Installed mine into a 68 Barracuda on the stock crossmember, onto the back of the A833.
After it was in the tunnel, I just pushed it up as high as it would go, found and marked the tight spots, puller her down, and clearanced the tunnel with a BFH.
When I found that the cross member was still low, I clearanced the tunnel some more.
And it was still too tight. Eventually, there was no going any higher, so I slotted the crossmember holes and dropped her down a tad to prevent rattles.
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the 727 ratios are 2.45-1.45-100 and GVod is .78
the splits are .59-.69-.78; which is a very nice progression.
Most guys or at least some, focus on the .78 as not being enough, but if you inshift it prior to going into Direct, your ratios are ;
2.45-1.45-1.13-.78 ... thus your splits are
.59-.78-.69; you see the .69 there, lol?
and you get the short 2-3 shift
With 3.91s, shifted as above, your roadgears are;
9.58-5.67-4.42-3.05
But you will have to bypass the slow-azz computer on this split-shift.
This makes 65=2500@ zero slip/ perhaps 2600@5% slip,
and at the top of second, 60=4700@10%
but if you power-shift from First into GVod instead of Second; then 60=6200 in First-over at 10% slip with 27" tires.
Since with 3.91s your starter gear is so deep, you can use the GVod to fine tune your rpm at 60 mph to suit your cam, with perhaps a lil less rear gear.
For instance;
With 3.55s; this will get you 5630@10%,
and 65=2350@4%;
but your starter is down to 8.70 so you might need some stall to satisfy your launch. But that will bite you a bit in the gas-mileage department, if you don't have a lock up.
The other option is to put second gear where you want it.
For 60=5500 in Second at 10% slip would take 4.56s. But yeah, the starter gear is now 11.14 a tad high, and cruising is 65=3000 again.
The final option is to just run what you got and that's that.
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As for me; for a short time, I ran a Commando 4-speed with 3.23s and got a starter gear of 9.98, and she cruised at 65=2060. 60mph was 4680 in Second or 5870 in First over.
I have tried many other rears but finally settled on 3.55s.
Enjoy!
