LSD Swap

[njh1964]

Hi All,

I have a 1969 GT1300 Junior (105.31), and I also have a complete LSD rear axle assembly from a later model 2lt 105... not sure exactly which model it came out of, or what ratio the diff is, but it does have the correct castings on the diff oil pan to indicate that it's an LSD.

Can anyone please advise exactly (and very specifically) what I'll need to do to swap out the Junior rear axle and install the LSD rear axle?

For example, are all the rear suspension body mounts on the Junior suitable for/compatible with those for an LSD axle? Can I modify, or will I need to replace part or all of the Junior's drive shaft assembly to suit the LSD axle?

Any advice would be very much appreciated.

Regards,


Nick

[105s alive alfa parts]

Hi Nick,
Are you changing the whole diff out or just the axles? because the axels cant be swaped between the 1300/1600/1750 to the 2000 if you are changing the whole diffs then thats easy,
You dont really have to do much, you have to either change your tail shaft as the bolt holes on that will be 8mm and on the diff they are 9 mm or you can do what i did when i changed my 1750 to a lsd is i just drilled out the holes the extra 1mm larger, but you do need to use the proper 9mm tail shaft/ diff nuts and bolts which are a high grade.

All the mounting points, springs, trailing arms should be the same i say should because i have seen some "different" modifications which have changed what it should be like.

To check the ratio and that the lsd unit is still in there and not changed out with a standard crown and pinion, undo all the bolts on the left side plus the big nut at the top, then open it up and pull out the unit with the crown, it will have what the ratio is stamped on it on the side of the crown, like 43/10 which means its a 4.3.1 ratio, after you close it back up make sure you put in lsd diff oil not just normal diff oil,

[njh1964]

Hi 105s Alive,

Thanks for that. I was planning on swapping out the complete Junior rear axle assembly (ie everything between the road wheels) and replacing it with the complete LSD rear axle assembly.

I like the idea of simply drilling out the 8mm Junior tail shaft flange holes to 9mm, as this seems a simpler and quicker procedure. However, given that I'm also dropping a Twin Spark engine, and a later model 105 2lt gearbox into the car, perhaps I should use a complete 2lt drive shaft assembly (ie assuming this is a stronger unit)? What do you think?

If I went the 2lt drive shaft route, would Junior need any modifications in or along the transmission tunnel to take a 2lt drive shaft?

Finally, you wouldn't happen to know what brand and specification of oil is needed for an LSD diff?

Thanks again for your feedback... this forum really is a great resource.

Regards,


Nick

[monoman]

Oh pooh. 

When I saw the thread I was hoping you had an LSD you wanted to swap, as in trade.  In case you would like to swap, drop me a line.

[njh1964]

Hi monoman,

Sorry, no. It took a while to track down my LSD, so I'll definitely be keeping it for Junior.

Cheers,


Nick

[GTV-074]

Nick,

Just curious here..... what are the casting marks on the oil pan that indicate the diff is an LSD?

Would be nice to know...

Cheers.

[ItalCarGuy]

This is off the alfaBB

[Paul Gulliver]

Great info  Derek. Just had a crawl around the underside of my of my 105 and all as is it should be.

Thanks

[105s alive alfa parts]

Thanks for that too, i have never taken any notice of those casting marks i go by the width of the axle and crown housing as it is wider on a lsd diff the a normal diff.

[GTV-074]

Thanks Derek much appreciated.....me too - I  had always checked by other means...

Cheers.

[njh1964]

Those are indeed the diff oil pan castings (ie in Derek's response) that I was referring to for externally identifying an LSD.

Any further feedback on the swap (ie 2lt drive shaft versus modified Junior tail shaft) would be very much appreciated.

[105s alive alfa parts]

Hi again

the drive shafts are pretty much all the same except for the flange holes, but if you are doing all that work it would pay off to get a good drive shaft and get it balanced plus put on a new flexi disk and prop center with new bearings, they dont cost much i think off the top of my head for the 2 without bearings i have them for under a 100 bucks, i will get back to you on that, changing them can save alot of hassle and a noisy car and not in a good way.

I used Penrite lsd diff oil, i will check when i go to the workshop tomorrow what the specs of it are.

cheers

Ang

[105s alive alfa parts]

Hi,

I used the penrite limited slip oil SAE 140.

hope this helps

Ang

[Nick Shardey]

HI Nick,

I'm not sure if you have found your answers yet but I have done this swap on my 64. It was a straight swap aside from the 2.0 drive shaft changed at the mid point. (You will need to use the special 2.0 bolts)
It was heavy work but easy with no other mods.
It makes a huge difference and you'll have to get use to the back slipping out ALL the time, great fun...

Good luck

Shards

[njh1964]

Hi Shards,

Thanks for the info. Any suggestions as to where I can get hold of the special 9mm diff flange nuts and bolts, or what the specs are so that I can get them from a nut & bolt supplier? Unfortunately, my rear axle assembly came without the flange nuts and bolts.

Regards,


Nick