Replacing the differential

Suspension related stuff goes in here.
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Redline
Posts: 631
Joined: Sat Aug 29, 2009 4:34 pm
Your car is a: formerly a 1971 Fiat 124 BC Coupe
Location: Switzerland

Re: Replacing the differential

Postby Redline » Tue Feb 02, 2016 8:33 am

I'll give them a call then. Maybe it's just a poor translation.
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vandor
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Joined: Sat May 23, 2009 1:23 pm
Your car is a: 1971 124 Spider
Location: Texas, USA

Re: Replacing the differential

Postby vandor » Tue Feb 16, 2016 4:24 pm

We now have the 3.90:1 third members in stock.
Csaba
'71 124 Spider, much modified
'17 124 Abarth, silver
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Co-owner of the best dang Fiat parts place in town

Betis
Posts: 109
Joined: Mon Nov 30, 2015 11:17 pm
Your car is a: 1981 Fiat 124 Spider FI

Re: Replacing the differential

Postby Betis » Sun Jun 11, 2017 10:52 pm

Someone told me that older rear diffs were more robust. Is there any truth to that?

Betis
Posts: 109
Joined: Mon Nov 30, 2015 11:17 pm
Your car is a: 1981 Fiat 124 Spider FI

Re: Replacing the differential

Postby Betis » Mon Jul 31, 2017 10:20 pm

Betis wrote:Someone told me that older rear diffs were more robust. Is there any truth to that?

Anyone?

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azruss
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Joined: Sun May 30, 2010 12:24 pm
Your car is a: 80 Fiat 2000 FI

Re: Replacing the differential

Postby azruss » Wed Aug 02, 2017 2:41 am

I just switched my early style (71) diffy to a 3.9. Very tricky getting the right lash and side bearing load without the special fiat tools. If you can find a good diffy in tact, then pulling the brakes and axles isn't a monumental job.

MonitorSteve
Posts: 3
Joined: Tue Jun 26, 2018 5:21 pm
Your car is a: 1976 124 Spider

Re: Replacing the differential

Postby MonitorSteve » Tue Aug 07, 2018 6:49 pm

I’m mid differential replacement and I can not definatively tell what the torque specs are for the eight bolts that hold the pumpkin in are? The Haynes manual has torque specs for setting up pre load and the bearings. The pumpkin is referred to several times as the “Final Drive” but there are no torque specs.

Anyone have an idea on what these should be torqued to?

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blazingspider
Posts: 173
Joined: Mon Jan 28, 2013 8:44 am
Your car is a: 1977 fiat spider
Location: Nanuet, New York

Re: Replacing the differential

Postby blazingspider » Wed Aug 08, 2018 9:39 am

When I purchased a new differential from AR I was told to torque those bolts to 16 ft. lbs.

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blazingspider
Posts: 173
Joined: Mon Jan 28, 2013 8:44 am
Your car is a: 1977 fiat spider
Location: Nanuet, New York

Re: Replacing the differential

Postby blazingspider » Wed Aug 08, 2018 9:50 am

FYI.......the shop manual I have lists the torque spec for those same bolts at 33 ft. lbs. go figure!!

MonitorSteve
Posts: 3
Joined: Tue Jun 26, 2018 5:21 pm
Your car is a: 1976 124 Spider

Re: Replacing the differential

Postby MonitorSteve » Wed Aug 08, 2018 9:06 pm

I found 33 lbs in the dark reaches of the net as well. Thanks much, I’m rolling already and I can’t believe how noisy it has been. The before and after is night and day.

SanJoseSteve
Posts: 35
Joined: Wed Aug 29, 2012 7:14 pm
Your car is a: 1971 124 Spider

Re: Replacing the differential

Postby SanJoseSteve » Wed Aug 15, 2018 12:26 pm

I recently replaced the 4.3 differential in my car, (1972 124 w/ 1600 motor) with a new 3.9 unit from AutoRicambi. It was easy….. (After burning $25 for the right angle snap ring pliers on Amazon.) Once the that was out of the way, my axle slid out with just a firm tug. My experience is that it drives great though initially I did manage to stall it in 1st gear 2-3 times until I re-calibrated my ear and left foot to the change. Previously I had changed from the 165-13 size tires to 185-13’s. I had also replaced my original transmission with a new Polski-Fiat unit with the taller 5th gear.

Driving on the highway at 70-75 mph is quite enjoyable. Sustained cruises at that speed had been quite manic. OK for a temporary burst of speed to pass someone, but I found it wearing after the 1st 10-15 minutes. Now I can hold that speed all day long and not feel like I’m about to get a face full of pistons at any moment. Holding ~50 and then ~70mph per the speedometer, the WAYZE App on my phone indicates 50 and 70 mph. Not bad……..

Steve (The Fiat driving) Ferrari

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nelsonj
Posts: 394
Joined: Thu Oct 14, 2010 5:37 pm
Your car is a: 1972 Spider 124

Re: Replacing the differential

Postby nelsonj » Wed Aug 15, 2018 7:53 pm

What RPM are you at at 70MPH? I'd love to be in the 3500 range instead of the 4500 I'm currently at.
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donm
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Posts: 294
Joined: Sun May 30, 2010 12:40 pm
Your car is a: 1980 spider [carb]
Location: Hamilton. MA

Re: Replacing the differential

Postby donm » Thu Aug 16, 2018 9:31 am

Is there a way to know which ratio you have? Is it stamped on the differential somewhere?
1979 Spider
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2004 Saab Aero
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SanJoseSteve
Posts: 35
Joined: Wed Aug 29, 2012 7:14 pm
Your car is a: 1971 124 Spider

Re: Replacing the differential

Postby SanJoseSteve » Thu Aug 16, 2018 12:39 pm

I have a 3.9 rear differential and indeed do cruise 70mph at about 3,800 rpm. BUT.... I also have a Polski-Fiat 5 speed with the taller 5th gear. The size of my tires 185/13 and 1600 engine all factor into the equation too. I'd think it would be an even sweeter set up in a 2L car.

-Steve (The Fiat driving) Ferrari


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