When I start out in low gear and shift up into high, my car jerks till the speed increases. Would adjusting the pressure plate fingers smooth this problem out? The car pulls very well on hills and flats once I get past the jerking period. Could it be the jerk behind the wheel? I just thought I'd beat you guys to that remark. Bob
Will it jerk again if it's still in high and you slow down to the same speed that it initially jerked at? I'm thinking you have a low speed misfire.
Yes, I can't cruise along at a slow speed in high with out it jerking. The motor seems to run very smoothly even when at idle. It pulls in low gear also smoothly. Bob
Check for excessive wear in your u-joint or in the torque tube ball & socket assembly.
Any of the above could be the cause. A couple of others I have found is the brake rods are adjusted too long which causes the equalizer shaft to rotate to the point the cam will touch the high clutch lever and when you shift to high it will still be in neutral until you push the parking brake lever forward. The other problem is when you shift from low to high, you must push the throttle lever up so that the engine slows down. That way the clutch will engage. If the engine is running too fast when you shift, it will slip.
A possible fix to the jerking at low speed would be to retard the spark a few notches.
Are you retarding the spark when you shift to high? If not, try retarding it a bit as you shift, then advance it as your speed increases in high gear.
If this jerk is an engine miss, then there are many possibilities. I had this happen exactly as you describe a few years back and the culprit was a bad seal at the intake manifold, and as rpm's increased, the missing smoothed out. Spitting back through the carb was noticeable while jerking was present.
If the jerk is not an engine miss, then my suspicion would be a weak clutch spring stuttering until all of the engine oil is squeezed out. Tightening the clutch fingers may help. Spring replacement may be necessary.
Also, shifting too early will create jerking and new T drivers will think there is a mechanical problem. Allowing low to wind higher, then reduce throttle at shift time eliminates the jerking. I feel the you have plenty of T driving experience that this is not the problem.
I feel I am shifting from low to high properly. I run out in low to gain some momentum speed, shut the throttle off, pause for a second to let rpm slow and then shift to high. I usually can get into high very smoothly. It's when I apply the throttle to speed the car up that it jerks on the level or hills. If I slow down to a crawl in high it will jerk. I have one of those things that the plug wires come out of the top cap and has points. (I'm afraid to use the word here) and I find that adjusting the spark seems to make no difference when pulling a hill once I adjust it after starting but I will try it while shifting up to high. The car pulls hills so well, I'm afraid to adjust anything.
John...Would I not be able to sense the miss at idle if I had a leak? It idles very smooth.
Hal...I'll check the position of the adjustment bolt on the cam when it's in the high position.
Thanks for all the suggestions. I'll try them all and check on the others.
Another thought...Once in high, should the car jerk at all when I'm applying the gas?
Thanks again, Bob
Bob- mine was a fresh rebuild just back from the rebuilder. The miss did not show up at idle, while in low gear, or running at speed in high. Incidently, motor was run on a test stand and it ran great.
It only stuttered when shifting from low to high on a slight grade. The tell-tale symptom was the spitting back through the carb. If yours does not spit, then move on.
IF you are adjusting the throttle...
IF you are adjusting the advance...
IF it runs well on flat-land...
IF you are running WITHOUT one of those stupid foam things as an air filter...
IF your intake manifold does NOT wheeze when you spray good stuff at the gasket/gland seals...
IF your sediment bowl filter is not a bit varnished up...
Take a run at a hill 'as is'...
Then go back to start, open the carb needle valve another 1/4 turn, try the run again...and see if there is a difference.
You just 'might' be running a bit too lean! (Same thing holds true of a 'flat' but harder to spot...on a flat, if you do get a hesitation/burp/or slight buck, let it buck when you shift for all of a second...and ONLY open the carb needle valve that 1/4 turn. See if the bucking stops...if it does...running too lean)
Another possibility is fuel starvation. You may just need to open the carb adjustment a little more.
George... All the "IF'S" are positive. I don't even need a hill. It happens on the level. Shift into high, apply the gas, starts to jerking until it gains speed. It's like the clutch is grabbing, releasing, grabbing, etc, etc. I can't travel around a parking lot in high at about 5-10 mph without it jerking. Once the jerking stops on a hill pull it never happens again and pulls great to the point that the car may stall and forces me to low gear.
I'll try to rich the carb a bit. We're going on a tour tomorrow, 150 miles, so I'll have plenty of starts and stops plus hills.
Thanks, again Bob
Should the car jerk at all while applying the gas when engaged in high gear. I know it might jerk once while shifting into high but once fully engaged? Bob
I sounds very much to me after reading the posts that you 1: you know how to drive the car and 2: this is a problem that developed on it's own and not due to some work you did prior to it's happening. You don't slip when starting off or on hills. This eliminates the clutch in my book. I don't see what the drive shaft/U-joint has to do with it either. Sounds to me like an engine (fuel/ignition) problem. Low speed miss as mentioned above. I'd check my fuel flow and settings as also mentioned but that would be a constant problem not just within a certain range of engine speed. I'm thinking ignition. Point setting, distributor shaft bushing's, ect. Check the easy bits first.
Bob, you don't say if you are running coils or distributor, however either one miss adjusted can cause that. KGB
Charlie... A little more info 4 you all.
1. The car has done this jerking since I purchased it a year ago and had sit in storage for 6 yrs before that.
2. I installed the distributor and new Holley NH since I purchased it.
3. My understanding of the transmission is that low gear is controlled by the low gear band and drum and that high gear is created through the pressure plate. Low gear is fine, no chatter only high gear. If my understanding of the trans is incorrect, somebody enlighten me please.
4. The trans in my car has been rebuilt at some time in the past evident by newer bands and special lock wiring on the clutch fingers.
I hope I'm not confusing the issue here with too much information.
Thanks Charlie for your suggestions and I'm going to try carb adjustment today to see if it is too lean. I'll keep you all posted as to outcome. Bob
Keith, I just answered your question in response to Charlie above. Are you riding with us tomorrow?
we will be near your home on our tour. You can drive my car. Nothing like hands on experience to understand a problem. Bob
OK. More info is good. You did some work and it didn't change an already existing problem so I'd forget the distributor and fuel checks we all mentioned. Second opinion sounds very good. Far be it for me to diagnose a trans problem as I'm not really "up" on them but I'll stick my neck way out and say, as I understand it, the only actual function of the clutch is to create neutral. It's either on or off and is on in first, high and reverse and disconnects the engine from the drive shaft creating neutral. Correct me if wrong.
Sounds like the clutch is slipping. Sometimes you can add a half turn to each of the clutch fingers to fix this type of problem. Be sure to tie the cotter pins with dental floss to something so they cannot fall in the transmission.
Also be sure to remove the key from the ignition switch so it cannot fall in.
Charlie, I don't think that is correct. When the emergency brake leaver sits in vertical position, it places the trans in neutral. While the trans is in neutral, you can engage the low and reverse bands to move the car, not high gear until you move the emergency brake lever all the way forward thus engaging the pressure plate. I don't believe the pressure plate has anything to do with low and reverse only high gear. Correct me if I'm wrong. Bob
I'm goin to try the carb adjustment but I also am starting to believe the clutch is my problem after hearing all the comments on here.
The clutch is only engaged in High Gear. It is disengaged under ALL other conditions (Low, Reverse, AND Neutral).
Like I said. Not really up on them.
Okay guys here is the rest of the story. I determined that I was giving the gas too slow once I engaged high gear and the more it jerked the less I gave it. Now when I engage high gear I pull the throttle down at least half way. No jerking and a constant increase in speed. There was a lot of merit to those who thought fuel the problem. Still not quite smooth enough if trying to idle around in a parking lot. I think I might give the clutch springs 1/2 turn to see if slow speeds smooth out. At least now I can clutch around a sharp corner and continue on in high gear. Thanks for all the positive input, this site is awesome when it comes to help. Bob
Check the integrity of the intake manifold gaskets and carburetor gaskets, tighten nuts/bolts.
You need to match the engine speed to what it would be in high gear after you shift. If you don't rev the engine in low, push the gas all the way up, but if you rev it in low, you need to give a little more gas when you shift to high. Try it on a lonely road or empty parking lot and experiment until you can do it smoothly at various speeds.