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Camaro 1968, going along with a propane powered BPE 383 ci, T56, Eaton Posi 4.10:1, MCB Big Brakes
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Discussion Starter · #1 ·
My camaro has been doing this since a long time.
It happens at low speed, in 1° or 2° gear with little gas, and RPM close to idle, you engage in a slow turn in city and it begins to shake , diving front stop and go..... Then I have to be very careful with the gas pedal and be constant to avoid it.
It is a manual transmission T56.
The reason I write here today is there comes a mechanical sound like there is a free play.
But all the drive line is totally new.
And I don't feel a free play anywhere that I can remember.

The car is at the Netherlands shop for diagnose and they told me this is not normal. I was thinking this was my driving that was no correct. But indeed no other new cars do that.
They say the engine is very strong and there must not be any free play anywhere in the drive line or I'll break things real quick.

I am thinking the only area where the sound can come from is the transmission?


Your experience shared is always welcome.

Marc
 

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Camaro 1968, going along with a propane powered BPE 383 ci, T56, Eaton Posi 4.10:1, MCB Big Brakes
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Discussion Starter · #4 · (Edited)
All right this makes sense...
Honestly I don't experience this a lot. And indeed I press clutch or change gear or spin to higher RPM.

The mechanics (electronics) at the shop told me they could improve a lot compared to initial configuration (with their electronic module tuning ignition / fuel) so I should experience a lot less bucking effect already. But they are always searching for some cause ...
I should get the car back by end of this week.

So this has nothing to do with free play in drive line components which was my initial concern?
 

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Marc, I may be misunderstanding your comments but on stick cars, very low speed (read barely moving) in 1st gear with clutch engaged, especially on cam motors, the car can surge and buck if that is what is happening. Just push in clutch to stop this and "feather" it out while increasing RPM slightly to get the car moving again without bucking.

Again, Not sure if I understand your description correctly but it may just be a left foot, right foot coordination thing

If you have EFI than maybe it's a tuning issue but again I may be misunderstanding the symptoms, you describe
 

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69 Camaro SS convertible
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I may be misunderstanding your diagnosis as well. If it has a relatively big cam (480 or above) and high compression and your not giving it enough gas at a low speed it will chug and "dive" a lot. Ride 1/2 clutch a bit when turning at slow speed, or push the clutch all the way in during the turn only then let it out with gas when you straighten out. All that if I'm understanding the issue correctly. Get a friend to do a short video while you're driving and post it.
 

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Camaro 1968, going along with a propane powered BPE 383 ci, T56, Eaton Posi 4.10:1, MCB Big Brakes
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Discussion Starter · #9 ·
Hi,
it happens at deceleration - no throttle, almost idle (+/- 1200 rpm ), but driving (slowly, like you enter a parking lot), and it is a 'jerk' thing. ; like if you push and release the gas pedal quickly.
You hear then a 'clonk clonk' noise.

Like if the problem was free play in the throttle body that makes it happen, but there is no such free play.. the gas linkage is new.

At idle , while parked with car not in movement, it never does it, car idles great.
That means also when it does it, if you press clutch, car rolls down smooth and engine idles smooth.

So the diagnosis from the mechanics came to say free play is somewhere else in the DL, but I don't see where it is... all is new, new cutch, new trans, new DS, new axle, new rear end built and all is pretty rigid no free play if you crawl under the car and try to move things...
 

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Old people call it "trailer hitching" similar to pulling a trailer down a rough road. Not knowing your specifics, betting you have a high HP engine with low torque at less than 2,000 rpm. You also have a relatively low numerical differential gear (e.g. 3.55 / 1.0).
With low torque and high load, you will get the "bucking" as if you are quickly varying the throttle. Generally when this happens with an older engine with distributor ignition, you can retard the timing and get some improvement.
I am OLD, so your EFI and ignition system are not within my comfort zone. As they stated, your technician should be able to make a timing / fuel adjustment to improve the torque at low rpm. If not, you need to look at higher numerical gears (3.73 / 1.0) to increase the torque at the rear wheels or a camshaft change to improve low end torque and improve drive ability.
Just $.02 to add to what others are saying, we are all talking apples and apples.
 

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It is you and your lack of experience. Bucking is normal depending on your setup. One of my cars "bucks" like you describe because of gear ratio. No big deal. I drive it accordingly. Other cars I own don't buck at low speeds. The fact you say it does not act up when at idle or stationary shows your lack of experience. Those of us who have been driving these cars daily for 50 years are used to it. Your shop that compares a brand new car not bucking to a classic lacks knowledge. Find a new shop or real gearhead that knows old cars.
 

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Camaro 1968, going along with a propane powered BPE 383 ci, T56, Eaton Posi 4.10:1, MCB Big Brakes
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Discussion Starter · #12 ·
Thank you for your help and explanation.

My concern was that it could be related to DL issues, which seems not the be the case. This is very fortunate!
This was the reason for posting this thread.

I have a 4.11:1 rear with a T56, so I can downshift also to avoid this issue.
 

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Hi,
it happens at deceleration - no throttle, almost idle (+/- 1200 rpm ), but driving (slowly, like you enter a parking lot), and it is a 'jerk' thing. ; like if you push and release the gas pedal quickly.
You hear then a 'clonk clonk' noise.

Like if the problem was free play in the throttle body that makes it happen, but there is no such free play.. the gas linkage is new.

At idle , while parked with car not in movement, it never does it, car idles great.
That means also when it does it, if you press clutch, car rolls down smooth and engine idles smooth.

So the diagnosis from the mechanics came to say free play is somewhere else in the DL, but I don't see where it is... all is new, new cutch, new trans, new DS, new axle, new rear end built and all is pretty rigid no free play if you crawl under the car and try to move things...
It is normal surging. There is nothing wrong with your driveline. Keep your rpm‘s up and you will be fine.

Don
 

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Even with your low gear (4.11), you are going to get the surging (trailer hitching) with your high HP engine. You need to spend more time in the car learning the minimum RPM at which you need to downshift to avoid the surging. If you are in the lowest gear 1st, then you may have to drive like Andretti. Other than the new performance cars, drive-ability has always been a compromise between horsepower and torque.
Like a woman, each car has it's own disposition and you have to learn how to live with it.
 

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Marc

Seems others understood your post as I do and you just need to "adjust" your clutch engagement & throttle (RPM) technique.

I also have a T56/383/4:10 gear car and can experience the same "bucking" aka "trailering" while in similar driving condition. Going slow, turning I have to feather the clutch. When I let my Son drive he sometimes also has the problem you have sometimes...so just push in the clutch when it happens then slowly re-engage it (without slipping it too much) while adding "slightly" more RPM.

I also have a McLeod Twin Disc clutch that does not have sprung hubs so it is even less forgiving in that situation but once you find the "sweet spot" on clutch release/RPM you are good
 

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.I agree with the others. It sounds like you may be lugging the motor (not enough RPM's too high of gear).
 

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Discussion Starter · #18 ·
Ok guys thanks for all reactions it is much appreciated :)

I just had the shop owner online : he could tune it with a slightly richer mixture at idle so he says now it barely not surges anymore... only in third gear going close to idle ...
He also admits there is no free play nowhere in the DL.

WIth all your comments and the verification of the shop, I am reassured that all is fine!

Oh you asked if it is a sniper, no it is a Dutch built system, called Skyfire. I have a module connected to lamblda for fuel control and another one that tunes ignition advance electronically + a new high energy coil for better spark at plugs.
 

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Ok guys thanks for all reactions it is much appreciated :)

I just had the shop owner online : he could tune it with a slightly richer mixture at idle so he says now it barely not surges anymore... only in third gear going close to idle ...
He also admits there is no free play nowhere in the DL.

WIth all your comments and the verification of the shop, I am reassured that all is fine!

Oh you asked if it is a sniper, no it is a Dutch built system, called Skyfire. I have a module connected to lamblda for fuel control and another one that tunes ignition advance electronically + a new high energy coil for better spark at plugs.
I guess what I was looking for is what the throttle body is like. Progressive or all four at once. All four can make driving crammed up cars very jerky and hard to modulate the throttle.

You may also want to check the decal fuel cutoff setting. Could be right at the rpm you are describing. Most systems have adjustment for it.
 
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