)? Yesterday I have changed transmission oil (ATF 4) and transmission oil filter but didnt fix the problem? Would you please guide me to fix this problem?
Tuesday, March 5th, 2013 AT 7:56 PM

5 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 34,330 POSTS
Most likely cause would be a collapsed engine mount letting the two pieces of the metal bracket hit each other.
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Tuesday, March 5th, 2013 AT 8:44 PM
Tiny
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It does not do this all the time, it makes the jerk when I am going a declination. And I have noticed that by the time it shift down it make the jerk and the sound. I though transmission is the culprit but you are expert and now better so how can I confirm if this is the engine mount?
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Wednesday, March 6th, 2013 AT 3:15 PM
Tiny
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Have to look at them to see if the rubber isolators are collapsed, torn, squished out, etc. Sometimes you can see them move when a helper runs the engine and shifts between reverse and drive.
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Wednesday, March 6th, 2013 AT 7:59 PM
Tiny
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OK, I checked it thoroughly with the help of a friend, and I found no such movement, no signs of smashing, all engine mounts looks good. I have noticed that the jerk is only when it shifts from 1st to second while the vehicle is going down a slope and if I am not pressing the gas pedal. With pressing the accelerator pedal (slightly) it shifts without a jerk but with a slight jump. And if I push the gas pedal (full) and keep it pressed it accelerates and shifts smooth without jerk or jump, but you can always do that, specially in traffic queues.
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Thursday, March 7th, 2013 AT 8:11 PM
Tiny
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What you're describing sounds like "bump shift". Mostly that occurs when the transmission engages one of the clutch packs with more force than is needed. That is felt when there is not enough load on it which is typically at low speeds. The dealer can reflash the computer's software with updated shift schedules to address about ten common complaints. I did that on my '93 Dynasty when it was new, but it didn't solve that. It's just the nature of the beast.

Since yours is also making a metallic sound, don't overlook worn universal joints. Look around the bearing cups for signs of reddish-colored rust.
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Thursday, March 7th, 2013 AT 9:55 PM

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