I have a chance to buy a 3.70 ten bolt rear end for my '63 Biscayne that I currently am running a 3.36 rear in. First, this is a DRIVER, not a drag, or race car, and I am very pleased with the performance/millage and overall fun of it as is. BUT, being close to 68 years old, and on limited funds, I am still young at heart so always thinking in the back of my mind about a little better performance!! Some facts on my drive train that is in a '63 Biscayne two door. Engine is a 283, bored .60 with 305 heads, Melling cam (close to the L79 Corvette cam) flattop pistons, Elelbrock Performer intake with a 550cfm Elelbrock carb, and a few other things. Running 2 1/2" Corvette Rams Horns with full 2 1/2" exhaust. Saginaw 4 speed with a 3:11 first gear ratio, and the 3:36 rear end. Sorry for the long paragraph above, but want to give all possible info. My question is with that info, will switching to a 3:70 rear make enough difference to be noticeable?? Fuel millage is not an issue, and cost is minimal...I can buy this 3:70 rear very reasonable. Just looking for a little more snap in 1st and 2nd gear... Thanks for any help. Cheers.....
Not knowing all the details of what you may have modified or not I would mention unless you have changed it a 63 Chev doesn't use a 10 bolt dif, so the gear set won't fit. I am not familiar with the 3.70 ratio but you may find you are reving quite high at freeway speeds with it.
3:11 first gear ratio, sounds "snappy" and the 3:36 rear end, sound ideal. 3:70, yeah, more snappy but they rev high on the freeway. Like you said its a DRIVER. Though the 283 is pretty neat, a good, even used 350 switch is the omgh your looking for.
is the rear axle an original style? The differential drops out the front if it is. 3.73 might be the ratio you are considering purchasing. If you want a bit more zip, it would be a good change. Your tires are certainly larger than OEM, so it might even make you speedometer accurate. good luck Bob
You won't really notice much difference... maybe a little more pep when you start off in first and about 300 more rpm in high gear at 70 mph (***uming ~27" tall tires). Regards, X
If I remember right the saginaw has a big jump from 1st to 2nd gear; anyway the setup you have gives the same launch leverage as a wide ratio T10 and 4.11 rear end. With a 3.70, it would give you practicaly the same as the T10 with a 4.56 rear.With the engine you have, you'll be shifting into second just as you clear the intersection. I would suggest keeping the rear gear and trading the trans for a Doug Nash 4+1 (Richmond Gear) 5 speed; the launc would be the same as T10 with 4.44 rear and the first 4 gears would be the fun setup, while 5th would be just like you have now. JMO
I believe the '55-64 drop out rearends are considered 10 bolts, but are not generally refered to as such. The stock ratio is 3:70 for these, the aftermarket gears are 3:73, as I recall. Of course, changing to a 3:70 will give you more zip, but you will pay for it at the other end. Run the numbers through an online gear calculator and see if the rpms at crusing speed are going to be to your liking or not. And be preparded to deal with the speedo accuracy issue, ***uming it's accurate to begin with...
Thanks for the quick replies, as always. Yes, it is the stock 55-64 drop out rear end that comes out the front, and has 10 bolts, which us old timers always called a 10 bolt rear end. Second, my current $$$ (retired on SS) does not allow me to change to the other suggested transmissions. Nice suggestions though.. I also totally under stand the 350 benefits, but wanted an "Old High School" type car, and I graduated in 1962, so deliberately went with this little warmed up 283, which I am totally happy with as is, but always wanting "Just a little more" !! As to the speedometer concern, my speedo cable hooks directly to the transmission, and is dead nuts on as it is. I don't run much interstate, and cruising at ~55 mph am running about ~2300 rpm's, so would not object if that ran up to ~2800 or so. Good point on shifting out of first gear before getting thru the intersection though...I need to think on that one, as the 3:11 first gear with my 3:36 rear gets you thru the intersection, but not by much before shifting. And I like that first gear zip, due to the lower end torque of the little 283 not being anywhere near to the 327/350's....... Gotta love this place, and thanks again for the info. I may just buy that 3:70 and put it in (can do myself) to try it. If I don't like it I can just put the 3:36 back in!! Cheers....
Like you said, if you don't like it you could swap it out to the other one. If you aren't doing much highway driving, it would probably work out well. Those cars were hefty by todays standards, and the added gearing wouldn't hurt when taking off. I did work with a guy who swaped out his 3.07's for a 3.73's in his pickup. At first he said it was like driving in second gear all of the time. But he liked it well enough to keep it that way.
You can also try shorter tires to see if you will like it. Its only a 10% change in ratios so I dont believe it will give a lot of noticeable power. But if the parts are free give it a try. Ron
I think the only way to be sure how it will work is to buy it and put it in. If you're not happy with it, it is not that difficult to go back to the 3.36's. Years ago I had a '55 with a warmed over 350, Muncie wide ratio 4-speed and several different gear sets. I had 3.08, 3.55, and 4.11. I changed them out depending on what I was doing with the car at the time. I left the 4.11's in most of the time because they were the most 'fun'! Turnipseed
If you're content to go 55 on the highway, then 3.70 gears will be fine. Youll need to change the speedo gear(s) in the transmission to make it read correctly after you change rearend gears.
For what it's worth, I had a stock '59 Corvette almost a hundred years ago with a stock-ish 283, 6.70-15 Michelin tires and a 3.70 rear. Turned right at 3,000 RPM at 70 mph. DD
go for 3.90 or 4.10 (stock 6 cyl gearing for cars and truck, just hunt) and a S-10 5 speed can be had cheap, nickel and dime it like the rest of us Social Security receipitants do.
I'll trade you gear sets. I have some 4:11s in a 58 and I want some higher gears of course you are a long ways away.
bob, my humble opinion is that you'll be real happy with that little change in gear. Its not a light car, and you sound like you want a little extra snap around town. I believe you'll be very happy. You'll tach out a little higher cruising on the interstate. One of the other fellows can fiqure it out real easy for you. Sorry i'm real tired right now LOL, or I would. Here in Florida the interstates are 70 MPH, which means you need to be able to cruise 75-80 or get out of the way. That extra buzzing for long periods of time might get to you, might not. Again, I think you will like the change. TR
I doubt you'll be doing 2300 -more like 3300 at 70 w/14" tires, geared with a 3:70. Had one in my 55 w/ a wide ratio muncie-as above. Hated it. Went with a 5 speed and 3:56 stocker rear--great combo for me. Made mine a really decent car. cooger
The 3.70 is a good way to go. I used to like anything from a 3.55 to 3.90 when I ran similar setups in my Belairs. Bob
I had a '65 Biscayne that came with a 283 and 3 speed. The rear had 3:08's. I put a 454 and a saginaw 4 speed into it but wasn't happy with the saginaw. I replaced the saginaw with a Richmond 6 speed (3:27 first gear and a .76 sixth) and replaced the rear with a 3:42 with a posi. That was a fun car after that.
3.11x3.36=10.4496 overall ratio taking off in low gear. Say you had a wide ratio Muncie instead (2.54:1 low gear) with a 4.11 rear end: 2.54x4.11=10.4394 overall ratio in low gear. You've already got as much dig off the line as you would with a Muncie and 4.11s---for a driver, how much more do you need?
I know this is late, but here's my $.02. You can generally feel a 1/4 ratio change. I had a '55 Chevy w/ 301 engiine, 3 speed trans and 3.70 gear. Tried a 3.55 with and without O.D. Best all round was 3.70 w/ O.D. Interestingly, the 3.55 w/ O.D. did not give better top end or fuel economy than the 3.70. Bruce Schneider Gearhead's Quickchange Exchange
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