Stronger Diff for X1/9 5 Speed

[GregS]

In 2017 Maxmod posted about the possibility of using a LSD from a Fiat Punto GT in an X1/9 box.

5 Spd Lsd possible option

Hey Guys, I thought I would post this up and maybe someone else can follow it through I have a Punto GT gearbox and an x19 5 speed on my bench stripped at the moment. The punto GT gearbox is a C510 which uses the QDH2K-10 Quaife LSD unit...

xwebforums.com

While some would like a stronger diff for motorsport use, not everyone wants or needs a LSD, a standard open diff would be ok. In searching for the maker of a LSD I bought I made a drawing of it for future reference, I also came across drawings of the diff for the Fiat C510 box as used in Abarth 500s and Puntos etc. (see list of all models). In putting the 2 drawings together I came up with an Adaptor Ring that could mount an X1/9 crown wheel gear onto a C510 standard open diff. As Maxmod showed, the C510 diff has the same major dimensions, bearings etc as the X1/9, it is just the OD, gear mounting diameter and flange location and bolt pattern that are different. If you have access to a machine shop, this project could be done on a budget, but if you have to pay commercial rates it could get expensive, as not only the Adaptor Ring has to be made, but also machine the OD of the C510 diff, and drill and tap 24 M6 holes in it. Also probably a Spacer Ring to locate the ID of the crown wheel on, because of the large chamfer on its inside edge it would otherwise only locate on less that 1mm of the edge of the diff.
Have a look at the data and see what you think.

Mfactory LSD Fiat C510 -(hole drawing is incorrect, they are not equi-spaced)

N
Note: The red semi-circles are what is left of the original mounting holes in the C510 diff. I don't have a diff to measure the exact location of these, so in the drawing it is an estimate by scaling off of photos. As some of the M6 holes are very close to what's left of these 10mm holes an accurate location of all the holes needs to be confirmed.

 

[GregS]

Another thing you need to check on the C510 diff is the mating of the speedo drive gear with the X1/9 gear, as Maxmod said, if you need to you can swap the gear off the X1/9 diff, the ID would need to be machined out from 88mm to 94mm.
The list from Quaife of cars their LSD fits covers a large range of models and I don't know if all the standard open diffs in all these are identical. I have read that the C510 box can handle over 200Nm of torque as in Abarth 500, 145hp, 206Nm. The USA Fiat site confirms the C510 box is used in the Fiat 500 Turbo, Abarth 500 and Esse Esse version. But not the Assetto Coarse, that uses the M32 box, I don't know about the Euro Abarth 595 Competizione, 180hp, 250Nm.

Fiat 500 transmissions: 5 or 6 speed, Dualogic or MTA...

Number 1 source for Fiat 500, 500e electric, and 500 Abarth information in the U.S. It's all here. Fiat news, info, how to's and much more!

www.fiat500usa.com

If all this sounds too hard, you could just the bullet and spend the 600 Euro or so for a LSD. The early Fiat Uno Turbo mk1 1985 to mid 1987 only, is a direct fit in the X1/9 5 speed box.
There is a torsen type from RSX Racing Solutions in Spain, and Gripper LSDs in the UK can do a clutch type on special order.

https://m.facebook.com/RSX.RacingSolutions/posts/we-make-torsen-type-lsds-for-fiat-uno-turbo-mk11301cc-and-mk21372cc-both-availab/877413242269678/

Or for more than twice the price from Bacci Romano or Classic Performance in Italy.

X 1/9 1500 (5 speed) - Bacci Romano Trasmissioni Meccaniche

The production of parts for vintage and modern racing cars has reached levels of excellence. A considerable number of preparers from all over the world rely on the Tavarnelle workshop, where bars of raw material come in and leave as fine-tuned gears, gearboxes, levers, limited slip differentials...

www.bacciromano.com

FIAT X1/9 5 SPEED GEARBOX LIMITED SLIP DIFFERENTIAL - Classic Performance Parts

Classic Performance Parts - FIAT X1/9 5 SPEED GEARBOX LIMITED SLIP DIFFERENTIAL

classicperformance-parts.com

Classic Performance can get a torse type from https://l.facebook.com/l.php?u=http://www.ingranaggiprina.it/differenziali_autobloccanti.php?fbclid=IwAR1TJuaBxtlhkyzgnP_0Sy-_VkA08ff8L0XraLh6aetdwjVfbPgkKS3He0E&h=AT3JuvRcrMI-4cmT6xpEV5L8aVnaEeQdsA_Vtbzo9mtZf-uomOqw88W1P_EclB7ZL6kOxoaYngR3afI2hp5e9AeBL7NUi93reIN7IwEkAgFyrCm9gS2sxHmApbkpPseM4y3GwVACCCUG4reYH1sm8XGAWwnPK9h_

 

[ng_randolph]

Another thing you need to check on the C510 diff is the mating of the speedo drive gear with the X1/9 gear, as Maxmod said, if you need to you can swap the gear off the X1/9 diff, the ID would need to be machined out from 88mm to 94mm.
The list from Quaife of cars their LSD fits covers a large range of models and I don't know if all the standard open diffs in all these are identical. I have read that the C510 box can handle over 200Nm of torque as in Abarth 500, 145hp, 206Nm. The USA Fiat site confirms the C510 box is used in the Fiat 500 Turbo, Abarth 500 and Esse Esse version. But not the Assetto Coarse, that uses the M32 box, I don't know about the Euro Abarth 595 Competizione, 180hp, 250Nm.

Fiat 500 transmissions: 5 or 6 speed, Dualogic or MTA...

Number 1 source for Fiat 500, 500e electric, and 500 Abarth information in the U.S. It's all here. Fiat news, info, how to's and much more!

www.fiat500usa.com

If all this sounds too hard, you could just the bullet and spend the 600 Euro or so for a LSD. The early Fiat Uno Turbo mk1 1985 to mid 1987 only, is a direct fit in the X1/9 5 speed box.
There is a torsen type from RSX Racing Solutions in Spain, and Gripper LSDs in the UK can do a clutch type on special order.

https://m.facebook.com/RSX.RacingSolutions/posts/we-make-torsen-type-lsds-for-fiat-uno-turbo-mk11301cc-and-mk21372cc-both-availab/877413242269678/

Or for more than twice the price from Bacci Romano or Classic Performance in Italy.

X 1/9 1500 (5 speed) - Bacci Romano Trasmissioni Meccaniche

The production of parts for vintage and modern racing cars has reached levels of excellence. A considerable number of preparers from all over the world rely on the Tavarnelle workshop, where bars of raw material come in and leave as fine-tuned gears, gearboxes, levers, limited slip differentials...

www.bacciromano.com

FIAT X1/9 5 SPEED GEARBOX LIMITED SLIP DIFFERENTIAL - Classic Performance Parts

Classic Performance Parts - FIAT X1/9 5 SPEED GEARBOX LIMITED SLIP DIFFERENTIAL

classicperformance-parts.com

Classic Performance can get a torse type from https://l.facebook.com/l.php?u=http://www.ingranaggiprina.it/differenziali_autobloccanti.php?fbclid=IwAR1TJuaBxtlhkyzgnP_0Sy-_VkA08ff8L0XraLh6aetdwjVfbPgkKS3He0E&h=AT3JuvRcrMI-4cmT6xpEV5L8aVnaEeQdsA_Vtbzo9mtZf-uomOqw88W1P_EclB7ZL6kOxoaYngR3afI2hp5e9AeBL7NUi93reIN7IwEkAgFyrCm9gS2sxHmApbkpPseM4y3GwVACCCUG4reYH1sm8XGAWwnPK9h_

I'm curious what the limiting factor is for the standard transaxle; Is it the actual differential (carrier & gears etc.) or is it the transaxle casing? I'm wondering if it is the latter.

 

[GregS]

It is the diff carrier casting that can break. Usually with modified engine and fast launches, especially with grippy tyres. The big worry is if it explodes it can smash the case.

 

[Rupunzell]

That is a stress riser induced failure. Diff carriers have a difficult life as they are subjected to high shock loads and load reversals in some times violent and rapid cycles.

This can happen to other diff carriers made in the same way. What can help prevent this is to de-burr the entire casting, then have it shot peened (and no, this is not the same as glass beading or similar cleaning process), then cryo treated.


Bernice

 

[ng_randolph]

It is the diff carrier casting that can break. Usually with modified engine and fast launches, especially with grippy tyres. The big worry is if it explodes it can smash the case.
View attachment 34297

Well, that certainly illustrates your point!

 

[kmead]

So how much bigger is the C510 than a existing X transmission out of curiousity, does anyone know?

Could a C510 be installed with modifications onto an X engine with an adapter or remachining holes for mating the SOHC? I presume this would require new drive shafts so not a cheap endeavor but there are a lot of C510s around and they are pretty cheap given the resale on a 500 is poor.

Just a thought.

 

[Dr.Jeff]

So how much bigger is the C510 than a existing X transmission out of curiousity, does anyone know?

Could a C510 be installed with modifications onto an X engine with an adapter or remachining holes for mating the SOHC? I presume this would require new drive shafts so not a cheap endeavor but there are a lot of C510s around and they are pretty cheap given the resale on a 500 is poor.

Just a thought.

Well, the 500's engine fits the C510 trans. That way no adaptation is needed. Just ask @TonyK

 

[Steve Hoelscher]

Well, that certainly illustrates your point!

I have exploded several differentials. Each one blew the case completely apart leaving the half shafts hanging in open space. It makes a BIG noise.

As with other failure points I have learned to mitigate the problem somewhat. As Bernice noted; de-burr, shot peen and cryo treat. I haven't gone as far as shot peening because I didn't have ready access to the equipment but I did de-burr and cyro treat one for my racecar. There are other things that can help. The torque suppressor I have discussed previously is a big one. Another is I replaced the racing clutch with an OE type Valeo. The softer clutch engagement cushions the driveline shock and thus the spike in torque loading on the diff carrier.

 

[GregS]

So how much bigger is the C510 than a existing X transmission out of curiousity, does anyone know?

Could a C510 be installed with modifications onto an X engine with an adapter or remachining holes for mating the SOHC? I presume this would require new drive shafts so not a cheap endeavor but there are a lot of C510s around and they are pretty cheap given the resale on a 500 is poor.

Just a thought.

They can be fitted in an X1/9, that's what Maxmod was in the middle of in the link at the start of this thread, there has been at least one more done in Australia. I don't know all the details as far as drive shafts, but you do have to sort out a cable shift gear change to go to the top of the gearbox.