gear ratio

[slim]

so can anyone tell me about what the difference is in gear ratios in a rear-end (top speed acceleration tire size etc.) I found a rear end with a 2.76? ratio

[phat69charger]

This is not a answer to your question but you can play around with this calculator and see some RPM and SPEED changes: http://users.erols.com/dmapes/GEARCLC.HTM

[morepower]

2.76 are gears that you would call highway gears..very friendly cruising down the interstate but lack great acceleration.

But if you had a set of 4.10 gears driving down interstates would be a pain in thebutt, motor revving way to much for the speed but at those stoplights...watch out

Of course thier are lower gears numerically higher, and higher gears numerically lower and all in between..To decide which gears are best for you, you really need to decidewhat your car is really going to be. A daily driver, a weekend cruiser, is it goin on long trips? Is it mainly going to the grocery store down teh street? Thier are ways to have the best of both worlds with an overdrive transmission also.

[Ghoste]

Your highway gear means the engine is turning fewer rpm (in this case 2.76) to turn the wheels one revolution.  This, as mentioned, is good for cruising economy or top end speed.  A ratio such as a 4.10 is going to take more turns of the engine to turn the wheel once but in terms of acceleration, it will allow the engine to reach it's powerband more quickly (because it has to turn that many more times to accomplish the same thing).  Reaching the powerband more quickly, naturally allows the engine to perform more work within a specific timeframe.  It becomes a point of diminishing returns thing as inertia overhwhelms the resisitance to move.  There are more physics at work there, but I think you get the basics.
If you have played with the posted calculator, you should be able to see how a change in wheel diameter alters the rpm needed to turn the wheel once.

[motoreese]

I have a 69 charger, with a 383ci engine, with a brand new Edlebrock 750 carb,  A727 tranny, I believe in has 3:23 gears and 275/60R15 CooperCobra GT tires. I cannot spin tires...is it the gear ratio that is hurting me or is my engine not powerful enough? The car runs great now that I've fixed all the tiny issues with her.  The tires are brand new so they have great tread but with a 383 I thought I should be able to roast them. Are 3:23 gears too high? Itis mainly for everyday driving but it would be nice to roast them if the time ever presented itself...lol

This is my first muscle car I've owed I've always been into big trucks.
Thanks

[Cooter]

so can anyone tell me about what the difference is in gear ratios in a rear-end (top speed acceleration tire size etc.) I found a rear end with a 2.76? ratio

With a 26-27" tall tire, the "2.76:1" means your engine turns 2.76 turns to ONE revolution of your tire.
4.10:1 would mean engine turns 4.1 turns to ONE TURN of rear tire.

You say you always been into big trucks? Ok...
I know you've seen this one before. Big ole jacked up truck, 44" Swappers, and stock 3.08 gears.....

[Ghoste]

Motorease, the 383 is not a high torque monster to begin with so with that rearend ratio and those big tires it is no surprise.  If the engine is a high mileage one and its bone stock but for that carb then it also will hurt your low end.

[motoreese]

Ok, now you put it in my terms. Yes 44's on a stock truck I get it. Next dumb question then can I get an over drive put into my A727 tranny? I'd then be able to chirp them while not killing the gas milage. I know we don't own muscle cars to worry about gas.....yes I kinda do. I would like to get the optimum power with the best gas milage if possible if not oh well.

[1974dodgecharger]

Looks like u want best of both worlds get. 3.23

[Ghoste]

There are kits to add an overdrive automatic to the car or a bolt on unit to go behind it.

[Cooter]

Ok, now you put it in my terms. Yes 44's on a stock truck I get it. Next dumb question then can I get an over drive put into my A727 tranny? I'd then be able to chirp them while not killing the gas milage. I know we don't own muscle cars to worry about gas.....yes I kinda do. I would like to get the optimum power with the best gas milage if possible if not oh well.

to put it in terms you can understand, how many 700R4's you see live with an OD and 44's?
OD have spoiled folks today. I had a guy come in the shop yesterday and ask me about his 1940 Chevy truck he's building with a 502 BBC. He asked about an OD trans. First thing I asked was how much cam? His reply: "a big un"
I needed specs as he also wanted to run a stall. Finally, about 3:00 yesterday, he comes by with the specs on motor and rearend gears.
cam is like a 260 @.050 and .640 lift. Wants to run OD to just keep R's down on highway. Mpg wasn't a concern.
with that much cam, I recommend 4.10 gear.

[motoreese]

I don't think were rather I don't know if my 383 has a cam and it or not. So you're saying it's ridiculous to put an overdrive and a 727 transmission? I too would like to keep the RPMs down but I believe I have 3:23 gears in the rear end.

[1974dodgecharger]

I don't think were rather I don't know if my 383 has a cam and it or not. So you're saying it's ridiculous to put an overdrive and a 727 transmission? I too would like to keep the RPMs down but I believe I have 3:23 gears in the rear end.

Depends on finances my man how much u want to spend.  4k will save u 300 rpms per gear it seems with overdrive unit.

[Cooter]

A 3.23 overdriven even with a 440 will be a dog below 85 mph.

[motoreese]

Is it worth putting a 4 speed in it? Or is that a costly conversion?

BTW...you guys have some really nice machines.

[Troy]

What's you're budget? Even cutting corners a full 4-speed swap will be $1,500. Buying a complete "kit" will put you over $4,000. I wouldn't run an OD with 3.23 gears. Actually, I don't! Especially if your tires are larger than stock. A 3.23 rear gear with 275/60-15 tires (very common for a Charger) has an "effective" ratio of just over 3.00. My Six Pack Challenger will cruise at 70 mph all day with this setup. Your 383 will rev a bit higher than a 440 so I wouldn't bother changing anything.

A 2.76 rear gear - specifically with large rear tires - will suck for just about everything but highway driving. I had a chart that I made (and a calculator to put on the site) but I don't have anything publicly viewable. Sounds like a project to tackle sooner rather than later.

Troy

[Cooter]

Is it worth putting a 4 speed in it? Or is that a costly conversion?

BTW...you guys have some really nice machines.

do search here on Vibrating and Overdrive. Loads of info to ponder.

[motoreese]

I got my charger in October 2013, so I'm rather new in the muscle car world. This is my first mopar so figuring out all the hiccups and corks are still new to me.
I've only ever owned Chevrolet 4x4's so I am pretty good in that department. I knew there would be growing pains, I was so glad to find this site, and to pick everyone's brains. It's great to find out so much knowledge out there. Plus I've been out of the "working on cars" game for many years. Now to brush the dust out of the old noggin' and get this girl running like she deserves. It's such an amazing car!
I love that saying "my girlfriend said she goes or the car goes, gosh I'll miss her!"

So I'm going to attempt a B&M ratchet shifter installation. I'd love to put a 4 speed in her but that'll have to wait. Military retirement and disability checks aren't as lucrative as some are to believe.

[XH29N0G]

Is it worth putting a 4 speed in it? Or is that a costly conversion?

BTW...you guys have some really nice machines.

do search here on Vibrating and Overdrive. Loads of info to ponder.

Cooter has a good point.  Things spin faster with an overdrive and low gears, which means you can get all sorts of vibrations.  If you search, you will find this is a problem I ran into.  Fortunately it was solved, but it made me appreciate that there can be a higher likelihood of issues when making certain changes.  I ran an OD transmission with at 3.23 (late 70's 4 speed van transmission).  The OD let me get good mileage on long hauls 16-20 mpg, so I liked it, but I don't think it was anywhere near an ideal transmission.  I would pay attention to the cost estimates from others. I think those are realistic.

[Cooter]

Thanks for your service brutha.

[motoreese]

I found a guy selling his A833 4 speed, linkage and shifter for $450 obo
I prefer manual tranny and yes hopefully the OD will help with Mileage. Hopefully we can work a deal.

You're very welcome, I loved my military service. It's great to know we are appreciated, so I thank you for your support.

[Cooter]

I've never really had a huge problem with 10-12 mpg and a big block. Tune your motor for mileage and you might be surprised.
problem with a four speed car as you will be in single digits for a while. Rear tires will get costly as well.
a straight drive will get better fuel mileage than an auto.

Converting isn't so bad as long as you can buy a little at a time.

An OD round town won't do as well on mileage as on the interstate.

[c00nhunterjoe]

I found a guy selling his A833 4 speed, linkage and shifter for $450 obo
I prefer manual tranny and yes hopefully the OD will help with Mileage. Hopefully we can work a deal.

You're very welcome, I loved my military service. It's great to know we are appreciated, so I thank you for your support.

Im hoping i am just interpreting that wrong but i read that as you thinking the 4 speed is an overdrive trans. Its not but i still say to do the swap. Its soooooooo much more fun. Mine is a 383 4 speed.

[motoreese]

I was told the 4th gear is the over drive and 3rd ratio was 1:1. Yes I agree, stick is definitely more fun to drive and I'm sure the first few days I'll be burning gas and tires lol.
That's the future project tho, right now I'm installing a B&M ratchet shifter. It's a lot more than I thought it would be but so far so good. I'm about to spot weld the bottom plate onto the floorboard that I bolt the shifter too.
Has anyone ever done this? I have tried shifting with the engine off but it won't go further than DRIVE. Can't get it into 2nd or 1st. I'm using a 4 foot cable instead of the 5 foot cable. I read somewhere that a guy had better luck with the 4foot cable.

ANY advice? Words of wisdom?

[c00nhunterjoe]

There is a 4 speed that is an overdrive. Usually an aluminum case gives it away.
The ratchet shifter reauires an adapter plate bolted to the pan, a different length shift lever, and the cable adjusted with the trans in 1st gear.