Technical High Final Drive

[Keeffy]

Hi All, new on here and have a 71' 500f with a 650 engine.
Interested to know if anyone here has a 126 synchronised gearbox with a 9/39 final drive and how they get on with it?
Is it worth the 9/39 over the 8/39 final drive or is the standard 126 gearbox just a better bet?

Cheers, Keith

 

[Bounding Bambino]

I just ordered and received a 9/39 gear set that i plan to put into my 67 500. Its the tallest ratio i could find before getting something custom made. The goal is to help eliminate the need to swap in a 5 speed kit, and keep top speed rpm down.

Are you needing more top speed and lower rpm?

 

[fiat500]

I used one with a standard 650. I liked it, but eventually reverted to an unmodified transmission when I tried a 594 engine in the car; the change wasn't earthshatteringly beneficial, but I sounded enthusiastic when I reported back.

Top speed increase with 126 BIS pinion. | FIAT 500 (Classic)

I noticed a useful lengthening of the gears when fitting the gearbox from a 126 and this uses the additional power of the bigger engine whilst keeping the high rpm reasonable at speed. Putting aside the fact that an everyday engine may not work well with the BIS crownwheel and pinion, does...

www.fiatforum.com

 

[Keeffy]

Hi, thanks for the replies so far..interesting.
My 650 engine is tuned, ported head and 35/75 cam. Really I'm just looking for more quieter/relaxed cruising to be honest.
Could I convert the standard 500 box with the higher final drive and synchronisation or go for a 126 synchro box or the 126p box - Just not sure which way to as I have little experience with theses transmissions..

 

[Bleeding Knuckles]

Hi Keith, I have a 9/39 Diff in my 126 box having taken a while over the merits of a five speed conversion. In the end I decided to go with a diff gear set from a 126 BIS gearbox. The swap over was simple enough, BUT the setting of the crown wheel backlash and the turning torque setting of the drive shafts took a little time to get right. Providing you are willing to do the job you will see some 60mph at approx 4000rpm, which for me is a steady cruise with a tuned engine.
Ian.

 

[Keeffy]

Thanks Ian that's really good info, appreciated.
May I ask where you got your Bis gear set from and did it fit straight into your 500 gearbox? Is there a supplier of Bis parts in the UK?

Keith

 

[Bleeding Knuckles]

Hi Keith, I obtained my BIS gearbox from a forum member and changed the diff myself. The change is a simple one for one and then the adjustments to suit, I used the late model 126 Haynes manual as a blueprint for the job. Not sure about BIS parts, I think that you will have to check around the bazaars to see if anyone has a set available, but with the mod getting popular they will be a little thin on the ground. Best to try any scrappers for a box complete or there is the expensive way of buying a set from Italy .
Ian.

 

[Keeffy]

Thanks Ian, again much appreciated!
Keith

 

[Bounding Bambino]

Axel Gerstl has brand new 9/39 gearsets. Its where i got mine. I had a lead for a set on ebay. But honestly, it was only 1/2 the price, and i didnt want to take the risk of buying something used that was worn and required such a deep tare-down of the transmission only to find out that it was bad.

Still cheaper then a 5 speed kit, and should suit what i wanted.

Bevel/ring gear 9/39 (long ratio) Fiat 126P/BIS - Spare parts Fiat 500 classic 126 600 onderdelen | Axel Gerstl

Bevel/ring gear 9/39 (long ratio) Fiat 126P/BIS

webshop.fiat500126.com

 

[Keeffy]

Hi, thanks for the Info !

Keith

 

[fiat500]

Back in 2018, I bought a brand new 9:39 crownwheel and pinion set from a company that doesn't seem to sell on UK eBay any more. The price hasn't changed at Euro199.00, and they do have an English translated website. They seem to have other stuff that some of us would all like to have. Worth a try?

Coppia conica Fiat 126 Bis 9x39

Coppia conica Fiat 126 Bis 9x39 SKU 7548082 Articolo Nuovo produzione Masiero Ricambi

store.tecnotrasmissioni.com

 

[Keeffy]

Thanks! I'll check their website out.


Keith

 

[the hobbler]

Back in 2018, I bought a brand new 9:39 crownwheel and pinion set from a company that doesn't seem to sell on UK eBay any more. The price hasn't changed at Euro199.00, and they do have an English translated website. They seem to have other stuff that some of us would all like to have. Worth a try?

Coppia conica Fiat 126 Bis 9x39

Coppia conica Fiat 126 Bis 9x39 SKU 7548082 Articolo Nuovo produzione Masiero Ricambi

store.tecnotrasmissioni.com

Thanks! I'll check their website out.


Keith

Yes, Axel Gerstl still sell the "Crown-wheel and Pinion" set-----E348 for the 8/39 set (part number C01137/1) or, the 9/39 set for E409, (part number 01071). Alternatively, you could contact Lucasz Reszczynski at LP Garage ( [email protected]) and see what he has to offer----you might find that buying a complete gearbox is the cheapest way to go. If you think that using me (Tom Montagu) as a reference will help, feel free to do so; I have done a lot of business with Lucasz; never had a reason to complain.

 

[Keeffy]

Thanks Tom, very decent of you!
I will send Lucasz an email. Thoughts on the quality of Bis parts/gearboxes compared to the Fiat Italian make?

Out of interest also but would all the internals of the 500, 126 and Bis gearboxes be interchangeable with each other would anyone know?

Keith

 

[the hobbler]

Thanks Tom, very decent of you!
I will send Lucasz an email. Thoughts on the quality of Bis parts/gearboxes compared to the Fiat Italian make?

Out of interest also but would all the internals of the 500, 126 and Bis gearboxes be interchangeable with each other would anyone know?

Keith

No, they are NOT---the 500 has NO synchro, whilst both of the 126 versions have synchro on 2nd, 3rd,and 4th. A friend of mine, who has a LOT of experience building and re-building 500/126 engines and gearboxes was recently asked to do such a 'mix' in order to re-build a 126 gear-box----I never realised he knew so many rude words! Eventually he raided his own extensive collection of parts in order to complete the job. A 126 gearbox can be made to fit onto a 500 as long as you (a) remove the bell-housing off the 500 gearbox and fit it to the 126 'box and, (b) fit 500 drive-shafts to the 126 'box---the 126 drive-shafts are too long.

 

[fiat500]

Thanks Tom, very decent of you!
I will send Lucasz an email. Thoughts on the quality of Bis parts/gearboxes compared to the Fiat Italian make?

Out of interest also but would all the internals of the 500, 126 and Bis gearboxes be interchangeable with each other would anyone know?

Keith

I owned a Fiat 126 BIS back in the late '90s and whilst I enjoyed the throwback feeling that made me reminisce about the earlier 500, I considered it to be an appalling car in many respects.
Relevant to this question, the gearbox on mine completely sliced up second gear. Undaunted, I got hold of a scrap car and dismantled the gearbox for spares, only to find the same issue there.

To be fair,it may have been that at 704cc, the engine was kicking out significantly more power than the gearbox was originally designed to handle. If you can get hold of a BIS gearbox you won't be able to bolt it to a 499 or a 652 engine without getting involved in so much work that you may as well replace the worn parts and fit any upgrades to your existing gearbox.

The best thing to do is to replace the 499 engine and gearbox as one chunk with the aircooled 126 versions. The most involved part of doing that is replacing the driveshafts, which once you've done it,, looking back, seems quite easy; maybe not so much when you're first tackling it.

You won't lose out on the "pleasures" of non-synchromesh as the chances are that your 126 box will have pretty crappy synchro in any case.