L-82kid

I have a 4spd with 336s now. I'm running 275/60 tires in the back.

How much diff will the car run? looking for more low end torque and to get my motor in its power range: 2200rpm +


what rpm can i expect at 65-70mph?

will the car feel quicker from stop light to stop light or just whine out eveywhere like I'm in 3rd gear.?


I had 355 gears when my car was a stock L82. I rebuilt that rear and swapped over to 3.73s about 4-5 years ago. Last summer I blewn up my 373 rear end. my father had an extra 3.36 rear so I put that in just to get the car going again. I felt the diff just from going from 3.73 to 3.36, the car got a little soggy down low. Because of a lack of funds and time, I ended up keeping the 336s for about a year. Now I have 4.11s coming in for the car.

also I went to the track a few summers ago with 3.73s and my 60ft times were about 2.2-2.3. I either bogged or burned out on every pass lol, I ran 3-4 times. I'm planning on going again this summer at least 1-2 times. Can I expect my 60ft and ET to improve with my gear swap??

thanks

Amelio

3.36 to a 4.11 is a pretty healty jump!!!! What is your basic engine setup and what is your max rpm? If you have a decent set up I am sure you would be happy with a 3.70 or 3.90 plus you would need to change your carrier unless you run a thicker ring gear for a 3 series carrier.

IMO a 4.11 is good for a 7,000 rpm engine or better, I have 3.70 in my car and I need to go to a 4.11 or 4.33. You will have a much better low end power but will top out much faster, this also depends on your trans.

avner

Hi L-82kid
now at 70MPH w/3.36 => 2822RPM
70MPH w/4.11 => 3452RPM
Go to this link, you can figure out all option:
http://www.differentials.com/calc.html
But every change in the rear and ration influence the speed reading.
Avner

Glensgages

MPH x GR (Gear Ratio) div/by .006 div/by 1/2TH (Tire Height) = RPM

example:

65 MPH x 4.11 div/by .006 div/by 13.75 (if a 27.5" tall-tire is used) = 3238 RPM

Back-when my Z28 ran 14.40s @ 97 MPH on 225/70R15 UNIROYALS, it had an almost identical (3.42:1) gear-set:
a switch to 4.11s resulted in 14-teens at the same 97 MPH..... at the time (1984), the track didn't have a CompuLink timing-system, so I can't offer help on incremental-time improvements.

gkull

You need to make the engine more powerful instead of worrying about gearing.

My 4 speed 67 Camero has a 2.73 rear end. It can spin the tires a long way in first gear

chevymans 77

I'm running 4:11's and right at 25.5" Tires, double your RPM's, 3000 is 60mph, 3500 is 70 mph, its pretty close. I'm running a solid roller cam 496 and its good to 7200 rpm's, I don't go above 6500 under normal conditions and the 4:11's are fine. The interstate is another story, need an overdrive. If the motor is not good for at least 6000 rpm's than the 4:11's may not be for you.

Neal

TheSkunkWorks

w/gkull...

I had a 4.10:1 (12-bolt IRS diff w/Moroso posi) for a few months, and tho it did result in improved bottom end acceleration compared to the original 3.55:1, I found the high revs at highway speeds with my 1:1 top gear just too much (not to mention the limited top speed) and consequently had Henry's build me a 3.55:1 (12-bolt IRS diff w/Eaton posi).

Thing is, tho it got out of the hole quicker I doubt it made as much as 2/10ths difference over a quarter mile (not that I drag race my C3), so I suggest another 3.73:1 would likely make you happier overall if you just have to change gears again.




Sidebar: Neal, what cam did you end up with in that 496, if you don't mind my asking?

C3 Stroker

If freeway driving is not the major concern ( and I suspect not, since you are looking for better ET), then you will love the acceleration increase with the 4.11's. You will appreciate it even more as you add engine mods for better performance.

L-82kid

I finally got my car running good. you commented my last post:

http://forums.corvetteforum.com/show....php?t=2005694

The car spins the tires really good now with the 3.36 gears, even gets a little loose when I hit second hard. it just doesn't have low end torque while cruising around, I have to get it over 2500rpm to make power.

I def want to make the engine more powerful but its not in the budget right now. I got the 4.11 rear complete for free, just had to paid for shipping. when it comes in i just have to double check it and put in fresh gear oil.

hopefully next step will be new engine. I already have parts waiting.
I have:
two 350 4 bolt blocks , an extra L-82 crank, new pro topline alum heads, new 1.6 harland sharp roller rockers, XS274S comp cam, and I can reuse my rpm intake, and carb. I just need machine work, pistons/rods, bearings and gaskets. Not sure about 355 or 383 storker.



I had 3.73s before so I know what they're like, the car ran good with them but now I want to try something different. plus the rear I have coming in is a good used one and all set up with 4.11s. Eventually down the road I'll have to build a new stronging rear and then I decide on what gear ratio I want.

my 275/60 tires are about 27.5-28" tall, so that will help keep revs down a little bit. I dont really go on the highway that much any more, just like to rip around town.






Nice I want to feel the difference. I don't go on long trips and I don't really care about the highway anymore. I just want a stop to stop/ 1/4mile for now. Then when I have a little more money Ill put in a 6spd and some 3.73