Spider axle ratios?

[Keyspider]

What was the correct rear axle ratio for a '74 Spider?
Was the '75 the same and what about the '81?
I seem to remember that they changed sometime around this time period.
If i put the assembly from an '81 in my Blue Spider what will the result.
I dont understand how the ratios work I guess!

[Alleggerita]

Up to about 1980/81 (don't know the exact cut-off) I believe all US Spiders were 9/41 (4.56). Then they became 10/41 (4.10). Euro Spiders (2 liter) had originally 10/43 (4.3) and later changed to the 10/41.

If you check on the transmission of the donor car - if it is still original - the ratio of the rear end should be stamped in.

[Vivace]

My info is that the 2 liter, 72-79, is a 4.56 LS.
80-94 is 4.10.
91-94 auto trans is 3.73

[Keyspider]

Great!
Ok, thanks guys!
So, to recap..
The '75 is same as the '74 with a 4.56 LSD.
The '81 should be a 4.10 and I visually confirm it has a LSD case too, the gearbox is long gone so I can only assume!

Now, please explain....
The 4.56 is shorter geared.. ie, faster acceleration/lower top speed?
The 4.10 is taller geared.... ie slower acceleration higher top speed?
Or do I have it wrong??
Would it make much of a difference?

[Tifosi]

Quote:

Originally Posted by Keyspider The 4.56 is shorter geared.. ie, faster acceleration/lower top speed? The 4.10 is taller geared.... ie slower acceleration higher top speed? Or do I have it wrong?? Would it make much of a difference?

[Alleggerita]

Quote:

Originally Posted by Tifosi Don't forget to change the trans speedo drive gear if you're changing ratios unless you want to spend the rest of your days treating it like that clock someone set 5 minutes fast so they'd never be late. It should be just a matter of removing the cover where the speedo cable screws on and pulling the gear out. The drive gear inside the trans should be the same across all models using that trans, with the only difference being the output/cable drive gear itself. (much cheaper and easier to manufacture all the drive gears the same then adjust the ratio at the output gear)

[Tifosi]

Huh.

Well, I'll add that to the 'learned something new today' list.

Thanks for the link.

[Keyspider]

Great, that works perfect... assuming the 4.56 from the '75 is good!

On a sidenote.... somewhere along its life my Blue Spider had a non LSD rear end swapped in. Its a good one, but here is the interesting bit.... it had left hand threads on the wheel lugs..
I assume it came from and earlier spider or Duetto... any ideas what?