Need gear ratio , tire and rear end ratio experts ! Green Rat Project

[ValerianMagnum]

hi Guys ! so ive decided to rethink everything since january and ill go with a 5.2 magnum , roller engine , maybe ported heads and a small cam but to start the project it will stay stock for a while , my goal is to have it under 2900 pounds , bought the 5,2 with a complete nv3500 _ 5 speed from a 2001 Ram 1500 2xd , i have 3 rear ends . 2x 489 cases with either 3.23 or 3.91 and 1x 741 case with a 3.23 too, all 8 3/4

Read that the nv3500 doesnt have the best gear ratio for a car : 4.02 - 2.32 - 1.40 - 1.00 - .73 but tjat it can be very nice with a certain tire combo and some good ratios , Am i better with 3.91s or 4.10 .. 3,23 or 2.76s , planning on going with the same tires than my duster = 275/6oR15

or any tire size and mag wheel suggestions , the car will be a ratty 2 door 69 valiant , so nothing around the factory look or factory parts will be there since its a low budget car and a fun project to do with friends and familly

 

[ValerianMagnum]

Some pics

 

[gzig5]

The OD should let you get away with the 3.91 or the 4.10. The gearing should allow you to run as tall a tire as you can fit in the well.

 

[Garrett Ellison]

Check your first gear ratio, as some of those NV3500s are reported to have had 3.45 gear ratios. 1st gear is going to be great for putting around at parade speed, but very traction limited. But are you prepared to make room for the NV? It's probably going to take some work to the torsion bar crossmember and definitely a redesign of the transmission tunnel to fit. And here's the thing about it. A stock 5.2 magnum with a mild cam (360 LA Hydraulic roller works very well, BTDT!) an airgap type intake, and a decent distributor curve makes earthmover bottom end torque. It works well with 3.21 gears and 31X10.50s in a loaded 4X4. So I would go with 3.23 and keep the 3.91s held back for when you go "all out". So by my own experience, you'd be highway only with 5th gear, but it would pull 2900 pounds very easily at highway speed. But, here's a helpful online calculator to help you determine what will work for you, click the button for MPH from KPH to go to standard tire measurement.
Gearing Calculator | RPM and Tire Diameter to km/h - mph with Shift Tracer

 

[ValerianMagnum]

Ohhh thats great ! Yes it will a carbed 5.2 with everything to help it perform quite well , yes me and my friend are very aware and we are ready to cut and weld what is necessary , its a valiant 100 , very basic car, i have a lot of experience about trowing money on the wrong cars ahaha , this was will be to drive everywhere and enjoy , im not putting 40k to restore a 69 valiant , put a Nice low budget build is very possible , the car is very very solid but ugly !

 

[33IMP]

Conundrum. The 4.02 first would work great with the 2.76 or 3.23. The overdrive fifth certainly won't.
The overdrive fifth would love the 3.91s, but your first gear would be good for about 10 feet (exaggeration!).
My choice would be 3.55s, but I see those aren't on your list.
I think I would go with the 3.23 (Assuming the 4.02 first is correct), and be very wary of lugging in fifth. I'd probably try to maintain 70mph or more in od.

 

[AJ/FormS]

At 2900 pounds, your 5.2M will probably like a starter gear in the range of 9 to 10, say 9.5

If your ratios really are; 4.02 - 2.32 - 1.40 - 1.00 - .73 (splits of .577-.603-.71-.71)
then 9.5/4.02= a rear gear of 2.36
Of course, in overdrive, this becomes .73 X 2.36 = 1.73, and with 26.5" tires this becomes 65=1440 rpm. Good luck tuning that for fuel economy, because I think it is as good as impossible to give the engine the timing it wants, using a stock-type mechanical distributor.Never mind that 2.36s have never been offered in a Mopar.

So then, lets flip it the other way.
2200 is about as low a cruise rpm, (at 65mph) as you can tune that distributor. With a .73od and the 26.5s again, this computes to a rear gear of 3.66; which I will round UP to 3.73s giving an actual 65mph=2250 , badaboom!.
But at the other end, this gear will get you a starter of 15/1, As others have said, this is Great for parading but not much else. That means that most of the time , you will be starting in Second which is a starter of 8.65. Ho-hum.

This trans was designed to work with the injected and computerized and beer-keg intake, and in a pick-up truck. The first two splits are way too wide for a 2900# car. There is no right rear gear for your application....... unless maybe, you just ignore First gear altogether, driving it as a 4-speed.
Then; 9.5/2.32Second=4.10 rear gear which is 2.94 in od; that's pretty good. 65=2465.... but with a 16.48 deep-Low, 1000rpm is 4.78mph........
The problem with this idea is that you have no decent gear to top out at 60mph with. Your choices are Second at 7240rpm, or Third at 4370 .... see what I mean?

IMO
At 2900 pounds, your combo is just right for the A833od 4-speed...with ratios of 3.09-1.67-1.00-.73od with nice progressive splits of .54-.60-.73
Using 4.10s, your starter is 12.68, and your cruiser is 65=2470, but the really big deal is this;
60mph in Second tops out at 5210,
just about right for a stock-cammed 5.2M .
Jus saying..........

 

[ValerianMagnum]

At 2900 pounds, your 5.2M will probably like a starter gear in the range of 9 to 10, say 9.5

If your ratios really are; 4.02 - 2.32 - 1.40 - 1.00 - .73 (splits of .577-.603-.71-.71)
then 9.5/4.02= a rear gear of 2.36
Of course, in overdrive, this becomes .73 X 2.36 = 1.73, and with 26.5" tires this becomes 65=1440 rpm. Good luck tuning that for fuel economy, because I think it is as good as impossible to give the engine the timing it wants, using a stock-type mechanical distributor.Never mind that 2.36s have never been offered in a Mopar.

So then, lets flip it the other way.
2200 is about as low a cruise rpm, (at 65mph) as you can tune that distributor. With a .73od and the 26.5s again, this computes to a rear gear of 3.66; which I will round UP to 3.73s giving an actual 65mph=2250 , badaboom!.
But at the other end, this gear will get you a starter of 15/1, As others have said, this is Great for parading but not much else. That means that most of the time , you will be starting in Second which is a starter of 8.65. Ho-hum.

This trans was designed to work with the injected and computerized and beer-keg intake, and in a pick-up truck. The first two splits are way too wide for a 2900# car. There is no right rear gear for your application....... unless maybe, you just ignore First gear altogether, driving it as a 4-speed.
Then; 9.5/2.32Second=4.10 rear gear which is 2.94 in od; that's pretty good. 65=2465.... but with a 16.48 deep-Low, 1000rpm is 4.78mph........
The problem with this idea is that you have no decent gear to top out at 60mph with. Your choices are Second at 7240rpm, or Third at 4370 .... see what I mean?

IMO
At 2900 pounds, your combo is just right for the A833od 4-speed...with ratios of 3.09-1.67-1.00-.73od with nice progressive splits of .54-.60-.73
Using 4.10s, your starter is 12.68, and your cruiser is 65=2470, but the really big deal is this;
60mph in Second tops out at 5210,
just about right for a stock-cammed 5.2M .
Jus saying..........

You are the person with the best numbers AJ ..and i appreciate it , but im pretty sure that a 3.23 gear could be ok , if i have no choice ill try and grab a set of 3.55s or so , but dont forget that i can go 14 15 16 17 even 18 inch in the back...it will never be a showcar so i dont cutting some stuff up..i just wanna build a nice little cruiser and reliable car , it will be very light and with 290-300hp and 350 ft or torque im pretty sure it would be nice on the highway at 60 mph...much more than my 76 duster with a 360 and 3.91s ( 727 ) * btw what doest mean " good for a parade" , doing burnouts in front of a public ? Ahahaha thx

 

[Ironracer]

OP, Please, do not take my input as an attack on Your build, or Your choice of Parts... just my take on what I consider a shitpiece transmission. Had one in a 01 Dakota Sport, single cab, shortbed. 4.7 w/ NV 3500, 3.92 rear, fairly big tires. 1st gear, Brutal Fun As Heck Clutch Dumps from 4500 or More rpms. TIRE FRYING FUN!!!!!! power shift 2nd? Nope, ain't happening. Final drive in 5th would Roll that Truck out Hard, and still get decent mileage. The PLASTIC shifter house/ retainer was crap, broke one... the Factory PLASTIC clutch slave was a POS. We hot glued that **** back together 2x. IF You Have a Factory set up, to bleed the SOB, ya need to remove the Clutch Master, turn it UPSIDE DOWN and have a Brother pump it, by Hand! They Don't sell any parts for the Slave, it's a Complete, sealed assembly. But when Ya get a METAL ONE, IT has a Bleeder Valve! YAY! sorry to rant! Other than those issues, it was an OK transmission. Oh, and a FBBO member, an Aircraft Mechanic (Propwash) Great Guy Alert!!!! He rebuilt one, chained it to the floor, to pull the guts, as NO side cover... well, there is this Lil clip thing, and some other balls or a spring or some ****. When he went to put it together, they popped all over the shop. Think he was over it then. Just my humble opinion I hope you have better luck with yours

 

[AJ/FormS]

but dont foeget that i can go 14 15 16 17 even 18 inch in the back.

The wheel size means almost nothing.
In an A-body from 67 to 76, the maximum tire diameter that fits without mods, is ~27.5. And the smallest that anyone is likely to run is a 24.5
My numbers are always done with 27s, unless otherwise stated, because 27 is the average of just about anything you would install.
3.23s will run ~1900@65mph which is fine. But for best fuel economy, your engine will want perhaps 50/55 degrees of cruise timing. You cannot get that much with the factory-type Distributor.
Typically, you might get 35*
If you mod your Vacuum advance can to 22*, then ~43.
If you way over-advance your idle timing, which will make her super jumpy in gear, then perhaps 47.
That's all I'm saying.
I ran 3.23s with a .73overdrive once; but not for long
In your combo, that will have a starter of 12.98. But in Second gear, it is 7.49, and that would be a tuff starter to pull even in your combo. (That would be like running the Standard 2.66Low/A833 and 2.76s). Thus you are forced to use First gear every time you start off. But the engine will rev up really fast, sorta encouraging you to short shift into Second. But then the Rs will fall so low, (to 60%) that the engine will struggle in that 7.59 ratio
To run that deep with my 3.09First gear, requires 4.30s; Hyup I pulled and sold them. That starter was just too deep for me.