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Posted: 12/1/2007 5:53:34 PM EDT
I have a 78 Chevy with a four speed. Alot of times when i pull up to a light and try to shift back into 1st it does not want to go in. It does not want to go into any gear for that matter. I have to force it in. What is wrong with it?
Link Posted: 12/1/2007 5:56:14 PM EDT
Is your clutch fully disengaging? How much free travel on the pedal?

You could have a bad clutch too. Or a hanging throwout bearing, pilot bearing or misaligned transmission.

But I bet the clutch needs adjustment.
Link Posted: 12/1/2007 5:57:42 PM EDT
How much free play should there be?
Link Posted: 12/1/2007 5:58:20 PM EDT
The above sounds right to me.
Link Posted: 12/1/2007 6:01:21 PM EDT
The guy i bought it from said he had just adjusted it. Could he have over adjusted?
Link Posted: 12/1/2007 6:01:38 PM EDT

Originally Posted By MUDLOG:
How much free play should there be?


The clutch should be fully engaged when the pedal is within 1" of the top of its stroke. (That is, the first 1" of pedal travel should do nothing on the clutch pressure plate itself.) 3/4" is OK, 1/2" and under is adjustment time.
Link Posted: 12/1/2007 6:01:40 PM EDT
Worn linkage? Does the shifter feel loose and wobbly during shifts?
Link Posted: 12/1/2007 6:03:02 PM EDT
No it has a nice tight shifter.
Link Posted: 12/1/2007 6:10:47 PM EDT
Worn synchros.
Link Posted: 12/1/2007 6:15:40 PM EDT
let the clutch out, then in again to get everything moving....then put it in gear

It's hard to get it in gear with the engine off, too, I bet
Link Posted: 12/1/2007 6:29:48 PM EDT

Originally Posted By Barrelburner:
let the clutch out, then in again to get everything moving....then put it in gear

It's hard to get it in gear with the engine off, too, I bet


Yup. If it's hard to get into 1st gear every time, then you probably have an issue. If it only does it occasionally and letting the clutch out a little solves the problem, it's normal.

RF
Link Posted: 12/1/2007 6:34:00 PM EDT

Originally Posted By Wack-A-Mole:
Worn synchros.


If it isn't the clutch...yep.
Link Posted: 12/1/2007 6:35:38 PM EDT

Originally Posted By refurb:

Originally Posted By Barrelburner:
let the clutch out, then in again to get everything moving....then put it in gear

It's hard to get it in gear with the engine off, too, I bet


Yup. If it's hard to get into 1st gear every time, then you probably have an issue. If it only does it occasionally and letting the clutch out a little solves the problem, it's normal.

RF


When in does this i cant get it into any gear.
Link Posted: 12/1/2007 6:39:50 PM EDT
[Last Edit: 12/1/2007 6:43:13 PM EDT by Veccio]
Make sure your clutch is adjusted correctly first, if it's still doing it then it's the synchros inside the tranny. If you practice a bit you can help it out by altering your engine RPM. After awhile, you can run up and down the gears without evening using the clutch, it's pretty easy.



*edit* I forgot to mention. I'm not 100% sure, but I'm fairly certain those transmissions had an unsync'd first and reverse, atleast most of the time period were.
Link Posted: 12/1/2007 6:45:58 PM EDT
Do you downshift through the gears when you decelerate to a stop or do you just throw in the clutch once and brake to a stop?
Link Posted: 12/1/2007 7:11:22 PM EDT

Originally Posted By Barrelburner:
Do you downshift through the gears when you decelerate to a stop or do you just throw in the clutch once and brake to a stop?


I brake to a stop.
Link Posted: 12/1/2007 8:22:53 PM EDT

Originally Posted By Wack-A-Mole:
Worn synchros.


Or the wrong weight of oil in it. It's possible the previous owner "thickened up" the oil to hide a problem.

Before tearing it down, I'd try changing the oil to Red Line MTL (Manual Transmission Lube) - There is NOTHING on the market that produces smoother gear engagements.
Link Posted: 12/1/2007 10:23:18 PM EDT
[Last Edit: 12/1/2007 10:23:57 PM EDT by MUDLOG]

Originally Posted By Skibane:

Originally Posted By Wack-A-Mole:
Worn synchros.


Or the wrong weight of oil in it. It's possible the previous owner "thickened up" the oil to hide a problem.

Before tearing it down, I'd try changing the oil to Red Line MTL (Manual Transmission Lube) - There is NOTHING on the market that produces smoother gear engagements.



He did not want to sell it, it was a wife unit forced event. I have his log book that desribes every little tiny detail of things he did to it. I do not think it is the clutch, it is almost brand new.
Link Posted: 12/2/2007 5:18:27 AM EDT

Originally Posted By MUDLOG:

Originally Posted By Skibane:

Originally Posted By Wack-A-Mole:
Worn synchros.


Or the wrong weight of oil in it. It's possible the previous owner "thickened up" the oil to hide a problem.

Before tearing it down, I'd try changing the oil to Red Line MTL (Manual Transmission Lube) - There is NOTHING on the market that produces smoother gear engagements.



He did not want to sell it, it was a wife unit forced event. I have his log book that desribes every little tiny detail of things he did to it. I do not think it is the clutch, it is almost brand new.


Well, it could be a clutch linkage or other adjustment. And if the clutch is nearly new, it could be a quality issue with the parts or service.
Link Posted: 12/2/2007 5:36:50 AM EDT
To clarify, are you talkiing about putting it back in first while the wheels are still rolling? If so, I'd suspect synchros.
Link Posted: 12/2/2007 9:11:35 AM EDT
No this is trying to put it in gear while not moving.
Link Posted: 12/2/2007 9:37:17 AM EDT
[Last Edit: 12/2/2007 9:43:25 AM EDT by refurb]

Originally Posted By MUDLOG:
No this is trying to put it in gear while not moving.


Does this occur after holding the clutch in for a while? How do you get started/stop?

If you hold the clutch in for a while, all the parts inside the transmission come to a stop (if the car is stopped). Then when you try and shift from neutral into ANY gear, sometimes it's impossible. Why? Because the dog clutch can't engage the gear. The teeth don't line up. It's like trying to put a socket over a bolt but you're not allow to rotate either one. Sometimes you luck out and they are already aligned, if not, no amount of pressure will make them fit. In this situation, it has nothing to do with synchros because the synchros only synchronize the speed of two moving parts (the dog clutch and the gear). If nothing is moving, they don't matter.

Usually if the synchros are going and the car is at a dead stop, you'll hear a grind as you engage the gear (if there is still some rotation of parts within the tranny). That's because the two parts aren't moving at the same speed and the teeth of the dog clutch grind as they engage. Most transmissions don't have synchros on the reverse gear, so it's often quite common to hear a gear grind when engaging reverse if you push in the clutch and quickly try to put it in reverse.

The comment about too thick a gear oil is a good one. If you have too thick an oil, the gears will slow down a lot and the synchros have to try and bring the gear back up to speed. Since the synchros weren't designed to fight this drag, you'll often get a gear grind when shifting into the highest gears. I can't really see it causing your problem.

Give this a try: When you are at a stop, in neutral, with the clutch to the floor, let the clutch out (with the car in neutral), push the clutch back in, then try to put it in first. If it works, then your tranny is fine.

Why does this work? Well, when you have the clutch out (you're not stepping on it), the engine is turning the input shaft to the transmission. Since something is spinning when you push the clutch in a try and shift into a gear, the synchros can match the speed and align the dog clutch so it can engage the gear.

If anyone is curious about how manual trannies work, this webpage gives a great explanation of dog clutches and synchros.

How Manual Transmissions Work

RF
Link Posted: 12/2/2007 9:50:10 AM EDT

Originally Posted By Veccio:
*edit* I forgot to mention. I'm not 100% sure, but I'm fairly certain those transmissions had an unsync'd first and reverse, atleast most of the time period were.



Ford started synchronizing 1st gear in the early 60s. I am fairly sure that everyelse starete shortly thereafter.

Unless of course it is an older model tranny.
Link Posted: 12/2/2007 10:11:31 AM EDT

Originally Posted By 72coupe:

Originally Posted By Veccio:
*edit* I forgot to mention. I'm not 100% sure, but I'm fairly certain those transmissions had an unsync'd first and reverse, atleast most of the time period were.



Ford started synchronizing 1st gear in the early 60s. I am fairly sure that everyelse starete shortly thereafter.

Unless of course it is an older model tranny.



Most of the time period trucks were using older trannies, i.e. NP435,T18,etc. which were unsync'd first and reverse.

The OP has stated that he is stopped when this occurs, so it sounds more like a clutch dragging issue.
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