Technical Gearbox jammed

[cinque500]

Gearbox locked solid recently doing the hill climb at Brooklands, no neutral either. Took the box apart and found the pinion bearing in very poor condition. Changed that and set the shims etc. All good on that front but having put the rest of the gearbox back in I find a still can’t select neutral and when I try to select other gears it just jams the box.
I know from my description it sounds very much like the interlock things, the two little kind of oval ballbearings and the pin in between could be at fault. But I’ve done those a few times over the years so I’m pretty familiar with those strange parts.
So then thinking I may perhaps have a bent fork I also looked at overriding the selectors by removing the 8mm bolts to manually (albeit perhaps moving things out of sync) try and find a neutral in there somewhere but I can’t no matter what I try.
Here’s a video, hoping it will help find a solution that evading me!

Dropbox

www.dropbox.com

 

[bugsymike]

Gearbox locked solid recently doing the hill climb at Brooklands, no neutral either. Took the box apart and found the pinion bearing in very poor condition. Changed that and set the shims etc. All good on that front but having put the rest of the gearbox back in I find a still can’t select neutral and when I try to select other gears it just jams the box.
I know from my description it sounds very much like the interlock things, the two little kind of oval ballbearings and the pin in between could be at fault. But I’ve done those a few times over the years so I’m pretty familiar with those strange parts.
So then thinking I may perhaps have a bent fork I also looked at overriding the selectors by removing the 8mm bolts to manually (albeit perhaps moving things out of sync) try and find a neutral in there somewhere but I can’t no matter what I try.
Here’s a video, hoping it will help find a solution that evading me!

Dropbox

www.dropbox.com

From your video it does seem to indicate a selector issue, holding a gear in when it should be in neutral, so when any other gears are selected you get instant lock up.
What gear are you getting when it turns but should be in neutral?

 

[fiat500]

It looks like the fifth gear, replacement, top selector rod, which would originally have been for reverse only, has a resting position where the detent ball would not be able to lock into its groove.
I remember the instruction to allow you to loosen the nut on the pinion shaft was to engage reverse and first at the same time to lock the box once the selector forks were loose. Can you get all of the selectors aligned properly, because they look a bit wonky.

 

[cinque500]

From your video it does seem to indicate a selector issue, holding a gear in when it should be in neutral, so when any other gears are selected you get instant lock up.
What gear are you getting when it turns but should be in neutral?

2nd 3rd and 4th gears are all meshed but which ones are actually engaged via the dogs and transmitting I don’t know
I’ll upload a link in a mo, see what you think

 

[cinque500]

It looks like the fifth gear, replacement, top selector rod, which would originally have been for reverse only, has a resting position where the detent ball would not be able to lock into its groove.
I remember the instruction to allow you to loosen the nut on the pinion shaft was to engage reverse and first at the same time to lock the box once the selector forks were loose. Can you get all of the selectors aligned properly, because they look a bit wonky.

 

[cinque500]

It does feel like the selector forks are out of alignment to cause such a lock up issue but I have tried to unbolt all the forks on the three rods and manually push the gears around to find neutral somewhere but cannot, there’s always drive or a lock up, just about to upload the link to video, hopefully something is obvious to you but I’m baffled. I wish I had the Nanni instructions, might reveal something more.

 

[cinque500]

I’m not cutout to be a film maker but I hope this helps you decipher what might be the issue!

Dropbox

www.dropbox.com

 

[fiat500]

I’m not cutout to be a film maker but I hope this helps you decipher what might be the issue!

Dropbox

www.dropbox.com

Second, third and fourth will be in contact with their respective countershaft part at all times, just that as you hint, they should not be engaged until the appropriate dog selects them.
When you say you were selecting first, that would be reverse.
The top selector rod that the 5 speed kit replaces should therefore still be for reverse and obviously also for fifth, and not second.
The bottom sector is not reverse, it is first and second. And the middle is third and fourth.
That's my understanding of a standard box, and my visual interpretation of what I see happening.
As you say, it might be those circlip/spring things, as we weren't sure. But it could also be a component misplaced or back to front.
I will try to get a spare gearbox out of my oddly inaccessible garage (too hard to explain here), and get one partially stripped.
PS. It would be a good idea to tighten the plate for the detent ball springs. I'm not sure if it's helping that you're not getting the exact positions for the forks. It might have repercussions for the interlocks too.

 

[cinque500]

Second, third and fourth will be in contact with their respective countershaft part at all times, just that as you hint, they should not be engaged until the appropriate dog selects them.
When you say you were selecting first, that would be reverse.
The top selector rod that the 5 speed kit replaces should therefore still be for reverse and obviously also for fifth, and not second.
The bottom sector is not reverse, it is first and second. And the middle is third and fourth.
That's my understanding of a standard box, and my visual interpretation of what I see happening.
As you say, it might be those circlip/spring things, as we weren't sure. But it could also be a component misplaced or back to front.
I will try to get a spare gearbox out of my oddly inaccessible garage (too hard to explain here), and get one partially stripped.
PS. It would be a good idea to tighten the plate for the detent ball springs. I'm not sure if it's helping that you're not getting the exact positions for the forks. It might have repercussions for the interlocks too.

Thanks for correcting me on which gears I was selecting, I was 100% out - consistent at least
With your experience I’m sure you’re right as the internals on the two shafts are std Fiat.
That would be amazing and I’d be so grateful if you do get the chance to look at one of your gearboxes. This has been my problem from the start of this, nothing to reference against.
Since the video I’ve stripped it down so I’ll take some pictures tomorrow afternoon of each subassembly.

 

[cinque500]

Thanks for correcting me on which gears I was selecting, I was 100% out - consistent at least
With your experience I’m sure you’re right as the internals on the two shafts are std Fiat.
That would be amazing and I’d be so grateful if you do get the chance to look at one of your gearboxes. This has been my problem from the start of this, nothing to reference against.
Since the video I’ve stripped it down so I’ll take some pictures tomorrow afternoon of each subassembly.

So here are the pinion shaft assemblies. With that sleeve in the middle, I’ve got the 3 sliders over the circular spring as per discussions on previous post because I don’t see how it can possibly work for the clip on the outside - but happy to be proved wrong!
Do you see anything else which could be wrong?
Other than that a discovery made as shown in the last pic, I think that the bush on 4th is seized as the one on 3rd gear on the other side moves freely
Update - Houston we have a problem! 4th is toast, can’t even get the bush fully out. I guess this is the cause of the lockup. The inside surface feels completely smooth, I suppose the bush is sacrificial? But whether it’s been heat damaged and tempered the gear unit I don’t know but at the moment although I can’t get it fully out yet, it looks okay??
Update 2 - 4th gear has molten bush material fused on it, see last pic
I wonder if the failed pinion bearing caused a skew on the shaft and the movement was most pronounced on these first adjacent components?

 

[fiat500]

It looks like you've definitely traced the locked gear issue!
I think the bushings are fairly easy to find.
The spring-rings are definitely in the grooves prior to fitting the fingers:

 

[fiat500]

IIRC, this happened when you were on a hill-climb event. That, and the fifth gear, imply that your Fiat probably has a bit of extra oomph? It's possible that the bushing seized because of the bearing collapse, but the entire problem may well be due to stressing the box beyond its design parameters.
Keep us posted...it's interesting to be able to watch, and get to be able to keep our hands clean.

 

[cinque500]

It looks like you've definitely traced the locked gear issue!
I think the bushings are fairly easy to find.
The spring-rings are definitely in the grooves prior to fitting the fingers:

Many thanks for finding this
I couldn’t find anything with this vital detail, video or pics.
Really good to see the spring confirmed going behind the fingers and seeing the guy fully assemble the whole shaft. Really puts my mind at rest as although it seems physically impossible to put the spring outside there’s always a nagging doubt. On Andrew Coles video he shows it going outside but I don’t think he fully assembles it. I can only think he must have corrected that afterwards but not in time for the video.
Super, thanks again

 

[cinque500]

IIRC, this happened when you were on a hill-climb event. That, and the fifth gear, imply that your Fiat probably has a bit of extra oomph? It's possible that the bushing seized because of the bearing collapse, but the entire problem may well be due to stressing the box beyond its design parameters.
Keep us posted...it's interesting to be able to watch, and get to be able to keep our hands clean.

Yes …. x4! I’m 99% sure the pinion bearing was knackered before the hill climb event. Thinking back, the transmission was noisy for God knows how long but I just didn’t take any notice as I just couldn’t remember if it was always like that or it only happened in the last year. But I really am the most unobservant (including listening) person around, ask the missus
Like your first thought I think there was a chain reaction, that pinion bearing was so shot it allowed the shaft to be out of alignment by say a couple of degrees. The 4th gear and bush were then trying to do the job of keeping the shaft aligned and is certainly not up to the job of a roller bearing, so overheated and seized.
I’d like to get a shorter fourth as it’s almost like an overdrive which I don’t need given I have an extra cog anyway. But I’m not going to do it as it’ll cost a fortune and I’ve already mortgaged the kids.
So I’ll go for standard bits. Ricambi appears to have the gear and bush so I’ll do an order in a mo.

 

[fiat500]

Yes …. x4! I’m 99% sure the pinion bearing was knackered before the hill climb event. Thinking back, the transmission was noisy for God knows how long but I just didn’t take any notice as I just couldn’t remember if it was always like that or it only happened in the last year. But I really am the most unobservant (including listening) person around, ask the missus
Like your first thought I think there was a chain reaction, that pinion bearing was so shot it allowed the shaft to be out of alignment by say a couple of degrees. The 4th gear and bush were then trying to do the job of keeping the shaft aligned and is certainly not up to the job of a roller bearing, so overheated and seized.
I’d like to get a shorter fourth as it’s almost like an overdrive which I don’t need given I have an extra cog anyway. But I’m not going to do it as it’ll cost a fortune and I’ve already mortgaged the kids.
So I’ll go for standard bits. Ricambi appears to have the gear and bush so I’ll do an order in a mo.

As for listening, I'm very good on mechanicals but equally bad as you on the maritals.
It's was bit quiet this morning because of some things I "didn't" hear.
Given that the fifth gear is effectively cantilevered out from the input and output shafts, and has no support from a bearing at the gear-linkage end, unless the car is cruising on the flat or on a downhill gradient, and not being put under any accelerative strain, I suspect that the load-bearing parts of the box will always be under damaging stress when in fifth.

 

[bugsymike]

Glad you have located the problem, sorry not much use, had a fall and told no driving for 6 months at least.

 

[fiat500]

Glad you have located the problem, sorry not much use, had a fall and told no driving for 6 months at least.

Wow,,,double whammy. No choice but to take it easy then. I hope at least it's not too painful Get well soon.