I have a 1969 Chevelle that I drive on a regular basis. Right now, I have a 4.11 12-bolt posi rear, getting power from a 350/350-turbo setup. The thing is SCREAMING at normal driving speeds. Until I get a 5-speed setup installed, I would like to re-install the factory 10-bolt once again. I have a set of gears from my uncle's '68. The ring has 37 teeth and is 8 inches tall and the pinion has 11 teeth. I'm assuming these are 3.36's for a 10-bolt.
My question is: Am I correct assuming that these are 3.36's? And if I install them, is it going to make that much of a difference in rpm and neck-snappin'?

Going from 411 to 331 will be a huge relief in cruise rpms.

Did you buy car with 4.11's in it or did you istall the 4.11's then later on realize they are way too much gear for street when running a non od trans setup and shorter stock height tires .

But of course with a smaller moter like your 350 with less trq going from the totally bad for street with non od trans 411s to 3.36 will also = a lot less perf out of the hole too.

Without an od trans you cant have best of both worlds.

Yes 37 / 11 = approx 3.36's

But with yor small 350 motor going from 4.11 to maybe 3.42-3.55 would be a considerable relief /reduction in cruise rpms & would also give you the best all arround comprimise between decent perf and reaonsable cruise rpm with stock hieght tires .

The 3.36's will get you even better cruise rpm reduction comming from 4.11's but at cost of a little less perf out of the hole as compaired to 3.42's or 3.55's.

I'd buy some 3.42's if i were you with a street 350 ,they will be a great reducion in cruise rpm over your current 4.11's bit still perf decent with a mile perf 350 sbc too.

Scott

Thanks Scott,
I bought the car with what I was told was a 3.08 10-bolt. The car was an A-title all original car. I just put a PST kit on the front end, switched the car to disc, put in the 4.11 12 bolt w/ 15" ralleys and 255/60/15's. Now I want to drive it all the time. The plan is to put in a five speed to make the 4.11's more streetable, but for now I just need a decent gear set in the rear so I can enjoy my car.

Going from a 3.08 to a 3.36 isn't going to be much of a difference. I doubt that I would go to the trouble of setting up the gears for that little change. I'd probably just run the 3.08 until the transmission was done.

Going from a 3.08 to a 3.36 isn't going to be much of a difference. I doubt that I would go to the trouble of setting up the gears for that little change. I'd probably just run the 3.08 until the transmission was done.

X2 - Just use what you've got. It will feel like you're starting out in 2nd gear now, but you will get used to it. I had a 4.10 behind my BB before switching to the 2.73 rear. Torque is your friend when you gear taller like that. But if it's just temporary until you get a new trans. I wouldn't sweat it.

I have a 1969 Chevelle that I drive on a regular basis. Right now, I have a 4.11 12-bolt posi rear, getting power from a 350/350-turbo setup. The thing is SCREAMING at normal driving speeds. Until I get a 5-speed setup installed, I would like to re-install the factory 10-bolt once again. I have a set of gears from my uncle's '68. The ring has 37 teeth and is 8 inches tall and the pinion has 11 teeth. I'm assuming these are 3.36's for a 10-bolt.
My question is: Am I correct assuming that these are 3.36's? And if I install them, is it going to make that much of a difference in rpm and neck-snappin'?

I've got a 68 Chevelle with a 350 and 4.11 posi too. I just got a 10 bolt with 3.08s that I'm hoping to swap out this weekend, so we'll see... Same thing, I'd be redlining the car in the city! Once I've got the new rear end installed I'll post results...
Graham

Perfect Post timing. Just got mine back from u-joints installed and run 350/350 turbo with 3.73 gears. The mechanic said a 700r overdrive would make driving on the freeway a breeze and also get better gas mileage as the RPM's are likely running 3000 at 60 mph. (dont have a tach-yet)

I will deal with it for now as I need to get the A/C running, new front and rear springs, shocks, and front disc conversion and tie rods, ball joints, swaybar etc.

I am in 3rd gear at 30 mph. Does not make for much fun on the freeway. I just rather get the car running solid with the suspension first. $2000 is just about the cost to get my disc brake conversion, new springs, shocks and bj, sway bar etc.

And I thought Jeeps were expensive. :sad:

Guys he said:

" I put in the 4.11 12 bolt w/ 15" ralleys and 255/60/15's. "

So he has 4.11's in it now.

He said he bought car with what he was told 3.08's then he installed 4.11 12 bolt but now that he driving it cruise rpm is too high which he plans to fix later with a 5 spd man trans to run with his 4.11'd 12 bolt.

But untill he can get the $ for that 5spd conversion he has a 10 bolt avail that he wants to change gear in for some cruise rpm reliefef that he will install & run for lower cruise rpms untill he gets enough $ for a 5spd coversion.

So him going from the current 4.11's to 342-3.55 max with his small mild 350 sc will get him a considerable amount of cruise rpm relief while still retaing some perf too that he would loose going with 308-3.36 gear with his somewhat small mild perf 350 sbc motor that doesnt have as much trq like a mild bbc does like even a baby rat 396.

And we all know that many people have big plans like in this case to go 5spd conversion but they never seem to get the time or money togther with life often getting in the way of goals like this and thats why i suugested going with 3.42's or 3.55's.

So if he doesnt relisitically doesn't ever get to it or it takes yrs to meet that goal in the meantime he has a better performing setup when he gets into it with 3.42-3.55gear vs 308-3.36 gear with a mild 350sbc.

Yeh theres not a huge diff from 3.36 to 3.42 but he's already loosing a ton of perf feel in the old BUTTOMETER with a mild 350 comming from 4.11 to 3.42-3.55 gear and and stepping down only a little more to 3.36 gear will be a little more perf feeling lost when he hits the gas with a mild 350 perf and auto trans.

Scott

Going to a 3.55 is going to cost money. Just put in the 3.08 and save the money for the 5 speed.

Going to a 3.55 is going to cost money. Just put in the 3.08 and save the money for the 5 speed.

I gotta agree with Freddie here.
Back in the days of cheap Ethyl (for those of you who don't know what that was, don't worry about it), 4.11 gears were routine, for ANY KIND of driving. But those days are long gone. A 3.08 or 2.73 is a much more economical choice if you're going to drive the car with any kind of regularity-----------------ESPECIALLY on the Interstate!
True, you won't have the pull out of the hole, but the choice is leaving strong out of the hole and screaming on the Interstate, OR, sacrificing some low end torque for acceptable rpm's during cruise on on the hiway.
Yes, another option is some kind of OD tranny, but that is going to be a considerable expense, PLUS the possibility of extra modifications to make everything compatable.
My vote is for a higher geared rearend and retain the stock type tranny. If your car has a healthy engine with plenty of low end torque, then leaving from a dead stop is usually no problem.
I have a healthy SB400 in the 70 with a 3.07 12bolt and wide ratio (M20) Muncie, and leaving from a stop is ZERO problem.
Also, I have a 2.73 12bolt posi waiting in the wings for a rebuild to go into the 70.

I agree with you guys " if he realistically can come up with the money "to do the 5spd conversion in the near future & it would be sa little wastefull to not use whats on hand if thats truely the case here

But i was comming from litterally a 100 times i have been at this stuff over the past 37+yrs when i was told by people for example something like ,yeh i am going to install an od trans in 6months-1yr so will be installing 4.11 gear now because i will be installing the od tran in near future that will reduce the 4.11 cruise rpm.

What happens when the day never comes which is often the case with these well meant plans,that person is left with too much 4.11 gear for reasonble street crusing.

I have found that over 1/2 the time i hear that type statement it never happens due to life getting in the way, money is short, or whatever the case is making the proposed upgrade never happen & the person is stuck with like in this example crappy 4.11 gear for the street for a much longer time then vere expected .

Thats why i suggested he spend the few hundred more $ now to go for gear thats a better comprise between perf & cruise rpm like 3.42-3.55 with his small mile perf 350sbc.

Then he will have a better performing car in for example this case if the proposed upgrade never happens untill yrs later then expected or maybe not at all while he owns the car,have seen that happen more time then not in cases like this example here.

I am just trying to get the poster to really think about the reality of achieving his 5spd conversion goal and or in what realisitc time frame before installing the 10 bolt which is still out of the car which isbest time for a gear swap if it wasg oing to be done,not after its in the car 2 yrs down the road when he realizes the 5spd covnversion isnt going to happen.

That was my point all aong.

Scott

I understand that. I've had that happen to me a few times. If it were me I would just take the 4.11 out of the 12 bolt and put in a 3.42 or 3.55 and use it instead of doing anything to the 10 bolt. The 5 speed would work well with either one of these gears too and there woudn't be any money wasted on the 10 bolt.

Freddie,way to go,now thats a best suggestion yet, but what else would i expect from an experienced pro like yourself./LOL!!!!!!

On 2nd thought what you just suggested is what i would do if i were him a this point.

Scott

I just threw in a 3.08 10 bolt rear, replacing a 4.11. Love the feel! Took 7 hours, but it was well worth it! Shame the days are so short in the North West...
Graham