[Fot] HELP! From Hawaii, and Happy Thankgiving

[Andrew Mace]

-----Original Message-----
From: robert smith <rsrpsmith at gmail.com>










...I have a Triumph Spitfire that was Bob and Jimmy Coan's
ex-race car, and I was doing very well with it at Hawaii's only race
track, which is an autocross cross course near Hilo. Then, I broke the
pinion gear, and maybe messed up a ring gear too. This car has an IRS
set up, and the third member I need has a stamping on it that is
either: FC16959, or EC16959. This is the stamping on the snout of the
two piece differential. What I would like to do is either have my
existing unit rebuilt, but with a 4:11 ratio for our little autocross
track, or buy a unit that will fit and is already geared low, in the
range of 4:11. ...



 ==AM==
Robert, FC would be correct, and that would be the original prefix for an early Spitfire. Originally, they were equipped with a 4.11:1, as were most Heralds (same diff.), but 4.55:1 gears were fairly common for racing applications (my old autocrosser, an ex-GP SCCA racer, has a welded 4.55), so it's likely(?) that your car has the 4.55 now. Anyway, again, the 4.11 is about the most common gearset for those cars, and it shouldn't be too difficult to get a decent used set. (They seem to be unavailable new.)

Canley Classics in the UK does list a "competition" 4.11:1 crown wheel and pinion; I'll assume that fits the later, beefier MkIV/1500 differential. And the 1972 model year "Federal" Spitfire MkIV came with a 4.11:1 diff, which might be the same. That would have the "FK" prefix as opposed to the more common "FH" prefix (3.89:1). You'd be able to use any later differential with only changes to the flanges on the driveshaft and axle shafts. U-joints are the same as are chassis mounts. (Only four stud holes on the later Spitfire cases to hold the swing spring, but that shouldn't be a problem, either.)


 

--Andy Mace

*Mrs Irrelevant: Oh, is it a jet?
*Man: Well, no ... It's not so  much of a jet, it's more your, er, Triumph Herald engine with  wings.
 -- Cut-price Airlines Sketch, Monty Python's Flying Circus  (22)

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