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Gear selection!

Sonny

It’s all fun til the rabbit gets the gun.
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Over the last 2 years, I’ve converted my 1970 318/904 Belvedere to a 440/727 road runner clone. With my engine swap complete, I jacked up the rear end, marked the tire and u-joint and spun the tire 2 rotations. The u joint made 2.75 rotations so it looks like I have a 2.76 gear. The rear end is a 8 1/4 (not 7 1/4).

Well that’s great on the highway, but no fun light to light. What is a good middle ground gear that will be fun 0-60 but tolerable on Power Tour? 3.23? 3.55? Other? I don’t have any desire to go to a 8 3/4 at this time if ever. Don’t have the funds left to go gear vendors either. Plus It’s a car show car not a race car.

I did replace the leaf springs with 440 leaf springs, have not added torque boxes.

Thanks!
 
I have 3:23 in my Bee and Im happy. I also have had 3:54 in my charger. Both 4spd 440 both sets are good.
 
Well, I went from 2.76 to 3.55 and now at 3.23 in my 68 coronet. 2.76 was great at 80mph ... 3.55 was in my opinion perfect, great get up and go ... but I did a long trip and felt like the rpms were too high, this was based off engine noise alone as I had no tach in the car. ... now I'm at 3.23 and although I do like it as an all around gear I do kinda miss the 3.55..... hwy cruising is great and it definitely has good get up and go but I do notice the off the line loss ...... .
I'd say make your decision off most of your driving. Most of mine is around town with a few long drives a year, usually to the tune of 200 miles plus so I do enjoy those 3.23's then ! I'm also running a 28" rear tire. ..
 
I run 3:23s in my old 67 65mph is right at 3,000 rpm. Tire dia. also comes into play you can raise or lower rpms a little also.

If your going to do long trips I would leave the 2:76 in place Jmho.
 
3:55 is the move. I have 3:91's and although I like it, the long drives on the highway kinda suck.
 
Drove from Ct to Niagara Falls with 3,54's. 3100 rpm 70 mph around 26/27" tires. Had a 64 Olds Starfire it came with 3.55's from the factory.
 
Do you have a sure grip ( ha ha, I didn't say posi!)? Do you care? You might want to find out what's available for your 8 1/4 carrier, or if you want to add a suregrip if you don't have one.
I'm definitely no search wiz, but I couldn't find a listing for 8 1/4 gears at summit or jegs.
3.23 for long trips, 3.55 for primarily around town.
A Quiet exhaust system makes a little too much gear more livable on a road trip. I drove a runner every day for five years with 4.10s, it was livable because of a stock exhaust system.
 
All good advise above. 3.23 for more highway, 3.54/3.55 for more fun. It all depends on how you plan to drive it
 
Can't add anything to what has already been said. I am running 3:23 in both of mine. Still has some get-up, but more friendly on the highway. I live in the country, so most of my driving is on country roads and highways.
 
You didn't mention how you built your engine (unless I missed that). If you went with a noticably larger cam with a stall converter, you would definitiely would want to go with at least a 3:55 to gain back the low end loss in your engine. If it's all stock, then 3:23 or 3:55 should be fine. As others have said, it depends on what type of driving you'll be doing but you mentioned light to light, therefore I think the 2:76 would need to go for sure.

now I'm at 3.23 and although I do like it as an all around gear I do kinda miss the 3.55..... hwy cruising is great and it definitely has good get up and go but I do notice the off the line loss ...... .

Is there really that much of a noticable difference between 3:23 and 3:55?.... because I've been wanting to change out my 3:23 to 3:55 with a tru-trac or sure grip.

Thanks!
 
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This is great advice guys. Thanks for taking the time to respond. I did find one gear (3.55) for an 8 1/4 Belvedere at summit.
Are there different spline counts?
 
That would be 23 spline, NOT 24.
 
Is there really that much of a noticable difference between 3:23 and 3:55?.... because I've been wanting to change out my 3:23 to 3:55 with a tru-trac or sure grip.

Thanks!
Some people say not much but I did notice it, especially around town driving stop light to stop light . Don't get me wrong, its not a pig and can still light the tires up but it doesn't pull the same. I'm ok with it because the Hwy trade off is worth it to me.....
 
3.23 is good highway gear, 3.54 will get you rolling a little easier from a light, 3.91 will be fun for around town but you'll get a bit tired of it on a long road trip.

I just swapped a Dana 60 with 3.23 gears into my Coronet last summer and I really like those gears, but I have a 5 speed transmission with a super low first gear so it isn't quite the same as what you have.
 
You're right on track. You'll need an 8-3/4" rear end with 3.23 or 3.55 sure grip & any of center sections will work, just get the correct rear end housing & axles.
 
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