CJS

What is the best gear ratio for a 57 with stock 245 hp/283, Tremec TKO 600 with 2.87 low gear and .64 overdrive 5th. I am going with 3.73's. It will be at 2150 rpm at 70 mph. Seems like 4.11's are too short for cruising and the 3.36's are a little too tall.

KyleDallas

You're on it!!

3.55, 3.73, 3.90 my favorite dual purpose ratios

you can "stoplight"
you can cruise comfortably...
-K

GO GIRL

With the 2.87 1st gear, 3:73 gears are really low and your first gear would be the same as running a wide ratio Muncie with 4:11's or a close ratio with 4:88's. On a different forum the concensus is to run the TKO with the .82 5th gear and use 3:36 or 3:55 rear gears. Most who have tried the .64 TKO either have changed the 5th gear or sold their tranny and gotten the .82.Check out this site and the part about the "split". www.secondstrike.com/Technical/GearCalc.asp

ghostrider20

I think your Revs are a bit low for your desired cruise speed. The motor is not a 350 with a truck cam.

I would go with the 4:11's and here is why.

It will give you great low end performance for around town.

And with the 0.64 Overdrive, your cruise numbers will be:

2500 RPM
76 MPH

3000 RPM
91 MPH

(With a 27" Tire)

toddalin

I have 3.70:1 and when I did the calculations, the 1st gear in the TKO-600 worked out to be equivelent to about a 3.90:1.

With 225/60/15 tires, Quarter Mile Jr. said that a 3.90:1 rear end was the best ratio for the 1/4 mile and my rpm range.

BTW, where do guys keep coming up with 3.73:1 unless you are using aftermarket gear sets???

60vett

Thats the way I am running. I will say that 2 lane roads and 5th gear are a bit much, but the interstate and 5th gear is a BLAST! Now I ned to change out the brakes!

MikeM

I'd go with the 3.70's. Chevrolet released the 283 with a 2.94 first gear three speed and 3.70 gears. Nothings changed. It's still a 283.

With the 3.70 and the overdrive, I'm afraid you're almost gonna' be overgeared with that 283. It may be a soggy dog on the road. On the other hand a 4.11 gear with that ratio low gear you're using means your first gear will be something similar to a lunge and then you'll have to shift. Great for drag racing, not much fun for street.

I'd left the four speed in there but you didn't ask me that.

Hitch

You can only get 3.73 gears anymore the 3.70's aren't available. As for running the 3.73 gears I've got a TKO3550 and it's got a .68 OD and first is a rip stomping 3.27 so the final in first feels like a 4.88. First gear is about useless. It's great for smoking the tires but you have to be REAL careful about over revn the motor because 6k comes quick. I would either chose 3.55's or even 3.36's or go with the .82 OD and the 3.55's.. Just my .02.. Dave

macdarren

Good question, I have the 3:73 rear and the .64 TKO. Haven't gotten it on the road yet and I am already wondering if I shouldn't maybe put in the 4:11 (I have one sitting just needs refreshed) I will try the 3:73 since that is what is in the car but have a feeling the cruise rpm will be a bit low. I made up a spreadsheet for the various gears and rear ends and added in my torque numbers from the dyno. Basically in the lower gears it doesn't seem to make alot of practical difference (drops my redline speed (6500RPM) in first from 45 to 41) but as you move up the gears it moves my 65mph cruise RPM from 2100 to 2300. I think 2100 is kinda low. I worked the 4:56 numbers and it gives 37 in first and 2550 RPM at 65mph which seems pretty nice.

Of note is that the 4:11 yields almost 500ft/lbs more torque (depends on engine) in first that the 3:73 which should be a noticeable boost in acceleration but you would have to shift 4mph sooner. Of course at some point more torque might hurt rather than help.....my very rough calculation say even with the 3:70 I will slip the tires in 1st 2nd and 3rd if I am not careful in the powerband moving to 4:11 or 4:56 gives possible slipage in 4th too.

As I said I will try the 3:73 and see how it goes, my motor seemed ok at 2100 on the dyno but in real life who knows it may be seriously bogged down.

Darren

Hitch

Sounds to me like you are to hung up on the 5th gear rpm at cruise. You will spend more time having a problem getting traction everytime you leave a light. Dave

60vett

I was hung up on the 5th gear thing. Living 20 miles from peoria I am always on the interstate right off the bat. That is about the only reason I bought the TKO. But like it was said, having a high 1st gear makes the stoplights in town fun.

macdarren

I want maximum acceleration with a reasonable overdrive that I don't have to always shift down. Keeping the right foot under control will control slippage....

I drove the car with a close ratio and 4:11s for years it was a blast, in town or on the freeway hit the gas and go, of course it sucked when cruising at any speed over 60....then I went with the 3:73 and the wide ratio 4 speed...overall that was just as much fun however I did miss that old first gear on the close ratio but it did drop the freeway cruise RPM some though it was still kinda high when doing 70 which is about my norm. So now I have the TKO which I bought primarily to get that freeway RPM down the question I have is it now too low....the .82 overdrive might have been a better choice. It is my understanding the TKO is pretty easy to change gears and while I am not sure what is available if the .64 is too much maybe I can find a .75 or something....or I can try the lower rear axle but that changes everything. I am sure like my paint decision (see other threads) this one will come down to what I like best and I will only know by trying.

Johns_65Vette

I can tell you from personal experience, that the 4:11's with the .64 overdrive is great. Cruises effortlessly at 80 MPH@2500 RPM. If your 283 is a dog, then I think 4:11's would be a good choice. I am running a dog motor 350, that is equivelant to a 283 in power. As far as first gear is concerned, it is not that much lower than the old muncie, but it is just enough lower to make traffic easier to deal with.

macdarren

Oh great, one more thing to delay me...seriously once I get this thing painted and rolling we will have to get toether and compare notes....I'll just stick with the 3:73 for now. One question what tire do you run, I ask becuase the numbers you gave, which I am sure are right, don't jive with my spreadsheet, so I must have done something wrong or there is some other difference...my original calculations were based on 811 tire revs per mile which is about a 25.7 inch tire.

CJS

I do have 3.36's in my 283 220hp 57 right now. It is at 1900 rpms at 70mph with a 26.5" rear tire. Suprisingly, that little stock engine will pull that tall 5th gear, no problem at all! In fact it I can use 5th at any speed over 55mph.
-----No it does not pull like crazy at these low rpms, but it runs smooth and accelerates smoothly too. The main thing I have noticed is that the car feels completely different at 70mph now. Before it felt almost a little crazy and slightly scary with the engine buzzing like that. Now it feels so smooth an quiet that I find I can get up to 80 and 85mph without any pits in the stomach!
-----But with mine the launch could use just a little more gear for even more ease of take off, It is actually just fine now but a little bit more should be just right! So I ordered the 3.73's, $209 from Jegs.

Johns_65Vette

I have a 26.5 (I think it's a 215 75 -15) inch tall tire if I recall correctly. On Keislers sight, they have a speed calculator, which said that I should run 79 MPH at 2500 RPM, and that is exactly what it does.
If you have a torquey enough engine, the 3:73's might be fine.

Boy do I agree with CJS on the ease of cruising now at 80, without the car feeling like it is coming apart.

macdarren

Okay I feel better the numbers match better now...if you really have a 215/75/15 then it will be about 27.5 inches with a 750 revs/mile....I have a shorter tire so that will help 'lower' my gear ratio a bit too, my concern is less how it cruises at 80 but how bad does the engine lug at 60. Who can go 80 where around here....maybe durning a 2am muchie run...

SMR 67

I've got the TKO 600 (.64 OD) w/ 3.73 rear and 215/65/15 tires. IMHO it's the perfect combo for stoplight to stoplight and low RPM highway cruising. Since you say you get right on the highway, I would stick w/ this combo. Enjoy!

Johns_65Vette

Most of my driving is hwy, and although Darren is somewhat right about how often you can go 80 around here, I do quite often find myself being able to cruise that fast, when going to early morning, or saturday cruise ins. 95% of my driving is freeway.

toddalin

You need to review your math. A 25.7" tire turns 785 revolutions per mile. A 24.9" tire turns 811 revs per mi.

5,280 ft/mi / (diameter x pi) / 12"/ft = 784.8 tire revs per mi.

BTW, I run 225/60/15" and that works out to 25.6" tall and 787 revolutions per mi