falling out of second gear when pushed

[dgym]

Hi gents,

I've done a couple of hillclimb events recently, (haunted hills and rob roy) and at both events , only once at each, the car fell out of second gear at around 5,500rpm
From memory this only happened when I'd been in second gear for longer than around 7 seconds.

It hasn't happened under normal driving conditions so it's easy to ignore, but I'm thinking it might be smart to get onto the issue before it gets worse.

I have a bit of experience rebuilding a spitfire gearbox a couple of times, so I feel ok about venturing into it. Just wondering If there are any ideas as to what the problem is.
I'm thinking it could be the loading on the little springs that hold the gear in the little groves on the mainshaft?
or could it be something more sinister? I guess worn bearings could lead to enough movement to

also, I have a spyder chassis, can I get the gearbox out without the engine coming out?

thanks!
-Jim

p.s. just realised I will have the failure captured on camera, so i will upload a video in the next couple of days.

[rgh0]

Hi Jim

The first check is to make sure the lever is moving fully and it is going completely into second gear. Check there is nothing around the lever restraining its movement and that the cap that screws the lever into the box is fully tightened.

Pulling the gear box apart is relatively easy but the engine does need to come out. What will be the cause could be a number of things such wear or loss of tension in the detent springs and balls or in the syncro hubs or in the bearings or the selectors so you need to go through the box completely to identify the potential problems.

cheers
Rohan

[Elan45]

Hi Jim,

Rohan is right. You should make sure that you are getting full engagement. Check the plastic cap that the selector is not running into interference. Could you have something else restricting movement such as a new console cover or new rubber boot?

If you go into the gearbox, a couple of things I'd check in addition to the detent springs and balls:

Worn shift fork. Usually a problem on 4th gear, but I've seen significant wear on the 1st-2nd fork also.

Check end float of the gears on the main shaft. Earlier gearboxes have a nut behind the back bearing, later boxes use a snap ring/ circlip. If you need to take up excessive clearance on a later box, you would have to use shims. Early boxes you just tighten the nut.

Also, check the small teeth on the gear that engage with the syncro hub. Also look at the inside of the syncro hub. Both of these sufraces will wear so that they are no longer parallel but actually ramp shaped which leads to an axial force trying to force the engagement apart.

Roger

[Chancer]

Also, check the small teeth on the gear that engage with the syncro hub. Also look at the inside of the syncro hub. Both of these sufraces will wear so that they are no longer parallel but actually ramp shaped which leads to an axial force trying to force the engagement apart.

Roger

Your competition use may be significant, if you beat the synchromesh giving a Crunch on the upshift to 2nd gear eventually the wear above will cause it to jump out Under power, the same on downshifting will wear the other flank causing it to jump out on the over-run. my memories are d?cades old so I may have got that backwards.

[dgym]

Thanks gents,

I DO have a new center console! so lets hope that's it. I have some time to investigate today so I'll check it out.

my competition use has been minimal but the guy before me I think did a few events too.

I do remember crunching once or twice in the heat of battle.

I've just watched Allan's gearbox rebuild video on youtube so my imagery of the internals is improving.


also today I need to do some window mechanism repairs, my passenger window decided it couldn't close right in the middle of a short storm we had here a few days ago. . It seems the pegs from the bracket on the motor that fit into the window winding wheel have broken off. It looks like someone has already tried brazing them on in the past. I'm gonna try the MIG.

cheers!

[Elan45]

Get all of the braze off before welding. The braze will contaminate the weld.

Roger

[dgym]

Thanks Roger,
took your advice, I'm an ugly welder but I'm getting better. It held up to some good bashing so will hopefully survive in the door.

[dgym]

just thought i'd follow up this post with what seems like a result. After replacing my engine mounts I went back to the same hillclimb and 2nd gear was fine for all four runs. fingers crossed the old engine mounts were doing something bad to the drive train?

[dgym]

well the problem has arisen again, this time it's constant, popping out of second.
I have the gearbox out and there is a large amount of forward/backward play in the mainshaft gears when i push/pull on the output shaft.
this is bad right?

here's a video https://youtu.be/dHYstdiqQVo

also when second is engaged and the shaft turned, i could feel/hear gear teeth clunking on something i guess they were rubbing against.

cheers!

[Craven]

Hi.
Location of the input ( 1st motion shaft ) shaft is controlled by the front bearing found under the housing that the clutch trust bearing rides. Mainshaft is located by the rear bearing held in a carrier at the back of the main case.
You may be lucky, if the large nut that hold the speedo drive and rear bearing carrier in place has come loose it will give your symptoms. You need to remove tail section to see this.
May help
Ron.

[dgym]

Thanks Ron, are you saying this could be as simple a fix as tightening that nut? and not pulling the whole gearbox apart?

[rgh0]

An S4 should have the snap ring style mainshaft - so no nut to come loose

Lots of other potential issues that may come out of a strip down and inspection

cheers
Rohan

[Craven]

Hi,
I?ll leave you in the more capable hands of Rohan.
Ron.

[dgym]

Hi Rohan,
it's an S3 but yeah You're right I should suss it out properly anyway.

[rgh0]

Sorry did not see the year at the bottom of your post. A 66 car may have the nut style mainshaft I cant remember exactly when they changed and I am down at Phillip Island so dont have access to my books.

As you pull the box down the problem source should be obvious.

cheers
Rohan