Your favorite rear end/final drive ratio and why?
My current engine is a Blueprint 408 stroker making about 460 at the crank driving an A833 4spd with stock ratios. There's more than enough power to overwhelm the tires in almost any gear...at least with my 255 no-season BFG T/As.
Would it be more fun with 3.23s or 3.55s? I just don't know and experimenting is outside of my budget currently... I'm hoping to learn from you guys before I invest.
I've done all the experimenting for you,lol, having run every chunk from 2.76 to 4.30 plus 4.88s and 5.13s, but not including 3.73s.
To answer your question, between 3.23s and 3.55s,
I would choose the 3.23s...... cuz 65=2519rpm
And it's hard to get the Cruise-timing optimized at any lower rpm.
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Let's talk street use.
There is no sense in comparing a car with an automatic to one with a manual... even with identical engines; because the TC skews your ratios, and autos only have three gears, which are considerably further apart..
With a 4-speed, IMO, the best gear to run is, the one
1) that keeps your engine on the cam, for how you are driving the car and
2) for me that is Second gear,
3) if you can burn thru 2nd at will, then you can easily run less gear.
Here's the quick test;
the easiest way to see if your engine will be Ok with a lower rear gear is to put yur trans in Second to start off with, INSTEAD of First, and see how your 4.08 handles it. Don't pay attention to JUST the take-off. Also pay attention to when the 1-2 shift naturally occurs at various Roadspeeds and throttle-settings. Also, what is the lowest rpm that your 408 will spin the tires without toeing the clutch. And the lowest rpm that it will take a large amount of throttle without complaining or, especially, detonation. Try it for several days. Then if the 408 says no way, consider a half-Roadgear change; which would be
(10.87 +7.82)/2= 9.34 first Roadgear
and 9.34/2.66= 3.51s rounds to 3.55s.
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What you are actually interested in is the roadgears.
You say you have 4.10s , and a stock ratio A833; but there are three stock ratios; The most common is the 2.66-1.92-1.40-1.00 So lets look at the roadgears, which is what I call the overall gearing, which is each transmission gear multiplied by the rear gear.. With the 4.10s they are
10.91-7.87-5.74-4.10 This is really good for low-powered engine.
Your stroker should have no problem annihilating the 255 street tires thru at LEAST the first three gears. Obviously then, you currently have too much gear for the chassis so the 4.10s can easily be ditched.
Look at that 7.87 gear. If you can spin that ratio at 3500/4000rpm, flat-footing it, then you already have more gear than your chassis can handle.
IDK what cam is in your engine but I'd guess about a
[email protected]; Which, if correct would put your Powerpeak around 5000, which would put your Torque peak around 3500, and with good heads, you should be able to run to well past 5400 still pulling hard. That sets your powerband from about 3500 to 5400= 1900rpm
That A833 trans averages a Powerband requirement of ~.72 which times 5400 is, to a lower limit of 3900; so 5400 less 3900= 1500, which is less than 1900, which is really good, and you can probably average like 95% or more of peak power, all the way from 3900 to 5400. Which means, depending on your Roadspeed, the tires are gonna break loose anywhere from 3900 to 5400, with that 7.87Second gear.
Now, I'm gonna guess that your 255s are about 28" tall. Therefore, the Roadspeed associated with these rpms from 3900>5400 in 7.87 Second Roadgear, is 41>57 mph.
If you can break the tires loose, in this window, then, you have way more gear than the tires can handle.
So then, if your fun window is
41 to 57 mph, then the 7.87 Second gear is just about right for you.
But guess what;
You can get the very same 7.87Roadgear, by running
7.87/2.66 (in First gear)=2.96 rear gears, or
7.87/1.40 (in Third gear)=5.62 rear gears .
The engine does not care how it gets 7.87, it will perform exactly the same, with any 7.87 ratio.
Ok but; IMO having your powerband at the ready from 41 to 57mph is too high, this is getting too dangerous for me. My skill-level for sliding and drifting, and driving like a maniac, rapidly loses confidence at around 40/45 mph. And my 367 has about the same powerband . Lets say your confidence level is a lil higher, and tops out at 48mph, and you want to be at 5400, I mean these are just numbers. To do that with the A833 would require a Roadgear of 9.38. You can get that in 2.66First gear with 3.523 rear gear. Badaboom~ Because 9.38 Road gear is quite a bit more TM(Torque Multiplication), than 7.87, and you are currently annhilating your 255s in that 7.87 gear, you will be super annihilating them with a 9.38 gear. So in this case, depending on your definition of "fun" the 3.55s could be; 9.38/7.87= plus 19.2% more fun at 48 mph@5400rpm. And the lower limit will be close to 5400 x .72=3900 rpm=34 mph.
This is why I have 3.55s.
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Now to be honest;
a 2.94 rear gear will get you a
First Roadgear of
2.94 x 2.66= 7.82, compared to
4.10 x 1.92=7.87 in the current 4.10/
Second gear combo.... so between these two combos there is ZERO performance difference, in these Roadgears.
Here are the Roadgears;
10.91-7.87-5.74-4.10 Your current A833/4.10 combo
------- 7.82-5.64-4.12-2.94 the Regular A833/2.94s
notice the 7.87 versus 7.82; same thing.
Where the differences are is;
1) the 2.94 x 2.66=7.82 First Roadgear, is too low a number for my 3.67; which much prefers the 3.23s. However, my thinking is that with 255s, yur stroker will be able to deal with that, on account of she will have way more take-off torque than mine. and
2) the cruise rpm with 28s, and 2.94s is 65= 2300, versus 3200 with 4.10s. That's 900 stinking rpm. And 2300 is about the lowest rpm that you can still optimize the cruise-timing, with the factory-type distributor.
3) now, to see these roadgears on paper looks like this;
10.91-7.87-5.74-4.10 Your current A833/4.10 combo
------- 7.82-5.64-4.12-2.94 the Regular A833/2.94s
---- 9.08----5.64-4.12-2.94 the Commando/2.94s
>Notice how close 9.08 is to 10.91. the difference is 17% , but 9.08/2.66=3.41 and that is how it will take off... like it had 3.41s
>Notice how the 2.94s trade away the 10.91 blast-off gear, to get the 2.94 cruiser.
