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I was sold what was supposed to be a US spec MK4 Spitfire diff. They fitted a 4.11 to try and gain back some of the acceleration that the emissions gear had taken away.
It is however a 1500 Spit 3.63 and really too tall to use with the MX5 gearbox.
Ideal if you're upgrading to a straight six, or want a more relaxed cruise.
It owes me £35 and is good and tight. I'll swap it for a good 3.89 if you have one.
Superb price! I wish you were selling this a few months ago as I paid much more than this for mine
I've got what I think is a 4:11 in the garage if that is any use? Although I will have to check the numbers to make sure its not a 3:89. Any idea where I can ref the casting number numbers?
I've got what I think is a 4:11 in the garage if that is any use?
Possibly!
Many 4.11 diffs are rather weak, it's not even recommend to put a 13/60 engine into a pre 1967 1200 Herald without uprating! The Vitesse 6 used a version of the early diff and was prone to output shaft breakage. They beefed up the output shafts for the post 1967 1200 and 13/60 Herald. I've got two 1200 diffs.
If your diff takes 3/8" (9/16" AF) bolts in the output flanges, it's probably the stronger version (or is the weak Vitesse 6 diff).
Although I will have to check the numbers to make sure its not a 3:89. Any idea where I can ref the casting number numbers?
You can't tell the ratio by the casting number (the stamped tag is probably long gone) and in any case bits have often been swapped around. You need to turn the flanges or count the teeth.
If everything else falls through I've got a perfectly good late mk1 Vitesse 2 litre 3.89:1 diff sitting in my garage and I'd be happy to swap it for the 3.63:1. I was hanging on to it as an emergency spare in case the GT6 diff I've fitted ever fails.
