4:11 rear gear swap

[Wayne H.]

Re: 4:11 rear gear swap

Hope this helps with your decision.
95B35DA9-160A-4E3B-AAA6-76681A635C20.jpg

[Michael J.]

Re: 4:11 rear gear swap

To each his won, but I changed out the 4.11 in my '63 fuelie for a 4.56 because the low end torque was so poor it was hard to launch, especially on hills I have around here. These SHP engines live above 4000 rpm, I have no problems being in that range most of the time when I am driving, I think they were engineerd for that. I like peppy performance when I drive.

[Gary R.]

Re: 4:11 rear gear swap

Did you use GM 456 with a 4 series case or thick 3 series gears?

[Michael J.]

Re: 4:11 rear gear swap

Yes, the GM 4.56 with the 4 series case.

[Gary R.]

Re: 4:11 rear gear swap

Good deal. As you know the case flange is thicker but is the way to go if using GM 4 series gears. A lot better than using a spacer with a 3 series case as was done back in the day.

The thick gears I do like and have used. Gives the owner the option of changing out 4 series gears back to 3 series if they want without changing the posi case. Of course, many times the stock posi case may have some issues when used with a 4 series gear, but that's another story.

[Mark E.]

Re: 4:11 rear gear swap

Save $5k and leave the '65 alone. Instead spend $12k for a clean C4. For a few extra $, you get another Corvette with six gears, 50% overdrive, 28 mpg highway, and more power. Not to mention comfy seats, AC and cruise for your highway use.

[Michael J.]

Re: 4:11 rear gear swap

Not the same to many......

[Chris H.]

[Terry M.]

Re: 4:11 rear gear swap

Wally,
I'm not sure whether your car is a judged car or driver or both. That said, you could consider an overdrive transmission. Several manufacturers make them and I believe some will fit inside the transmission tunnel without modifying the tunnel. It would give you the best of both worlds. Low first gear to pull away from a stop without clutch slipping and reduced final drive ratio for better mileage. For example, if you have a 5 speed overdrive trans with a fifth gear ratio of 0.85:1, the final drive for your 4.11 rear will be reduced to 3.49 (0.85 x 4.11 = 3.49). Just a suggestion but this might be a better option than changing the gear or complete housing in your car.

Terry

[Mark E.]

Re: 4:11 rear gear swap

Not the same to many......

Michael,

Well, I appreciate our polar opposite out-of-the-box replies: you suggest 4.56 gears; I suggest a C4.

[E S.]

Re: 4:11 rear gear swap

HI- Back in the day, Motion Performance (Long Island NY) advertised an overdrive unit for Corvettes -installed in the driveline at the rear end.
I considered it at the time, but did not follow up- Maybe an alternative?
I think it was a 30% reduction
E.J.

[Bill B.]

Re: 4:11 rear gear swap

I installed a Gear Vendors OD unit (0.778 - a 22% reduction), so my 4.11 differential is equivalent to an approximate 3.36 ratio differential.

The big difference in my situation, however, was I installed it while I had the body off and reinstalling the rebuilt components. Had to have a custom driveshaft made (rather than shortening the orig one). The OD Unit was not cheap. $3K about 5 yrs ago. The other bad news is the body had to be slightly modified in a couple of area for clearance. It was a tight fit, but ... it is what I wanted to do and planned around it.

It would have been much easier to install a Tremec 5-speed. However, I wanted the singing sound of the M-22 ... music to my ears!

All good suggestions on the postings, but in the end, it is up to the owner on the final decision, even the suggestion of buying a "travel" Corvette for highway driving.

Even though I have the equivalent of a 3.36 ratio rear for highway driving, I still get lousy gas mileage from the slightly massaged LT-1.

I'm trying to convince my wife for us to buy a base C8 for trips, etc, as I don't want to drive the 52 yr old car too far from home. I get too nervous that something may break and leave me stranded out in the middle of nowhere ...

[Michael J.]

Re: 4:11 rear gear swap

True Mark, different people will have different solutions to this problem.

[Richard G.]

Re: 4:11 rear gear swap

I didn't know you could get a GearVendor OD into the Corvette.

My 63 340hp had 4:11 from the factory. Sometime in it's first 5 years of life it was converted to 3:36's.
It has GM gears with a 1965 date on them. Seems the original owner got tired of them fast!
Since I have the 340hp I also have the close ratio four speed.
Yes it takes a little slippage to get it going. I wouldn't call it excessive.
If one has the wide ratio with the lower 1st gear I doubt anyone would even notice.
I have gotten 18mpg on the highway with my car.
I limit my spirited driving with the 63.
I have stock sized tires and the 340hp and 4:11 never made sense to me.
Spin and go? LOL Not sure it works out except for the guys that manufacture tires.

And yes my speedometer is off, as mentioned. The steel gear on the output shaft has to be changed to a different diameter. Interesting only the diameter changes not the tooth count. The count only changes on the driven gear.
Cheers

[Michael J.]

Re: 4:11 rear gear swap

Just remember the words of the great one: "Carroll Shelby: There’s a point – 7000 RPM – where everything fades. The machine becomes weightless, just disappears. And all that’s left is a body moving through space and time. 7000 RPM that’s where you meet it. That's where it waits for you. You feel it coming. It creeps up on you, close in your ear. Asks you a question? The only question that matters. Who are you? "