28x10.5 SS Guys...What are you 60 footing?

the Coug wrote:

bruno wrote:looks like we will be switching to a 2 speed 400 .....

YOU DO KNOW YOU CAN SWITCH THE FIRST GEAR RATIO OUT IN YOUR GLIDE MUCH CHEAPER DONT YOU? OH I FORGOT YOU LIKE TO SPEND MONEY WASTEFULLY....

Coug, tell me of a good gear set for this conversion.

whatbumper wrote:

the Coug wrote:

bruno wrote:looks like we will be switching to a 2 speed 400 .....

YOU DO KNOW YOU CAN SWITCH THE FIRST GEAR RATIO OUT IN YOUR GLIDE MUCH CHEAPER DONT YOU? OH I FORGOT YOU LIKE TO SPEND MONEY WASTEFULLY....

Coug, tell me of a good gear set for this conversion.

he dont ...just more of his bs ...he is still living in the flinstone era

Bruno if you were going to Race in some sort of a race where you are competing against someone it would be something, but you just go run to run and maybe a few times a year....just so you can blow smoke up someone A$$.... Go Ahead and build what ever you want
We will end up paying for it in the end anyways....

i dont understand you animosity/hatred/ jealousy or whatever issues you have with me but its ok ---you cant please everyone ........ but i do have to say you have wrong info about the glide at the power levelsof these small tire deals ...especially running at the marginal track here locally ....... here is a great read by scott from the yb :

Some shops prefer to set up the trans as a two speed only. Some others have it set up as a three speed only, and others have it where you can leave in 2nd OR 1st. I feel fairly confident in saying at this point that any of them are capable of setting them with any of those options, and 2 or 3 speed are not that different in cost. However, when you get one set up to do BOTH at any time without internal modification is (one place) where the price goes up. Also, if you want to be able to run it as a 2 OR a 3 speed, there are compromises in gearing options, and I'll elaborate on those later. In a nut shell, the less torque your engine has, the more pronounced the compromises become, and who wants to pay extra for compromise?

In my case, one of the biggest reasons I want to go to the 400 is because I want to be able to run a rear gear in the 4.xx range so my little short stroke engine can reach the operating RPM where it makes it's power in high gear before reaching the finish line.

With a glide with a 1.80 1st gear, if I go any lower than a 3.89 rear gear, the odds are slim I would be able to consistently get the car off the line on a 275 tire. With a 2 speed combo, it's necessary to leave at as high an rpm and boost as you can to insure a good 60ft time, so going lower than a 7.00 final drive ratio (3.89x1.80=7.00), is "hit or miss" on a 275 tire (or at least it is in my personal car).

On the flip side, I've run my car with as much as a 3.50 rear gear and a 1.80 1st gear, and it left fine and the 60ft wasn't horrible, but just not very good. 3.50x1.80=6.30 final drive ratio. Keep in mind, with a 6.30 final drive, it was going to get off the line consistently, just without stellar 60ft times.

If you really want your car geared optimally, you really need to start with answering the question: "what rear end gearing do I need to enable me to reach my optimum RPM in high gear at the finish line?" Unless your power output changes or the weight of the car dramatically changes, the answer to that question will never change.

To know that, all you need is to look up one of the many online performance calculators. You will need to know the mph your power level should allow you to run, the RPM you want the engine to reach by the end of the run, and the height of the tire you are running. Keep in mind, most of these calculators give the number as though you have a true 1:1 crank to driveshaft relationship in high gear, so they are not incorporating converter slip percentage into their calculation (*unless specified*), and some of the better ones allow you enter converter slip. Once you have determined what rear gear is needed to reach your target engine rpm, only then can you accurately begin sorting out the rest of the combination.

When it comes to accelerating the car, TORQUE is king. Ideally, when you shift, you want the engine to fall back to the sweet spot in your engine's torque curve. That is a huge part of what it takes to give your engine the ability to continue to build rpm throughout the run. If the next gear ratio in the trans lands the engine rpm well below the torque peek, the engine is going have a tough time continuing to build rpm after the shift. That's the main trouble with smaller cubic inch engines. They don't have as much torque to begin with, AND it's in a narrower rpm band, AND that rpm band is higher than the bigger engines, which makes gear selection more critical for a smaller engine than the 400" and above crowd.

You want to find best balance between "how much final drive will the car leave on" (1st gear ratio x the final drive ratio), vs. the rear gear that will allow your engine to reach it's max power RPM in high gear, and hopefully have the right ratios to land the engine in the torque sweet spot on the shift.

With a glide with a 1.80 1st gear, the answer for just about anybody with a 360" engine combination is: you can't put enough gear in the rearend to reach your optimum rpm by the time you reach the traps (1/8th mile), and still be able to launch the car without blowing the tires off. For example, I probably need something in the range of 4.30 to 4.56 gears out back for the engine to be able to reach 9000 rpm through the traps. With my current 1.80 1st gear in my glide 4.30x1.80=7.74 final drive!! Getting a car with a final drive ratio of 7.74 to leave on 275 radials with a 2 speed would need both a track that was on "KILL", and an UBER talented tuner.

And yes, there's a readily available 1.69 1st for a glide. 4.30x1.69=7.26 and you still aren't going to leave on that much final drive ratio on a 275 at any RPM and boost worth talking about with consistency. So you drop the rear gear down to 4.11. 1.69x4.11=6.94 so you are back in "hit or miss" territory of what a 275 will take off the line (*again, this is MY car, yours might be different), but now you've killed the rear gear to the point where when you make the shift, you are well below the engine's torque peak, and now the car just "rides the converter" down the track in high gear, lugging along, unable to gain more than a few hundred rpm between the shift and the finish line. In that scenario you are giving away both ET and MPH due to the compromise in rear gearing, and your still hit or miss off the line because of the high final drive ratio with the small tire.

OK, so now lets talk Turbo 400. There seem to be two prevailing schools of thought. 2 Speed mode, and 3 speed mode.

Option A -- run the trans as a 2 speed and optimize the launch vs the target trap rpm. For example, in my case I need a 4.30-4.56 rear gear to reach my target trap rpm, but I want to be able to leave at the most the tire will take. From experience, so far I've learned my car seems most consistent getting off the line with a good 60ft when my final drive is in the 6.6-6.7 range. If I go lower than that numerically, the 60ft slows too much, and any higher than that numerically the car MIGHT 60ft better, but also might NOT get off the line, so for my personal car (yours may be different) 6.6x-6.7x is a consistently quick, but acceptably safe final drive ratio range.

So to get that done, what 1st gear x my 4.30-4.56 rear gear would put my final drive off the line in that consistent leaving 6.6-6.7 final drive range?
You can just start plugging in the available 2nd gear numbers for 400's, and keep in mind this is assuming you are in 2 speed mode, leaving at all the rpm and boost you think you can for the best possible 60 time. And BTW, you better have a mid 9000rpm or higher engine in a 150mph car if you are going lower than 4.56 with this scenario in an 8th mile.

Potential 4.11 rear gear combos in 2 speed mode:
4.11x1.31=5.38
4.11x1.34=5.50
4.11x1.36=5.58
4.11x1.40=5.75
4.11x1.44=5.91
4.11x1.48=6.08
4.11x1.56=6.41

Potential 4.30 rear gear combos in 2 speed mode:
4.30x1.31=5.63
4.30x1.34=5.72
4.30x1.36=5.84
4.30x1.40=6.02
4.30x1.44=6.19
4.30x1.48=6.36
4.30x1.56=6.70

Potential 4.56 rear gear combos in 2 speed mode:
4.56x1.31=5.97
4.56x1.34=6.11
4.56x1.36=6.20
4.56x1.40=6.38
4.56x1.44=6.56
4.56x1.48=6.74
4.56x1.56=7.11

And just for giggles
Potential 4.88 rear gear combos in 2 speed mode:
4.88x1.31=6.39
4.88x1.34=6.53
4.88x1.36=6.63
4.88x1.40=6.83
4.88x1.44=7.02
4.88x1.48=7.22
4.88x1.56=7.61

Option B - Use all three gears in the 400. After I actually did the math, ANY 3 speed 1st gear ratio seems too low for a 4.30-4.56 rear gear combo, so I'll start with 3.40 rear gear info:

3.40 rear gear final drive ratios with 3 speed 1st gears:
3.40x1.86=6.32
3.40x1.95=6.63
3.40x2.00=6.80
3.40x2.10=7.14
3.40x2.21=7.51
3.40x2.33=7.92
3.40x2.48=8.43

3.50 rear gear final drive ratios with 3 speed 1st gears:
3.50x1.86=6.51
3.50x1.95=6.82
3.50x2.00=7.00
3.50x2.10=7.35
3.50x2.21=7.73
3.50x2.31=8.08
3.50x2.48=8.68

3.60 rear gear final drive ratios with 3 speed 1st gears:
3.60x1.86=6.69
3.60x1.95=7.02
3.60x2.00=7.20
3.60x2.10=7.56
3.60x2.21=7.95
3.60x2.33=8.38
3.60x2.48=8.92

3.73 rear gear final drive ratios with 3 speed 1st gears:
3.73x1.86=6.93
3.73x1.95=7.27
3.73x2.00=7.46
3.73x2.10=7.83
3.73x2.21=8.24
3.73x2.33=8.69
3.73x2.48=9.25

3.89 rear gear final drive ratios with 3 speed 1st gears:
3.89x1.86=7.23
3.89x1.95=7.58
3.89x2.00=7.78
3.89x2.10=8.16
3.89x2.21=8.59
3.89x2.33=9.06
3.89x2.48=9.64

4.11 rear gear final drive ratios with 3 speed 1st gears:
4.11x1.86=7.64
4.11x1.95=8.01
4.11x2.00=8.22
4.11x2.10=8.63
4.11x2.21=9.08
4.11x2.33=9.57
4.11x2.48=10.19

4.30 rear gear final drive ratios with 3 speed 1st gears:
4.30x1.86=7.99
4.30x1.95=8.38
4.30x2.00=8.60
4.30x2.10=9.03
4.30x2.21=9.50
4.30x2.33=10.01
4.30x2.48=10.66

4.56 rear gear final drive ratios with 3 speed 1st gears:
4.56x1.86=8.48
4.56x1.95=8.89
4.56x2.00=9.12
4.56x2.10=9.57
4.56x2.21=10.07
4.56x2.33=10.62
4.56x2.48=11.30

As crazy as all those numbers seem, I believe it's even crazier than that. I think the REAL advantage of using all 3 gears is really the same as it would be if you were running a naturally aspirated combination, where you don't have the luxury of staggering HP and torque. It allows you to use 1st gear ratios you be accustomed to seeing work well with dramatically lower power levels. What I'm really saying is, for the lower gearing to actually work, you have to leave on dramatically LESS power. Think about it ... with the extra gear, you have the mechanical advantage (lower final drive ratio) to be able to get the car moving without the need to leave with the engine "on tilt".

So you can't hit the tire with 5000 rpm and 10 psi boost with an 8.00 final drive ratio ... who cares! I bet you CAN at 3800 or 4000 or maybe 4200 at 2 or 3 or 4 psi boost .. right? With a much higher numerical final drive ratio, the engine is able accelerate it's rpm at a rate it never could have with a lower numerical final driver ratio. You simply don't NEED to leave on tilt when you have the luxury of a much lower final drive ratio (and you CAN'T).

Think about it .. why do we leave with the engine on tilt with a 2 speed? It's so engine is turning enough rpm to move enough air to get that turbo spinning and building boost when you let go of the trans brake, instead of staying stagnate at whatever boost you were making when you let go of the trans brake, or worse .. LOSING boost momentarily till the rpm comes back up high enough for the boost to recover.

So you've left the line and because you had so much mechanical advantage due to the super low final drive ratio and the car still accelerating well despite the lack of power ... (even thou is sure as hell doesn't SOUND like it). Now what? ..... now the car is "planted" and the chassis has "taken a set" and is settled enough to take more serious power, so if your a blower guy you bring in the timing (or boost if you have a wastegate or blow off tied to a boost controller), or the boost and/or timing if your a turbo guy, or the nitrous, or 2nd kit (or whatever nitrous guys do these days ), and just about the time the power is about to come in like an avalanche, you shift.

Think about this: the rpm was already coming up quickly and car is accelerating nicely (simply due to the higher numerical final drive ratio), so the engine is capable of building boost more quickly (especially when load hits a turbo at a higher rpm), and the chassis is set with the tires planted.

Because you didn't leave hard against the converter (for lack of a better way to say it), it still isn't fluid coupled (or "locked up" as some like to say), so when the power starts to come hard and fast, you shift, but since the converter is still basically flashing, all that new power drives into the converter instead of instantly blowing the tires off and suddenly it's HANG THE FUGG ON!!!!

Since the converter is still basically "flashing" (not yet fluid coupled), there is not much rpm drop (if any). 2nd gear in the turbo 400 is taller (lower numerically) than 1st was in your old powerglide, so it will see you out to mid track, but still land you in the sweet spot of the torque curve when you grab high gear due to the fact that you now have a lower RPM drop at the shift with the closer ratio, and by that point the converter is TIGHT. Since you now have enough gear in the rear end to reach your target peak power rpm in high gear, you will also get there quicker. I'm pretty sure there is some torque converter magical Unicorn stuff going on in there too, but I haven't quite got a bead on that part just yet (or maybe I'm just not telling? )

For the longest time, I've struggled to understand what I was HEARING at SGMP back when the guys suddenly smashed the 4.50 barrier and never looked back. I think Joe (Rivera) definitely found something in converter technology, but the turbo 400 just happened to have entered the drag radial scene at the same time. It sounded like the baddest cars were leaving the line SO soft and slow, and then it seemed like they brought ALL the power on at once, like they were shot out of a cannon, and yet somehow they were still running their personal best 60ft times. I just couldn't make sense of it. Honestly, it's STILL purely "conjecture" at this point for me, but I'd like to believe I've finally made sense of what I was hearing and seeing.

Even with all that said, if you aren't on a stellar track, being able to pull the scenario I just described off would probably be hit or miss. The safest, most consistent route (in my personal opinion), would be to stay with a 2 speed and optimize it for what your combination needs. Your chances of getting down a slippery track in the heat of summer are going to be improved by using a final drive that isn't so "track conditions dependent".

Now for Option C - Two speed and Three speed in one:

Trying to select ratios that would allow you to switch back and forth between 2 and 3 speed mode without a rear gear change is difficult if not down right impossible. You are either going to need a LOT of power and torque to make up for the compromise in final drive ratio when you leave in 2nd vs 1st, or be extremely selective in the ratio combinations you choose. With a short stroke engine, I would think you would have to sacrifice too much performance with a trans you can run in both 2 and 3 speed modes unless you changed rear gearing when you switched modes and I think the math on the final drives I wrote out earlier bare that out pretty clearly.

I've already spelled out the final drive ratios for 2 speed mode and for 3 speed mode. What I haven't yet spelled out is what leaving in 2nd looks like when you have a trans built where you can leave in 1st OR 2nd gear any time you want without having to go into the valve body to make the change.

If you make your gear ratio selection with intentions of primarily running the trans as a 2 speed, your 1st gear is most likely going to be WAY off (final drive way too high numerically) when you run in 3 speed mode and you will face power management issues getting it off the line when leaving in 1st, and I've already spelled out the math on those final drive ratios earlier, but I add the "leaving in 2nd, vs leaving in 1st" data further down. It's not hard at all to see what I'm saying when you see the final drive numbers in each mode side by side.

If you make your gear ratio selection with intentions of primarily running the trans as a 3 speed, your 2nd gear ratios will be way too steep (low numerically) to ever get the car to leave well in 2nd gear (not ENOUGH final drive ratio). Again you will see the "leaving in 2nd, vs leaving in 1st" data further down.

Here's the math so it's easier to understand.

3.89 rear gears:

With a 1.86 1st gear 3 speed, 2nd gear is 1.31, so leaving in 2nd final drive is: 3.89x1.31=5.09 and 7.23 if you leave in 1st

with a 1.95 1st gear 3 speed, 2nd gear is 1.34, so leaving in 2nd final drive is: 3.89x1.34=5.21 and 7.58 if you leave in 1st

with a 2.00 1st gear 3 speed, 2nd gear is 1.36, so leaving in 2nd final drive is: 3.89x1.36=5.58 and 7.78 if you leave in 1st

with a 2.10 1st gear 3 speed, 2nd gear is 1.40, so leaving in 2nd final drive is: 3.89x1.40=5.75 and 8.16 if you leave in 1st

with a 2.21 1st gear 3 speed, 2nd gear is 1.44, so leaving in 2nd final drive is: 3.89x1.44=5.91 and 8.59 if you leave in 1st

with a 2.33 1st gear 3 speed, 2nd gear is 1.48, so leaving in 2nd final drive is: 3.89x1.48=6.08 and 9.06 if you leave in 1st

with a 2.48 1st gear 3 speed, 2nd gear is 1.48, so leaving in 2nd final drive is: 3.89x1.48=6.08 and 9.64 if you leave in 1st

4.11 rear gears:

With a 1.86 1st gear 3 speed, 2nd gear is 1.31, so leaving in 2nd final drive is: 4.11x1.31=5.38 and 7.64 if you leave in 1st

with a 1.95 1st gear 3 speed, 2nd gear is 1.34, so leaving in 2nd final drive is: 4.11x1.34=5.50 and 8.01 if you leave in 1st

with a 2.00 1st gear 3 speed, 2nd gear is 1.36, so leaving in 2nd final drive is: 4.11x1.36=5.58 and 8.22 if you leave in 1st

with a 2.10 1st gear 3 speed, 2nd gear is 1.40, so leaving in 2nd final drive is: 4.11x1.40=5.75 and 8.63 if you leave in 1st

with a 2.21 1st gear 3 speed, 2nd gear is 1.44, so leaving in 2nd final drive is: 4.11x1.44=5.91 and 9.08 if you leave in 1st

with a 2.33 1st gear 3 speed, 2nd gear is 1.48, so leaving in 2nd final drive is: 4.11x1.48=6.08 and 9.57 if you leave in 1st

with a 2.48 1st gear 3 speed, 2nd gear is 1.48, so leaving in 2nd final drive is: 4.11x1.48=6.08 and 10.19 if you leave in 1st

4.30 rear gears:

With a 1.86 1st gear 3 speed, 2nd gear is 1.31, so leaving in 2nd final drive is: 4.30x1.31=5.63 and 7.99 if you leave in 1st

with a 1.95 1st gear 3 speed, 2nd gear is 1.34, so leaving in 2nd final drive is: 4.30x1.34=5.76 and 8.38 if you leave in 1st

with a 2.00 1st gear 3 speed, 2nd gear is 1.36, so leaving in 2nd final drive is: 4.30x1.36=5.84 and 8.60 if you leave in 1st

with a 2.10 1st gear 3 speed, 2nd gear is 1.40, so leaving in 2nd final drive is: 4.30x1.40=6.02 and 9.03 if you leave in 1st

with a 2.21 1st gear 3 speed, 2nd gear is 1.44, so leaving in 2nd final drive is: 4.30x1.44=6.19 and 9.50 if you leave in 1st

with a 2.33 1st gear 3 speed, 2nd gear is 1.48, so leaving in 2nd final drive is: 4.30x1.48=6.36 and 10.01 if you leave in 1st

with a 2.48 1st gear 3 speed, 2nd gear is 1.48, so leaving in 2nd final drive is: 4.30x1.48=6.36 and 10.66 if you leave in 1st

4.56 rear gears:

With a 1.86 1st gear 3 speed, 2nd gear is 1.31, so leaving in 2nd final drive is: 4.56x1.31=5.97 and 8.48 if you leave in 1st

with a 1.95 1st gear 3 speed, 2nd gear is 1.34, so leaving in 2nd final drive is: 4.56x1.34=6.11 and 8.89 if you leave in 1st

with a 2.00 1st gear 3 speed, 2nd gear is 1.36, so leaving in 2nd final drive is: 4.56x1.36=6.20 and 9.12 if you leave in 1st

with a 2.10 1st gear 3 speed, 2nd gear is 1.40, so leaving in 2nd final drive is: 4.56x1.40=6.38 and 9.57 if you leave in 1st

with a 2.21 1st gear 3 speed, 2nd gear is 1.44, so leaving in 2nd final drive is: 4.56x1.44=6.56 and 10.07 if you leave in 1st

with a 2.33 1st gear 3 speed, 2nd gear is 1.48, so leaving in 2nd final drive is: 4.56x1.48=6.74 and 10.62 if you leave in 1st

with a 2.48 1st gear 3 speed, 2nd gear is 1.48, so leaving in 2nd final drive is: 4.56x1.48=6.74 and 11.30 if you leave in 1st


When you do the math and spell it out, it's not hard to see that there really aren't many combinations of 1st gears and rear gears that will work with both a 2 and 3 speed. I don't really think ANY of them are optimum for both 2 and 3 speed. Some might be "livable" at best, but even then, both ends of the spectrum are far less than ideal.

So with that long winded explanation of all this stuff, what I did I really learn? The short answer is: you really need to figure out if your going to run a turbo 400 in 2 or 3 speed mode and buy one optimized for whichever of those two directions you are going. They both have advantages and disadvantages, but it would seem to me that there IS no "optimized version" that will work as BOTH a 2 AND a 3 speed without changing you rear end gearing to bring it into line for whichever mode you are running it in at the time.

If you are one of those "I only run the BIG races" and your car never sees anything but KILLER tracks, prepped to highest level, I think you certainly have the potential to go quicker with a 3 speed. But for hot, humid, nasty summer conditions, where the track temps get so hot that no amount of prep will put them "on kill", I think the 2 speed option is going to dramatically improve you potential ET over a powerglide, and still get you down the track more consistently than the 3 speed version.

For those who are like me need to have thing presented visually to understand them, I hope this helps.

So I guess Rossler is no longer the only game in town when it comes to a 2spd TH400.

DILLIGASDAVE wrote:So I guess Rossler is no longer the only game in town when it comes to a 2spd TH400.

Still a GREAT piece...

the Coug wrote:Bruno if you were going to Race in some sort of a race where you are competing against someone it would be something, but you just go run to run and maybe a few times a year....just so you can blow smoke up someone A$$.... Go Ahead and build what ever you want
We will end up paying for it in the end anyways....

Shake the sand outta ur vag.

Don' know if this will help or not. But before we switched to bbf stuff (haven't been out yet) we had a sbf on 26 x 8.5 Hoosiers @ 3200 lbs with single adjustable struts and double adjustable shosck (all strange) and we were at 1.23 on a good track and 1.27-8 on a marginial track. With the 28 x 10s in the bbf ford we are hoping to do low 20's to high teens. Both set ups are/were pg. 1.69 gear and 4.10s in the sbf and will be 1.69 in the pg with 3.73s. Might have to take the gear higher on the rear end with the additional tork. Our sbf was 457 c i. Nitrous set up with nos controller and msd 7531.