Technical I just may have screwed up

Well I thought I scored a really sweet deal at a local junk yard today... I got a gm 12 bolt for $100 out of an A body for my 53 Chevy. I originally had planned to use an S 10 axle but only could find 54"ers no 4x4 axels. So as I was leaving and the owner of the junk yard pointed out the 12 bolt sitting on the ground and I thought to myself score, totally not needed (I'm planning on staying with the 235) but it was the right length and I told him I would take it. So I got it home and in my defense I will admit that I am not a axle guy, the axle is a type O 12 bolt with 2.56 gears.

So I need some help, will that high of gears work with my plan:

Original 235
T-5 out of an S 10
And not 2.56 gears

 

You may never use that 5th gear.

 

...I would think you need 3:50 gear or so...others will chime in.

 

You'll need a push car to get you moving but you should hit 150 mph.

Gobs of more low end torque from an engine for 256 gears.

 

on the other hand you can sell it to somene with a 350 turbo..........and then have more money for the 4 x 4 rear. I have bought whole S 10's cheaper that buying an axle at the boneyard, check your local ads and see if any are around cheap.................. good luck

 

For Sale......

 

Or 4th.

You need 3.73:1 gears.

Stovebolts do not like to be under-revved.

 

My stock 1980's S10 with a 4 banger and 5 speed has 4:11 gears.

 

2.56 rear gear plus 4.03 1st gear in an S-10 trans = 6.59 ratio. Same as a guy with a muncie close ration[2.20 first gear] and 4.40 rear gear. Not unreasonable for a 1st gear ratio and totally driveable in town but lets take a look at final gear ratio...
2.56 ratio with a .83 overdrive in 5th gear = 2.12 top gear [5th gear] ratio. That's do-able with a light car on the interstate with a "grunt" motor. The 235 in good condition would probably do fine on level ground and no/light wind with this ratio.
I ran a final ratio of 2.29 with 30 inch tall tires in a 3300 lb car with a 406 small block and a mild cam. Ran 16--1800 rpm on the freeway at cruising speed [no speedomeeter...guessing 70 mph] all day long. Had to drop a gear for hills.. but the 4.03 first gear ratio is your saving grace for "in town" driving.

 

I need a little education, what is the difference between an "O" & "C" type besides the cover ?

 

No big deal, just get the right gear set installed for your use. Stronger than the s-10 rear in case you ever get the itch for a big H/P engine.

 

I have always wanted to go to Bonneville speed week

 

Nope, you need a 4.10 gear maybe you can get by with a 3.73 but a 4.10 will suit you better.

His carrier will not carry the big ring gear required to get his gear low enough to use the 5 speed. I personally have never seen a 2.56 geared 12 bolt, but I guess it could have happened. Never the less it will need a different carrier to get his gears low enough to use the 5 speed.

 

Well from what info I have came across, the biggest difference between the two is the type "O" uses an 8.5" ring gear not the larger one from the "C" type. The axle shafts are also retained differently with plates not "C" clips. Apparently there more like a 10 bolt than a 12 bolt.

Just no one makes parts any more...

 

I can probably find parts for it if you get stuck drop me a note. Some of the parts may have to come from a different source that the normal avenues. Aside from gears what do you need?

 

FWIW 3.42 & 4.10 were common gear sets in the S trucks, depending on power combos. I'd look in that direction, gotta be thousands of 'em out there. Changing gears in that housing is a possibility. Probably require a spacer, then the gearset, installation kit, etc ($ adds up)...makes the S route in the desired gearing look a lot simpler. Of course you could use what you got as is, just drive around in 3rd gear.

 

I had a 2.56:1 gear in the 12-bolt, that was in my Chevelle.

It was great on the freeway. Of course it had a 4-speed, and 400-hp.

 

I see a trip to Bonneville in your future.

 

4.10:1 gears were a stock gear in the banger powered S-truck. I suggested the 3.73 option because the 235 won't rev like the S-10 banger. We ran a 235 with an S-10 5 speed and a 3.08, it got about 12 mpg on a good day and wouldn't run in 5th gear below about 80 mph.

The average rodder in todays world doesn't get it, with an OD if you want it to actually do what it is supposed to do you have to run a deeper gear then you do without one.

 

Yeah, just watch them try to wrap their heads around a 0.50:1 overdrive.

 

First gear would be 4.03 x 2.57 or 10.35 first.
Not bad but The s10 trans' first gear is a granny gear, watch what happens in 2nd
2.37 2nd 257 rear = 6.09 that's over a 40% change.
Second gear here is remarkably close to stock configuration 1st gear.

The 235 with powerglide had a 3.55 rear gear and the pg had 1.84 first.
1.84 first 355 rear = 6.53
1.00 x 3.55 = 3.55


Third gear of the S10 t5 is 1.49
1.49 3rd 2.56 rear = 3.81
Not too far off from stock in its final but a bit above stock here, so rpm and milage will be above also if you drive around in 3rd gear.

Forth gear is 1.0
1.0 fourth 2.57 rear = 2.57
Basically a 31% overdrive compared to the stock configuration.
There's another gear but I doubt the 235cu and 2.57 rear will ever make use of it under 100mph.

IMO that will drive and sound like a heavily weighted dump truck.
Winding 1st gear high to compensate for the 40% change coming in second gear.
Second and third will be usable but down in power or up on milage compared to stock.
4th gear for highway and required down shift for a head wind.

I wouldn't do it.
Maybe something like a nail head that has 450 ft lbs of torque at 2800 rpm.
Then 1st gear would be only for exhibition of 1000 ft long burn outs. Can you imagine 4500 ft lbs of torque at the axle
And 5th gear for bonneville. A leisurely 5000 rpm would put you at 202 mph with 30" tire.
Just a bit more than fast idle will but you at 65 mph

 

Aint no head wrappin to be done, they just think that if its OD its better. I don't really care for OD all that much, but if I have one and its geared right I am good with it.

I just hate to climb in a car with a 5 gear or an AOD and an airplane gear. In OD the car is running @ a little off idle @ about 10 MPH above legal and it won't pull itself at that speed because it hasn't started climbing up on the cam at idle.

 

Me nether Beano, but I did once have a 'Camino w/a 12bolt 2.73, pushed by an LT1. Not much outa the gate, but cruisin' triple digits was never a problem.

 

Yea we did a ponch-imino with a 2.73 gear back in the early '90s with a 2.73 gear. Actually it was originally an El Camino but the fella that owned it ran from St Jo to KC with a hyway patrol after him ( or so he thought) and we bolted the poncho front sheet metal that night. I think he imagined the hyway patrol because they own radios but I don't think that he imagined the triple digits, it took me half an hour to get ti his place and it was still poppin' and tickin when I got there.

 

Starting at the beginning helps.
The development of OD was to increase road speed.
2 speed rear axles do the same thing.
Once engines developed more power and more RPM, the OD trans or gear wasn't really needed.

Back in the anemic and smog requirements laden engines, the only to get them moving was to increase the rear gear leverage, however that decreased their road speed. Soooo enter the OD trans again best of both worlds. (What's old is new again )

 

And that's why my Falcon just got a 6-speed.

 

Friends right? You ought to put a cammer in that falcon.

 

On my budget?

It won't fit between the shock towers.

Frends, of course. I only have one enemy, and he is me.

 

Nobody has mentioned this, but isn't a 12 bolt a bit heavy for your application? Like 100+ lbs too heavy?

 

These were used in Oldsmobiles, and possibly Pontiacs. Hard to find parts for (and limited at that), 12 bolt cover, 10 bolt ring gear. One of GM's oddities of the time. I think you have spent $100 for scrap metal worth about $20. JMO, not ragging on you. If it was a "performance 12 bolt" from a Nova/Camaro/Chevelle, then it would have been a good score. The only thing good about the O-type, is the method of axle retension. Maybe a 442 owner would be interested in it. I am Butch/56sedandelivery.