4spd or 5spd what is the difference ?

[steven polaski]

The p.o. installed a 915 trans in my 930s I know the gearing in the 4spd suits the turbo motor but are there any advantages of the 5spd ? Is there a different top end ?
Thank you in advance
Steven

[WydRyd]

Different gear ratios make the 915 quicker off the line, however, don't abuse that g/box. It's weaker than the 930 or G50 boxes

[RarlyL8]

Bruce Anderson has a few blurbs in his book about folks fitting 915s into a 930 in the days before the G50.

The bad news is the 915 5spd is not nearly as strong as the 930 4spd. The good news is that if your engine is stock it doesn't need to be that strong. More good news is that for the cost of a set of core Webers you can buy a good 915.

I have a 915 in my widebody 3.3L turbo powered SC. The gearing is great for a stock 930 engine, it make it feel like 100HP more than it is. The gearing becomes not-so-good once you hit the 275RWHP figure. At that point (in my opinion) you have enough brass to use the long legs of the 930 4spd.

The top end will be gear limited with a 915. I can pull about 155mph at close to 7000rpm in 5th gear. Very fun stuff!

Again, with a stock or warmed-over engine a 915 is great fun. With a built engine it is a liability.