What gear is best.

[tls630]

I have a 69 L-46 M-21 4-speed with a 4:11 rear end. I have it out to change the spring and do some cleaning and painting. It has quite a bit of axle end play.What would be the best axle ratio for me. It now turns 3500 AT 65 -70mph.As long as it needs work I might as well change it now.I was thinking a 3:70 ratio ? Would a 3;55 be to high?The m-21 is 2:22-1 in 1st gear so I don't want to go to high in the rear.Thanks in advance for the help.
Tom

 

[bradfordsvettes]

i have 3:73s in my 69 w 4speed they are great around town gears great pick-up and torque but borderline for the highway if i ever change it would be the 3:55 for me only my 2 cents steve

 

[tls630]

rear gear...

Steve
What tranny do you have? I have a m21 and the low gear is a little high.2:22-1 It would be better with a wide ratio but oh well.I don't know if that will be hard on the clutch with a 3:55 or not. That is what I am leaning toward.Thanks for your help.
Tom

i have 3:73s in my 69 w 4speed they are great around town gears great pick-up and torque but borderline for the highway if i ever change it would be the 3:55 for me only my 2 cents steve

 

[jim coulter]

I've got 3.55's in my 71 with a m-21 4-speed and wouldn't want any more. I haven't driven it much, maybe a couple hundred miles, but it does good on the expressway and around town. I have often wondered about 4.11's, but that would be too much for expressway driving in my opinion.

 

[tls630]

Jim
I think the 3:55 is just what the doctor ordered. Now I have to find one for sale.I want to keep mine for origanality reassons. thanks for the input.
Tom

 

[bradfordsvettes]

close ratio in the 69 I have afriend with 3:55s with a wide ratio I like that seens to have good balance. still would tame your car for the highway may not be hell out of the hole but suspect it would still be respectable Steve

 

[resto75]

I have a 3.55 in my car with a 4sp and I think it works out well for all around driving.

 

[rainman]

A lot of people like their 3.55s, but it makes a difference if the tranny is M20 or M21. 3.55 or even 3.36 work well with M20. With M21, I would be careful with going to a 3.55. You may be disappointed in your off the line acceleration, but the difference at highway speeds from a 3.70 would be small.

 

[81 Corvette]

81 w/ th350 and 3.54


3.54 is a great gear imo. good off the line performace and acceptable cruising rpm's

 

[tls630]

Thanks for all the input. I got a deal on a 3.36 so am going to try that.I wanted to get as high as I could AS the 4.11 is just to low.I now hope that the 3.36 isn't to high in 1st.I don't want to have to slip the clutch to get rolling.We shall see.Thanks again. Viet

 

[TWINRAY]

Thanks for all the input. I got a deal on a 3.36 so am going to try that.I wanted to get as high as I could AS the 4.11 is just to low.I now hope that the 3.36 isn't to high in 1st.I don't want to have to slip the clutch to get rolling.We shall see.Thanks again. Viet

Man O' Man are you going to notice a big difference. I had a '68 GTO with the 3.90 rear and CR 4 speed. The 3.90 blew and I put a 3.36 in it. What a dog off the line it turned out to be even with the torque of 400 cubes and 360 hp. It probably would have been OK if I didn't have the CR box. With the 3.90 gear, when you hammered it off the line, you had to steer it 90 degrees off center to keep it going straight - it was a fast car.

 

[thirdtimevetteowner]

I owned a '66 Roadster w/a 327, 350, m21 close ratio w/3:70's and I think they are perfect. It was sure fun doin some mild "s" bends, droppin down from 3rd to 2nd and the engine staying in the torque range because of the close ratio (the tach would only drop 500 rpm or so). Then pullin out of the other side and hammering it back into 3rd, feelin those 350 horses comin on strong as h***. It even turned some decent times in the 1/4 mile- 14.21@102 thru the mufflers, on skinny radials. Loved that car, but unfortunately, had to sell it (2 kids in college at the same time). Oh well, got my '89 now, which ironically is the same color scheme the '66 was, cept it's an automatic. Now, if I can get this L98 to run as good as that L79, I'll be happy, well almost (can't have too much HP, ya know?)

 

[john1977]

I hope 355s are good with th350 trans (since i just switched from 308s) havent had the weather here to try it out yet. For the cost I sure hope Im pleased.

 

[81 Corvette]

I hope 355s are good with th350 trans (since i just switched from 308s) havent had the weather here to try it out yet. For the cost I sure hope Im pleased.

I'd be shocked if you were not pleased. I went from 2.87 to 3.54 and what a difference it made.

 

[john1977]

81 corvette, what size tires are you using? Still have the stk 225/70-15s and with the 308s it was hard to smokem even with my 350/330hp engine. After the change to 355s i also put a 2400 stall conv.and went back to stk 9 leaf. Was thinking of going to 255/60-15 if it will lightem up? Just been waiting for the weather to find out if my winter projects will make any differance.new springs front and rear/2400 stall/355 gears/body mounts & a shift kit.

 

[81 Corvette]

225/70/15 kelly charger rubber. i can't sit and "smoke em" but before all the upgrades even a little chirp was rare, but now i can make some nice tire noise from a stop. much much much more peppy, even with the L81. the other major mods are rpm air gap, demon carb and headers with a hi flow cat.

The headers made a world of difference as well.

 

[curtis]

Running 275/60/15 Kelly Chargers on the rear and I fry em all the time. Somethin to do with floorin it and dumpin the clutch I think.

 

[81 Corvette]

could also have something to do with Kelly Charges being a hard compound. Thats been my take on em. They look nice and handle the rain good, but they seem to loose grip when the hammer is dropped or a corner is cut.

 

[tls630]

Thanks for all the input. I got my 3:36 rear in and all new suspenion to go with it. I am very happy with the 3:36 gear. The 4:11 was a pain to drive even in town.The new gear makes it drive like a totaly different car . Thanks again for all the input.
Viet
P.s.
I was worried about it being a dog on take off, but it's not bad.Top end what a difference.