what's max power 124 gearbox can handle?

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sonoramicommando
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what's max power 124 gearbox can handle?

Post by sonoramicommando » Thu Dec 06, 2018 12:18 am

Hi all,
What is considered to be the maximum power / torque the 124 5 speed gearbox can handle?
Also, does anyone know its weight and that of 131 gearbox?
Cheers
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rridge
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Re: what's max power 124 gearbox can handle?

Post by rridge » Thu Dec 06, 2018 9:55 am

Sam,

Don't expect a clear cut answer, too many variables such as driving style, road conditions, time between overhauls, quality of parts, etc. The Volumex Spider was probably the most powerful car built with a 124 trans and a factory warranty. Its peak torque was about 150 ft/lbs. In the 1970's street versions of the Abarth Spiders with peak torque of about 120 ft/lbs had 124 trans. Group 4 rally Spiders and 131's used custom trans.

A closely related question is how much torque can the rest of the drivetrain handle. I believe the Volumex Spider may have used an uprated diff. from the 132/Argenta.
Richard
'81 Turbo Spider
Rockville, MD
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sonoramicommando
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Re: what's max power 124 gearbox can handle?

Post by sonoramicommando » Thu Dec 06, 2018 1:53 pm

Thanks Richard - I'm not using any other part of the Spider drive train, actually - it's a spare gearbox I have, which I'm thinking of using for a non-Fiat project.
What is the weakest link, would you say? Rubber donut? or Diff?
Cheers
Sam
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bartigue
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Re: what's max power 124 gearbox can handle?

Post by bartigue » Thu Dec 06, 2018 2:35 pm

I’d say the weakest link is the synchronizers; they’re brass and soft. Easiest way to keep them happy is shift patiently and not rest the hand on the shifter
-----------------------------------------------------------
Brad Artigue
1982 Spider 2000
I've restored, worked on, sold, bartered, and bled for:
1970, 1979, 1980, 1981, 1982 124 Spiders -- 1969, 1970 850 Spiders -- 77 X1/9
http://fiat.artigue.com
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rridge
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Re: what's max power 124 gearbox can handle?

Post by rridge » Thu Dec 06, 2018 2:39 pm

I believe Jim Scurria has had a donut failure while racing. Could be the shock load from racing clutches rather than torque capacity. His cars still have (very well set up and serviced) 124 transmissions and diffs.

My own mostly stock Turbo Spider was rated at 130 ft/lbs (dynoed at 115) and I have no concern about drivetrain longevity. If I were to do the considerable work to fit a 131 transmission it would be to gain a useful rpm drop in fifth by using a late Australian box. If you want to know the weight of a 131 trans with bellhousing I'll take a scale up to the garage attic and stick it on.
Richard
'81 Turbo Spider
Rockville, MD
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sonoramicommando
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Re: what's max power 124 gearbox can handle?

Post by sonoramicommando » Thu Dec 06, 2018 6:16 pm

Thanks guys - the box has been "supposedly" rebuilt so I hope the synchros are good.
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Re: what's max power 124 gearbox can handle?

Post by cgranju » Thu Dec 06, 2018 7:23 pm

So, this would be a 124 gearbox with a non-Fiat engine ? if I'm understanding that right, maybe your greater value is selling/trading the 124 box for another?
Chris Granju
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Re: what's max power 124 gearbox can handle?

Post by fp55scca » Thu Dec 06, 2018 7:48 pm

sonoramicommando wrote:
Thu Dec 06, 2018 1:53 pm
......I'm not using any other part of the Spider drive train, actually -
......it's a spare gearbox I have, which I'm thinking of using for a non-Fiat project.
......What is the weakest link, would you say? Rubber donut? or Diff?
Cheers
Sam
--------------------------------------------------------
--Sam, I'm a little confused. You indicated that you were not going to use any other part of the Spider drivetrain? Well, in reference to the "weakest link", if driven normally [and properly] for street use, I would say the 124 Spider drivetrain is fairly well balanced throughout. Like anything however, if you operate improperly, or abuse the equipment, the pinion gear in the diff will likely give up on you first, and like Brad says, you will eventually wear the syncros in the gearbox. Add 60 to 80hp to a typical 124 Spider [and race conditions], and the flex disc and differential must be upgraded. Under normal driving conditions, the 124 gearbox can easily take a power increase of 60-80hp.

--I have raced the OEM transmission for over 16 years now, and I can attest that this gearbox will take a lot of abuse. I mostly run a dog-cut Colotti box now [with a Torsen LSD and a two-disc Quartermaster race clutch], but occasionally, I still use a stock box for the gear ratios.
Jim Scurria
Norfolk, VA

1972 Fiat 124 Spider
1971 Spider - SCCA FP-24
1974 Fiat 124 Spider
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sonoramicommando
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Re: what's max power 124 gearbox can handle?

Post by sonoramicommando » Thu Dec 06, 2018 9:52 pm

EV conversion on non-Fiat 124 based chassis, to be exact.
I know it's usually a bad idea to use parts just because they are handy, but I thought I'd ask anyway.
The weakest link question, I guess isn't really relevant but something I was curious about.
The market for Fiat parts here is pretty slow I think - not many 124 era Fiats are around, I'd say they all rusted away...
Thanks guys.
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Re: what's max power 124 gearbox can handle?

Post by SimcaBertone66 » Fri Dec 07, 2018 10:37 am

Dude dude.... nice parting comments …….. your welcome
Joe DeGasperis
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