Hot Rod Forum banner
1 - 20 of 43 Posts

·
Registered
Joined
·
77 Posts
Discussion Starter · #1 ·
I have a 350 engine with a Magnum 224/224 Hydraulic Roller Cam. I also have a Muncie 4 speed. The current axle ratio is 4.10. The tires are approximately 25 inches in diameter. Currently the engine is doing about 60 mph at just over 3000 rpm. I am not looking to convert the car into a daily driver, but I would like to start using it more for pleasure rides. But doing 50 to 60 mph at 2500 to 3000 rpm is a bit of an overkill I think. I am considering dropping the gear ratio, but haven't quite decided to what. Ideally, it would be nice to do 60 mph at about 2000 rpm. Is that even attainable with a 4 speed tranny? And if so, how much power would I need to give up in 1st if I floor it? Will it be a situation where I won't even be able to do a burnout?
 

·
More for Less Racer
Joined
·
20,218 Posts
2000 rpm @60mph with a trans having a 1:1 4th gear and a 25" tire means rear gearing of 2.48 to get that rpm target.

That is doldrums of the late 1970's smog years mileage gear territory....just awful for any spirited driving.

About as low as you dare go on rear gearing and still feel like it has some performance is about 3.23-3.42 or so and that would give you about 2600-2700 rpm @60 mph
That's still a pretty good drop from the 3200-3300 rpm you are turning now with the 4.10's

Going to a larger tire diameter would help a lot too. Every inch of tire diameter is worth about 100 rpm drop at the 60 mph cruise speed.

Or, you leave it all the way it is, sell the Muncie off to fund a Tremec 5-speed overdrive swap and actually get cruise rpm very close to your 2000 rpm target or just a little above it.
 

·
Registered
Joined
·
77 Posts
Discussion Starter · #3 ·
2000 rpm @60mph with a trans having a 1:1 4th gear and a 25" tire means rear gearing of 2.48 to get that rpm target.

That is doldrums of the late 1970's smog years mileage gear territory....just awful for any spirited driving.

About as low as you dare go on rear gearing and still feel like it has some performance is about 3.23-3.42 or so and that would give you about 2600-2700 rpm @60 mph
That's still a pretty good drop from the 3200-3300 rpm you are turning now with the 4.10's

Going to a larger tire diameter would help a lot too. Every inch of tire diameter is worth about 100 rpm drop at the 60 mph cruise speed.

Or, you leave it all the way it is, sell the Muncie off to fund a Tremec 5-speed overdrive swap and actually get cruise rpm very close to your 2000 rpm target or just a little above it.
Swapping the tranny is also an option certainly, but realizing it would be a much bigger project, I was loath to explore it. How much different is a Tremec from a Muncie? Meaning is a there a lot of cutting / drilling / grinding I gotta do to fit it in on a 74 Nova?
 

·
Registered
Joined
·
901 Posts
To get performance that you want out of the hole AND cruising down the highway, you need an overdrive transmission. Whether it be an automatic or manual trans with 5 or 6 speeds. Why do you think auto makers did it. Click below and input your info to try different combinations.

Vehicle speed calculator with engine/road speed graph for each gear

 

·
Registered
Joined
·
564 Posts
Just to offer an extreme, I lived with 2.73 gears behind a wide-ratio Muncie in my daily-driver 402 El Camino for years. That was pretty-much the tallest gearset you'd ever want to go with and be practical on the street and it worked for me partly because the torquey motor, even so forget about burnouts unless you can either start in water or do it coming out of a corner, then hoon away... It was a pain in stop-and-go traffic, and 1/4 e.t.s the couple-times I ran it were a second over what they should have been. Periodically I'd need to tow a loaded car-hauler trailer and have to back up a driveway, which use would invariably fry the clutch and it would chatter until re-surfaced...again. All that said, it was lovely on the highway which is where it was mostly used.

I'd later install a Richmond 5-speed.

You'll never get the best of both worlds, good street launches and reasonable hwy rpm with that four-speed, but I think most people would say that the 3.5 rear gear range is about where you get a happy balance w/ a Muncie if it's wide-ratio (2.54 1st gear), 3.7 if it's short (2.2 1st).

Lots of Muncies sit on shelves these days since decent overdrive 5-speeds have become common and their desirability/value is a bit lower than it once was...still lots more fun than an automatic IMO. A '74 Nova w/ a manual trans is a pretty rare beast anyhow.

If I were you I'd gear for decent street manners now (3.43-3.55) and suffer on the highway a little, then later when you're into it move into whatever 5-speed overdrive fits best which in the Nova should only be a matter of crossmember and shifter hole. Don't hack up the trans tunnel much as it's needed for unibody strength.
 

·
Registered
Joined
·
3,898 Posts
Tremec TKO in a Nova takes no cutting of floorboard.
You can buy a kit with trans, crossmember, driveshaft, and do it in a day.
 

·
1949 Ford Coupe RESURRECTION
Joined
·
899 Posts
Watch everybody here throw darts at me.

A 700 R4 will probably bolt right up. Of course you will have to expend a bit of effort on a shifter (you only drill about a half-inch hole for the shifter cable), driveshaft, TV cable, carb mount, linkage compensator, a bit of wiring with a switch to select when to lockup or not lockup , and maybe a crossmember.

Without doing something about that rear end, you might find that first gear is annoyingly low, but the 30% overdrive and lockup converter are a dream on the highway. Perhaps it's because I'm getting kinda old, but I don't think I could live with a standard shift...

I'm running a 383, 700R4, 2400 converter, controllable lockup whenever I decide (2, 3,and, 4th, or 4th only, or none at all), Jag XJS rear end (2.88 gears) and big ass tires. 1,500 rpm @ 60 mph...14.1 mpg on the highway and loving it. And I can easily break the tires loose if I choose with that extra low first gear that everybody hates about 700R4s.

It's all on my website.
 

·
Registered
Joined
·
5,087 Posts
You dont "need" an overdrive. The "need" is a lower final drive; and one way to do it is with an OD. The other is, as you suggest; changing the axle ratio. Follow along for some math; or skip to the bottom for the straight up recommendation.

If you have an M20 (2.52 1st gear) and a 4.10 axle then 2.52 x 4.10 = 10.33
If you have an M21 (2.20 1st gear) and a 4.10 axle then 2.20 x 4.10 = 9.02
We can see above that the typical minimum for a street performance car out of the 60s and 70s was 9:1, the modern day musclecars are running 10:1 total gear reduction.
So, theres the ball park for us to play in.
Definitively figure out if you have an M20 or 21...don't just go by some random collection of wives tales. Pop the sidecover off and count teeth.
Then decide if you want to go a bit upscale, and go with the rockcrusher style gears. There are Italian gears and there are Chinese & Taiwan gears; each priced accordingly.
M22w (2.56 1st) x 3.73 = 9.55
M22 (2.20 1st) x 3.73 - 8.21 (this is bordering on pretty dull to drive in 1st gear)
****
If it were me; I'd go with a 2.98 1st gear (M22Z) Italian gearset with a 3.42/3.31/3.23 rear axle. Thats 10.33/9.86/9.62 respectively. It'll pull like an old school car in 1st and second, have the strength and cache of the Rockcrusher and go down the roads about 2500rpm +/- depending on axle and tire height
 

·
Registered
Joined
·
5,087 Posts
Tremec TKO in a Nova takes no cutting of floorboard.
You can buy a kit with trans, crossmember, driveshaft, and do it in a day.
TKO's are well on their way to being disco'd - no reason for tremec to have a tkx and a tko.

Parts availability is already a problem with no end in sight
 

·
Registered
Joined
·
201 Posts
Why build a hot rod and then strangle the motor with a high (numerically low) geared rear end? The one correct answer to your problem is a transmission with an overdrive. Most people balk at the cost of a Tremec TKX and convince themselves they can find a cheaper way.
A Muncie or any of the older four speeds has been beaten to death for 50 years already, and they only increase in price as time goes by. If you tear one up, you will invest a large sum of money or sell it to someone for little money. Buy a TKX new and it will bolt into your vehicle. You can get one with 600 ft lbs of torque capacity and its new. If you ever decide to sell your current car, put the four speed back in it and keep the Tremec for the next vehicle. In the long run, the Tremec will be your best value because it should last and give good mileage. If you take the short term view and stick with the four speed you will be miserable driving it no matter which gear ratio you choose. The other side of it is that a Tremec will be worth 75% of its new price for many years to come.

You just have to make the commitment to spend the money and do it right.
 

·
Registered
Joined
·
3,604 Posts
Put a 9" in it then you can run 2 ratios and switch them in under a hour.

I have run 3.08 and run 4.56 in the same ride(I swapped axles). I hated the 3.08. The diffrence is more then noticable. It makes the thing a dog.

If your motor is built to rev then let it rev. With a good cooling setup a sbc can rev for hours at 4000 rpm. 3000 was common place as a weekend trip in most of my direct rides driving for 2 or 2.5 hours before stopping for a gas station break before leaving and driving another 2 to 3 for a hotel. Then driving back the next day without issue.

Now more higher rpm does mean worse fuel mileage and increased wear. Which is why we have overdrive. But if your spending several thousand on a overdrive to save 3mpg then thats alot of mileage before it pays off.

Most of overdrives have issues with 5th. Not all but generally that 5th gear should be treated nicely. It is a cruising gear and generally you should drop into direct if you want to be agressive.

For me the overdrive is not worth the mileage/reduced wear(unless already installed) because I am hard on everything I drive.

I also feel comftable driving at 3000rpm no matter the gear ratio so not having overdrive keeps the "15+" tickets down.
 

·
Registered
Joined
·
1,904 Posts
Why build a hot rod and then strangle the motor with a high (numerically low) geared rear end? The one correct answer to your problem is a transmission with an overdrive. Most people balk at the cost of a Tremec TKX and convince themselves they can find a cheaper way.
A Muncie or any of the older four speeds has been beaten to death for 50 years already, and they only increase in price as time goes by. If you tear one up, you will invest a large sum of money or sell it to someone for little money. Buy a TKX new and it will bolt into your vehicle. You can get one with 600 ft lbs of torque capacity and its new. If you ever decide to sell your current car, put the four speed back in it and keep the Tremec for the next vehicle. In the long run, the Tremec will be your best value because it should last and give good mileage. If you take the short term view and stick with the four speed you will be miserable driving it no matter which gear ratio you choose. The other side of it is that a Tremec will be worth 75% of its new price for many years to come.

You just have to make the commitment to spend the money and do it right.
Course you need money to spend first ...
 

·
Registered
Joined
·
77 Posts
Discussion Starter · #16 ·
Why build a hot rod and then strangle the motor with a high (numerically low) geared rear end? The one correct answer to your problem is a transmission with an overdrive. Most people balk at the cost of a Tremec TKX and convince themselves they can find a cheaper way.
A Muncie or any of the older four speeds has been beaten to death for 50 years already, and they only increase in price as time goes by. If you tear one up, you will invest a large sum of money or sell it to someone for little money. Buy a TKX new and it will bolt into your vehicle. You can get one with 600 ft lbs of torque capacity and its new. If you ever decide to sell your current car, put the four speed back in it and keep the Tremec for the next vehicle. In the long run, the Tremec will be your best value because it should last and give good mileage. If you take the short term view and stick with the four speed you will be miserable driving it no matter which gear ratio you choose. The other side of it is that a Tremec will be worth 75% of its new price for many years to come.

You just have to make the commitment to spend the money and do it right.
This is pretty much the conclusion I have drawn after reading everyone's take. Especially this part: "If you take the short term view and stick with the four speed you will be miserable driving it no matter which gear ratio you choose."

To be frank, I am not concerned about the cost of a new transmission. My primary concern lies with opening a can of worms by trying to fit it in. Has anybody installed a Tremec on a Nova? I am assuming I need to purchase a kit (with the tranny, driveshaft etc.), correct?
 

·
Registered
Joined
·
5,669 Posts
‘Twas mine I’d lever her alone!
How do you know the rear gear ratio?
Did you pop the cover off and check the gears and numbers or did you turn one wheel and count the driveshaft turns.
reason I ask is your info of 25 inch tires, 60 mph and 3000 rpm computes to a 3.73 gear.
Are you positive you’ve got a 4.10 gear?
 

·
Registered
Joined
·
77 Posts
Discussion Starter · #18 ·
‘Twas mine I’d lever her alone!
How do you know the rear gear ratio?
Did you pop the cover off and check the gears and numbers or did you turn one wheel and count the driveshaft turns.
reason I ask is your info of 25 inch tires, 60 mph and 3000 rpm computes to a 3.73 gear.
Are you positive you’ve got a 4.10 gear?
The info I got is from the previous owner. He was the one who put the rear end together. I have not independantly verified the ratio. The speedometer is not working so I have tested it with an app. it does 60mph at just a hair over 3k rpm. Also the tire diameter is 24.4 to be exact.
 

·
Registered
Joined
·
5,669 Posts
You say 24.4 inches!
Whats it say on the sidewall of the tire?
Like this example.
195 75 R14 or 225 60 R15.
give us those numbers.
they’ll tell us how tall they are.
 
1 - 20 of 43 Posts
Top