5 Speed Gear ratio advice?

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demon322

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Preparing for a possible 727 to 5 speed swap. I am looking at SST and I was quoted the TKO 600 which has ratios of 2.87, 1.89, 1.28, 1.0, 0.64.

Their other option is the TKO 500 with ratios of 3.27, 1.98, 1.34, 1.00, 0.68.

I am not ashamed to admit that I know next to nothing when it comes to this so any advice would be appreciated. Would the 600 be better for my needs?

71 Demon, 340, 3:91, 28 in rear tire. Most all of my driving will be highway with possibly a track day once or twice a year. I recently swapped an open 3:23 rear for the 3:91 with sure grip. I love the difference on the low end but cruising is pretty brutal at 3k rpm at close to 60 mph.

Thanks.
 
This may help a little;

Final drive ratio feel.
3.91 X .68 = 2.6588
3.91 X .64 = 2.50

FWIW, I'd go with the 600 for anbetter first gear ratio. 3.27 is very deep. Same deal (multiplication) applies.
 
This may help a little;

Final drive ratio feel.
3.91 X .68 = 2.6588
3.91 X .64 = 2.50

FWIW, I'd go with the 600 for anbetter first gear ratio. 3.27 is very deep. Same deal (multiplication) applies.
Thanks for the reply. I'm going to show my ignorance here. I appreciate you helping me understand. The final drive you mention means that in 5th gear the 3.91s will feel like 2.50s at cruising speed?

Also, what do you mean about the 3.27 being 'deep'? Too low geared? As in since I am already low geared in the rear the 2.87 would be better for 1st gear?

Thanks.
 
Your welcome. In the future, you may want to even try a higher gear ratio.

4.30's = 292 gears.
4.56's = 3.10 gears

Just be careful of the first gear ratio change as it drops as well.
LMAO! You may need bigger fatter tires....
 
Preparing for a possible 727 to 5 speed swap. I am looking at SST and I was quoted the TKO 600 which has ratios of 2.87, 1.89, 1.28, 1.0, 0.64.

Their other option is the TKO 500 with ratios of 3.27, 1.98, 1.34, 1.00, 0.68.

I am not ashamed to admit that I know next to nothing when it comes to this so any advice would be appreciated. Would the 600 be better for my needs?

71 Demon, 340, 3:91, 28 in rear tire. Most all of my driving will be highway with possibly a track day once or twice a year. I recently swapped an open 3:23 rear for the 3:91 with sure grip. I love the difference on the low end but cruising is pretty brutal at 3k rpm at close to 60 mph.

Thanks.
i am running 275 60 out back with a 4spd and 355 gears...3k at 60mph
 
I just switched from the TKO 500 to the 600 with those ratios and a 3.91 out back. I don't notice the difference in first much, but I like the closer ratios (1st through 4th) on the 600. The taller 5th gear is a little better on the highway. I can cruise at 80 all day. It is a bigger step from 4th to 5th, but even on a bigger road course that's only one or two shifts per lap. I vote for the 600.
 
I am running the TK5 00 and the 3.91, It suits my need very well.
 
Your welcome. In the future, you may want to even try a higher gear ratio.

4.30's = 292 gears.
4.56's = 3.10 gears

Just be careful of the first gear ratio change as it drops as well.
LMAO! You may need bigger fatter tires....
That does sound interesting down the road.
 
I just switched from the TKO 500 to the 600 with those ratios and a 3.91 out back. I don't notice the difference in first much, but I like the closer ratios (1st through 4th) on the 600. The taller 5th gear is a little better on the highway. I can cruise at 80 all day. It is a bigger step from 4th to 5th, but even on a bigger road course that's only one or two shifts per lap. I vote for the 600.
Sounds good for sure. This is what I was looking for. 80 on the interstate would be ideal and the lower gears sound much better as well for everyday driving. Thanks for sharing!
 
this is not as simple as it seems.
A friend with a 408 and 3.91 gears installed a Mopar auto overdrive in his pick up and his mileage went down.Your most efficient low speed torque must be your cruise rpm and that is determined largely by your cam.If you just want to lower the rpm on the highway, have at it!
 
If your cam is slated to "Cruise" @ 3000 rpm and the overdrive drops the rpm's down to 2200-2400, the efficiency of the engine drops.

This is where you tune your engine. In the area of cruising or where it is making the best torque for you to be cruising in. A lot of people have dismissed that fact.

If your running rich or lean at the cruise rpm (say 3000 rpm) while your going down the road, your giving up mileage.

It isn't necessarily the lowest gear ratio that will net the best mileage. That could be a miss match in itself.

A crazy example would be 2.45 gears, 32" tires and a huge race cam like a solid roller @ 272@.050.
 
Probably the novice question here... how do you determine what the best torque is for cruising

You would have to look at the whole build but everything mechanical has a sweet spot where you get the most for the least.Like Rumble explained your camshafts' operating range plays a big part.If it operates from 2500 - 6000 rpm it would struggle cruising at 2200 rpm.
 
That is a true mystery a Dyno reveals. But who has dynoed there engine to know this? A bit can be revealed with the detail of your engine and drivetrain. Every detail must be known for this.

Crane cams list there cams with helpful tips to how & where the cam performs the best. Between your gear ratio & tire size, this should give you a certain rpm at speed.

Let's say your normal cruise mph is 75. What is the rpm? Does it fall somewhere within the range of cruise listed?

If you have a desk top Dyno coumputer simulation program, you can get a decent idea. While it is not a great substitute for a actual Dyno test, it is pretty good.

Making sure your engine is running its best through out the rpm range is a trick and a half with a carb. (F.I. takes care of that.)

I think that tuning your engine to run best at 3500 isn't going to help a ton if your cruising at 2600. As allways with drag racers, it is so with everything else for regular guys just putting down the Hwy. chances are your not making the most of your combo for the drag strip or the Hwy.

Just tune tune tune your engine at your Hwy. speed and you will be fine. Make it as efficient as possible.

Most street engines have a broad long flat torque curves. This is what a regular street engine should have. Stock or modified. When the torque curve becomes more peaky you have a harder time in that narrower range to tune and cruise in.

Of course, turning 3500 @ Hwy. and being super tuned isn't going to get you high mileage.
 
Preparing for a possible 727 to 5 speed swap. I am looking at SST and I was quoted the TKO 600 which has ratios of 2.87, 1.89, 1.28, 1.0, 0.64.

Their other option is the TKO 500 with ratios of 3.27, 1.98, 1.34, 1.00, 0.68.

I am not ashamed to admit that I know next to nothing when it comes to this so any advice would be appreciated. Would the 600 be better for my needs?

71 Demon, 340, 3:91, 28 in rear tire. Most all of my driving will be highway with possibly a track day once or twice a year. I recently swapped an open 3:23 rear for the 3:91 with sure grip. I love the difference on the low end but cruising is pretty brutal at 3k rpm at close to 60 mph.

Thanks.
The splits are;
600: .66-.68-.78-.64od
500: .61-.68-.75-.68od


The 500 works well with a smaller engine or one with limited torque off idle, or allows about 13% less rear gear.
Say you are a streeter with a stock 268 cam and you love the 3.91s. So your current trans has ratio of 2.66-1.91-1.39-1.00 and splits of .72-.73-.72 . With your current 3.91s the final drive ratios are 10.40-7.47-5.43-3.91. For a streeter, it's the first two ratios that count. That 268 cam wants to be shifted at about 6000 maybe 6100. with the A833. At the shift, the Rs will drop to 72/73% so from 6000 to about 4350, for a powerband of 1650, centered at about 5175. This will get you 60mph @ 5600 with 27" tires, just about perfect for a streeter with a stock 340. So then it follows that you want your new trans to be about the same. So the we take the target 7.47 second gear ratio and divide it by the new second, say 1.98 and you come up with the proper rear gear for it, which is 3.77. Rounded down to 3.73s.
For the TKO 500 with ratios of 3.27, 1.98, 1.34, 1.00, 0.68. Now the new final drives with the 3.73 gear and the 500 are; 12.2-7.39-5.00-3.73-2.54.
Now lets look at those other ratios. The 12.2 is an excellent drag-race starter, and a fabulous first gear for a teener. It's a bit much for a 360 tho. And a 340 is right up the middle. But I like the 61% 1-2 split. Now the hiway gear at 2.54 will bring the Rs up to 80=2524 with 27s. That's pretty sweet. Except the 65 =2050. And the 268 cam is not known to get good fuel economy down there. What I do is rev the engine up in Neutral and measure the rising manifold vacuum. The last RPM when it stops rising, that is the first rpm that the engine is finally becoming efficient. From there it will linger for a while, then begin to drop again.With a 268 cam in a 360 this occurs at about 2200, so 2200 is probably the best cruise-rpm for it. Ima thinking in the 340 the cruise Rs might be about 100 rpm higher. That puts you at a minimum cruise of 2300 in terms of fuel efficiency. And with 2.54s this would be 70mph. So you're in the ballpark.
Then the other two ratios. The 5.00 ratio is good for 98@6100 in the 1/4, and the 3.73 is good for nothing except getting into od,lol. So that's all about the 500. So this is a poor choice for drag racing a stock 340, cuz you never get into 4th. To be able to use 4th, you might need 4.30s and that would kill the starter gear. So bad trade.But it's a great trans for a streeter that hits 98 in the quarter.

Now lets take a look at the 600 which has ratios of 2.87-1.89-1.28-1.0-0.64.
To get the same second gear of 7.47, you'll need 7.47/1.89= 3.95s, rounds to 3.91. Which you already have. So the road ratio are 11.22-7.39-5.00-3.91-2.50..
So the the starter gear will be 3.91 x 2.87=11.22. This is a very nice street starter gear; so we're 2 out of 5.
Next is the cruiser gear; 3.91 x .64= 2.50 and 2200=71 mph just about perfect, so 3 out of 5.
The 5.0 is the same as the 500, and the 3.91s are the same as you currently have. That 5.0 btw is a great passing gear at 60/65 where the Rs will drop right into the peak-torque zone at about 3880
This trans also has better ratios for a streeter going weekend racing, cuz the 4.30s will drive the starter gear to only 4.30 x 2.87=12.34, very nice. (Too much for street IMO, but great at the track). And those same 4.30s are good for 108 at 5800ish. And if you must know,those 4.30s will cruise with a FD of 2.75 which I really like. It makes 65=2220,lol; 80=2730

So you're probably thinking,that I'm thinking,that the 2.87 low is the way to go.... and for a street 340 you'd be right; with anything 3.91 or bigger, that's what I'm thinking.
 
Last edited:
Hey the title of the post is
5 Speed Gear ratio advice?

If newbe-OP is gonna spring a wad of cash, he deserves to know why.

Besides, you knew I'd be coming around sooner or later,lol; right?

 
Lol!......................................the OP is in the closet in the fetal position randomly exclaiming numbers & shaking, occasionally making RUMM RUMM-purrrrr sounds...........
:eek::eek::eek:....................:lol:...........................
 
Hey the title of the post is
5 Speed Gear ratio advice?

If newbe-OP is gonna spring a wad of cash, he deserves to know why.

Besides, you knew I'd be coming around sooner or later,lol; right?

Why yes I did and welcome back!
Where the hell have you beeeeeen!
Detention for you!
LMAO!!!!
 
That is a true mystery a Dyno reveals. But who has dynoed there engine to know this? A bit can be revealed with the detail of your engine and drivetrain. Every detail must be known for this.

Crane cams list there cams with helpful tips to how & where the cam performs the best. Between your gear ratio & tire size, this should give you a certain rpm at speed.

Let's say your normal cruise mph is 75. What is the rpm? Does it fall somewhere within the range of cruise listed?

If you have a desk top Dyno coumputer simulation program, you can get a decent idea. While it is not a great substitute for a actual Dyno test, it is pretty good.

Making sure your engine is running its best through out the rpm range is a trick and a half with a carb. (F.I. takes care of that.)

I think that tuning your engine to run best at 3500 isn't going to help a ton if your cruising at 2600. As allways with drag racers, it is so with everything else for regular guys just putting down the Hwy. chances are your not making the most of your combo for the drag strip or the Hwy.

Just tune tune tune your engine at your Hwy. speed and you will be fine. Make it as efficient as possible.

Most street engines have a broad long flat torque curves. This is what a regular street engine should have. Stock or modified. When the torque curve becomes more peaky you have a harder time in that narrower range to tune and cruise in.

Of course, turning 3500 @ Hwy. and being super tuned isn't going to get you high mileage.
This makes sense but could be a problem. The engine has a crower cam but I have no idea what the specs are as it was installed in the engine when I bought it and the po didn't know either. I plan to buy a new cam set in the future so I can know exactly what I am dealing with and one that is best for my setup.

So for now I just hope to keep my good low end torque but still be able to drive it from time to time on the highway at as comfortable an rpm as possible. Sounds like both of those are possible with the 600.
 
The splits are;
600: .66-.68-.78-.64od
500: .61-.68-.75-.68od


The 500 works well with a smaller engine or one with limited torque off idle, or allows about 13% less rear gear.
Say you are a streeter with a stock 268 cam and you love the 3.91s. So your current trans has ratio of 2.66-1.91-1.39-1.00 and splits of .72-.73-.72 . With your current 3.91s the final drive ratios are 10.40-7.47-5.43-3.91. For a streeter, it's the first two ratios that count. That 268 cam wants to be shifted at about 6000 maybe 6100. with the A833. At the shift, the Rs will drop to 72/73% so from 6000 to about 4350, for a powerband of 1650, centered at about 5175. This will get you 60mph @ 5600 with 27" tires, just about perfect for a streeter with a stock 340. So then it follows that you want your new trans to be about the same. So the we take the target 7.47 second gear ratio and divide it by the new second, say 1.98 and you come up with the proper rear gear for it, which is 3.77. Rounded down to 3.73s.
For the TKO 500 with ratios of 3.27, 1.98, 1.34, 1.00, 0.68. Now the new final drives with the 3.73 gear and the 500 are; 12.2-7.39-5.00-3.73-2.54.
Now lets look at those other ratios. The 12.2 is an excellent drag-race starter, and a fabulous first gear for a teener. It's a bit much for a 360 tho. And a 340 is right up the middle. But I like the 61% 1-2 split. Now the hiway gear at 2.54 will bring the Rs up to 80=2524 with 27s. That's pretty sweet. Except the 65 =2050. And the 268 cam is not known to get good fuel economy down there. What I do is rev the engine up in Neutral and measure the rising manifold vacuum. The last RPM when it stops rising, that is the first rpm that the engine is finally becoming efficient. From there it will linger for a while, then begin to drop again.With a 268 cam in a 360 this occurs at about 2200, so 2200 is probably the best cruise-rpm for it. Ima thinking in the 340 the cruise Rs might be about 100 rpm higher. That puts you at a minimum cruise of 2300 in terms of fuel efficiency. And with 2.54s this would be 70mph. So you're in the ballpark.
Then the other two ratios. The 5.00 ratio is good for 98@6100 in the 1/4, and the 3.73 is good for nothing except getting into od,lol. So that's all about the 500. So this is a poor choice for drag racing a stock 340, cuz you never get into 4th. To be able to use 4th, you might need 4.30s and that would kill the starter gear. So bad trade.But it's a great trans for a streeter that hits 98 in the quarter.

Now lets take a look at the 600 which has ratios of 2.87-1.89-1.28-1.0-0.64.
To get the same second gear of 7.47, you'll need 7.47/1.89= 3.95s, rounds to 3.91. Which you already have. So the road ratio are 11.22-7.39-5.00-3.91-2.50..
So the the starter gear will be 3.91 x 2.87=11.22. This is a very nice street starter gear; so we're 2 out of 5.
Next is the cruiser gear; 3.91 x .64= 2.50 and 2200=71 mph just about perfect, so 3 out of 5.
The 5.0 is the same as the 500, and the 3.91s are the same as you currently have. That 5.0 btw is a great passing gear at 60/65 where the Rs will drop right into the peak-torque zone at about 3880
This trans also has better ratios for a streeter going weekend racing, cuz the 4.30s will drive the starter gear to only 4.30 x 2.87=12.34, very nice. (Too much for street IMO, but great at the track). And those same 4.30s are good for 108 at 5800ish. And if you must know,those 4.30s will cruise with a FD of 2.75 which I really like. It makes 65=2220,lol; 80=2730

So you're probably thinking,that I'm thinking,that the 2.87 low is the way to go.... and for a street 340 you'd be right; with anything 3.91 or bigger, that's what I'm thinking.
I read this. Then I read it again. After the third reading I think I finally understand .... about 1/4 of this ha. I think the take away is for my purposes and having the 3.91 rear, you also feel the TKO 600 is my best bet.

I do appreciate all the information and time. I did actually learn some things here.
 
Hey the title of the post is
5 Speed Gear ratio advice?

If newbe-OP is gonna spring a wad of cash, he deserves to know why.

Besides, you knew I'd be coming around sooner or later,lol; right?
The 'wad of cash' is not lost on me. I've been wanting to do this swap for quite some time. I very much appreciate the advice.
 
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