Educate Me...Diff and Trans...combo...
Thread Starter
Team Owner
Joined: May 2006
Posts: 37,671
Likes: 1,115
From: CA
Educate Me...Diff and Trans...combo...
Okay I'm trying to get better gas mileage in my 66...
I have 3:70's and BW trans now, "lost the muncie in a trade a long time ago"
...
Question....
How do the two together work in determining the best Diff ratio, I know its 1:1 in fourth gear...
Or do they?
Right now my RPM's are around 2900+/- on the freeway
I was thinking of 3:36 but my engine builder say's 3:55 would be a better match..
What kind of rpms would the differences be between the gears at highway speeds...?
Give me your thoughts on a good all around gear.
Cannot afford a 5 speed yet..
Thanks for you input...
I have 3:70's and BW trans now, "lost the muncie in a trade a long time ago"
...Question....
How do the two together work in determining the best Diff ratio, I know its 1:1 in fourth gear...
Or do they?
Right now my RPM's are around 2900+/- on the freeway
I was thinking of 3:36 but my engine builder say's 3:55 would be a better match..
What kind of rpms would the differences be between the gears at highway speeds...?
Give me your thoughts on a good all around gear.
Cannot afford a 5 speed yet..
Thanks for you input...
Last edited by 66jack; May 7, 2014 at 12:43 PM.
Team Owner
Joined: Mar 2002
Posts: 44,681
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From: Huntsville AL
I don't think the trans matters from a 4-Speed standpoint because 1:1 is always 1:1, the rear gears will determine RPM.
My 66 had a stock 350, M20 Trans and 3:08 gears and that car got better gas mileage than my 6 cyl CJ-7.
My 66 had a stock 350, M20 Trans and 3:08 gears and that car got better gas mileage than my 6 cyl CJ-7.
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
Okay I'm trying to get better gas mileage in my 66...
I have 3:70's and BW trans now, "lost the muncie in a trade a long time ago"...
Question....
How do the two together work in determining the best Diff ratio, I know its 1:1 in fourth gear...
Or do they?
Right now my RPM's are around 2900+/- on the freeway
I was thinking of 3:36 but my engine builder say's 3:55 would be a better match..
What kind of rpms would the differences be between the gears at highway speeds...?
Give me your thoughts on a good all around gear.
Cannot afford a 5 speed yet..
Thanks for you input...
I have 3:70's and BW trans now, "lost the muncie in a trade a long time ago"
...Question....
How do the two together work in determining the best Diff ratio, I know its 1:1 in fourth gear...
Or do they?
Right now my RPM's are around 2900+/- on the freeway
I was thinking of 3:36 but my engine builder say's 3:55 would be a better match..
What kind of rpms would the differences be between the gears at highway speeds...?
Give me your thoughts on a good all around gear.
Cannot afford a 5 speed yet..
Thanks for you input...
Thread Starter
Team Owner
Joined: May 2006
Posts: 37,671
Likes: 1,115
From: CA
Only a MAJOR ratio change is going to make any noticeable difference in fuel mileage. Forget 3.55, it's not enough different from 3.70 to make a difference. 3.36 is a good all-around gear, especially with a low first gear like your B-W trans (or an M20) has. Whatever you do, it'll take years of minor fuel savings to pay for the diff ratio change. The best plan is a 5-speed overdrive Tremec TKO, but that's even more expensive - but better if you're going to to a lot of freeway travel.
How do i determine what i have...trans wise?
EDIT: Who makes the BEST aftermarket gears beings GM Gears are not available other than used ones on ebay...
Last edited by 66jack; May 7, 2014 at 01:18 PM.
Race Director
Joined: Nov 2000
Posts: 10,343
Likes: 668
From: Beverly Hills (Pine Ridge) Florida
With the 3.55 rear gear, short rear tires (26.1: tall), and .73 OD, I am turning 2000 @ 60.
But the engine must have a broad strong torque band to run this trans (very wide drop between gears - 3.09 first, 1.68 2nd, 1:1 3rd, & .073 4th). The trans also is not a "racer" trans (hard to upshift quickly for the track), but is the same basic size as the Muncie and uses the same driveshaft & splines. But getting very difficult to find..........
As for running at a lower rpm, engine needs to be setup for running at that rpm. A high rpm "winder" will not be efficient at lower rpms.
Plasticman
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From: Bowling Green, Kentucky
For a trans that is in the car, I would take the car out and drive it. Then check RPM versus MPH in first gear and in fourth gear. Say 40 MPH indicated speed on your speedometer. Then divide first gear RPM by fourth gear RPM. This should get you close.
A Corvette factory BW from the early 1960's had a 2.20 first gear ratio according to my books. Not certain what you may have now.
Larry
EDIT: A second source indicates that a 2.54 ratio BW is possible. There are ID tags on the trans that identify the ratio. Does your trans have this tag??
Last edited by Powershift; May 7, 2014 at 01:34 PM.
Team Owner
Joined: Oct 2000
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From: Washington Michigan
Thread Starter
Team Owner
Joined: May 2006
Posts: 37,671
Likes: 1,115
From: CA
If the trans were out of the car, we could count input shaft and output shaft revolutions.
For a trans that is in the car, I would take the car out and drive it. Then check RPM versus MPH in first gear and in fourth gear. Say 40 MPH indicated speed on your speedometer. Then divide first gear RPM by fourth gear RPM. This should get you close.
A Corvette factory BW from the early 1960's had a 2.20 first gear ratio according to my books. Not certain what you may have now.
Larry
For a trans that is in the car, I would take the car out and drive it. Then check RPM versus MPH in first gear and in fourth gear. Say 40 MPH indicated speed on your speedometer. Then divide first gear RPM by fourth gear RPM. This should get you close.
A Corvette factory BW from the early 1960's had a 2.20 first gear ratio according to my books. Not certain what you may have now.
Larry
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Race Director
Joined: Apr 2005
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From: Bowling Green, Kentucky
The ratios I posted were for a standard BW T-10 Corvette trans from the early 1960's time period. If Jack has a BW SUPER T-10 from the 1970's, than other ratios as you posted are possible.We need to get some transmission info and numbers from Jack to help pin it down………….also whether it is a T-10 or a SUPER T-10??
Using RPM versus MPH will also give the ratio.
Larry
Race Director
Joined: Apr 2005
Posts: 11,277
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From: Bowling Green, Kentucky
You have to be difficult.
I believe what you have is a "first run/design" Super T-10 that was used in cars like the 1969 AMX, GM, and others, and also sold over the counter.
The T-10 V should indicate a "close ratio" with a 2.20 first gear. I will double check this, but I believe that I am correct.
My 1969 AMX had the same/similar trans.
Larry
EDIT: Here is an old post from a few years ago. http://forums.corvetteforum.com/c1-a...ission-id.html Best I can determine the first gear ratio is 2.20 or 2.23, with a possibility (according to some sources) of having a 2.41 first gear for some applications. Not certain I believe this.
The trans on my 1969 AMX was AS4-T-10V to indicate the input shaft was built for AMC shaft length and pilot bearing requirements. The AS3-T-10V was similar for GM cars.
Last edited by Powershift; May 7, 2014 at 02:33 PM.
Drifting
Joined: Jul 2012
Posts: 1,952
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From: Grants Pass Oregon
The only worthwhile change is still a 5 or 6 speed. as mentioned, any ratio change won't ever pay for itself in fuel mileage alone, but the lower wear and tear on the engine, and your nerves, is WELL worth the od swap. Your 370 rear ratio is also perfect for the od swap as is. the way you drive the car a WC T-5 would hold up for an eternity and not be all that expensive a swap. I bought a good WC from a Z-28 on CL a couple years ago for $250.00 . any od trans will transform the the enjoyment level of these old cars.
Russ
Russ
Drifting
Joined: Jul 2012
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From: Grants Pass Oregon
Built by Borg-Warner and later bought out by and sold as Tremec.
WC = world class. there was an early and late version of the T-5. the WC is the more desired version (used in 88-91 V-8 Firebird and Camaro)
edit to add:
You'll want to verify the numbers when you go to buy one, but if you get an 88-91 from V8 Camaro/Firebird you'll be set.
http://www.britishv8.org/articles/bo...t5-id-tags.htm
WC = world class. there was an early and late version of the T-5. the WC is the more desired version (used in 88-91 V-8 Firebird and Camaro)
edit to add:
You'll want to verify the numbers when you go to buy one, but if you get an 88-91 from V8 Camaro/Firebird you'll be set.
http://www.britishv8.org/articles/bo...t5-id-tags.htm
Last edited by MrPbody; May 7, 2014 at 04:05 PM. Reason: ad link
Drifting
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From: Grants Pass Oregon
Melting Slicks
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C2 of Year Finalist (performance mods) 2019
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Come down to Fresno and drive my 63 with the RS500...youll want to trade me on the spot. 20mpg in the hills cruising with a little spirit in the corners. (and 70mph +)