# your thoughts on these ratios



## Duff (Jan 12, 2020)

Once again I'm looking at replacing the muncie in my 66 and have come across a good TKO that has the following ratios: 2.87, 1.89, 1.28, 1:1, .64od. I'm running a 28" tall tire with 3:73 gears. Is the 2.87 too deep for this setup?


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## Baaad65 (Aug 29, 2019)

I'll be interested in the opinions too because I will have the same setup maybe, already running 28" tires, ordering my 3.73 diff this week so the last peice would be the TKX and I think the 2.87 would be the ticket over the 3.27 first gear.


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## NYTrainer (Sep 19, 2012)

That TKO is a wider gear spacing than 2.52 Muncie ratio as far as % drop between gears. With 3.73’s overall 1st gear ratio for M20 (2.52 1st gear) is 9.4 vs 2.87 1st gear overall at 10.7 As a comparison if you ordered the 4.33 rear back in the day you’d get the M21 close ratio (2.20 1st gear) and that overall 1st gear was 9.53 so the 10.7 would be shorter. 
1-2 gear drop for TKO is 34% vs M20 at 25%, 2-3 32% vs M20 at 22%, 3-4 is 22% vs M20 32%. 5th gear for TKO would be like 4th gear in an M20 with 2.38 gears out back.
I’m betting it’d be a fun addition to your car and that deep OD gear would work well with the 3.73. I have 3.23 gears so that OD gear would drop my final drive to 2.06 rear gear equivalent which would be too tall IMO.


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## 67ventwindow (Mar 3, 2020)

Here is mine 2.97 2.10 1.46 1.00 .80 .63 arriving in the am, with 28 inch wheels with a 3.23 rear. Going to a 3.70 9 inch.with this years tax money. With my 1 gallon tank setup I don't think I get the full feel of everything until I upgrade that.


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## lust4speed (Jul 5, 2019)

Exactly the same trans ratios, rear end gear, and tire size on my blue GTO and I love it. Never has felt too low off the line and that low gear is appreciated idling along in heavy traffic.


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## Duff (Jan 12, 2020)

Thanks for all of the input, I'm supposed to pick up the trans this Week, I'll post results.


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## 67ventwindow (Mar 3, 2020)

lust4speed said:


> Never has felt too low off the line and that low gear is appreciated idling along in heavy traffic.


 You must be thinking the christmas light shows,


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## Baaad65 (Aug 29, 2019)

Here's a sloppy chart I made from a calculator when trying to pick my rear cog, it's only final drive numbers but I'm a visual person...idk maybe there's something someone can use?


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## armyadarkness (Dec 7, 2020)

lust4speed said:


> Exactly the same trans ratios, rear end gear, and tire size on my blue GTO and I love it. Never has felt too low off the line and that low gear is appreciated idling along in heavy traffic.


I have the 3.27 first gear, with 3.36's and 26" tires... First is a bit too low for me. Im considering going up to 255 70 15


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> I have the 3.27 first gear, with 3.36's and 26" tires... First is a bit too low for me. Im considering going up to 255 70 15


Do you mean 255/60/15 ? Those fit on mine with room to walk around the tire holding a tray of cookies 😉 now I have 275/60 but needed a little trimming and no cookies...I know you have the wider axel than my '65.


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## geeteeohguy (Feb 2, 2008)

In a word, no. Not too deep. Do you need that low of a first gear with a 3.73 rear end? No. Is it a granny gear that will be useless? No. 
You will be just fine with that low first and that really long-legged overdrive, IMO. 
Now, the 3.42 first gear in my '61 Corvette with a 3.36 rear end is waaaaay too deep. Good for half way across an intersection. Or pulling stumps. Useless otherwise. I wish they made a 2.75 third member for the old solid axle 'vettes, I would drop it in in a heartbeat.


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## Duff (Jan 12, 2020)

I've owned some nice vettes, but the solid axles have always evaded me, hopefully I'll find one someday. I got used to the 2.20 first gear in the close ratio muncies usually with a 3:73 or stiffer gear, just wasn't sure on the 2.87. I'm still not 100 % sold on the Tremec 5speed yet, I'm old school and just love the 4 speeds.


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## Jetzster (Jan 18, 2020)

Baaad65 said:


> the last peice would be the TKX and I think the 2.87 would be the ticket over the 3.27 first gear.


Are you doing the TKX soon also? 😳


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## Baaad65 (Aug 29, 2019)

Jetzster said:


> Are you doing the TKX soon also? 😳


No I can't see doing it until '24, I have to replace the rear end and want to get the body and paint repaired. So I'm just going to have a high winding dump truck this year but it will be fun stop light to stop light and maybe a better time at the track 😉


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## armyadarkness (Dec 7, 2020)

geeteeohguy said:


> Now, the 3.42 first gear in my '61 Corvette with a 3.36 rear end is waaaaay too deep. Good for half way across an intersection. Or pulling stumps. Useless otherwise. I wish they made a 2.75 third member for the old solid axle 'vettes, I would drop it in in a heartbeat.


That's how I feel about my 3.27/ 3.36 combo. Ironically, the wide ratio/ 3.27 TKX was IMPOSSIBLE to get for almost a year, and I couldve gotten the close ratio at any time... but I thought I needed more grunt down low.

I was wrong.

Anywho, I only have 26 tires and am considering going to 28"s, so that will help. It's amazing how quick my car gets into and uses 5th gear. Much lower than where you'd expect.


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## geeteeohguy (Feb 2, 2008)

I have 29" tall tires on the back of the '65 with a 3.36 gear and the original 4 speed. The 3 inch taller tires effectively make it a 3.23, and brought the cruise up to 70 mph from about 62 mph. Good enough for what I'm running with the cam, etc.


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## Duff (Jan 12, 2020)

Well, I picked up the TKO 600 yesterday, still trying to decide if I'm going to use it or not, I'll post a picture tomorrow.


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## armyadarkness (Dec 7, 2020)

geeteeohguy said:


> I have 29" tall tires on the back of the '65 with a 3.36 gear and the original 4 speed. The 3 inch taller tires effectively make it a 3.23, and brought the cruise up to 70 mph from about 62 mph. Good enough for what I'm running with the cam, etc.


I can cruise comfortably at 80-90, with a ton of get up and go, and yet it's still a burnout beauty in 1st. The TKX is a beautiful thing.

I have 235/60/15 out back... what would I use to keep the same contact patch, but go up in height?

Maybe this?





255/70-R15 vs 235/60-R15 Tire Comparison - Tire Size Calculator | Tacoma World


235/60-R15 tires are 2.95 inches (75 mm) smaller in diameter than 255/70-R15 tires and the speedometer difference is 10.2%




www.tacomaworld.com


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> I can cruise comfortably at 80-90, with a ton of get up and go, and yet it's still a burnout beauty in 1st. The TKX is a beautiful thing.
> 
> I have 235/60/15 out back... what would I use to keep the same contact patch, but go up in height?
> 
> ...


I'm pretty sure you could fit 255/60 on it unless a '67 well is way smaller than a '65.


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## Duff (Jan 12, 2020)




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## armyadarkness (Dec 7, 2020)

Baaad65 said:


> I'm pretty sure you could fit 255/60 on it unless a '67 well is way smaller than a '65.


But that's not as tall, so it would defeat the purpose. A 255-70-15 would be two inches taller and almost an inch wider, than my existing 235-60s


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> But that's not as tall, so it would defeat the purpose. A 255-70-15 would be two inches taller and almost an inch wider, than my existing 235-60s


My bad I didn't consult tiresize.com first....then try and get 275/60's stuffed in there 😉


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## Duff (Jan 12, 2020)

275 60 15 will fit no problem, if you use the 64 65 Pontiac 10 bolt or a 64 -67 Chevy 10 or 12 bolt rear. I know it also depends on the BS of the wheel, but I've run this size tire on several 66 GTO cars, using swap meet Cragars or aluminum slots.


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## Baaad65 (Aug 29, 2019)

Gee I happen to have one of those rear ends for sale....Amy? 😁


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## Baaad65 (Aug 29, 2019)

I know this thread was on trans ratios but since we've drifted into tire size I have a question...I probably will use these drag radials one more season and race it once more then they might be wore out so I've been looking for a replacement that's not a drag radial but need good traction. I would like to keep a 28 or 27" tire for the lower rpms and a decent width (mine are 9.3 tread) but can't find anything that size in a 15 or 17". I have thought of switching to the 17's or even 16" but that's a hard size to find tires and rims for. The wheels I have come in 17", I like the Firestone Firehawk Indy 500 or the M/T Street Comp but they're all 25" also don't want a Japanese tire. I need a 275/50 or 275/55 or would even consider a 275/45 but can't find much at all, 40 is too short. And some need a 10-11" rim. The American Racing wheels I have do come in 17x9 with a 5.47 bs.


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## goat671 (Apr 13, 2019)

Baaad65 said:


> I know this thread was on trans ratios but since we've drifted into tire size I have a question...I probably will use these drag radials one more season and race it once more then they might be wore out so I've been looking for a replacement that's not a drag radial but need good traction. I would like to keep a 28 or 27" tire for the lower rpms and a decent width (mine are 9.3 tread) but can't find anything that size in a 15 or 17". I have thought of switching to the 17's or even 16" but that's a hard size to find tires and rims for. The wheels I have come in 17", I like the Firestone Firehawk Indy 500 or the M/T Street Comp but they're all 25" also don't want a Japanese tire. I need a 275/50 or 275/55 or would even consider a 275/45 but can't find much at all, 40 is too short. And some need a 10-11" rim. The American Racing wheels I have do come in 17x9 with a 5.47 bs.


How about these


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## Baaad65 (Aug 29, 2019)

goat671 said:


> How about these
> View attachment 160630
> 
> 
> ...


I saw those and I had MT Sportsmans before these but they didn't have very good traction for my torque that's why I went to the drag radials, and it's going to be even worse upping my gears to 3.73, maybe I'll be forced to keep drag radials on it but thanks for the suggestion 👍


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## armyadarkness (Dec 7, 2020)

Baaad65 said:


> My bad I didn't consult tiresize.com first....then try and get 275/60's stuffed in there 😉


One of the oldest, unanswered questions, on this forum, is "Will 275-60-15's fit a GTO". Ive never seen it be answered, yet.


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## ponchonlefty (8 mo ago)

Baaad65 said:


> I know this thread was on trans ratios but since we've drifted into tire size I have a question...I probably will use these drag radials one more season and race it once more then they might be wore out so I've been looking for a replacement that's not a drag radial but need good traction. I would like to keep a 28 or 27" tire for the lower rpms and a decent width (mine are 9.3 tread) but can't find anything that size in a 15 or 17". I have thought of switching to the 17's or even 16" but that's a hard size to find tires and rims for. The wheels I have come in 17", I like the Firestone Firehawk Indy 500 or the M/T Street Comp but they're all 25" also don't want a Japanese tire. I need a 275/50 or 275/55 or would even consider a 275/45 but can't find much at all, 40 is too short. And some need a 10-11" rim. The American Racing wheels I have do come in 17x9 with a 5.47 bs.


do you have the rear end you ordered yet?wait till its installed. you may have more or less room under there.


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> One of the oldest, unanswered questions, on this forum, is "Will 275-60-15's fit a GTO". Ive never seen it be answered, yet.


They fit on mine, only problem is my rear end is off center of the body maybe a 1/2" so it's close on the drivers side. Other thing was on a big bump with a full tank they would rub on that protrusion up in the wheel well so I solved that


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## Baaad65 (Aug 29, 2019)

ponchonlefty said:


> do you have the rear end you ordered yet?wait till its installed. you may have more or less room under there.


It's ordered and although it says available in custom widths they told me it's going to be stock the width for a '65, I'm going to call them today or tomorrow and make sure the order through Summit is correct and ask again about a custom width and see if the Ford drum brakes will change anything. And yes the rear will be installed way before any tire changes will be made.


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## Greek64GTO (Dec 13, 2015)

Duff said:


> Once again I'm looking at replacing the muncie in my 66 and have come across a good TKO that has the following ratios: 2.87, 1.89, 1.28, 1:1, .64od. I'm running a 28" tall tire with 3:73 gears. Is the 2.87 too deep for this setup?


My friend who owns Modern Driveline tells me the "Sweet Spot" formula for first gear is 9.5 to 11.0 to 1

Multiply your 2.87 x 3.73 = 10.70

Right in the sweet spot.

Naturally tire size is going to sway it up or down. Then ultimately you need to look at your final gear ratio for the upper end.


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## Baaad65 (Aug 29, 2019)

Greek64GTO said:


> My friend who owns Modern Driveline tells me the "Sweet Spot" formula for first gear is 9.5 to 11.0 to 1
> 
> Multiply your 2.87 x 3.73 = 10.70
> 
> ...


Well I just ordered a 3:73.... so you're saying I need a TKX with a 2:87.....Honey! guess what...do you really love me


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## Duff (Jan 12, 2020)

You need my TKO 600 kit which has the 2.87, I'm probably going to sell it.


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## Baaad65 (Aug 29, 2019)

Duff said:


> You need my TKO 600 kit which has the 2.87, I'm probably going to sell it.


Won't fit in my '65 without surgery but thanks.


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## Duff (Jan 12, 2020)

I'll sell you some fiberglass matting with it, no one will ever know!


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## 67ventwindow (Mar 3, 2020)

Baaad65 said:


> Won't fit in my '65 without surgery but thanks.


 They sent me a 50 gal barrel for the t56. It should fit no problem. Honey I have to buy a sheet metal brake now. Ooops!


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## ponchonlefty (8 mo ago)

Greek64GTO said:


> My friend who owns Modern Driveline tells me the "Sweet Spot" formula for first gear is 9.5 to 11.0 to 1
> 
> Multiply your 2.87 x 3.73 = 10.70
> 
> ...


very useful thanks.


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## Baaad65 (Aug 29, 2019)

No surgery, the interior is done thank you 😉


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