Modern Drivetrain Swap into '65 Valiant

AJ/FormS said
This driveshaft rpm increase causes your governor flyweight to fly out at a quicker rate, which increases it's pressure, which then over-rides the line pressure+throttle pressure, and this action causes your shifts to occur earlier than before.
You can change your throttle-pressure at the KD mechanism, but if when it is maxed out, your auto upshifts are still too early, then the only other thing you can do is go into the governor and reduce the pressure by delaying the flyweight by making it lighter.

I understand how the interaction between the diff gearset and the trans gear ratios will change rpm at a given speed. Really i was asking about the mechanics of it. The sentence in bold seems important. A steeper rear will increase engine rpm at a faster rate. Is it this change in rate what actually causes the earlier shift? Because really when I’m matted I don’t care about what speed i shift at, only rpm, so that i can take full advantage of the motor. So even tho a different rear will have a different speed at a certain engine rpm, I’m still not positive how the governor (which you said is ONLY rpm dependent) will actually end up shifting at a different rpm. (Whether it shifts at a different speed is irrelevant in this particular case.)

I’ve helped blow a few motors, but I’d like to avoid it if possible, haha.

AJ/FormS said
I think you misunderstood my meaning.
With an open diff, it is almost impossible to initiate a sideways skid, unless there is close to zero traction. This is because at least one wheel back there is always fully connected to the road. This is why you cannot make your one-legger fishtail, unless you get violent with the steering wheel..
However, with a Suregrip, both rear tires want to turn at the same rpm. So if you get into a skid, adding power will make it worse, and lifting off the throttle MAY make it worse. If you want to recover from the back-end stepping out, your only option is to restore the tires to the exact right roadspeed, so the rubber can do it's job.
A very long time ago, I figured out that the best way to do this is to disconnect the tires from the engine, by clutching it, or popping the auto-stick into neutral. If the road is icy, wet, or somehow slick, once a skid starts, you only have milliseconds to react, so you have to be prepared beforehand; this action has to be instinct. And that my friend, takes practice; lots and lots of practice. If the back-end steps out more than a few degrees and loses grip, it is coming around to pass you and there is capital ZERO that you can do about it. You only have milliseconds to restore grip, or pray.
Friend, this is why my car has 295s on it. I was tired of losing grip and spinning out, altho I must admit, I was pretty good at going off-road ....... backwards, lol. These 295s have a lot of sideways rubber, so when I sense an impending spin-out, I just disconnect the power and let the tires save me. I can't tell you how often this trick has saved the day. Nor can I tell you how many passengers have had their necks massaged by it, and they no longer beg for rides. lol.
A SureGrip is only good for two things, namely;
1) straight line torque-splitting for traction under power, and
2) show-off drifting
both of these are best done on a clean, dry, level, hard, and flat surface; I think that is called "prepped", lol.

I think in my case the 5” wheels may have had something to do with it… you’re absolutely right that more rubber usually makes for safer driving. But I’ve learned from the track that the most controlled way to recover from a slide is to slowly reintroduce traction which is easier with a posi because neither wheel will unexpectedly grip. With a peg-leg it can be hard to be sure which wheel will have traction, which makes controlling a slide by modulating throttle much more difficult. Certainly for guys like me who had all the wrong instincts anyway! Lifting off completely, overcorrecting on a slippery road! I was lucky traffic wasn’t close. Anyway maybe a driver mod was more important than the new rear, but I’ll still take it.