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At the local track, I always find that there's more drop from 2nd to 3rd than I'd like. Since I don't have the $$ to go all out for a Bacci gearset, I consulted fellow guru Micke and the result was an interim and useable (ie cheap) solution to the problem: replace the 3rd and 4th gear cluster with those from the 4cyl Alfetta box. We therefore have a very good 2 to 3 shift, dropping only 1500rpm fom 7000 to 5500, instead of 2000rpm with the std ratios.
Today I went and pressed out/in the clusters on the shaft. Will have more details when I assemble the box and certainly more news when I take it to the track!
Jim K.

So what's the original box u r using Jim ?

what happens to the rest of the gearing?from 3 to 4 and from 4 to 5
is this also better?seems to me that you get an enormous rev drop from 4 to 5

All this is being done for a TS box (4.1 diff) which I will install when its assembled.
There is a drop of ~1700rpm from 3th to 4th, shifting at 7000 and ~1800 from 4th to 5th but it doesn't really bother me as 5th is not used in the track and on the road I wouldn't really worry about it (hell, a good 3liter with a TS box can afford an 1800 drop in 5th!). What we must also look at is the speeds involved with the 'new' box. An 1800rpm drop at 184kph is probably not as bad as a 1300 one at 212kph!
Jim K.

Depends on the power-curve and wind resistance.

mats,

Jim has no wind resistance. He doesn't wear any undies under that Greek toga I am told !!

I haven't torn a gearbox apart yet, but isn't the lay shaft with it's gears all one piece ? Or is it a shaft with pressed on gears ?
Seems like a neat way to eliminate the 2-3 gap.
Thanks,
Merril

1-2 are solid, 3-4 are pressed on and of course 5-reverse is held on with the nut.

This is from memory, haven't had a GB apart in about 2 weeks now.

Thanks Mats!
That kind of gear swap may create increased demand for Alfetta gear boxes!

From what I remember it's not a bolt off/on exactly...

You'd have to get the shims correct to put the diff pinnion back in the right spot once you change the 3-4 cluster wouldn't you ?

Not sure about this but the diameters of the shafts between the Alfetta and 75 boxes are not the same, neither is the splines for the fifth/reverse gear assembly.

I wont ever get it together enough to try something like this, but I look forward to reading more about it. Good luck Jim.

So far all I've done is press the Alfetta 3/4 gears onto the TS shaft with the fixed 1/2 gears on it. My mechanic is too lazy to mess with the rest of it now and I'm waiting for someone to cart over a TS box from a used parts store. I have a completely rebuilt TS box (and still unused) on the side but its a shame to open it up. I also want to finish the 12v engine dyno with the same box in the car (1.8Turbo).
I haven't checked what Mats says about possible fitting problems, but if its true, it may be a good excuse to start saving $$ for a Bacci gearset!
Jim K.

Jim,

Have you emailed Beninca? He listed a few used close ratio box on his website. last time I asked about Colotti boxes, they're very very expensive, like you can get a nice 75 24V for the same price.