Jumps and jerks in 1st and 2nd gear

[29FordRoadster]

Good Morning Everyone, My 29 roadster jumps and jerks when I start off in 1st and 2nd gear. In first it is smooth up to 5 mph, and in second it is smooth up to about 10 mph. In 3rd gear it is smooth unless I hit a speed bump or railroad track then it jerks till I am on smooth pavement. I can ride the clutch lightly in 2nd gear and the car will move fine. I am thinking my transmission bearings are worn out causing the problem. Does anyone out there have a different suggestion as to what my problem is? It will be two months before I can get the car in a shop to take it apart to see what is wrong. I will let the board know what is wrong when we find out.

[Jacksonlll]

Before you start taking things apart, let someone who knows Model A's listen to it and drive it.

[Patrick L.]

Don't start tearing things apart until you kinda sorta figure out what the problem is. I doubt the problem is with the transmitter bearings.
I think I need more of a description of the problem, I guess I don't completely understand what you are saying.

[Ray64]

sounds like fuel starvation 2 me

[daveymc29]

I had a similar problem and found that it had to do with my foot and the gas pedal. If I step on both the foot rest and the pedal, rolling my toe a bit to accelerate no more jerking and bucking. As the car would jerk I would also and that only increased the problem. Firmly planting my foot on the footrest the rolling motion to speed up cured that one for me.

[29FordRoadster]

Sponsored Links (Register now to hide all advertisements)

Thank you fellows for the above comments. The motor is running fine, my problem is not a lack of fuel,I have a good fuel flow. The motor is reving properly but the car just jerks in the two lower gears unless I ride the clutch. As soon as I shift to high everything is fine.

[René W]

Does the jerking also appear when you accellerate full throttle?

[larrys40]

Not saying this is it but it sounds like your rear engine mounts have issues. Stock or are they "float A "mounts but it sounds like they are loose,broken or the rubber is missing or shot.

Inspect and take a look at the rear brake cross shaft to see how close the torque tube is setting. You should be able to get a finger in between. If not your rear mounts are sagging.

When you hit a bump it puts pressure on the wishbone ball and socket and if the engine is moving and not tight you can get some if the symptoms you describe.

In addition you may have front end issues as well but that's another one to look at.

Larry Shepard

[Dick Steinkamp]

Has the car always done this or did it just start?

[Terry, NJ]

The trouble is that "Jerks" really doesn't tell you much. Yesterday, coincidentally, my coupe started to "Jerk" too. I'm in a state of thorough disgust with it so I haven't looked into it yet, but I'm pretty sure it was somehow getting into two gears at once, They jerk to a sudden stop then! I see a major rebuild coming up and I'm not looking forward to it!
Terry

[Bill G]

My jerky car is due to the same thing as daveymc29 says in post #5.

[Jacksonlll]

Here is an easy one to try. Push on the brake pedal and see if your shifter knob goes up and down. I have seen the trans sitting on the cross shaft. Would mean your rear eng mount has failed.
Also, while it is jerking, does the shifter go up and down?

[Marvin/TN]

Seems simple but are you using the foot rest on the floor? It sure helps keeping the gas feed smooth.

[1930artdeco]

Is it possible the clutch is the issue? You say that you ride the clutch lightly and the car smooths out. my 2 cents worth.

Mike

[daveymc29]

Try a trip around the block with your accelerator foot resting on the footrest and accelerate by rolling the front of your foot (big toe) onto the accelerator button. I'll bet that will help cure it no matter what the real problem may be.

[29FordRoadster]

Perhaps I can be more clear on describing my problem
1.The car just started acting up about two weeks ago. Up until then 1st and 2nd gears allowed the car to move very smoothly.
2. I have float-a-motor motor mounts that appear to be in good shape. The bottom rubber is a little flatter than top but not much.
3. The gear shift does not bob up and down when I press on the brake while moving. Also, the gear shift knob does not move when the car is jerking.
4.I have a v8 clutch and pressure plate and a lightened flywheel.
5. The car does not display this behavior every time I start out, but probably about 90 percent of the time. It does run smoothly in high gear at all speeds.
I really appreciate all the suggestions that have been offered. I wish I could explain more clearly what the car does. I can only say I almost get whip lash from the way the car moves in 1st and 2nd gears.

[Brian in Wheeling]

Yer lugging the motor!
Brian

[Dick Steinkamp]

Originally Posted by Brian in Wheeling

Yer lugging the motor!
Brian

So he changed his driving style over the last 2 weeks?

[Benson]

Could it be "the death wobble"?

[Simonpie]

It sounds like the gearbox is slipping and then catching. If it was a motorcycle, I'd say bent shift forks. On a Model A, the same thing can happen, but it wouldn't pop back into gear, just grind. Either way, a cheap and easy first step is to pull the tranny tower and look for wear or bending of the control parts (forks and round ball on the shifter).