gruveb

I was just wondering if anybody runs 4.10 gears. How does it affect mileage and performance?

Did you use the same rearend or go with something bigger?

jcb999

mileage.. not too much of a concern for me.
But, the overdrive puts it at about 2500 at close to 70.

I found a 7.5" on ebay for 400 bucks. It had an auburn, gm motive gears and about 5000 miles. So far has held up ok.

Mark A Shields

@70mph I'm @ 2500rpms with 3:73s.

One thing to remember, your gears have to be matched to the rest of your powerband, this is critical, as I found out the hard way. I went from 2:73s to 3:73s and didn't gain anything in the 1/4 cause of my cam. Not sure if you knew this or not, just wanted to say in case you didn't so you don't make the same mistake I did.

Oh, I didn't notice any mpg loss either.

gruveb

Well I have 3.73 gears right now. I have a Comp Cams XE-262H-10 in there right now. I don't know if 4.10 gears would do any good with this cam or not....would anybody know.

jcb999

I would say u would need something closer to XE274.

Black 84 Z

I would think that the 3.73's would be good with that cam. I doubt that mileage would drop off much, if at all. On the flip side, performance would prolly not increase a great deal either. i think your money may be better spent beefing up your current rear-end. 7.5" ten bolts are not known for excessive strength.

DG

Mark A Shields

I'm not sure but with that cam, I think even the 3:73s are too much, a XE268 has power up to 5600 rpms which is about perfect with 3:73s, like said you would need a bigger cam with 4:10

cp87GTA

If you're already running 373s, 410s shouldn't be much differance on fuel consumsion. I'm doing the switch right now myself. I'm running the xe268 cam, should have went bigger. I've even thought about trying some 456 gears, maybe later this summer.

86TpiTransAm

My friend went from 2.73s to 3.73s with a 262H or 268H cam and he said it made a world of difference for him. I would say what you have would probably be your best bet with that cam.

FWIW, lower ratio (numerically higher) gearing won't hurt your gas mileage much if at all. One of the reasons for this is that the engine doesn't have to work so hard to move the car when the ratio is lower like that.

Tom84L69

i'm switching to a 4.10 when i get the money. my 3.73 finally broke. i was happy with the 3.73 but i'm looking forward to a 4.10. what are the cam pecs for xe268, 274,252 etc? these numbers mean nothing to me.

jcb999

http://www.compcams.com/catalog/056_057.html

Mark A Shields

Look in the Jegs catalog, those 4:10 are going to hurt you with a 268 cam, it stops power past 5600 rpms.

cp87GTA

Comp cams site says 1600 to 5800 on the xe268. What does gears have to do with rpm on a street motor anyways? All the rear gears do, is multiply the the power. Now if you're talking about a strip car, you want to be hitting the traps at the top of the power range of the cam. In 1970 I was running a 69 Camaro SS in the 1/8 mile with 513s in the back. My buddy was running a nova with 292 and 617s out back. You just gotta shift quicker.

Tom84L69

i don't have a "268." my cam is in my sig and makes power to over 6000. 4.10 will help, it's only logical.

gruveb

Now this doesn't quite make sense to me......

bigger cam usually means more power in higher rpm's.

larger gears makes the engine wrap out more quickly (essentially...)

And I can see how a larger gear can help take advantage of a large cam's power range...however, I don't see how a set of larger gears would hurt you.

How could that happen. Keeping the engine in the optimum power range is the key to making it go faster....So even with the cam I have (262) I would still reach the real power more quickly than with the 3.73 gears, right?

I would perhaps have to shift sooner than I do now, not according to engine speed, but actual vehicle speed right?

I obviously need further explination on the subject.

Mark A Shields

Not sure if this will answer it for you, sure you may be able to shift sooner, but will you still be passing the 1/4 mark above your powerband.
I know right now, my cam stops making power past 3500rpms which is worse than yours, but if I say shift at that point I still run out of power by 3rd gear, cause shifting that early I just bang thru the gears real quick.

gruveb

I guess this is what doesn't quite make sense to me. Maybe I'm comparing apples and oranges here....

In a truck or a 4x4 you want taller gears to pull a trailer or to get unstuck...whatever. 4.10 gears ( I think are what are in my Bronco). It's a 351 small block, factory....makes all it's power below 3000 rpm. Now it's NOT fast, but it weights over 5000 lbs and is very tall.

The taller gears allow me to reach my power sooner.......

So my understanding is that a set of 4.10 gears would make you quicker than 3.73 gears while perhaps lowering maximum speed....but how often do you go max speed? (I've never gone over 120).

I can't quite see why 4.10 gears would be slower than 3.73 gears...I just can't figure it out yet....I'm not doubting what you're saying Mark, but could you explain just a little further for my education....

rx7speed

the taller gears in general will not really make you have a loss of power so to speak

but if you are going in a 1/4 mile race
since each shift will go over less distance you might end up using your OD
that is a big no no in racing
even if you have lots of gear

so in a street race it will help lots
but in the 1/4 you might be using that nasty OD to help you out

gruveb

Well I'm not doing much, if any quartermile racing, and not really any street racing. What I love to do is going on canyon roads and just tear them up!

So for that type of thing 4.10 gears would be a good application?

Mark A Shields

Canyon roads, as in long stretches of highway?, meaning top speed, 2:73s would be best for that.

jdhommert

If you have say 2.73 gears and you go to 3.45 or 3.54, or even 3.73 gears, by how many mph would your top speed be limited? I have always wondered this.

cp87GTA

A lower gear ratio WILL produce a quicker 60 ft. time provided you have the engine to do it. Mark clearly has done his mods backwards. You can't just change to a much lower gear ratio if you don't have the power to pull it. IF you have an engine capable of say 6000 rpm, the lower gear will be a benefit. Lower gears also make for traction problems. I'll say it AGAIN, rpm at the traps is what you're after. My engine pulls real good at 6000 rpm, even though comp cams say 5800. SO I want to be turning 5800 to 6000 at the lights, 1/8 mile. Only track around here. I'm figuring I'll be at the top of 2nd gear going through the lights.

Mark A Shields

Yep, I went from 2:73s to 3:73s and didn't gain anything in the 1/4, it knocked off a little from the 0-60 time, but at higher rpms the cam doesn't make the power to push me along. That's why I plan on a cam swap, but when I get it, watch out, probably feel like a new car.

Tom84L69

mark, i don't understand this, if your engine makes very little power, it is best to multiply that power through larger numerical gears. a 2.73 vs. a 3.73 shouldn't even be a contest, the 3.73 should accelerate better. Why would gm offer a performance axle that is numerically higher than standard?

now there is no way any stock or mildly modified fbod will ever need overdrive in a 1/4 mile race, even with a 4.10. It should be faster than with a 3.73 and much faster than a 2.73, mark's experience aside. Mark, maybe your car isn't running right because it should be quicker with 3.73s.

Trucks use high numerical gears to grunt things like trailers out of the hole and to offset the large tire diameters they usually run.

Cams in our thirdgens at the worst stop making power at like 4000 rpms (ie LG4), not 3500 rpms, even diesels can spin that high.

I would recommend 3.73s to anyone with an overdrive and a 4.10 to most any non daily driven car. With a 3.73, my car topped out at 148 (i've done it) at 5000 rpms in fifth gear.

Fuel economy also doesn't always suffer from higher numerical gearing (mark, i think you talked about this in another post).

No offense meant here, just telling it how i understand it and have learned it from my knowledgable elders(engineers).

Mark A Shields

My situation makes perfect sense no matter how you look at it. Sure my 0-60 time increased but that's it.
If you have lower gears they'll make you run at a higher rpm and that's a given, well if you don't have power at high rpms then you're going to lose time. You want your gears to keep you in your powerband.
And don't recommend gears to everyone, say you have 3:73s and you cross the 1/4 line at 5300 rpms, well a stock TPI peaks at 4500 rpms, so you're wasting time.
I wish some of the experts could chime in, I'm not the best to describe this.
Just PM, RB83LB9 or five7kid, Vader . Maybe they can touch on this.

RICHRAD

Shouldn't torque convertors be brought up about NOW!

Mark A Shields

Here's my numbers on the G-Tech
w/ 2:73s and a burnt plug wire 15.41 @ 93mph
w/ 3:73 posi, new wires and Hooker cat-back 15.32 @ 95mph

LilJayV10

iTrader: (5)

i dont know if its been said yet or not, and i might be wrong, but you can over gear your car. for example, if your cars hp peak is at 4500, like a stock 305TBI car, IMO 4.10s would be a bad idea because you dont have the powerband, nor the rpms to support that much gear. the 4.10's wouldnt keep you where the engine is making power, it would go past it. now if your car make power at say 6500, and needed more gear to get to that rpm, and make up for the lost tourqe, yes deeper gears, 3.73's/4.10 would be good. typically, if you have more hp and rpms, and less tourqe, deeper gears will help, but if you are running at a lower rpm with more tourqe, its better to run a higher gear, 3.23 and so on. thats why you see ponitac 455's and BBC running 3.23 and 3.42 gears because they have enough tourqe that they dont need gear, and also a deeper gear would pull the engine out of its low rpm power band and would be counter productive. these are just my thoughts, if i am wrong please some one let me know, i hate being ignorant to things. later. lil jay

LilJayV10

iTrader: (5)

an example to follow up my previous post, on the motor swap board i think, mike crews has an awesome awesome 383 TPI car that runs mid 12's. he said his problem was high rpm horsepower, and that he was in the process of finding more. he also said that he went from a 3.70 to a 3.27 rear gear, his 60 fts didnt change but he picked up a solid 2mph in the trap speed. the deeper gear was "over revving" his engine at the top end if you will, and pulling it out of where the engine made its power, thats why he picked up a higher trap speed with the 3.27 because the engine is staying in its power band longer and pushing the car faster down the track . obvioulsy he has enough tourqe to make up for the less gear hence no change in his 60's. again, this is only my obersvation, in no way am i trying to take his information, or mis use it, if i am wrong on anything of his please correct me, i am just trying to use his case an example. again his car is sweet. :hail: :hail:

rx7speed

on my second gen camamro I had 4.10 gears
driving on the freeway was hell with the TH350
if I ever was to 1/4 mile the thing I wouldn't be shocked if I was to overrev the motor b/c of too much gear

top speed was around 90-95 mph or so

now on my rx-7 I have 4.10 STOCK and I can hit 120 in 4th at a 1:1 ratio.

but I have the revs to back it up also

nesluopetan

the reason im doing 4.10's in my 3sp is because i want to win light to light races.. now days most people race for only a block or so, which is not as long as a 1/4. im sorry to say, but our cars are getting beat by these new imports, and thats why I am building my 4.10 posi, because now days races evolve from light to light, and i do not use my car as a daily driver.. is there really a big diff between 3.73 and 4.10 anyways? a huge noticable diff? thats my reason for installing 4.10's

nate

RB83L69

What happens with too much gear for the engine's RPM range, is that the RPMs build up quickly to the point where the engine is no longer producing power, so the car doesn't continue to speed up no matter how long you keep your foot on the floor. You get into a situation where the car has a terrific jump off the line, but by the time the transmission's logic tells it that it's time to shift, the engine has fallen off the cliff, and it's just hanging at some RPM where it has ceased to push the car.

Ideally, you choose a gear to match the engine's peak output RPM range, such that the car goes through the lights in high gear at the engine's peak HP RPM, the torque converter stalls at just below the engine's peak torque, you shift at or just below peak HP, and after you shift, it's back at the peak torque RPM.

Obviously the "perfect" gear depends on what you intend to do with the car. Like one of the other posts said, if you are interested in very short bursts of power at low speeds, then a high gear might work. That's why the serious racers might run 4.10 or 4.56 gears on a 1/4 mile track, but switch to 4.56 or 5.13 on a 1/8 mile. The NASCAR guys run 5.33s and such at Martinsville where they only do 120 MPH at 9000 RPM down the straights and 5500 at 60 MPH around the corners; but then they switch to low 3s at Talladega and Daytona where they're doing 190 MPH non-stop with restrictor plates at 6600 RPM.

I recall someone once for whom we built a 429 SCJ (the only F*rd motor I know of to come from the factory with a Q-Jet!!! I guess if you want a F*rd to go fast, you put GM parts on it); it came with 3.30 gears IIRC, and of course a C-6. We put a Comp 268 cam in it, got rid of the stupid F*rd rocker crap and put some Comp big block Chevy steel roller tip rockers on it, rebuilt the Q-Jet, put a set of some kind of headers on it, and put some kind of a TCI off-the-shelf converter in it. His very first pass down one of the local 1/8 miles he pulled a 8.80 something, where the pro classes started at 8.60. The he had somebody else put 4.56s in it (against our advice), and lost over a tenth. He finally blew up the motor over-revving it. It never again went as fast as it had with the stock gears.

gruveb

When I get on it, I shift at about 5,500 rpm....And I've taken it to 6k a few times.

I don't have TPI or TBI, I have a carbed 305. Before I decide to do anything I'm going to finish my exhaust and see how I like the overall performance.

How much faster will 4.10 gears make my engine max out than the 3.73's do?

I've got a 5 speed, (and pie in the sky is an eventual 6 speed). Like I said before, I'm not too worried about 1/4 mile times. 0-60 mph times are more important to me and for my application. Now where I live I have to do a bit of highway travel to go anywhere, but with the 5 speed I think that should be fine.

So would a 4.10 swap be a good swap? I've never done a gear change before. I see that Jegs sells a kit for about 300 bucks or so...contains everything you need...good deal?

The other thing is that I'm not jumping from 3.23 gears to 4.10 gears....I've already got 3.73 gears, so it's not that huge of a jump. Will I see that much of a difference, will it be worth the work and cash?

Tom84L69

probably not worth the cash to do it.

If you have a stick shift, you don't have to wait for the transmission's "logic" as stated by RB83L69. now where is the argument about keeping the engine in the powerband? You shift the car when rpms hit redline or peak hp rpm, and if the engine gets to rev quicker due to higher numerical gears, the car is going faster!!

I guess i never thought of the automatic problem because my car is a manual and that's how i think. For Gruveb with his 5 speed, the gears would help him, i just don't think it's worth the money to upgrade from 3.73s unless something is broken.

Mark A Shields

The problem still exists with a stick, if you have 4:10 and your car stops producing power past 5000 let's say, you're going to have to shift into 4th early and you'll be past 5,000 before you cross the line (causing you to be slower), that is if you're only interested in 1/4, but 0-60 then it's ok.

cp87GTA

You won't see much differance between the two gear sets. If you don't have anything wrong with the 373s, then you'd be wasting your cash. Just my 02 though. Only reason I went to 4.10s from the 373s is I'm rebuilding the complete rearend, everything is new except the housing. This thread has all examples of why deeper gears should or shouldn't be used. We went from your 305 to pontiac 455s. Comparring a 305 and 455 is like comparring a dog and a cat. WHEN you tear up those 373s, 410s would be a good gear as a replacement. I'd spend the money where you need it most, not the gears at this point.

LilJayV10

iTrader: (5)

when i was comparing dogs to cats, i was trying to explain the difference tourqe makes and powerbands and ahh hell nevermind