Limited Slip Diffs

yng · #1 (**permalink**) 03-07-2005, 06:43 AM

Hi all,

Just wondering whether anyone knows if Alfa ever fitted a 4.56 ratio LSD rear axle (for US spec 2l cars apparently?). There is a guy here in the UK selling what purports to be one off the back of a Californian 1973 2000 Spider.

Is there an easy way of telling whether an axle that isn't attached to a car is fitted with an LSD (other than by disassembling it?)

cheers

**papajam** · #2 (**permalink**) 03-07-2005, 08:04 AM

Yes, the US bound 2l Alfas from 72-80 (or was it 81) were fitted with a 4.56 LSD as standard equipment. In 80 or 81 the ratio was changed to 4.10.
The LSD differential housings have a ribbed casting in the shape of a triangle that the non-LSD diffs don't have. So you can tell to difference without opening up the rear. I'll see if I can find a pic......

Oh, and welcome to the BB!

**conedriver** · #3 (**permalink**) 03-07-2005, 08:13 AM

yng,

The U. S. spec. cars recieved limited slip differentials with the introduction of 2000cc models in 1972. If the axle you are considering is off of a 1973 U. S. spec. car, it should be a limited slip. Try this; hold one wheel, raise the other and try to turn it. If I remember correctly, the resistance specification for a LSD in good shape should be 21 ft. lb. If less, these units can be shimmed to provide more lock-up.

Quote:

Originally Posted by yng

Hi all......Is there an easy way of telling whether an axle that isn't attached to a car is fitted with an LSD (other than by disassembling it?)
cheers

yng · #4 (**permalink**) 03-07-2005, 08:21 AM

nice one - thanks

jpv · #5 (**permalink**) 03-07-2005, 12:07 PM

Here are some fotos of an LSD diff. This one is a 4.3 LSD diff from a euro berlina 2000.

**papajam** · #6 (**permalink**) 03-07-2005, 04:47 PM

Great shot, jpv. (hope you don't mind I borrowed it)

yng,
One arrow points to the triangular shaped ribbing I mentioned. Non-LSDs do not have this triangle. In addition, the second arrow points to the three center cooling fins on the oilpan. These three fins on an LSD rear are longer than the other fins; on non-LSD, the cooling fins are the same length.

jpv · #7 (**permalink**) 03-07-2005, 07:00 PM

I think that the top of the diff casing is also diferent. It doesn't have so much finns...
Papajam, use the pictures as you like! We're here to help each other!

**conedriver** · #8 (**permalink**) 03-07-2005, 07:54 PM

Group,

Papajam is correct. I compared the casting design between my '76 Spider differential, and an old '71 1750 diff. I had underneath the workbench, and the LSD from the '76 has the trangular shaped ribbing. Pretty neat communication between distant locations.

Quote:

Originally Posted by papajam

Great shot, jpv. (hope you don't mind I borrowed it)

yng,
One arrow points to the triangular shaped ribbing I mentioned. Non-LSDs do not have this triangle. In addition, the second arrow points to the three center cooling fins on the oilpan. These three fins on an LSD rear are longer than the other fins; on non-LSD, the cooling fins are the same length.

**conedriver** · #9 (**permalink**) 03-07-2005, 08:05 PM

Group,

Papajam is correct. I compared the casting design between my '76 Spider differential, and an old '71 1750 diff. I had underneath the workbench, and the LSD has the trangular shaped ribbing.

Quote:

Originally Posted by papajam

Great shot, jpv. (hope you don't mind I borrowed it)

yng,
One arrow points to the triangular shaped ribbing I mentioned. Non-LSDs do not have this triangle. In addition, the second arrow points to the three center cooling fins on the oilpan. These three fins on an LSD rear are longer than the other fins; on non-LSD, the cooling fins are the same length.

yng · #10 (**permalink**) 03-08-2005, 04:05 AM

This is all great stuff guys. Thanks again.

One more slightly more obscure question if I may. Can the half shafts and halfshaft housings of a non-LSD 4.56 differential be bolted onto a 4.56 LSD differential?

The reason why I ask this is that I currently have a recently rebuilt 4.56 non-LSD axle and the LSD axle I am buying sounds as if it is a little worn. Clearly, it would great if I use the half shafts from my existing axle, with its new bearings and oil seals. It also avoids having to hassle with moving the brakes and whatnot.

regards
Yushan

**papajam** · #11 (**permalink**) 03-08-2005, 06:00 AM

My understanding is that the LSD axles are slightly larger in diameter and have a different number of splines than the non-LSD so they are not interchangable. But don't quote me on it. Unless someone else posts in the meantime, I'll have a look in the parts books tonight.

jpv · #12 (**permalink**) 03-08-2005, 11:25 AM

I think papajam is correct (although don't quote me on it either...). On his website, Mike Valant says that they are not interchangable. Go see it.

http://engr.smu.edu/rcam/cpm3v/mygs/mygs19.htm

alfacorse1965 · #13 (**permalink**) 04-05-2008, 06:48 AM

I am working right now at a rear lsd axle and I can tell you for shure that you can,t use any part for a non lsd axle in a lsd axle.They look very similar but they aren"t.The crown and pinion are diferent monting sizes ,the bearings are all 4 diferent,the lenght of the diff housing is different,the halfshafts are diferent.It's imposible to mix them without expensive machining.Like Jim k said (I purchased his book after i start the transplant) better buy the whole lsd axle and restore it ,or buy a lsd that fits directly in a non lsd axle from Alfaholics or other suplier.

**Alfar7** · #14 (**permalink**) 04-05-2008, 07:28 AM

If you are working on a 105 type car the simple solution is to just swap out a 115 complete diff assembly, as all the mounting bolts & hardware are similar and in the same location on the axles.

BUT, for you few enquiring minds:

The 115 LSD unit can be modified to fit into all the other rear end configurations. The 750, 101, and 105 series.
I won`t tell you how but there are pics at :Install of a 2 L Into The Giulietta Spider
It requires having the right machinist, metalurgist, and fabricator

harryf · #15 (**permalink**) 04-05-2008, 06:55 PM

I have heard very good things about the aftermarket 'gripper' LSD's available from several of the UK specialists and I believe they are available to fit non LSD diffs and cars with the narrower splined axles.

Its the next item on my upgrade list if nothing else pops up to swallow the budget.

They are not cheap, but I don't know how much you're paying for the californian rear end so it may be viable, particularly if you save work and the benefits are of interest.

You would probably need to be an enthusiastic driver to make full use of one but they are apparently very long life and much more effective. If you trackday the car I have heard of the standard diff friction plates being considered as consumables needing frequent replacement.