Technical synchronizing an unsynchronized gearbox

[gordinir8]

I have three options for my forthcoming engine/gearbox overhaul.

1. Rebuild the stock 500 gearbox. (Not sure what is the average o/h cost or average parts that need to be change)

2. Buy a synchronized 126 gearbox and rebuild it. (Gearbox price+ average o/h cost).

3. Synchronize my current stock 500 gearbox? Is this possible? (sounds cheaper than 2. , more expensive than 1.

Thomas

 

[AndrewHarvey]

No option to synchronize a 500 box. Buy a 126 box and expect to replace 1st and reverse shaft - approximately €150

 

[gordinir8]

I local mechanic told me that he have done it, so since i will overhaul it i said why not synchronize it?
If it can't be done i stay with the stock 500 which i guess if i exercise the double clutch technique it is fine, not to mention it is cool also.

Replacing 1st and reverse shaft for what i understand is a common thing on those gearboxes.:bang:

Thomas

 

[fiat500]

I think it can be done but would be very expensive. Evidence that it is available ready-made here:
https://webshop.fiat500126.com/kata...n-with-differential-8_39-rebuilt-_synchonized
If not worn, some items are transferrable between both types of box.
I really enjoy driving with the non-synchro and honestly have no more crunches than with my modern car ie. very rarely and only when I am hurried..
I read that the older type box is stronger; I don't know if that's true.

 

[AndrewHarvey]

A straight cut non syncro box has far less delicate parts in it...the syncro rings have very small machining works.....so a 500 box will be much tougher

 

[jjacob]

A straight cut non syncro box has far less delicate parts in it...the syncro rings have very small machining works.....so a 500 box will be much tougher

Although it's not like your pushing 200 horsepower through either gearbox. I doubt there is any real difference in longevity between the two boxes. More likely due to the drivers ability to shift correctly!
John

 

[fiat500]

The thing is, people get a bit mixed up about these non-synchro boxes as technically, on both types of box, all of the gears apart from first and reverse are always engaged in mesh and are helically cut; it's just that only one output gear can be locked with the shaft at any time.
It is the engagement dogs, which are present on both types of gearbox that are assisted by synchromesh to allow smooth engagement without crunching.
On both boxes, an identical degree of caution is needed when engaging first and reverse.
I drove a Fiat 126 BIS for a couple of years (I had hit hard times) with the synchro box and despite its low mileage (but admittedly huge power output (704cc)), it quickly needed a replacement second gear.

By the way, I thought the BIS was a horrible car, no end of trouble, nothing like the 500 although superficially with some similarities.

 

[fiat500]

Although it's not like your pushing 200 horsepower through either gearbox. I doubt there is any real difference in longevity between the two boxes. More likely due to the drivers ability to shift correctly!
John

I'm not too sure about that....you're replying to Andrew there.

 

[the hobbler]

The gearbox in the 500 that I owned the longest (JJJ 43D) had over 100,000 miles on the clock by the time I sold it on (to my younger brother!). It still had the original 'box in it. Used carefully, these gearboxes are long lasting, but you do have to drive them sympathetically--well defined double-declutching and only change into 1st gear when the car is STATIONARY. I used it for day-to-day commuting into Chelsea (Radbourne Racing, just off the North-end road) from South London as well as long trips (Edinburgh/South London). I can honestly say that I never had a moments trouble with it.