Your favorite rear end/final drive ratio and why?

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My 68 Cuda has 4.30s 727 and an RB. Probably go back to 3.91s.
My 87 SS Monte hauler has 3.42s Turbo 400 and a big inch SB.
 
I have a 383 727 in my 69 Barracuda 25.6" tires Mopar performance 280 .474 cam 2800 converter 3.23 Gears. if the Gears were 2.90 it would be better. no problem smoking the tires for a block no power brake
 
MRGTX said:
What did you pick? Why? Are you happy? Do you wish that you picked something different?


About four years back, after saving up a wad of cash, I had the chance to pick out my "dream" rear axle assembly. My vision for my car was to make it as fun as possible on curvy back roads, probably take it to the autocross at some point, and to generally make it exciting and engaging to drive. To me, this usually means higher revs and lots of shifting.

With that in mind, I chose a mechanical limited slip (Eaton Truetrac) with 4.10 gear ratio. After living with it with two different engines and two different transmissions (just did a 4spd swap), I am not sure if I would have been better off with a lower numerical (more highway oriented) ratio. The main problem seems to be the lack of an overdrive gear and engines that don't exactly love to rev. The two 5.9s I have had tend make their power down low where they don't need as much help from the short gears.

My current engine is a Blueprint 408 stroker making about 460 at the crank driving an A833 4spd with stock ratios. There's more than enough power to overwhelm the tires in almost any gear...at least with my 255 no-season BFG T/As.

Would it be more fun with 3.23s or 3.55s? I just don't know and experimenting is outside of my budget currently... I'm hoping to learn from you guys before I invest.
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My dream? To have any ratio I want, and my E body I have a quick change sitting in the shelf to make that happen.
Not yet sure about all the weight carried in the trunk for all the needed ratios.:lol:
In the meantime 3.55 works for me in the 8.75"
 
3.70 with 27.5 inch tire. Nice on street and 1/4 mile strip. 3 speed. (shortened Ford 9 inch in a Duster)
 
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Your favorite rear end/final drive ratio
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Whatever which one puts the middle of the engine's torque peak in the middle of the speeds I intend to drive, given my tire size, nudged this way or that way depending on what kind of transmission, whjether I anticipate having a lot of hills to climb, whether I'll be spending more time in stop-and-go traffic or cruising, etc.

And why
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Because that way I get the most smiles per gallon.
 
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i have used 3.91 gears and hated them
i have used 3.55's and disliked them
i have used 3.23's and they were pretty good
to answer your questions
which gear...gonna try 2.94 in the new project
why...i'm spoiled by our modern cars that cruise so nice around 2200 rpm
 
93 V/8 Dakota. 3.91 auto overdrive. Nice around the suburbs.
98 360 B3500 van 4.88 auto over drive. That's the hot setup for heavy towing at 55 mph overdrive off.
64 413 New Yorker 2.92. Sweet at 80 all day.
And others.
 
ir3333 said:
i have used 3.91 gears and hated them
i have used 3.55's and disliked them
i have used 3.23's and they were pretty good
to answer your questions
which gear...gonna try 2.94 in the new project
why...i'm spoiled by our modern cars that cruise so nice around 2200 rpm
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FWIW Mopar made a 3.08 for 8.75's, but it is extremely rare, I have been looking for a set for over a decade, I think it was a Nascar gear before everything went 9".
 
2.94 works well in my `cuda with the Gen III and NAG.
a 2.76 would have been as good.
 
ir3333 said:
i have used 3.91 gears and hated them
i have used 3.55's and disliked them
i have used 3.23's and they were pretty good
to answer your questions
which gear...gonna try 2.94 in the new project
why...i'm spoiled by our modern cars that cruise so nice around 2200 rpm
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Or could go the other way around if all built similar hp and making around the same peak tq per cid (efficiency) a 440 with 2.94 gears would put similar torque to the ground as each of those cid gear combos. To me the main reason for displacement.

273 x 4.88/2.94 = 453 cid
318 x 4.10/2.94 = 443 cid
340 x 3.91/2.94 = 452 cid
360 x 3.55/2.94 = 434 cid
408 x 3.23/2.94 = 448 cid
 
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OLD IRON said:
93 V/8 Dakota. 3.91 auto overdrive. Nice around the suburbs.
98 360 B3500 van 4.88 auto over drive. That's the hot setup for heavy towing at 55 mph overdrive off.
64 413 New Yorker 2.92. Sweet at 80 all day.
And others.
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V8 Dakota 3.91 w/AOD is pretty much the tow package. My 2000 Dakota 3.9 w/AOD and 3.55 gears runs down the Hwy at 100KPH or 62MPH at about 1900 RPM.
Yup heavy tow in the 1 ton with OD off but the revs will be up there.
The New Yorker w/2.92 is good for a lux barge. That 413 just running nice at 80. Throw an OD trans in and probably run about 1600 or a bit more at that speed and get good economy doing it.
 
Dale Davies said:
V8 Dakota 3.91 w/AOD is pretty much the tow package. My 2000 Dakota 3.9 w/AOD and 3.55 gears runs down the Hwy at 100KPH or 62MPH at about 1900 RPM.
Yup heavy tow in the 1 ton with OD off but the revs will be up there.
The New Yorker w/2.92 is good for a lux barge. That 413 just running nice at 80. Throw an OD trans in and probably run about 1600 or a bit more at that speed and get good economy doing it.
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Yep, the one ton 360 with 4.88 and 245/75-16 tires is turning 3600 rpm at 55. But it's worth it to tow the 14000-pound backhoe around the county. It's under all axle and 26000 restrictions. But way over what Dodge says it can tow. It don't care.

I don't think economy with the 1964 413 New Yorker is part of the program with any rear gear. It gets 16 at 70, no wind, no hills, good tune, stock carb. And to top it off, must use premium 93 gas.
 
Enough gear and convertor to make it get squirrely when I mash it at 55. lol
I didn't build the car to run the salt flat.
 
OLD IRON said:
Yep, the one ton 360 with 4.88 and 245/75-16 tires is turning 3600 rpm at 55. But it's worth it to tow the 14000-pound backhoe around the county. It's under all axle and 26000 restrictions. But way over what Dodge says it can tow. It don't care.

I don't think economy with the 1964 413 New Yorker is part of the program with any rear gear. It gets 16 at 70, no wind, no hills, good tune, stock carb. And to top it off, must use premium 93 gas.
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After my youngest brother was born a Valiant just did not function for two adults and four children from newborn to 14. So dad traded the Valiant for a 67 Merc Montclair in 69. Had a 390 2V. Probably 2.75 gears. I ended up with a 65 Galaxie more door with the 390 4V and 2.75 gears. Both got about 20 MPG US. Mine has a burned valve and it still got that mileage. Used to put $5 premium in and fill with regular with no problem. Could probably put $20 of 91 in and fill with the "cheap" stuff. Is better than an 80 LTD wagon with either a 302 or 351W in it.
 
Been with 8.75s in all my car with the exception of the Dana 60 i had in my 71 RR. Mainly 3.23s, 3.55s and 3.91s. I have a 8.25 with 3.21s I’ll put in my 66 Valant.
 
Dale Davies said:
After my youngest brother was born a Valiant just did not function for two adults and four children from newborn to 14. So dad traded the Valiant for a 67 Merc Montclair in 69. Had a 390 2V. Probably 2.75 gears. I ended up with a 65 Galaxie more door with the 390 4V and 2.75 gears. Both got about 20 MPG US. Mine has a burned valve and it still got that mileage. Used to put $5 premium in and fill with regular with no problem. Could probably put $20 of 91 in and fill with the "cheap" stuff. Is better than an 80 LTD wagon with either a 302 or 351W in it.
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My tired but sound 78 Mercury Grand Marquis 400 gutless wonder gets 20 at 70. Probably a 2.80 or so rear? Filled it today at $2.50.
Smooth quiet car. But slooow.
 
For a healthy A-body small block? 8 3/4 4.10 gear with 1:1 out of the trans. For a B-body? With a healthy BB. Dana with 3.54. Also assuming 1:1 out of the trans. For Street.

I would love to try that Passon 855 in my GTX. Change rear to 4.10. Or even think 4:56 with that .70 final trans ratio out the A855 trans.

I've had my share of Dana 60 vs 8 3/4" The Dana drives heavier and tougher. Because it is. It also has more forgiveness for Street mishaps. Especially in a heavier car.

All out drag race build? One wants the lightest and highest gear set that engine/chassis setup can support. A race A-body? 8 3/4" with aftermarket gears/axels with spool can go to 1k HP. Anything over? Race Dana setup. At the minimum is my recommendation. Rear gear set determined by tire height and RPM capabilities thru the traps.
 
Probably a little late, but.....
If I were the O.P., I'd consider an overdrive five speed, and retain the 4.10s
I understand that is a mega-dollar solution, but I feel it is the best one.
For a gear change, I would probably go with 3.23, but 3.55 is a more compromise gear, the 3.23 are for more of a long freeway cruse situation.
As far as MY personal choice, I have 4.10s in my road runner, 3.91s in my 440 62, and I just bought a blackfriday deal on an aluminum center for my nine inch, with 4.10s and a spool. Very tall tires used with the new gears however. (to use in my Opel GT.)
 
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ocdart said:
As said in an earlier post, rear gearing is application dependent. My current '69 Dart build is going to be a weekend car, not a daily driver. It's based on a 380-horse 360 crate motor that I plan to modify a bit to get over 400hp out of it.
Since it's going to be more 'toy' than anything I'm going with a 4.30 rear gear behind a 200-4R OD trans. I had the trans built as a manual-shift, reverse-pattern with a 2800-rpm lockup converter. Theoretically this combo will give me the best of both worlds. The 4.30 gears will be fun around town and the 0.67 OD will make them behave like 2.88 gears on the freeway. Others here on FABO with a similar lockup 200-4R have stated it almost feels like a 5th gear when lockup hits.
Other deciding factors for the 200-4R were that it fits in an A-body tunnel without major tunnel surgery and there is no computer involved with the transmission. Since mine was built as a manual-shift, I don't need to worry about a throttle valve cable or adjustment.
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Can you give a little more info about your 200R4? Where did you get it? What has to be modified to install it behind a 440 in a '68 Dart? How much did you spend? I'm looking for over drive alternatives to the 4000 RPM I'm running on the interstate right now. I was also considering a Gear Vendors O.D. unit. Any thoughts? Thanks!!

BTW...........I have a 505" stroker, a Hughes 727 with 2500 converter, 3.73 gears and normal size 15" tires. (not sure how tall)

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@SleeperDart505
I had my 200-4R OD trans built by Extreme Automatics located in Amelia, OH. It was built several years ago so I suggest you
check with them on current pricing for how you want your tranny built.

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I had them remove the existing factory GM bellhousing from the 200-4R and replace it with a Reid Racing bellhousing to mate up to my smallblock Mopar. I don't know if a Reid Racing bellhousing is made for a BBM. Again, you should check with Extreme Automatics (www.extremeautomatics.com) to find out.
No tunnel surgery required to fit the 200-4R in your '68 Dart.
There are a bunch of threads on FABO about this trans. Check 'em out.
 
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