FI with 3.70 rear end and a close ratio best?
hi all, I'm about to get a T10 built for my 59 FI 290 HP and I would like to know if I should stick with a close ratio for the gear set? The rear end is 3.70. From what I can tell from other threads this would be the recommended way to go based on the rear end I am going to use. Thanks in advance!
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Re: FI with 3.70 rear end and a close ratio best?
Ian 3.70 gears is lots of fun, but by the time you get your car on the road I presume the car will be pampered being all new and shiny. So you wont be driving it like my pig. I know when my body does come off I wont be abusing it like I do now. The 3.70 and close 4 gears help the loss of torque from the bigger 327 and 350 stuff. I have a healthy 350 in mine with 3.70's and 1st gear is useless it just spins. So with the smaller 283 it should be more user friendly. I just purchased a spare diff for mine and are in the process of getting it geared for long cruises. The 3.70 gets tiring after an hour at 60 miles an hour. But around town the 3.70 are great. Stewy -
Re: FI with 3.70 rear end and a close ratio best?
Ian, I have the identical set up (290hp, 3.70 rear, w/close ration T10), and this is a great combo. The car has very good launch characteristics as well as mid range performance. My only complaint is the fuel economy for long haul trips. The RPMs in 4th gear @ 65mph are above 3K and I long for a 5 speed. But if you are going original - the close ratio 4 speed and 3.70 rear is perfect.
Don
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Re: FI with 3.70 rear end and a close ratio best?
Hi Don, That's the info I was looking for! Thanks very much!
Stewy, you gonna go for a 3.08 for your rear end? Yeah I went for 3.70 for originality with the 290 horse engine and am hoping highway driving will be tolerable.
I finally managed to find someone with the correct numbers matching T10 for me! Only took about a year and a half... :PComment
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Re: FI with 3.70 rear end and a close ratio best?
Although no C1s came with the wide ratio, wouldn't a wide ratio geatset with a 3.55 rear be more streetable? This would still have good acceleration with the 2.52 first gear, combined with less revs in fourth gear on the freeway.Comment
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Re: FI with 3.70 rear end and a close ratio best?
Ian I have 2 diffs, one will be a posi 3.70 and that is the numbers match job that I will use 90% of the year and the 3.08 single spinner for the massive interstate Corvette get together's. I also took 1 1/2 years to buy a T10 with good numbers. If you plan on doing a lot of large runs maybe you can try 3.55 Like Loren said. Those big revs on the long hauls gets very tiring. StewyComment
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Re: FI with 3.70 rear end and a close ratio best?
This would be a sweet combination. I don't think you will regret having it.
My '60 (also a 290 HP car) has a 3.55 rear and a close ratio T-10. It's a little soggy off the line (but a great hiway cruiser). For my car a wide ratio box would be a better choice.
For yours, with the 3.70 rear, the close ratio box is, in my opinion, the way to go.
JimComment
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Re: FI with 3.70 rear end and a close ratio best?
I realize that most people here have, or either prefer to have the smaller, original type engine (283) for thier early cars and thus feel something in the range of a 3.70-3.55 and a close ratio 4sp is a better combo.
I have a 3.08 posi in the 56 (and most of my other cars), but of course it also has a SB400 with much more torque to turn a 3.08 gear. It also has a wide ratio Muncie and the combination works very well in the city as well as on the interstate. At 76mph, the tach is sitting on 3000.
And as far as a well built 283 turning a 3.08 gear, even in town, especially with a wide ration 4sp, I'm convinced it would be a very acceptable combo. And here's why. Back in the mid-late 50s, when 3spOD cars were fairly common, those cars had a 4.11 rear and MANY of them had a 6cyl engine instead of a V8. The OD of the tranny was about .75. So, a 4.11 rear, with the tranny in OD, equals about a 3.08 final drive (.75 x 4.11=3.0825). And this is in a bigger, heavier car with a weaker 6cyl engine. Consequently, I don't see any negative issues with a 283, wide ratio 4sp and a 3.08 rear in a much smaller and lighter Corvette. No, it may not be a rocket off the line, but once above 5-10mph, it's going to run great as well as wind out much further and longer in each gear with a 3.08 rear.
And if a person is obcessed with the tranny/rear being absolutely correct numbers matching, then it is tooooooooooo easy to change the gear sets in both the tranny case and rearend case.Comment
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Re: FI with 3.70 rear end and a close ratio best?
for now I'll stick with the close ratio and 3.70 rear, since that seems to be the consensus for what I have. I may try a 3.55 or 3.08 later, but for now, never having driven it, or owned one in the past -- I want to go for the original experience
It might be cool to go 4.56 for around town and 3.08 for driving to meets on the freeway. But I'll probably be lazy and stick with the current combo... Thanks all!
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Re: FI with 3.70 rear end and a close ratio best?
A 3.70 with a close ratio 4-speed is my favorite all around combination.for now I'll stick with the close ratio and 3.70 rear, since that seems to be the consensus for what I have. I may try a 3.55 or 3.08 later, but for now, never having driven it, or owned one in the past -- I want to go for the original experience It might be cool to go 4.56 for around town and 3.08 for driving to meets on the freeway. But I'll probably be lazy and stick with the current combo... Thanks all!
I've never liked wide ratio transmissions in any old Corvettes and a 3.08 is miserable/depressing unless you plan on a lot of cross country trips. Even then, I'd have a 3.36.Comment
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Re: FI with 3.70 rear end and a close ratio best?
My daily driver is over 3K RPM at highway speeds, so I'm used to it anyway. Seems like 3.08 would be giving up a lot of the exhileration of driving it!Comment
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Re: FI with 3.70 rear end and a close ratio best?
my '62 still has the 3.36 I put in it to go Road Touring about 10 years ago. With the 327/360 at least and a close box it works just fine.Bill Clupper #618Comment
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Re: FI with 3.70 rear end and a close ratio best?
Ummmmmmmmmmmmmm, not if you have a motor to go with the combination of a wide ratio and a high gear ratio rear (ie 3.08)!!!
What I particularly like about the M-20/3.08 combo in the 56 (behind a HEALTHY SB400) is that by the time it's only half way wrapped up in 2nd gear on the Interstate, it's WELL ABOVE the speed limit. Actually, 60mph in 1st gear is nothing. By that time, many other cars have already made 2 shifts!
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Re: FI with 3.70 rear end and a close ratio best?
my "other" weekend car is a 49,000 mile 138 code '66 Chevelle SS396, that left the Fremont assembly plant with four speed and factory air conditioning (also AIR).
I have run the original 325 horse 396 with 3:08 rear and M20 wide ratio for ten years to car cruise night with acceptable power. Does it scream like a 435hp with a 4:11 and close ratio?.......no, but will out-perform 90% of new cars leaving showrooms today. Actually, plenty of street power.
Ridge.
Good carburetion is fuelish hot air . . .Comment
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Re: FI with 3.70 rear end and a close ratio best?
THANK YOU SO MUCH FOR THAT INPUT!!!!!my "other" weekend car is a 49,000 mile 138 code '66 Chevelle SS396, that left the Fremont assembly plant with four speed and factory air conditioning (also AIR).
I have run the original 325 horse 396 with 3:08 rear and M20 wide ratio for ten years to car cruise night with acceptable power. Does it scream like a 435hp with a 4:11 and close ratio?.......no, but will out-perform 90% of new cars leaving showrooms today. Actually, plenty of street power.
Ridge.
I needed someone in my corner!
My 70 Chevelle conv has factory air (it was originally a 307 3sp), a well built SB400 (probably close to a 350hp/396), M-20 and 3.07 12bolt posi. It makes a few passes at the strip each year at Chevellabration and it is DRIVEN to and from the event each year (OKC to N'ville) as well as local crusin' and Interstate driving. The SB400-M20-3.07 combo does just great for all around driving.
Oh ya Ridge, just to be picky on petty stuff, if your 66 Chevelle is a factory 396/4sp car, then your rear is a 3.07 12bolt (the 10bolt rears had a 3.08). The 12-bolt rears were std equip behind all BB engines.
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