gear shift stick movement in 3rd gear question

[recordsj]

1500 midget

In 3rd gear I notice that the gear shift stick will move a bit when I press the gas pedal (and then move back a bit when I let off of the gas). I did remove the stick shroud and didn't notice an equivalent movement of the transmision housing movement (I looks like the majority of the movement is in the stick).

Any ideas on what is causing this and should I be concerned?

My first idea is that since it doesn't do it in the other gears it is a sign of some wear/slop in the 3rd gear causing the gear shift stick to move.

 

[bthompson]

Here's some thoughts off the top of my head. I'm no expert, but I've been up to my elbows in a 1500 box very recently.

It <span style="font-style: italic">might</span> be wear from the shifter end...there's a ball-and-socket arrangement at the end of the stick, and a spring that puts downward pressure on the shifter. It would probably take very little slop at that end to telegraph into a lot of movement at the shift knob. Before you panic about the gears, pull the shifter itself out and see if there's anything obviously wrong down there. It might be "normal" movement that just, (for some reason when the lever is in that position,) looks bad.

What direction does the stick move? If it's left-and-right, it probably <span style="font-style: italic">is</span> just the torque from the engine moving things a little. (Better check your tranny mounts; the rubber mount on the right side might have torn?)

Because of the way the shift mechanism works, the only way I can see a wobble happening because of the <span style="font-style: italic">gears</span> would be a front-and-back movement. If you aren't having any trouble in second, it probably isn't the Evil Circlip.

<span style="color: #339999">Brainstorming: </span>

It may be third gear is loose on its bushing, which may cause it to "walk up" the laygear on acceleration, and "walk back down" when the force is the other way? That might cause a bit of movement, but I imagine it'd be fairly loud.

It may be that the shift fork is loose in the synchro, but I'd think that would cause more of a vibration than a certain movement.

Perhaps if the synchro teeth weren't engaging fully (if they were <span style="font-style: italic">really</span> worn, maybe) the synchro would try to pull off when accelerating? If the shifter tries to pull toward neutral on acceleration, my bet would be on the worn synchro idea; I bet that's the first stage of the "popping out of gear" problem.

 

[recordsj]

Thanks for your input.

Also my gearbox is a new rebuilt 1500 gearbox by a area british car shop. At this point it has about 4k miles on it.

The movement is forward and back (I don't remember off hand which direction it moves when accelerating and letting off of the gas, I will have to check that tomorrow on a drive). Again the issue is only in the 3rd gear.

3rd gear is not noisy and nothing else is out of the ordinary in comparison of the other gears (which are not noisy either).
No weird vibrations either.

 

[bthompson]

Now <span style="font-style: italic">that </span>makes a puzzle. If it's a rebuilt, we can assume that the bushings, endfloat, tolerances, etc., are all in spec, and the gears and synchros are all sharp. And with no noise or vibrations...? I'm stumped. Wierd.

"Enjoy my new gearbox and don't worry about it," is what I'd tell myself. If it's trying to pull out of third, keep an eye on it. If it's pushing the other way, harder <span style="font-style: italic">into </span>gear, I'd say hooray.

 

[recordsj]

After a drive yesterday, I noted that the shifter stick moves forward when you put on the gas and then goes back when you let off of the gas

 

[recordsj]

I have the engine out for a rebuild and finished that part of the project.

Before tearing everything apart, the stick shift (this issue only happens in 3rd gear), would move forward when I put on the gas and move backwards when I let off the gas.

I have the transmission out. When I move the input shaft with my hand, I don't see any movement in the stick shift in 3rd. I figure that the engine is putting a lot more HP through the transmission than I am. Removed the top cover plate to see what I can see. Is there anything I should be looking for or movement in anything that I can do with my hands on components (which the movement shouldn't be there) to help diagnose this issue?

 

[Deleted member 8987]

That was a long engine rebuild.
18 months?
On the trans....not LBC, but I have seen that, a lot. Always something on the main line moving.
I have seen rear bearings moving in the case, front bearings moving in the case, loose shimming on gears on the main shaft.
Since 4th is direct, and locks to the input gear, the thrust movement of the other gears to induce a fore-aft movement on the output shaft is minimized, but if rear beaing, it should manifest in 1st and 2nd.
Pull the tunnel, and the top cover, and pry 3rd back and forth carefully, with a good light, loking for movement.

 

[recordsj]

I started the engine rebuild at the beginning of this year actually...

Thank you for your ideas, I will take a look at those things you pointed out.

 

[recordsj]

Took a look at the gears, no damage or unusual wear. With a screw driver I could not move the 3rd gear. I could though move the synchro hub still back and forth to cause forward movement of the shift stick. So I am thinking I am ok then?

 

[Deleted member 8987]

So, the hub itself is moving, as opposed to the outer ring?
Hub ain't supposed to move, if I recall......

 

[recordsj]

by hub, I mean item 23 from the Moss catalog see link (https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29288).
Mainly the hub ring (which connects to the shift fork), still has movement to cause the shift stick to move forward.

 

[Deleted member 8987]

23 right, yes, 23 left, no.
Been a lot of years since I did one, but the circlip should hold the synchonizer hub to the mainshaft, whicjh then holds thrid gear to the adjustment shim.

 

[recordsj]

23 right, yes, 23 left, no.
Been a lot of years since I did one, but the circlip should hold the synchonizer hub to the mainshaft, whicjh then holds thrid gear to the adjustment shim.

please clarify what you are talking about?

 

[Deleted member 8987]

23 has two legs. One left, one right. The right one is a ring, for the shift fork, the left is the fixed hub, fits on splines on the forward end of the mainshaft.
Left (hub) is not supposed to move, right (ring) is.
If your lever is moving, something in the trans is causing it, if not third gear shims, then the hub moving.

 

[recordsj]

23 has two legs. One left, one right. The right one is a ring, for the shift fork, the left is the fixed hub, fits on splines on the forward end of the mainshaft.
Left (hub) is not supposed to move, right (ring) is.
If your lever is moving, something in the trans is causing it, if not third gear shims, then the hub moving.

the left one will move in and out (about 1/8 to 3/16 of an inch) in-line with the mainshaft it sits on, but it is fixed (will not rotate) relative to the mainshaft, so this is not ok?

 

[Deleted member 8987]

I've worked on more transmissions than I can remember, so forgive me if I cannot recall exactly how that one is set up.
GENERAKKY (and we all know LBC's don't always fit the "generally" part), there is a circlip retainer on the end of the mainshaft that holds the 3-4 syncho in place. Third gear rubs against the rear portion, and is shimmed with washers.
The hub is being forced to move by the angle of the gear mesh under load and coast, forcing the hub and ring to move fore and aft, making the end of the lever move.
4th gear is direct, so you have none of that thrust from the angle of the gears meshing to force anything to move.
I have never seen a hub move like that that my fuzzy brain can remember, unless it wasn't secured with a circlip or the hub faces were wore out.
Are you having any issues with 3rd or 4th grinding on occasion?
Somebody with a more recent trans apart experience is going to have to tell us both how that hub is secured, but the shop manual should indicate how it is loaded so it doesn't move.
3/16 is one helluva lot of movement in a trans, for a part that should be set.
Probably gives you 1.5" at the shift knob.

 

[recordsj]

Never had an issue with 3rd or 4th grinding

 

[recordsj]

23 right, yes, 23 left, no.
Been a lot of years since I did one, but the circlip should hold the synchonizer hub to the mainshaft, whicjh then holds thrid gear to the adjustment shim.

please clarify what you are talking about?

See Jon Twist of University Motors YouTube video, take a look at 4:30 and notice that he points out the hub moves
https://www.youtube.com/watch?v=-lAXy3teCLw&feature=related

So why would there be more movement available on the hub to cause the stick shift to move on my transmission?

 

[Deleted member 8987]

That I don't know. Doesn't look like 3/16" by a long shot.
All we need to know is why your shifter moves in ONLY 3rd, and nothing else.
3/16 seems like an awful lot. If we had a spec on clearance, maybe...
I suppose a worn synchro ring (balk) or the ears worn could allow more movement, buty that would cause grinding into gear (which is why I aasked about gear grinding earlier).
Once you are "engaged" fully, the grooves on the inside of the ring are mated to the teeth on the appropriate gear, and you should have no movement,
I keep thinking third gear is not properly shimmed (that would cause it for sure), but you said it did not move.
Now I'm puzzled.

 

[Deleted member 8987]

I did make a call this morning, and asked, but the person did not know 1500 transmissions, which, he said, are different.