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Car slamming from park to reverse

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65ramwgn View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 65ramwgn Quote  Post ReplyReply Direct Link To This Post Topic: Car slamming from park to reverse
    Posted: Jun/21/2022 at 7:30pm
My 1965 rambler American with a flash o matic transmission is having an issue. When the car is running if will slam out of park and the really SLAM when reverse engages. The shift is pretty typical when going from neutral to drive, however the huge BANG returns when going to neutral. The u joint feels pretty solid (although there is a bit of play in the rear end) as well as the motor mounts look good. I couldn’t see the transmission mount from where the car was sitting. Any ideas?
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Heavy 488 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2022 at 7:46pm
What rpm is the curb idle set at?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 65ramwgn Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2022 at 7:56pm
It seems a bit high, however would high rpm cause it to seem to slam right out of park immediately even before reverse engages?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2022 at 9:04pm
Originally posted by Heavy 488 Heavy 488 wrote:

What rpm is the curb idle set at?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2022 at 9:08pm
Originally posted by 65ramwgn 65ramwgn wrote:

It seems a bit high, however would high rpm cause it to seem to slam right out of park immediately even before reverse engages?
yes it will.   If your choke works properly.  It will idle fast. Then once its running smoothly lighty press the gas pedal and you should have the fast idle off the high step. It should slow down some, then shift in R or D. Shouldnt be harsh.  And when its at curb idle...which means choke is fully open and idling like 600rpm or so
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wittsend Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2022 at 10:25pm
A car doesn't "slam" out of Park or Neutral. In those positions there is no application of clutches or bands. Therefore there is nothing to come out of.  What you are experiencing is slamming into Reverse which you need to pass through to get to (or back from) Neutral or any forward gear. 

 While a high idle can be a contributor internal valving might be putting a higher than normal pressure to the clutches and bands. Is the throttle valve cable that attaches at the carburetor hooked up and adjusted properly? That controls the internal pressure. You might also have the gear selector lever out of adjustment. Thus what seems like slamming out of Park or Neutral  is actually going into or out of Reverse though it does not appear that way on the lever display because of mis-adjustment. Internal clutches and band servo applicators often have springs to cushion engagement. When these break the cushioning effect goes away and the application can be quite abrupt.

As mentioned ensure the idle speed is correct. When moving the gear selector do it as s-l-o-w as possible and note where the indicator is pointing when the selected gear engages. Check that any rubber bushings on the lever mechanism are intact and firm. Oil can soften and deteriorate rubber over time.  Adjust the lever as per the manual if needed. Check the throttle valve cable at the carburetor. A manual should be use to test and adjust as necessary. If none of those have any positive effect the problem is likely internal.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2022 at 6:16pm
Sounds like too high throttle pressure at idle. Check the kick down linkage to make sure it’s in proper adjustment. Idle speed needs to be in the right ballpark as well. If all checks out then you may have a broken spring in the rear band servo.
Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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