Treblig
Well-Known Member
The 2004r and the A999 have the same first gear...2.74 if I remember correctly. But the 2004R has .67:1 overdrive!!
Easy (?) OD Auto Install
- Thread starter Topless69
- Start date
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Topless69
Well-Known Member
Yeah I’d been looking for wider tires for a while in the 26-28” range, but choices are limited for 15” wheels. Using an online tire size calculator, I ended up ordering what I thought were just over 26” but when mounted were only 25”, about 1.2” shorter than planned.
Oh, as far as MPH... 70 to “I hope there’s no cops around”
Topless69
Well-Known Member
Man that .67 overdrive would be sweet!
There are plenty of 15s around that height. You're not lookin in the right places.
Treblig
Well-Known Member
I was running 29 inch tall tires. I even modified the stock shifter detents to be able to catch all the gears for the overdrive. It was really easy!!
Topless69
Well-Known Member
I bought Hankook 265/50/15’s and they’re a bit short, but I also wanted to lower the car 1” so it should work out.
Treblig
Well-Known Member
Here's the modified original shifter, you can't hardly tell that I modified it!!
Right but you still have the short tire. 275 60 is the go to size when I think 27-28 inch tall tire.
Topless69
Well-Known Member
You’re right, looks factory. Nice work!
Topless69
Well-Known Member
Yep. It looks a bit small in the well and will be turning higher RPM, I’ll just see how it goes.
Kendog 170
Let the boy go !
Treblig , I lived in my early twenties in Corpus. Worked at The Cullen Mall Shell if it's still there. A guy named Joe Cast owned the place (I'm sure not anymore.) I worked every otherday so every nite was a Friday nite ! The women ratio was 4 to 1. Crazy times at a bar called Inza's lonesome coyote . Great memories. Was friends with Freddy Fenders Daughter Tina. Freddy had 40 + cars we use to service. Lot's of days on Padre Island too.
Treblig
Well-Known Member
Sounds like you have good memories of Corpus!! Is this it??
Bygone bar: Inza's Lonesome Coyote Saloon in Corpus Christi
There are still lots of women here!!
Kendog 170
Let the boy go !
Yes! Friday night was $10 cover charge. Lot of money back then. They would give you 2 16Oz plastic cups. The Bar was lined up with multble kegs (self serve) of beer. If you lost your cups you were done unless you stole someone elses.They had multible bands and if people didn't like them they raised a net for flying objects. The night ended with brawls so we would leave earlier bacause of our Boston accent everyone wanted to fight us.I loved it there, people were soo friendly (When not drunk) lol
I heard it burned down.
I heard it burned down.
Treblig
Well-Known Member
Why would you ever leave this sandy, sunny paradise to move up North and FREEZE???
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383Scampman
Well-Known Member
MOst good tire people publish the tire height @ recommended pressures for a specific rim width . A 28.5-"29" tall tire is good for highway but in traffic sucks unless you have a low first gear . It's all about revolutions per mile .
Kendog 170
Let the boy go !
I'm an idiot
Joe was going to retire and give me the Garage. But my family was back North
Topless69
Well-Known Member
I’ve never seen anything that specific - Would you post links that show such info?
Topless69
Well-Known Member
...But my family was back North
Sounds like as good a reason as any to stay in Texas. LOL
Sounds like as good a reason as any to stay in Texas. LOL
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 25,870
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- 13,175
Try this on for size;
your current combo is 25" tires/A904/3.55s/ and 70=3340@zero-slip; could be 3500 on the tach@5% slip.
Your starter gear is 3.55x2.45=8.70, and corrected to a 12" radius is; 8.70x24/25=8.35 that is a good number for a street-automatic.
Lets say you installed an A999 lock-up, with 3.23s and 28s;
70 would be 2710 in loc-up.
Your starter gear is; 3.23 x2.74 x24/28=7.59
that is a loss of 9% TM(Torque-Multiplication)
You didn't mention your current stall rpm, but since the A999 has a lock-up, you can run about anything you want, so the 9% shortfall can easily be made up for by increasing it. Easily. Unless you are running something already crazy..... which your cruise-rpm does not point to.
So here you have a low-cost simple and effective way to lower your cruise-rpm AND simultaneously increase your take off power.
How's that? you might ask.
Well say your current TC stalls at 2200, and your engine makes 120 hp/280ftlbs there; I mean just let's say.
To the road at WOT this might translates to 4210 ftlbs @ a TC ratio of 1.8 @ zero mph, with 2.45 x3.55 gears.
>So,how about the A999/3.23@ 2800TC
Lets say the HP is now 155/290, and that might translate to 4435 . This is now an increase of 5.3%
>lets try@ 3200TC
Lets say the HP is now 180hp/300 ftlbs. And at zero-mph this might translate to 4590. Ok now this calculates to an increase of 9% torque to the road.
Don't look at the numbers; instead look at the percent increases.
That's how you do it.
But there is no free-lunch;
with the current combo, 60mph=about 4775rpm in second@WOT..
With the A999/3.23/28s; 60 in second at WOT,will be about 4120; a loss of 14%. Most of this is in the tires. With the 25s, the Rs might be 4615, a loss of only 3.4%.
To understand this;
a 25" tire has a roll-out of 78.54 inches, whereas the 28 has 87.96; a difference of exactly 12%
Knowing that;
swapping 28s into the current combo, will drop your cruise rpm, the same 12%, or from 3500 on the tach to 3100, with no other changes. This has the same effect as decreasing your gearing from 3.55s to 3.12s.
I thinkit was @RustyRatRod , who first mentioned the A999, And I agree with him.
The slip at 70 is likely to be in the range of 5 to 8% ; so 175 to 280
So leaving the 3.55s in there with the A999, and swapping to the 28s will get you 70=2980 in LU. That is a drop of 520rpm or nearly 15% This is a pretty cheap solution. And
no cutting required, no engineering, and the driveshaft even swaps over.
So to recap;
the 28s are worth 12% rpm reduction, over 25s
the LU is worth 5% to 8%, rpm reduction
and 3.23s are ~9% rpm reduction
And the A999 low gear,is an INCrease~11.8%, makes up for the drop in gears, to 3.23s
And the stall will make up the difference in first gear, to at least maintain the current performance.
The ratios are;
2.45-1.45-1.00 for the A904
2.74-1.54-1.00 and LU for the A999
Be careful; AFAIK; the A998 could have either ratio, and comes with or without LU! depending on application.
HappyHotRodding
EDIT;
math corrections
your current combo is 25" tires/A904/3.55s/ and 70=3340@zero-slip; could be 3500 on the tach@5% slip.
Your starter gear is 3.55x2.45=8.70, and corrected to a 12" radius is; 8.70x24/25=8.35 that is a good number for a street-automatic.
Lets say you installed an A999 lock-up, with 3.23s and 28s;
70 would be 2710 in loc-up.
Your starter gear is; 3.23 x2.74 x24/28=7.59
that is a loss of 9% TM(Torque-Multiplication)
You didn't mention your current stall rpm, but since the A999 has a lock-up, you can run about anything you want, so the 9% shortfall can easily be made up for by increasing it. Easily. Unless you are running something already crazy..... which your cruise-rpm does not point to.
So here you have a low-cost simple and effective way to lower your cruise-rpm AND simultaneously increase your take off power.
How's that? you might ask.
Well say your current TC stalls at 2200, and your engine makes 120 hp/280ftlbs there; I mean just let's say.
To the road at WOT this might translates to 4210 ftlbs @ a TC ratio of 1.8 @ zero mph, with 2.45 x3.55 gears.
>So,how about the A999/3.23@ 2800TC
Lets say the HP is now 155/290, and that might translate to 4435 . This is now an increase of 5.3%
>lets try@ 3200TC
Lets say the HP is now 180hp/300 ftlbs. And at zero-mph this might translate to 4590. Ok now this calculates to an increase of 9% torque to the road.
Don't look at the numbers; instead look at the percent increases.
That's how you do it.
But there is no free-lunch;
with the current combo, 60mph=about 4775rpm in second@WOT..
With the A999/3.23/28s; 60 in second at WOT,will be about 4120; a loss of 14%. Most of this is in the tires. With the 25s, the Rs might be 4615, a loss of only 3.4%.
To understand this;
a 25" tire has a roll-out of 78.54 inches, whereas the 28 has 87.96; a difference of exactly 12%
Knowing that;
swapping 28s into the current combo, will drop your cruise rpm, the same 12%, or from 3500 on the tach to 3100, with no other changes. This has the same effect as decreasing your gearing from 3.55s to 3.12s.
I thinkit was @RustyRatRod , who first mentioned the A999, And I agree with him.
The slip at 70 is likely to be in the range of 5 to 8% ; so 175 to 280
So leaving the 3.55s in there with the A999, and swapping to the 28s will get you 70=2980 in LU. That is a drop of 520rpm or nearly 15% This is a pretty cheap solution. And
no cutting required, no engineering, and the driveshaft even swaps over.
So to recap;
the 28s are worth 12% rpm reduction, over 25s
the LU is worth 5% to 8%, rpm reduction
and 3.23s are ~9% rpm reduction
And the A999 low gear,is an INCrease~11.8%, makes up for the drop in gears, to 3.23s
And the stall will make up the difference in first gear, to at least maintain the current performance.
The ratios are;
2.45-1.45-1.00 for the A904
2.74-1.54-1.00 and LU for the A999
Be careful; AFAIK; the A998 could have either ratio, and comes with or without LU! depending on application.
HappyHotRodding
EDIT;
math corrections
Last edited:
Topless69
Well-Known Member
Lots of useful information in your post.
Maybe I’d be happy just swapping a 999 with LU in and tweaking gears and tire size. Anything that would keep it under 3000 on the highway and improve launch times without breaking the bank (or my back) would be awesome.
Thanks AJ!
66jim
Well-Known Member
Have a built LU 999 its an improvement over 904. LU feels direct like a manual trans. If your not all about drag race its great, engine with good torque 2.xx gears
won't even notice any off line laziness. 200r? went thru 3 of them in my 87 Grand National (2 under warrenty) without to much trouble.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 25,870
- Reaction score
- 13,175
If you liked that, then here's one more;
the A999LU with 2.94s, and a 3200TC and keep the small tires.
It looks like this;
70=2770 in LU..That is a drop of 730 rpm or 20.8%. this is equal to an overdrive gear of .79, and all other things remaining as in the current combo.
Your starter gear is only 2.94 x2.74=8.06 but with the 3200, and the same 180/300ftlbs input, this maths to a possible 4180ftlbs at zero mph and [email protected] ratio.
This compares favorably to the 4210 of the current combo, so as good as no loss of take off at zero mph. however; 60mph in second is now maybe 4400...... which could be a GREAT passing gear. but not the best place to trap 60 with, unless the cam is a stocker.
If you wanna play the numbers, here are the formulas;
For cruise rpm;
mph=(rpm x Tc)/(1056 x R1 x R2);
this is for Zero slip; add 5 to 8% for TC slip, if NOT a LU. And
Tc is tire circumference, AKA roll-out, which is diameter x 3.1416aka pi,
and R1, R2 are the gear ratios; trans and rear.
Also,
to figure the torque to the road;
crank torque times ,all the gear ratios, times the TC ratio, and corrected to a 1ft radius so I can play with tire sizes. Lessee that would look like;
ET x TCr x R1 x R2 x (24/Tc); where
ET is Engine-Torque, TCr is Torque-convertor ratio,
R1/R2 are the gears, and Tc is installed tirecircumference
The TCr, at WOT, varies from about 1.8 at zero-mph to something like 1.1 at the top of the track. It is constantly changing with torque input and load. So it is greatest at zero-mph, until the tires slip, and diminishing with rpm and speed.
So, I used 1.8 for all your calculations, just to gross up the numbers for effect,lol. The number you need to think about, if you want to spin the tires, is about 3000. It doesn't take that much to break them loose, but it will take that much to keep them spinning when the TCratio starts diminishing. Unless you just whack it up to peak horsepower and hold her there,lol, which is a lottta fun too.
the A999LU with 2.94s, and a 3200TC and keep the small tires.
It looks like this;
70=2770 in LU..That is a drop of 730 rpm or 20.8%. this is equal to an overdrive gear of .79, and all other things remaining as in the current combo.
Your starter gear is only 2.94 x2.74=8.06 but with the 3200, and the same 180/300ftlbs input, this maths to a possible 4180ftlbs at zero mph and [email protected] ratio.
This compares favorably to the 4210 of the current combo, so as good as no loss of take off at zero mph. however; 60mph in second is now maybe 4400...... which could be a GREAT passing gear. but not the best place to trap 60 with, unless the cam is a stocker.
If you wanna play the numbers, here are the formulas;
For cruise rpm;
mph=(rpm x Tc)/(1056 x R1 x R2);
this is for Zero slip; add 5 to 8% for TC slip, if NOT a LU. And
Tc is tire circumference, AKA roll-out, which is diameter x 3.1416aka pi,
and R1, R2 are the gear ratios; trans and rear.
Also,
to figure the torque to the road;
crank torque times ,all the gear ratios, times the TC ratio, and corrected to a 1ft radius so I can play with tire sizes. Lessee that would look like;
ET x TCr x R1 x R2 x (24/Tc); where
ET is Engine-Torque, TCr is Torque-convertor ratio,
R1/R2 are the gears, and Tc is installed tirecircumference
The TCr, at WOT, varies from about 1.8 at zero-mph to something like 1.1 at the top of the track. It is constantly changing with torque input and load. So it is greatest at zero-mph, until the tires slip, and diminishing with rpm and speed.
So, I used 1.8 for all your calculations, just to gross up the numbers for effect,lol. The number you need to think about, if you want to spin the tires, is about 3000. It doesn't take that much to break them loose, but it will take that much to keep them spinning when the TCratio starts diminishing. Unless you just whack it up to peak horsepower and hold her there,lol, which is a lottta fun too.
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Too bad the A999 cannot bolt to a big block. I might consider one in Vixen.
Treblig
Well-Known Member
700R4...all you need is the TV cable and a non-lock up convertor, nothing else to hook-up but the shifter!! Of course you have to buy an adapter.
Yeah but then I have to cut the car.
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