Technical Fourth gear not completely engaging

[S854]

I’ve only driven my new toy 10 miles or so, generally it’s very solid for a 57 year old car.

One item I noticed which may need addressing is fourth gear. It seems shift lever throw should travel another 2”. The rest of the gears have that travel.

I’m unfamiliar with the FIAT gearbox in general and have yet to climb under the car to see if there’s an obstruction causing the linkage to not move its entire length.

Another sensation: I’ve tried pulling the knob “harder” into fourth, when I do, I can feel a slight, rapid thumping (that’s a bad description, can’t think of the right word)… not a gear grinding, but maybe like the synchro is attempting to engage the gear.

Fourth gear drives fine, no whining, grinding or other strange noises.

Once, as I was on trailing throttle, decelerating, the trans did go to neutral… don’t know if it was something I did (bump the lever) or the trans itself… like I said, I have 10 miles under my belt and was concentrating on other things.

The seller had “gone through” the trans, new synchros, shift forks seals, etc. Currently, the fluid used is Valvoline 75-90 Synthetic.

A quote from the seller: “Many people will tell you not to use Synthetic gear oil owning to the material of the synchros, the car has new synchros with metal compatible with synthetic fluid. The trans shifts so much better cold with synthetic fluid. A downside is they tend to leak easier and are noisier as the fluid has a lower viscosity.”

One last observation… I went to the garage this morning after the car had cooled down… as I worked the lever (engine off, no clutch), all the gears were available… the lever “hung up” just a bit engaging fourth, but the lever throw was pretty much the same as the remaining gears. Odd…

So… I’m looking for suggestions on how to proceed… and thanks in advance…

 

[bugsymike]

I’ve only driven my new toy 10 miles or so, generally it’s very solid for a 57 year old car.

One item I noticed which may need addressing is fourth gear. It seems shift lever throw should travel another 2”. The rest of the gears have that travel.

I’m unfamiliar with the FIAT gearbox in general and have yet to climb under the car to see if there’s an obstruction causing the linkage to not move its entire length.

Another sensation: I’ve tried pulling the knob “harder” into fourth, when I do, I can feel a slight, rapid thumping (that’s a bad description, can’t think of the right word)… not a gear grinding, but maybe like the synchro is attempting to engage the gear.

Fourth gear drives fine, no whining, grinding or other strange noises.

Once, as I was on trailing throttle, decelerating, the trans did go to neutral… don’t know if it was something I did (bump the lever) or the trans itself… like I said, I have 10 miles under my belt and was concentrating on other things.

The seller had “gone through” the trans, new synchros, shift forks seals, etc. Currently, the fluid used is Valvoline 75-90 Synthetic.

A quote from the seller: “Many people will tell you not to use Synthetic gear oil owning to the material of the synchros, the car has new synchros with metal compatible with synthetic fluid. The trans shifts so much better cold with synthetic fluid. A downside is they tend to leak easier and are noisier as the fluid has a lower viscosity.”

One last observation… I went to the garage this morning after the car had cooled down… as I worked the lever (engine off, no clutch), all the gears were available… the lever “hung up” just a bit engaging fourth, but the lever throw was pretty much the same as the remaining gears. Odd…

So… I’m looking for suggestions on how to proceed… and thanks in advance…

I tend to agree with you it is as though the syncro hub is jamming or bulking. If the syncro cones were at fault they usually cause grating as their job is to act like a sort of clutch to match the two gears speeds so they engage quietly, hence as they wear out gear changes grate. when rushed.
I have a van that does similar when you go to engage first gear to pull away.
What I do is push it towards first gear then slightly lift the clutch which turns the gear a little and then I can feel it go all the way in and then it works perfectly and doesn't jump out, but if I just try to drive off the gear will jump out as it isn't totally engaged.
Can you try to engage fourth gear whilst parked and see if it goes all the way in how I described by lifting the clutch slightly to start to take up drive but gently pushing the lever in to gear to see if it does the full travel?
It isn't going to help you much but it does suggest the gearbox may need further attention regarding that syncro hub, it may even be possible that something is jamming in the hub so box needs stripping again.
Was it rebuilt with genuine Fiat parts or pattern?
Is it possible he had an issue and is trying the synthetic oil to "fix it"?

 

[gengis]

Dropping out of fourth gear when off the gas is a common symptom of bad syncros on the 124 gearbox. Your options would be…to get it rebuilt, swap it out for a second hand unit, or convert it to the better and stronger 131/132 gearbox, my choice would be a Super Mirafiori or 131 Sport as they have a remote extension gearstick which comes straight up, and would be positioned where your ashtray is at the moment.

I have done this modification on my Spider 25 years ago and is a really good modification. Incidentally I have always used ATF in all of my older Fiat’s without issue.

 

[124BC1]

I wouldn't panic (at least not yet!).

There is no external linkage outside this gearbox on your car, nothing to see, everything is done inside the gearbox and remote control extension housing.
Given the thoroughness of the work carried out, I'd be surprised if the previous owner got anything wrong. I certainly wouldn't go changing the g/box!

It seems to me more likely that something is possibly hindering the movement of the gear shift lever when going into 4th gear, rather than there being some problem inside the gearbox. The 'slight, rapid thumping' that you can feel if you try pulling the knob harder into 4th gear, could simply be engine vibration - if the gear lever is pressed against something connected to the body e.g. centre console shifter panel, it could be transmitting vibration.

I would suggest removing the wood panel surrounding the gear shift lever in the centre console and see if the lever then goes fully into the 4th gear position. I noticed in the Auction ad. photos, it appears that a possibly homemade?/ aftermarket? wood panel is installed - the original (on the Coupes at least) was a metal panel, covered in faux wood veneer (i.e. plastic) and surrounded by a shiny metal rim/band.
It might simply be that this wood panel might need a little modification to allow full movement of the gear lever when selecting 4th gear. The gear lever should travel the same distance when selecting 4th as it does for 2nd gear.

What is mysterious is that you can apparently (if I'm understanding you correctly?) select 4th gear with full movement of the gear lever with the engine turned off but not when the engine is running. If you select 4th gear with the engine off, hold the clutch pedal down and then start the engine does the gear lever move forward or remain 'fully selected'? The engine rocking while being started could cause the gear lever to move away from being fully rearwards?

There is also an additional metal cover plate surrounding the gear lever and covering the opening in the transmission tunnel (below the 'wood' panel mentioned above) but to remove this iirc requires removal of the central console unit - I'm not suggesting you do this, at least not just yet!

P.S. I'm familiar with these Fiat gearboxes, here's one I rebuilt a while back :-

 

[S854]

I wouldn't panic (at least not yet!).

There is no external linkage outside this gearbox on your car, nothing to see, everything is done inside the gearbox and remote control extension housing.
Given the thoroughness of the work carried out, I'd be surprised if the previous owner got anything wrong. I certainly wouldn't go changing the g/box!…

The one, possibly important detail I omitted in my original post: The reconditioning/restoration of this car (rebuilt 1608 engine and gb - among other things) has all of 375 miles on it.

I’m the one responsible for the remainder of the break-in period.

Apologies for the faux pas on my part…

The weather’s gonna break here in the next couple days… I’ll get the car out and see if I can come to a positive outcome…

Tomorrow I’ll look through the 3” thick binder of receipts… see if I can determine where the gb work was performed… maybe give them a call and get their take


…

 

[124BC1]

I was aware that the car had only covered 375 miles since the rebuild, I think this figure was mentioned on the auction website?

I had looked through all the pics included in the auction listing, including the parts invoices that were shown and iirc I saw several that related to gearbox parts, supplied on different dates - sounds more like the Op did the rebuild himself? (couldn't tell as name/address was understandably blanked out on invoices ).

Why would he order the parts and then rely on someone else to do the work?
I think that most trans. specialists wouldn't want to use parts supplied by the customer, would have their own parts stocks or suppliers and wouldn't want the customer to see from where he was sourcing his parts or how much (or little) he was paying for them - more likely the specialist would want to handle the job from start to finish and just supply one invoice detailing the work done , the parts used and their cost and the labor charge.

And if you were to find that a specialist did indeed perform the g/box work, you're not their customer, they're probably in another state and they can't reliably / accurately diagnose what may have gone wrong (if anything) over the phone and therefore suggest a solution, they'd have to get the car in for examination. If you were to bring the car to them, what happens if they were to then find the issue was e.g. that the shift lever wood panel surround in the centre console was impeding the gear shift lever travel and the gearbox had been installed by the OP after they had rebuilt it?

Regardless of the weather, the checks I suggested could be done in your garage - i.e. engage 4th gear fully with engine off, hold down clutch pedal and start engine, see if this causes the shift lever to move forward a bit from the fully rearward position. If it does, it suggests that the movement/rocking of the engine when starting is causing the lever to move. Switch off engine. Then you could remove the wood panel around the gear shift lever and see if the lever stays fully engaged when the engine is again started. This problem is likely something small, and unlikely to be anything wrong inside the gearbox.

 

[bugsymike]

I wasn't aware of any aftermarket wood obstruction around the gear leaver area, but if that is eliminated I would still be looking in the direction I mentioned.
Is it worth contacting the supplier of the vehicle regarding the issue?
I see in @124BC1 photos of a similar gearbox apart from the extension housing (which I do wonder if anything fouling in that area) they are almost the same design as the Lada ones I worked on in the 1970s at a Dealership, although I expect the Fiat a much higher build quality as those were only built under license in Russia.

 

[S854]

I’ll get out to the garage today, see if I can replicate my issue with the car static…

 

[S854]

Just got back from the garage… started the engine, fourth gear, clutch disengaged… let the clutch out slowly and the engine began to die, no movement in the shift lever… shifted first, second, third then fourth… letting the clutch out just a bit each time… again, no movement in the lever…

So… could be a couple things: 1st - my ham-fisted approach during my short maiden drive (the car came from sea level to 4,500’ and didn’t want to idle… which was my primary area of focus), 2nd, could be there’s slight movement in the engine/tranny as I’m driving causing “something” to get in the way of the lever, or 3rd, this is all in my head… I drove heavy truck for the past 40 odd years… the throw on the lever is definitely substantial there and I’m expecting too much…

I’ll be getting the car out for a drive tomorrow… I’ll report back my findings…

 

[S854]

I had the car out yesterday, paying close attention to the fourth gear engagement (instead of just “flicking” it into gear)… deliberate shifting results in slightly better engagement…

I did have it pop out once as I crossed three railroad tracks under trailing throttle… mid-to-low RPM… never could get it to pop out under any other circumstances… and I was trying to induce failure…abrupt on/off throttle, other bumps/dips, carrying fourth gear way to long as I slowed…

I’ll look into the possibility of console interference soon… I need to replace the original seatbelts as the plastic hardware bits have become rather brittle… probably do both these tasks at the same time…