C1 rear gears

[Thomas H.]

The 60 I am working on has factory 4:56 gears. The car originally came with a three speed. The original owner had it changed over to a 4 speed (T10 with a 61 date code on it) in the early 60's. Engine is a base 230hp 283.

What kind of driving can I expect with the T10 and 4:56's? Other the the trans, the car is all original. Is it worth looking into a different ratio while I have the rear apart?

Tom

[Domenic T.]

Re: C1 rear gears

Thomas,
That depends on your 1st gear ratio. I believe they had a 220 and 254 first gear.
You would want the 220 ratio if you are going to keep the 456 and the car would be a good town car.

If you have the 254 trans with the 456 rear you might look into changing the rear ratio and get the best out of both Worlds.

A 336 rear was popular and should be easy to find but all the way up to a 370 would be great.

The 456 was a racing gear and a lot of fun back then but could put you in jail now.

DOM

[Thomas H.]

Re: C1 rear gears

Thomas,
That depends on your 1st gear ratio. I believe they had a 220 and 254 first gear.
You would want the 220 ratio if you are going to keep the 456 and the car would be a good town car.

If you have the 254 trans with the 456 rear you might look into changing the rear ratio and get the best out of both Worlds.

A 336 rear was popular and should be easy to find but all the way up to a 370 would be great.

The 456 was a racing gear and a lot of fun back then but could put you in jail now.

DOM

Thanks Dom. We ran 4:56's in our racecar. Just enough to plant the tires..........

I will check out the ratio in the trans and do some calculations tonight. There are all sorts of internet rpm calculators............ fun stuff.

Tom

[Bruce B.]

Re: C1 rear gears

Since your current rear end is 4.56 the lowest (number) gear ratio that will work in the carrier I believe is 3.70.
The 4.56 is fun to drive but forget it on the highway. The 4 speed you now have has the same 1:1 ratio in top gear as the 3 speed.

[Robert K.]

Re: C1 rear gears

Years ago I ran 4.11 and like them real well, but it was an 8000 rpm solid lifter engine. Now I've got something real low, 2300 rpm @60 and it is not enough, except the gas milage is real good over 20. With a base engine I would vote for 3.55 or 3.23. It will still go pretty good, but will be real nice on the highway.

[John F.]

Re: C1 rear gears

If you are not drag racing, I would go with 3.08, 3.36, or 3.55.

[Stan G.]

Re: C1 rear gears

Its hard to beleive that somone would order a base engine 3 speed car with a 4:56 rear end but I guess stranger things have happened before.Sounds like they may have changed the rear when they put the 4 speed in it . My 58 had a 3:70 in it when I had it rebuilt and the rebuilder talked me into replacing it with 3:55 gears .no regrets. Has plenty of grunt for me , its also a 230 hp .
Stan

[Thomas H.]

Re: C1 rear gears

I was baffled myself as to why this car had 4:56's in it.

A couple of shots. Looks like early 60 date code on carrier. Car has a 5/24/60 build date.

I can smell the old gear oil just looking at the pictures............ Don't know if I'll ever get the smell out of the garage!

Tom

[Tom P.]

Re: C1 rear gears

Since your current rear end is 4.56 the lowest (number) gear ratio that will work in the carrier I believe is 3.70.
The 4.56 is fun to drive but forget it on the highway. The 4 speed you now have has the same 1:1 ratio in top gear as the 3 speed.

Nope, won't happen. ONLY 4 and 5 series gears will fit a 4-series carrier.
To install ANY CHEVY 3-series factory ring gear (57-64) in the case, a 3-series carrier MUST be used. Thus, to install a FACTORY 3.08, 3.36, 3.55, 3.70 gear set in the case, a 57-64 3-series carrier (either posi or non-pos) is all that will work.

Now, speaking to the existing 4.56 gear. In this day and time, and the price of gas, if you drive the car much at all, that 4.56 is going to get REAL OLD, REAL QUICK!

[Thomas H.]

Re: C1 rear gears

Now, speaking to the existing 4.56 gear. In this day and time, and the price of gas, if you drive the car much at all, that 4.56 is going to get REAL OLD, REAL QUICK!

I did some research last night and with these gears, 85mph is around 5000 RPM! I think I'm going to start looking for a 3 series assembly. I'll put the original away in a sealed enclosure (to keep the smell in!)for the future owner.

According to the Black Book, only 457 cars were made with 4.56 gears in them in 1960. I must have a rare care here............


Tom

[Paul D.]

Re: C1 rear gears

Tom P is right. I just this morning found out that you cannot put a 3.70 on a 4.56 carrier. Now I'm looking for a 3 series carrier, now that I have the whole posi rebuilt. I just have to learn everything the hard way.
Paul

[Tom P.]

Re: C1 rear gears

The guts in a rearend CANNOT be seen, thus, they cannot be judged.
So, with that said, if a person is going to add a posi, or a new posi is needed (such as replacing a 4-series with a 3-series), I'd really suggest buying either an Eaton or the Nitro posi unit.
A few years ago, Eaton (FINALLY) built a 3-series posi to fit the early Chevy rears (56-62 Vette/55-64 pass car). And just recently Nitro has introduced a posi unit (Powerlock) that is a near copy of the original GM posi unit (made for GM by DANA). Either are a good choice for a new posi.
Until these two posi units came on the market, original posi units had become VERY pricy. Now you don't have to get a second mortgage to either replace or add a posi to your 56-62 Vette.
I like the Eaton because the posi unit is a ONE-piece case with more clutch plates than the original DANA posi.
I like the Nitro (it's still a 2-piece case) because the axle gears are now a one-piece gear.
In my opinion, it really comes down to personal preference.

Here is the new Eatio unit (left) compared to the original DANA unit.





Here is the new Nitro Powerlock posi unit. ALMOST identical to the original DANA unit, but with some upgrades.






Original 2-piece DANA axle gears compared to the new Nitro 1-piece axle gears.

[Bruce B.]

Re: C1 rear gears

My Beige 62 had a 3.70 in it which drove great.
I changed it out for a 3.36 but with a wide ratio trans it is not fun to drive.
I have a 3.55 open rear in the garage that I'm going to put in soon, it's the best of both worlds in my opinion.

[Duke W.]

Re: C1 rear gears

A '61 T-10 would be a close ratio - 2.20 first gear. (I don't think the WR can along until '62.)

The 283/230 has broad torque bandwidth, and it will be a pleasant driver with a 3.36 or 3.08 axle, but it needs more reduction in the lower gears.

Since the trans is not original, but may be valuable, I suggest you install a Richmond Super T-10 (2.88, 1.91, 1.33, 1.00:1) with a 3.36 or 3.08. That will yield peppy around town performance and relatively easy freeway cruising. Notice that the spacing on this gearset becomes closer as you move up through the gears. The 1-2 intergear ratio is 1.51 and 3-4 is 1.33.

This is how a properly thought out ratio set should be. GM's expedient of just changing the counter gear ratio in the CR to create the WR yields the same 1-2, 2-3 intergear ratios, but a HUGE 3-4 gap.

Base engines have such broad torque bandwith that "close ratios" in the lower gears are next to useless. Some base engine, four-speed owners have told me they often skip second and go from first to third. In fact, if you look at the early WR ratios, first and third are about the same as first and second on the three-speed.

A couple of month ago I started a thread on gear charts and posted an Excel gear chart that I developed. Anyone can download it and do all kinds of "what-ifs" with transmission, axle ratios, and tire sizes to determine the best combination for your driving enviroment and torque/power characteristics of the engine.

A search for threads started by me should quickly reveal the link.

Duke

[Thomas H.]

Re: C1 rear gears

Wow, I see this thread got resurrected from when I first posted it back in 2011. I suppose an update is in order.

I decided that the 4.56:1 ratio was not conducive for the driving I would be doing with the car so I pulled the original 4 series center section, boxed it up and put it on the shelf. I was able to locate a properly dated center section with a Dana 3 series carrier. I installed 3.70:1 gears, new bearings and clutches. I find that the 3.70 gears work fine for the driving I do and I'm happy with my decision.

Now I'm working on a 58 that has an open end carrier with 3.36:1 gears. I'm contemplating changing over to a posi but will probably stick with the same 3.36:1 ratio. Should be interesting to see the difference between the two.

Tom