I've heard all the diffs in the cars were the weak link, not just s4 or s3. Rebuild her and smile.

 

I've heard over the years that S4 Spider Diffs are weak, & that most people us S3 Diffs or earlier.

In the USA, there was no difference in the differentials used in Spiders from 1981-on (save the diffs from the automatic S4), so I don't know why the S4 would have any particular wear problems.

The LSD unit was actually the same as used from ~1972-on. The only changes during this time span were the ratios of the differential.

Joe

 

Wheel bearings can be replaced fairly easily with the help of a machine shop.
Play could be a loose pinion nut.

 

The only thing I could see potentially causing issue would be the extra weight of the S4's over the previous model spiders the diff was used in, though not knowing how much other cars in the line that had it also weighed, (a GTV had the same diff too didn't it? What's one of those weigh in stock form compared to the somewhat piggardly S4?), I might be off by a couple light years on that theory.

 

The pinion nut is very commonly loose on all Alfa axles. I just checked my Berlina (4.56 LS), and the nut was barely hand tight. On my Super (4.56 non-LS), the nut was stripped and not doing any holding really at all. In both cases, though, the diffs worked fine, though maybe a little noisy. The Super's wasn't any quieter when I got a new nut and tightened it up.

The diffs are fundamentally strong, I think, but can get noisy with age, and if the oil gets low. Change the oil regularly. Also, wheel bearings and seals do wear out, but those are normal replacement items on all cars.

The LS function will wear out with age unless rebuilt, but it doesn't present real problems, especially on a street car. On a track car, you want to rebuild it so it LSes.

Andrew

 

Jamie,

I don't accept that Alfa differentials are weak. Given that S4 units are the same as those on earlier cars, here's my experience: Both my wife and I have driven my '76 Spider in autocross events since the early 80's. I used the original 4.56:1 differential until 1995, then changed to a 4.11:1 from a S3 Spider. Both units have performed with no problems and, aside from shimming both LSD's several times to maintain lockup, the only maintainance has been to replace axle seals once and the occasional lube change.

This car gets driven hard. During my ownership I have used progressively stickier "R" compound tires that certainly add stress on the drivetrain (I haven't used my G-Analyst for some time, but remember reading 1.2 G side thrust on asphalt pavement even before the current generation tires). I do lots of standing starts, and have shimmed the LSD to a very high lock-up state.

 

but seeing as finding another Diff of an S3 with an LSD & a known history is like trying to find a virgin in a *****house, I'd rather get mine rebuilt.

You should have what ever Diff you buy rebuilt and reshimmed or just rebuild the one you have.

 

My guess is that the S4 is more quiet and less road feel and some folk don't shift as smoothly due to this. I beleive that it causes more jerky shifts which puts more stress on the differential. It is amazing how badly some forks shift
and the poor drive line snaps back and forward constantly. Eventually somethings gotta give. Matching engine speed to gear speed is the trick to saving the differential.
I hate to ride with someone who doesn't have a feel for shifting, especially if it's my car! I have seen Alfas that belonged to very consevative drivers that
the differential was slammed on because of horrible shifting. It first kills the seal and then leaks all the oil out and then overheats for years as they jerk the shifts up and down with poor gas feed from the pedal. I've seen Push in the clutch, release the gas pedal completely, shift, let out the clutch, then feed the gas. YuK! Let me OUT and give me the KEYS.

 

I think it applies just to the "some folks" you are reffering to. Unless you have non-stock exhaust/intake, all of the spiders are equally quiet (or should I say noisy ) and road feel isn't that bad either even with the power steering stsyem IMHO (and yes, I have driven all kinds of 105/115 spiders).

My guess is that the S4 is more quiet and less road feel and some folk don't shift as smoothly due to this.

 

There is nothing wrong with Series 4 diffs. In fact, all the 115 diffs are stronger than they need to be. They will handle double the stock power output with little difficulty. Course if you let all the oil leak out, you will tear it up. But that's true of any car, isn't it? For what it's worth, sloppy shifting will tear up a tranny, but it won't hurt the diff. It is nicely protected by a rubber donut, a couple u-joints, a splined shaft and spider gears!

Erik

 

going to get mine rebuilt, & already checked the pinion nut - solid as a rock