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Topic: Transmission Jerking

in Forum: C3 Driveline Components


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Transmission Jerking (1/8)
 10/15/12 3:35pm
Vetto1974
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Hayward, CA - USA

Vette(s):
I have 1974 Corvette, with white exterior and silver interior. It has 350.


Joined: 10/9/2012
Posts: 30

Hi, Question on my tranny and need your help. Everytime I put the car on Drive, I can feel some sort of jerking. I am not sure if the flexplate needs to be replace, or some sort of adjustment. I have 350, 3 speed automatic. Sorry, I just want to tag this question to this post. Which one is better, side exhaust pipes or full lenght headers, as far as performances. For the side pipe exhaust, do you know where is the best place to get them? I have a white car, to be painted soon to pearl white, do you think black side exhaust pipes will look good? Thank you

|UPDATED|10/15/2012 12:35:40 PM (AZT)|/UPDATED|


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Re: Transmission Jerking (2/8)
 10/15/12 4:44pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#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: 20126

Do you hear any noises/clucks when you put it in gear?
Does the rear of the car "squat" in drive, and rise up in reverse?
Is your engine idle too high?
Has there been any work done on the trans in the past or recently?

I doubt you have a flywheel issue....those, when cracked, will normally let you know while it's idling in gear, as a clicking noise.
You may have a suspension or differential bushing that is damaged, and causing the jerk. Need to verify first that the idle is not too high on the engine.


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Re: Transmission Jerking (3/8)
 10/15/12 5:50pm
Vetto1974
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Hayward, CA - USA

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I have 1974 Corvette, with white exterior and silver interior. It has 350.


Joined: 10/9/2012
Posts: 30

Hi, Thank you. No Noise or clucks when put into a gear. No squat or rise up. The issue is of which I can tell if the it is idling, is, the tach is broken. I already order it and its on its way. How can I tell if it is idling too high? I don't have the history of work done with the tranny. I just got the car about 1 month ago. I am thinking of wear and tear of the flexplate? Will that be possible?

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Re: Transmission Jerking (4/8)
 10/15/12 10:57pm
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


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Flywheel will NOT cause a jerk when put in gear. How hard of a "jerk" are we talking about, anyway? A slight jerk could be considered normal. I would really try to determine the idle speed first. Try lowering the idle speed, to see if the "jerk" stops.
Do you have to push fairly hard on the brake pedal to keep the car from moving when you put it in gear?
A, older Corvette is not a Cadillac, so you can't really expect it to operate like one. You should be able to feel it actually shift gears, and you might also feel a little bump/thump when you first put it in gear. How hard that bump/thunk is is the real question. If it barks the tires, and you have to use both feet on the brake pedal to keep it from moving, that's a problem! LOL
You may want to take it somewhere and have the suspension, u-joints, and differential bushings looked at, especially if you just bought the car recently. It's also possible that the trans has had some work done on it that could be causing the harder-that-normal bump. How does it shift when driving?


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Re: Transmission Jerking (5/8)
 10/16/12 7:40am
Case75
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, - Canada

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1975 Corvette 383 stroker w/Patriot 190 heads, Eagle stroker kit, Comp 279TH7 cam, DUI distributor, Edelbrock 7116 intake, Edelbrock 1806 carb, Hedman Hedders, TH400 w/TCI Breakaway 2400 stall, Transgo 1-2 shift kit.


Joined: 6/19/2012
Posts: 230

I agree Adam. My '75 has the THM400. When it's cold it has quite a clunk from the u-joints/rear snubber bushing and the rear of the car goes up when I put it in reverse, down when I put it in drive. I'm sure the snubber bushings need changed. They're 37 years old!
 
When the tranny is warmed up the clunk is much less. Likely as the idle has come down. I remember as a kid most cars clunking a bit when put in reverse/drive.


|UPDATED|10/16/2012 4:40:57 AM (AZT)|/UPDATED|


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Re: Transmission Jerking (6/8)
 10/16/12 12:07pm
Vetto1974
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Hayward, CA - USA

Vette(s):
I have 1974 Corvette, with white exterior and silver interior. It has 350.


Joined: 10/9/2012
Posts: 30

Hi, I didn't have to press on the brake really hard. It's just jump a little. I was once told, it is pretty normal for the older car to do it. Maybe the previous owner had work on the car. I am not sure. Shifting while driving, I have not done yet. I will bring it a mechanic to look at. Thank you.

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Re: Transmission Jerking (7/8)
 11/15/12 10:50am
tonytheroofer
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Rochester, NY - USA

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1980 L- 82 fully restored and upgraded.


Joined: 6/12/2012
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Get it on a lift and check the transmission mount , check U - Joints and then make sure your idle is set correctly. In thses cars when you do put them in drive you should feel the car sitting down not pushing forward and a bad mount and or high ldle will affect this feel . 

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Re: Transmission Jerking (8/8)
 11/16/12 8:48pm
VetteSpecialties
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Mounds View, MN - USA

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70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe


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I too agree with the comments above.  If you do not have to hold the brake hard, it seems like it might be looseness in the driveline.  This could be any of the six U-joints or slop in the differential, or possibly real sloppy suspension.

As for the exhaust, side pipes require quite a bend to get the exhaust lined up with the pipes, so they are not very efficient.  The exception is if you get headers that turn into side pipes, but they still need quite a turn.  Unless you are heavily modifying your engine, the existing exhaust manifolds are adequate.  They used them on 370 HP cars.  I would go to an exhaust system that is true duals, and jumps to 2 1/2 inches right after the manifold.  We carry that system in heavy aluminized steel for $389.00 including donuts and clamps.

Good luck
Larry
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