The Stovebolt Site Forums The Shop Area Engine Shop clutch slippage

Hi all, I have a 58 3600 4 on the floor. Problem is when cold truck jumps. For ex if i am starting out going a short distance in second it can really jerk when cold and the clutch out. Also when cruising in 4th it seems to go faster and slower ever so slightly. I have heard this can be a clutch problem. Is there an adjustment or test I can do. I did the peddle adjustment and that helped a bit
Thanks Rick

your only adjustment is the peddle on the older clutches. you want about an inch of free play in the pedal. if its slipping you should smell a nasty burning smell. once you've smelt a slipping clutch you will never forget it. you could also have some contamination of the clutch thats burning off when cold. check if you have any leakage around the bell housing. oil and contamination will take out a clutch prematurely. anyway good luck MO

good to know. there is no stink. so thats a good thing

I hear you describing an engine that is surging--pulsating in speed with the throttle being steady.
The clutch is less prone to slip in lower gears.If you can spin the wheels in lower gears there should be no problem attributed to slippage--in lower gears.
Clutch "chatter" or "judder" occurs as it is being slowly engaged but goes away after engagement.
Clutch "drag" occurs when trying to dis engage and the gears clash or the machine trys to keep pulling.
When it jerks , cold with the clutch (pedal) out, probably the engine is stumbling due to incomplete warmup.
Have you mastered the art of modulating/varying the choke to drive away smoothly with the engine cold?-- My guess is; not very well.
Don't feel bad, most people raised in a time when engines had automatic chokes or fuel injection were taxed to learn the art.Why, even when all had manual chokes there were many who never learned what their engine was telling them it wanted to run smoothly under varying speed and load.They just thought choke on to start then off after that.

Thanks everyone, I must say I am perplexed. You are right Bob I am not the best manual driver. However I drove it around the neighbourhood a lot over the weekend and there just doesnt seem to be a lot of consistancy. I can be in 2nd or 3rd holding the gas steady as I can and it will still jerk . But then it might not the next time. I guess it tends to be smoother the slower I go. If I take off very slow it tends to be smoother. And it was well warmed up

Good Ricky, I think we have eleminated the clutch slipping possibly as the jerking cause so now maybe we can focus on the symptoms.
A few questions:
How smoothly and regular does the engine idle( at operating temp of course)any surging?
When slowly speeded up with no load and then slowed, is it smoothly progressive or seem to have sensitive spots in the accelerator?
When you punch the accelerator to about 1/2-3/4 , but don't overspeed, then let off does it respond sharply or stumble/
How old is the fuel?
Wrong point setting/condition and over advanced ignition can show up these symptoms.
Disconnect the distributor advance and plug the carb end and see what result you have.I believe you will see a difference.
Oh the fun and learning experiences these old girls provide.Thanks for sharing with us as we learn from your machine.

Hi Bob, Thanks very much for your help on this.
1. Idle - Engine idles pretty good when warm. I ccan leave it sitting there, no problem
2.speeding up and slowing down - Increased speed creates sensitive spots - jerking. Gearing down is ok
3. punch the gas - it could respond well or not, sometimes a little bogged down. And I am unclear if that is the truck or my skill set. Letting gas off same as above its ok
4. fuel - brand new
Bob as you may know I am very new to all this stuff. But one thing I do know is to never ever ever touch the Distributor. However I will try anything once. Can yo tell me what the dist advance is so I can plug it

Wrong point setting/condition and over advanced ignition can show up these symptoms.
Disconnect the distributor advance and plug the carb end and see what result you have.I believe you will see a difference.

Before you look elsewhere, be sure the motor mounts are in good shape. Chock the rear wheels tightly ahead and behind both wheels, and try to move the truck forward and back while someone watches the movement of the engine. There should not be a great deal of movement. If the engine shakes violently or has a lot of motion side to side as the load goes on, look for broken or deteriorated motor mounts. If it's chocked properly, the truck won't move, so don't expect to jump the chocks.
Jerry

Thanks Jerry, I have checked the motor mounts and they appear to be in very good shape. Although I have not done your test and will certainly give it a try Thanks Rick

Ricky,
We may understand your reluctance to work with an unfamiliar componant such as the distributor but be assured, if you run the vehicle someone will.It usually is the most touched componant involved in ROUTINE tune ups.
The people on this forum know these machines, their parts, and their peculiarities well but they don't know your machine unless you tell them about it--mainly it's condition, history, maintenance done in the last months, what you expect of it, and maybe your expected level of involvement in it's repair.
Looking forward to hearing you work through this yet to be determined problem.

Hi Bob, I tried to answer your questions above. I'll throw in some more info. It is a 58 3600 4 on floor. I bought it last fall and got it cert and plated just in time to put it away for the winter. Recently I have replaced all the hoses, fan belt, fuel pump, thermo, speedo cable, wiper motor, spark plugs, oils, oil filter. (blew the heater in the process) The motor and tranny was apparently rebuilt. The truck looks very original. faded paint etc. Someone mentioned chatter. I think I have that as well. Everytime I take off in 2nd there is what I am sure you are referring to as chatter. (is this bad, normal, fixable) Then there is the jerking. Let me know if there is anything else I can tell you. I want the truck for putting around the neighbourhood in the nice summer weather. But want it to be as dependable. And I would like to try tackile the problems myself with everyones assisstance but realize I may have to take in for some things.

I'd say you have 2 problems, first is a bad clutch disk [oily likely, and flywheel glazed], one way to tell is when starting from a stop, rev it a bit more and "slip" the clutch by engaging it as slowly as you can - you'll likely need to replace the clutch and resurface the flywheel ..... the "jerking" at a fairly steady speed may be coughing or misfiring, maybe timing as said above, or it could be the carb

Bill

Ricky,
Sounds like you have a reasonably fresh "runner" there to work with but we need some help in interpretation of what you are hearing the old girl tell you.

1) If you dont have already, start looking toward repair manuals to help you see how the componants you will learn to deal with are made and what they are expected to do.
Easily found will be "MOTORS" or "CHILTONS" manuals of vintage or 2 years newer than your vehicle AND genuine Chevrolet shop manual of your vehicle + or - 2 years.They don't have to be beautiful--shouldn't pay more than 15.00 for either.

2) Go to the oldest parts house around and ask what old fart in the area you could to for an analysis/test drive of your truck.
optional location to obtain may be local coffee shop(not fancy)or maybe McDonalds.Go early in the morning--it won't hurt long for you to get out before 7:00 and the wife doesn't get anything out of you that time of day anyway.
You will find somone willing to mentor or give an opinion after a test drive or ride with you-- it may cost you a cup of coffee but there will be many benefits if you are selective.
What we can gain here for consideration of the problem(s) is a learned feel for what the truck is doing compared to what can be expected.

Not sure if I should start new topic or not. I dont think it is the clutch entirely now. I have analized it closer. I know the truck is54 yrs old but it seems to be working to hard and at to high of rpm to do what it is doing. I am new to this and dont have anything to compare it to. I am thinking it has something to do with the points. I have replace plugs, wires. points, rotor, cap. When I tride adjusting points I noticed sa difference at different speeds. Sometimes I can get it to run better at slow speeds and sometimes better at fast speeds but I cant get it to run good at both high and low. I have st points to .019. Below I pasted Bobs comments from a previous reply. He said to disconnect the dist advance and plug it. Is this the steel tube that runs from the carb to the dist. And if it is, when I disconnect it will gas pour out. And do I leave it plugged and just run the truck like that?
Thanks Rick

Wrong point setting/condition and over advanced ignition can show up these symptoms.
Disconnect the distributor advance and plug the carb end and see what result you have.I believe you will see a difference.
Oh the fun and learning experiences these old girls provide.Thanks for sharing with us as we learn from your machine.

Rick,
I'm glad to hear you are learning that distributor.The reason suggested disconnect the VACUUM line to advance chamber is to see if lack of VACUUM advance would lessen the tendency to "buck".If the timing were too high at idle, when the throttle were above idle and vacuum advance added there could be increased tendency to buck.
The line conducts vacuum only and will not leak gasoline and may not have to be plugged to run ok temporarily.
When you are sure the point setting is correct then timing at idle should be set then the vacuum line reconnected.
Did you learn about proper lubrication of the point opening block or cam follower.This is important to the point setting remaining as set since wear of this block WILL reduce the point opening and retard the timing---many times in a matter of a few hundred miles.
I am suspecting that the reported occasional "bucking" is caused by over advanced timing--would like to hear you make a test with timing retarded from the original point.

Hi Bob, Yes I think I have the points set perfectly now. I am thinking it is the timing now as well. I dont have a timing light . Can you set timing any other way. Is it a metter of loosening the dist base and turning it. And yes I did lub the cam follower

I am also noticing the cam that the points ride on is worn. starting to look a little bit round . I ssume this could be contributing to my problem as well

Rick,
I would say it would be rare for the breaker cam to be worn enough to cause your problem.For a good anylisis of the cam contour clean it up good and compare the cam profile adjacent to the contact area of the rubbing block.
Rotating the distributor in it's clamp will change the ignition timing all through it's range of automatic advance/retard.I think it would be good for you to move it slightly to test the result.To turn the body in the direction of shaft rotation will deliver the spark later (retard) and vice versa.
A retarded spark from optimum will make the engine seem lazy to respond to throttle opening, possibly backfire through the carburetor, and lessening of power.
An spark advanced much from optimum will give a sharp resposive engine off idle but reduced power as the automatic advance comes into play, limited usable RPM, bucking and jerking when under load and possibly coming off load, pinging or knocking under load, and irregular idle and light load.
Many people setting the timing"by ear" set too advanced because they mistake the quicker response off idle as an indication of a more favorable setting not realizing what happens when the automatic advance comes into play.
Is this jerking you describe something you can repeat or just a random thing that happens under varying conditions?
Under what load(throttle opening) and speeds does this happen?
When driving in top gear, level road, at 35-40 MPH if you step down on it some for 10 seconds then let up slightly what happens? smooth transition back to lower throttle opening?

The irregularity is mainly in 2nd. Example if I am going a short distance down the road where I dont want to go into 3rd. If i hold the gas steady it will go faster and slower faster and slower. It also seems that the truck is working to hard in 4th. It tales a long time to get to 50 and feels like there is a lot of vibration in the motor area, and the rpms are high

Ricky,
Please disconnect the line from the carb to the distributor advance chamber---whittle out a stick to plug the end going to the carb and retest the truck and tell us what the results are.

You are describing a surging which would be exaggerated in the lower gears if it were engine related.
From a cold start, drive about 1 mile using the brakes a minimum or preferably, not at all.Then immediately go around feeling the brake DRUMS comparing the temperature--be sure to include the parking brake if it is on the rear of the transmission.We are looking for a difference in one indicating the drum is not round or not fully releasing.
While driving at a speed and load where the surging is very noticable take the truck out of gear and coast.The surge should stop when the engine is disconnected if it is the source.
Give us some "feel" we can use.

Hi Bob, I just want to make sure I have this right. Once I disconnect the line at the advance chamber, Do I plug the hole on the advance chamber or the tube going to the carb

I wilol try thr advance chamber and breat test hopefully Monday night