rt 440 8 3/4 diff gears

[ozchargerguy]

just bout to buy set of diff gears thinkin of 3.73 has any1 used motive gears?

how bout this ratio is it ok for street driving too iv got 3.23 in it now its a 440

any ideas boys......

[elacruze]

I've had 2.73s and 4.10 (now) in the Charger and 3.55s in my pickup. 4.10 will make you sweat on the highway, although millions of motorhomes have made millions of miles winding up high. I just drove my 3.55s 400 miles to the Don Garlits Museum show this weekend and running ~70mph never gave it a thought although an overdrive would certainly be useful.

IMO 3.73 is the wrong gear-I'd go with 3.55 straight or 4.10 with  overdrive, if you do any regular highway work. If you care more about the open road than around town/drag racing, 3.55 with overdrive is what I'm taking on the Power Tour and Rte. 66 trips.

YMMV. Remember that big engines and street tires can use a lot higher gears than small engines on slicks.

[Troy]

Some background info: I have 28" tall tires on all my cars.

To be honest, I'm most comfortable with 3.23 gears. I've had 3.91s and you really can't do a lot of highway driving like I do. I think 4.10s would be nearly useless on the street. I've also had 2.76s and they are awesome on the highway but the car is tough to get moving - especially with a clutch! The 3.23s allow me to cruise at a reasonable speed without running high RPM and drinking too much fuel. I think that 3.55s would bump the RPM just a little too much for my taste at the highway speeds that I run (73-78 mph) - and I'm not going to slow down. If you're more excited about tearing up the pavement between stoplights and only make short trips then 3.55 and up would be better. If you never test the acceleration but spend a lot of time on the road then go the other way.

Troy

[ozchargerguy]

Some background info: I have 28" tall tires on all my cars.

To be honest, I'm most comfortable with 3.23 gears. I've had 3.91s and you really can't do a lot of highway driving like I do. I think 4.10s would be nearly useless on the street. I've also had 2.76s and they are awesome on the highway but the car is tough to get moving - especially with a clutch! The 3.23s allow me to cruise at a reasonable speed without running high RPM and drinking too much fuel. I think that 3.55s would bump the RPM just a little too much for my taste at the highway speeds that I run (73-78 mph) - and I'm not going to slow down. If you're more excited about tearing up the pavement between stoplights and only make short trips then 3.55 and up would be better. If you never test the acceleration but spend a lot of time on the road then go the other way.

Troy

cheers buddy thanks for the advice

[ozchargerguy]

I've had 2.73s and 4.10 (now) in the Charger and 3.55s in my pickup. 4.10 will make you sweat on the highway, although millions of motorhomes have made millions of miles winding up high. I just drove my 3.55s 400 miles to the Don Garlits Museum show this weekend and running ~70mph never gave it a thought although an overdrive would certainly be useful.

IMO 3.73 is the wrong gear-I'd go with 3.55 straight or 4.10 with  overdrive, if you do any regular highway work. If you care more about the open road than around town/drag racing, 3.55 with overdrive is what I'm taking on the Power Tour and Rte. 66 trips.

YMMV. Remember that big engines and street tires can use a lot higher gears than small engines on slicks.

cheers buddy thanks.....

[charger Downunder]

I am for 3.23s a good street ratio.

[Brass]

You might want to save yourself the hassle and stick with the 3.23.  I keep tempting myself to switch to a lower gear for more torque multiplication but my car sees a lot of highway time.  For that reason, I love the 3.23.  Longer legs and good mid-range pull.  No slouch off the line either.  It's a great, all-around gear to have on the street. 

[sixty8charger]

hmmm... i have 3.91... havn't installed the diff yet... but then again i havn't installed the motor either.  is 3.91 a good ratio for the street or is it just too much?  right now i have the stock 7.41 case with probaly 2.70something gears... (original gears that was for the 318)... but they are not sure grip.

[mikesbbody]

I have 3.55's in mine I don't do many Highway miles and when I do, it doesn't bother me.
I drove a similar Charger with 3.23's what a difference! (not in a good way either IMO)
I have a 3.9 sure grip all ready to go with my 28 inch tire on the back if I drove more Highway
Miles, I wouldn't use it so IMO 3.5's are better than 3.23's the choice is yours   

[b5blue]

3.23 here and keep in mind to consider your whole engine set up, and your driving habits/style, and use. If you mostly "cruise" and/or do road trips with lots of miles the 3.23 is nice. If every light is a chance to chirp the tires and bang the gears go lower. 

[doctor4766]

I'm about to swap out my 2.76 to a 3.23.
I do a lot of highway driving on our club runs, but like Troy said it's tough to get moving but great for long distance cruising with the 2.76 ratio.
Just this weekend we took a spin down south with the club. I sat on 2000 rpm at 62mph (100kmh) for 200 miles and the temp sat at a steady 180 all the way.
Having never ever changed a diff ratio in any of my cars it will be very interesting to see the difference it makes off the mark.
I've been told that with my camshaft and new gear ratio combo that even @ 100kmh if my revs go up to 2400 the engine will be running more efficiently and may even be better on fuel.
Can't wait to try it out.

[adauto]

I am for 3.23s a good street ratio.

Agreed! I'm at about 2800RPM on the freeway... As long as I keep my foot out of it the milage is not any worse than any of the pickups i've had!

[doctor4766]

I am for 3.23s a good street ratio.

Agreed! I'm at about 2800RPM on the freeway... As long as I keep my foot out of it the milage is not any worse than any of the pickups i've had!

What is your freeway speed?

[mikesbbody]

Maybe this will help    http://vexer.com/automotive-tools/speed-rpm-calculator

[doctor4766]

Yeah I've seen that but there's no 2.76 to check that against my current speed and rpm.
Thanks just the same.

[tan top]

Yeah I've seen that but there's no 2.76 to check that against my current speed and rpm.
Thanks just the same.

you can change the ratio on that chart ,  just delete  whats ever in box & type in the ratio you want ! 

[doctor4766]

Wow that's cool.
It appears to be correct for my current setup.
So at 100k's I'll only be doing around 2500rpm 

[tan top]

    remember to select  your rear tire hight /size

[adauto]

I am for 3.23s a good street ratio.

Agreed! I'm at about 2800RPM on the freeway... As long as I keep my foot out of it the milage is not any worse than any of the pickups i've had!

What is your freeway speed?

65 MPH @ (about) 2800 RPM   275/60/15 BFG's on the rear

[Wicked72]

Im going with 3.91 since im most likely going with a 6spd. But 3.23 would be fine and 3.55 for some more grunt. 

[SFRT]

since I am 'special needs' I run 4.56 gears. its fun.

[hemi-hampton]

I had a 4:56 in mine but switched to a more streetable 3:91. I don't take long trips on the highway anyways. LEON.

[TK73]

3.55

275/60/15    28" tall

I like   

[greenpigs]

4.10 & I will take a back road before attempting highway speeds, been there @ 3500 RPM to keep up with traffic. NO THANKS!

[tan top]

 sure griped   2:94
255/60/15

for me  

[Long Island RT]

This is probably why I was not going to rebuild my car unless I could afford an Overdrive.
The Tremec is probably the best thing I did.

Imagine cruising the side roads and stop and goes with 4:11 4 speed. 
Then get on the highway and slap in into 5th - 2050 rpm @ 65mph and at 75mph only @ 2400rpm!   

[Brass]

Of course a Gear-Vendors unit would be great too.

[Wicked72]

from what ive heard the gear vendors isnt all that great. But thats coming from rival trans companies.  So you gotta 5spd with 4.11s and only running 2050rpm at that spd? imagine a 6 spd which is what im looking at...maybe ill go with a 4.11 instead of 3.91

[Long Island RT]

from what ive heard the gear vendors isnt all that great. But thats coming from rival trans companies.  So you gotta 5spd with 4.11s and only running 2050rpm at that spd? imagine a 6 spd which is what im looking at...maybe ill go with a 4.11 instead of 3.91

That depends on what the overdrive ratio is on your final gear.

What are the ratios on that 6speed?

[Wicked72]

Ill have to check. I am currently looking at a T56 with a bit of an upgrade to handle my hp output.

[doctor4766]

I'm about to swap out my 2.76 to a 3.23.
I do a lot of highway driving on our club runs, but like Troy said it's tough to get moving but great for long distance cruising with the 2.76 ratio.
Just this weekend we took a spin down south with the club. I sat on 2000 rpm at 62mph (100kmh) for 200 miles and the temp sat at a steady 180 all the way.
Having never ever changed a diff ratio in any of my cars it will be very interesting to see the difference it makes off the mark.
I've been told that with my camshaft and new gear ratio combo that even @ 100kmh if my revs go up to 2400 the engine will be running more efficiently and may even be better on fuel.
Can't wait to try it out.

Well, just tried it out and wooohooooo!!!!
Can't believe how much difference the new gears have made. It's really transformed my car from a lumpy sounding old slug to a bitchin wheel spinner!!
Turns out that my 2.76 was in fact a 2.71.
Now she chirps into gear not only from 1st to 2nd, but from 2nd to third!!



Do I sound excited??

[elacruze]

Well done! Nothing left now but the 200 mile weekend trip and a mileage report. 

[hemi24]

i use to run 3.91 with M-50-14 tires on my charger it was just a little to low for hwy use great on the city street though.

[RIDELIKEHELL]

I have 3.23's in my 68 from the factory so that is what we've chose to leave in the for now. I had planned on putting a 4.10 with an overdrive setup but finances won't let that happen. I plan on driving this car on the hiway to shows etc next year so I hope I have made the right call here. I put a 2500 stall in so that should let me chirp a wee bit

[doctor4766]

Well done! Nothing left now but the 200 mile weekend trip and a mileage report. 

Actually it looks like we might be heading down south again on the 28th to the same town we visited last weekend.
There's a big car show on so could be worth the trip. Let yas know.

On a side issue, I think my speedo is outta whack now as it just doesn't seem to correspond with how fast I'm travelling.
Should I be looking to change the cog in the box?

[Troy]

Well done! Nothing left now but the 200 mile weekend trip and a mileage report. 

Actually it looks like we might be heading down south again on the 28th to the same town we visited last weekend.
There's a big car show on so could be worth the trip. Let yas know.

On a side issue, I think my speedo is outta whack now as it just doesn't seem to correspond with how fast I'm travelling.
Should I be looking to change the cog in the box?

Well yeah. If you changed the rear gears you need to match the speedometer pinion (in the transmission). The tires are spinning faster now so you need to slow down the speedometer.

Troy

[doctor4766]

So with 295/50/15's and a 3.23 rear end what should I be looking for?

[Troy]

Probaly something in the 30-31 spline range. There's a reference somewhere but I don't have time to find it (sounds like something useful to add to the site huh?). Google "mopar speedometer pinion chart" and you'll find a table with tire sizes, gear ratios, and the appropriate pinion.

Troy

[doctor4766]

Thanks Troy.
I did find a link for a formula a bit earlier on here but or course can no longer locate it.

[greenpigs]

Here ya go http://www.moparts.org/Tech/tech/pages/speedo.html

[Troy]

This is better since most used gears are sold by color instead of part number:
http://www.mopartech.net/showthread.php?p=439

Formula:
http://www.moparchat.com/forums/showthread.php?s=&postid=372505

Troy