How big of a difference between 3:73 and 4:10 gears?

[Painter D]

So I currently have 4:10's in my truck , and I'm almost done with my 502BBC motor swap and I'm thinking I don't need that low of a gear in the rearend anymore. I would prefer something in the range of 3:55's or so ,"but" and this is a big but since I have 4:10's the highest gear the Auburn posi unit will allow is a 3:73. If I want to go any higher than that I have to get a different carrier (posi unit) which increases the price of things dramatically.



So my question is:

Is it worth to spend a "little" cash to swap from 4:10's to 3:73's? Is it that big of a difference?

Or am I stuck spending "alot" of cash on a different carrier and gears if I want to go higher than 3:73's?

[Zoomin]

Maybe you can find someone with a small block that would want to swap. I wouldn't think the 3:73's will help much at all with a 502...

[btullis99]

what trans are you running? i'm running 4.10's with a 700r4. first gear doesn't last long. i debated on and on between 3.73 and 4.10's. before i made the posi swap, i worked out all the math on cruise rpm at 65mph and shift mph at 6000 rpm between the 2 and settled on 4.10's. but to answer the question, "whats the difference?", about 10 percent. i wouldn't change them. if you drive it and don't like it, change em up.

[special-K]

You could find a taller rear for cheap and put the Auburn in that.But,3.08s are probably too tall.I think 3.42s would be more what you`d want.They are a bit leggy yet still have grunt.4.10s and 3.73s are pretty close,about 1/4 turn,then 3.08s are a full turn different.

[Fitz]

Originally Posted by 69chevyshort

So my question is:

Is it worth to spend a "little" cash to swap from 4:10's to 3:73's? Is it that big of a difference?

Or am I stuck spending "alot" of cash on a different carrier and gears if I want to go higher than 3:73's?

The 502 probably has enough torque to take advantage of the lower gears but the difference is so small unless you are bracket racing and your suspnsion/tire combination is dialed in perfectly you will never see the difference. If your shift point is 6000 rpm the speeds in mph for both rears are below:

Trans700R..1st..2nd..3rd...4th
4.10..........44....82...130...192
3.73..........49....92...150...213
Not a lot of difference between the two, but i would stay with the 4.10 rear.


When I built my truck I was trying to balance the better launch with the 4.10 rear with lower RPM on my morning commute so I went with a 4.10 rear driven by a turbo 400 running through a Gear Vendors overdrive
.............1st....1st over....2nd....2nd over.....3rd....3rd over
4.10........52.....77............91......130...........134....192

it should be clear from the numbers that the overdrive makes the 4.10 look like a 3.73 but demands much more torque. Since I'm running a ZZ572 with about 650 ft lbs @ 3000 rpm I really don't care about torque as long as the tires bite. If they don't the truck will roast them.

And at 75 on the freeway the beast is ticking over at 2300 rpm

[Hart_Rod]

I'm going to do the opposite - 3.73s to 4.10s. Wanna swap rearends?

[Fitz]

Originally Posted by Hart_Rod

I'm going to do the opposite - 3.73s to 4.10s. Wanna swap rearends?

SuperBurb...Wanna run that thang?

[Ackattack]

I'd say keep the 4:10s and put that money towards an OD tranny.

[Hart_Rod]

Originally Posted by Fitz

SuperBurb...Wanna run that thang?

Soon enough....... I was actually thinking of changing the gears in the 68 S/C truck...

Originally Posted by Ackattack

I'd say keep the 4:10s and put that money towards an OD tranny.

+1

[shawn57nomad]

Call Randy's R&P and ask them about the thick and thin ring and pinions that yukon has. A buddy of mine installed a few sets for guys in the same situation. Also you could just save your money for a Gear Vendor OD unit and have a six speed automatic! Three forward gears all with/without Overdrive...... greatest thing since sliced bread! 2 cents

[prostreetC-10]

The change from a 3.73 to a 4.10 is not nearly as dramatic as going from 3.08 to say 3.31. The lower the gears are, the less you notice the change. It's surprising that although the number jump is big from 4.10 to 4.88, the acutal in the pant diff is not as much as you would think.

Just so you know, a BBC (especially a 502) doesn't need the gearing like a small block. You can run a 3.31 or 3.42 behind that and still scoot big time. The SB muscle cars all had the 3.73 plus gears in most just because the power curve of a SBC VS a BBC. I'd love to ditch the 3.73's I have for 3.42 or 3.31 so I can actually go down the highway. If they ever blow (and there's a good chance the way I drive) I will not go back to 3.73's.

[Painter D]

Originally Posted by Hart_Rod

I'm going to do the opposite - 3.73s to 4.10s. Wanna swap rearends?

Possibly




Thanks for the info guys. I guess I should have been more descriptive in my first post, I'm running a 700R4 trans., and my rear tire is 29" tall. If I remember right I'm turning 2400 or so R.P.M. at 70 mph. All I'm really wanting to do is bring the rpm's down some since I do actually drive this truck quite a bit on the highway. From reading all the above posts it sounds like it might not be worth changing..

[Painter D]

Oh yeah, and getting a taller rear tire isn't an option. Tires that fit 20"X12" wide rims aren't cheap.