How to determine T-10 wide vs. close ratio tranny

[Troy P.]

Are there any codes on the tranny case that tells if it is wide or close ratio? If not, how can one tell which it is? The small metal screwed on tag is missing.

[Leif A.]

Re: How to determine T-10 wide vs. close ratio tranny

Troy,
To the best of my knowledge, there was no such thing as a Borg-Warner T10 transmission with both wide ratio and close ratio gearing options.The Borg-Warner T10 was a popular 4-speed manual transmission used in many American muscle cars and high-performance vehicles in the 1960s and early 1970s.
However, it only came in one gear ratio spread, which was considered a relatively wide ratio:

• 1st gear: 2.88:1
• 2nd gear: 1.91:1
• 3rd gear: 1.38:1
• 4th gear: 1.00:1

This wide ratio gearing provided good low-end acceleration in the lower gears while allowing decent highway cruising economy in 4th gear.
There was no factory "close ratio" version of the T10 with more tightly-spaced gears optimized for acceleration over fuel economy. The gear ratios were fixed.
Some performance transmission builders may have custom-modified T10s with different gear sets over the years. But from the factory, Borg-Warner only produced the T10 with its standard wide ratio gearing setup. It did not offer multiple gear ratio options like some other transmissions of the era.

[David B.]

Re: How to determine T-10 wide vs. close ratio tranny

Troy,
To the best of my knowledge, there was no such thing as a Borg-Warner T10 transmission with both wide ratio and close ratio gearing options.The Borg-Warner T10 was a popular 4-speed manual transmission used in many American muscle cars and high-performance vehicles in the 1960s and early 1970s.
However, it only came in one gear ratio spread, which was considered a relatively wide ratio:

• 1st gear: 2.88:1
• 2nd gear: 1.91:1
• 3rd gear: 1.38:1
• 4th gear: 1.00:1

This wide ratio gearing provided good low-end acceleration in the lower gears while allowing decent highway cruising economy in 4th gear.
There was no factory "close ratio" version of the T10 with more tightly-spaced gears optimized for acceleration over fuel economy. The gear ratios were fixed.
Some performance transmission builders may have custom-modified T10s with different gear sets over the years. But from the factory, Borg-Warner only produced the T10 with its standard wide ratio gearing setup. It did not offer multiple gear ratio options like some other transmissions of the era.

Leif'
Not sure where you got your information but I think you might want to do a little more research.

[Ray K.]

Re: How to determine T-10 wide vs. close ratio tranny

Troy,

Remove the transmission side cover ( 9 bolts ) . Count the number of teeth on the main drive gear ( input shaft ). All BW T-10 close ratio ( 2.20 ) had 27 teeth. All BW T-10 wide ratio ( 2.54 ) had 25 teeth . Re-install side cover with the shift forks in position onto the transmission.

Ray

[Leif A.]

Re: How to determine T-10 wide vs. close ratio tranny

Leif'
Not sure where you got your information but I think you might want to do a little more research.

David,
Well, I did say "to the best of my knowledge"...apparently, my knowledge just got updated. Thank you.

[Troy P.]

Re: How to determine T-10 wide vs. close ratio tranny

I was pretty sure there was a close and wide because I researched the forum archives before posting.

One post said all 340 and 360 HP optional engines had close. Mine is a '63 360 HP. Then I see the screw on tags are sold for both.

Since, per every number on it, I have the original tranny can I just assume it is a close ratio without counting teeth?

[Bob J.]

Re: How to determine T-10 wide vs. close ratio tranny

Any paint on the side cover ?

[Patrick H.]

Re: How to determine T-10 wide vs. close ratio tranny

How about grooves on the input shaft?
I see either no grooves or one groove when I check out ones for sale.

[Jim L.]

Re: How to determine T-10 wide vs. close ratio tranny

If the T10 is in the car, there is a simple way to determine if it's a wide ratio or close ratio box.

Drive the car in 4th gear with the tach reading exactly 1000 RPM and note the vehicle speed.

Shift into 1st gear and return to the previously noted vehicle speed.

Note the tach reading. If it's now 2200 RPM, the transmission is a close ratio box. If the tach reads 2520 or 2540 RPM, it's a wide ratio box.

BTW, this process works with any transmission, not just T10.

[Patrick H.]

Re: How to determine T-10 wide vs. close ratio tranny

For those of us looking at a transmission for sale, it would be nice to know of there's an external sign of what gears were installed.

[Jack M.]

Re: How to determine T-10 wide vs. close ratio tranny

David,
Well, I did say "to the best of my knowledge"...apparently, my knowledge just got updated. Thank you.

Leif- I just wanted to take the opportunity to acknowledge ALL the unselfish help you continually provide the Corvette Communities.
Your posts are usually prompt, insightful, and typically 99% correct... way better than needed, to get into the Hall of Fame.
PLEASE don't let any derogatory comment slow you down... your help is GREATLY appreciated!

[Ray K.]

Re: How to determine T-10 wide vs. close ratio tranny

Troy,

The published power team charts for 1963 L76 ( 340HP ) and L84 ( 360HP ) clearly define that they were equipped with only the 2.20 close ratio BW T-10 4 speed transmission. Unless you suspect that yours may have modified , then your assumption that it a close ratio would be correct.

Ray

[Duke W.]

Re: How to determine T-10 wide vs. close ratio tranny

Prior to '62 all T-10s were close ratio (2.20, 1.64, 1.31, 1.00:1) The wide ratio version (2.54, 1.89, 1.51, 1.00:1) was introduced for the 1962 model year for the two hydraulic lifter engines (250 and 300 HP) The two mechanical lifter engines (340 and 360 HP) continued to receive the close ratio. These choices could not be overridden and were carried over to '63 and through '64 and '65 with the Muncie. The first year the customer could select between the CR and WR four-speed was '66 with either L-79 or L-36/68 engine options.

The two ratio sets were made by changing the counter gear ratio via a different tooth count clutch gear and meshing countershaft gear. This simple change shortened first, second, and third while maintaining the same 1-2 and 2-3 intergear ratios. The downside was a HUGE gap to fourth, which you should be able to feel SOTP.

If not, find a road where you can drive to 3000 RPM in third gear, which will be about 47 to 60 MPH depending on transmission type and axle ratio. Then attain the same speed in fourth gear. If revs are about 2000 it's a wide ratio. If about 2300, it's a close ratio. There is absolutely no need to remove the transmission side cover and count gear teeth.

Later Muncie four-speeds have slight variations in first through third ratios due to different tooth counts of the two sets of meshing gears that determine the overall ratio of each of the first three gears, The later Super T-10 close ratio is 2.43. 1.61, 1.23, 1.00:1, and the wide ratio is 2.64, 1.75, 1.34, and 1.00:1. There is also a 2.88, 1.91, 1,34, 1.00:1 version of the Super T-10, but I'm not sure if it was ever used in production. These three ratio sets are still available in the Super T-10 manufactured by Richmond gear'

Duke

[Duke W.]

Re: How to determine T-10 wide vs. close ratio tranny

For those of us looking at a transmission for sale, it would be nice to know of there's an external sign of what gears were installed.

If the transmission is out of the car put it in third and count input shaft input shaft turns for one turn of the output shaft. If about 1.5 it's a wide ratio. If more like 1.3 it's a close ratio.

BTW industrial gearbox ratios are usually expressed as output shaft speed divided by input shaft speed. In the case of the early close ratio T-10 this would be (rounded to two decimal places) 0.45, 0.61, 0.76, 1.00:1. I figure the reason for this convention is that back in the early days of the automobile, manufacturers figured that most people were probably not familiar with decimal fractions, and that may remain somewhat the case today.

Duke

[Jack M.]

Re: How to determine T-10 wide vs. close ratio tranny

I've posted these 1963 documents/images in previous threads... it just backs up the 'text' that has been discussed.

1963_Corvette_Power_Teams-01.jpg
1963_Corvette_Power_Teams-02.jpg

1963_M20-01.jpg

ENLARGED:
1963_M20-02.jpg