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Clunk when shifting form reverse into park (1/6)
 6/10/19 1:27pm
Freelandguy
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Hazle Twp, PA - USA

Vette(s):
1976 Mahogany L82


Joined: 8/26/2017
Posts: 11

I get a clunck when I shift into reverse from park when the car is cold, if the car warms up it doesn't do it ? Any help greatly appreciated.

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Re: Clunk when shifting form reverse into park (2/6)
 6/11/19 8:33pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 19623

What is the idle RPM when shifting into rev when cold? High rpm can cause this.

Cold trans fluid is thick...it can also cause a firm/harsh engagement when cold. 

Also, check your u-joints, and the front diff mount, as any of those can create clunks or other noises/feels.



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Joel Adams
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Re: Clunk when shifting form reverse into park (3/6)
 6/12/19 6:04am
Freelandguy
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Hazle Twp, PA - USA

Vette(s):
1976 Mahogany L82


Joined: 8/26/2017
Posts: 11

Thanks for the response, I think its gotta just be cold fluid. I adjusted the rpms at idle to about 1100, this is after it drops down from the initial high idle of about 1400. While driving after its warm I idle about 700 and it shifts into R fine. Also and this might sound crazy but if the car sits out in the sun for a couple hours it also shifts into R fine after startup. I changed all u joints and the differential mount as well. Somebody also said perhaps there is a shift kit in the car but I'm not sure how to verify that.

Re: Clunk when shifting form reverse into park (4/6)
 6/12/19 9:51pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 19623

1100 rpms is a bit high....you have to expect a harsh engagement at that rpm, hot OR cold. Let 'er warm up a bit more to get the idle speed down before taking off...or just live with the firm engagement. Fluid viscosity at that rpm is moot. 👍



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Joel Adams
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             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Re: Clunk when shifting form reverse into park (5/6)
 6/13/19 6:01am
Freelandguy
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Hazle Twp, PA - USA

Vette(s):
1976 Mahogany L82


Joined: 8/26/2017
Posts: 11

Joel thanks for your help and I agree, lately I have been warming up the car a bit more and the shift engagement is pretty mild. I just wanted to make sure I didn't have a problem developing. Thanks again !

Re: Clunk when shifting form reverse into park (6/6)
 6/13/19 9:26am
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 19623

😃

As far a shift kits, they typically don't create harsh engagements, depending on how the unit was built. If the 1-2 and 2-3 shifts are always firm, but on time, then it's possible someone has done something to the unit such as a shift kit. Hard to say unless you dig into the trans. The calibration on Corvette transmissions were a little more aggressive than for Ma's Impalla, so they shift a little better to start with. 



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Joel Adams
C3VR Lifetime Member #56    

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(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"