Titosvette78

I have a 1978 corvette with a 350 built by Phoenix engine pushing around 360 to the crank and I getting a new tranny due to the lags and slips and not getting enough power to the wheels while being in 2nd, 3rd gear and I'm wondering if I should replace the stock gear ratio with a 3.73 or a 4.10s.
Ps. I daily drive my car

cagotzmann

Are you interested in spinning tires then you will need to change the rear gears with only 360 HP.

You then get a city only daily driver. Forget about lengthy highway driving with a high reving engine.

3.08 rear makes a very good overall daily driver. Fix the other issues before making the change

Rescue Rogers

3.70 in mine. I keep it at 75 @ 3500rpm for long drives. I can easily get it up to 85 but it will start to get hot keeping at high revs for long periods.

CPTCroaker

What gear ratios will your new tranny have? There are some useful apps out there (TREMEC) that will help you figure out RPMs and speed using different gears sets. Recommend you at least take a look and see if the overall combination is something that will work for you.


I also used this one when getting a T56. You can swap out the numbers so it will work for any tranny. https://shiftsst.com/speed-analyzer

gdh

I went the other way 2 years ago when I was given a 3.36 that was in excellent condition. I had just swapped in a new zz383. I ran with the original rear for a few weeks and then swapped in the lower 3.36 rear. I love it as it revs a fair bit lower at highway speeds and it is fine around town. Most of the driving we do are on the secondary highways in our area which have 80 kph (50 mph) limits. Now the new 383 is 450/450 hp/tq which is a bit less than the previous stroked original engine. The previous engine was built more with the eye to running 1/4's with its power band coming in btn 4750 and 7200 rpm. For that engine I would have kept the 3.70 rears but with the flatter tq curve of the new one I am glad that I made the swap to the 3.36. Since you are talking about using the 78 as a dd with no mention of a swap to a 5/6 sp transmission I would stick with your current rear gearing and as previously stated fix the existing issues.

JW3101

Mine was born with a 3.70, bought it with a 4.11 and replaced it with a 3.55. The 4.11 was a killer on gas mileage.

c3_dk

The best solution, in my mind, is 4.11 with a TH2004R.
Together with your 350/360 you will get a good/fun driveline with low rpm om the highway.

My 69 Coupe will have a sbc 427, 3.70 rear and TH2004R all in stock and ready to install in the car.
Maybe I will change to 4.11
If I had to buy today, it would have been 4.11 rear for sure.

c3_dk

Same here, my 69 Convertible is a L46 car with 3.70, and 4 speed M21
I have a T5WC 1988 0.63 in 5th gear that I will install (and a 2.95 in 1th:-)

joewill

bought mine with a 4.56..UGH! never even used 1st gear.. it was a granny gear.

my 1st project was to replace with a 2.73. it cruises at idle now. the best money I ever spent. It whispers down the street...
of course I am not the kind of guy that wants acceleration and to do donuts in a parking lot.

you will ultimately regret a 4.11 in a street car.. stick with the 3.08.

of course if you want to change gears and get an overdrive tranny, plan on at least 4 grand.

Titosvette78

The transmission I'm getting is a tranny from monster transmission and it's 3speed auto and (th350) I'm wondering if I swap the tranny will it fix my problem. The problem I'm having is every time I step on it when I'm on 1st gear the car takes off but when I shift to 2nd the car stays on 1st for a while and red lines for a few seconds and then it shifts to 2nd and it does the same with 3rd but when I'm 2nd and 3rd I feel no power at all. I feel like I'm going no where when I step on it while being on those gears. So I'm wonder if I swap the tranny and the rear gears, will it fix my problem?

bj1k

I know a guy that has had what he says are 4.56's in his 70 Camaro for years . He won't attend any cruises any further than 5 miles from home because it revs in 4th like it's in 1st. He sounds like he's doing 60 when he is doing 35 but he still loves it . You have to decide what you want.

c3_dk

Please remember he is asking for 3.70 or 4.11 not 4.56

bj1k

Just saying that you have to be careful when going to gearing that low. Some are not practical off of the strip.

c3_dk

I agree, but I see no reason to compare with a ratio he doesn't want.
I my mind it is a long way from 3.70 to 4.56

My 69 was born with a 3.70 and it is fine (in my mind), and I don't race.

Just my 2 cent.

OMF

Of the two ratios you posted, for a daily driver I'd definitely choose the 3.73....

Duane4238

The 3.70's would be the better choice. Stay away from the 4.11's. I've had them and you will literally watch the gas gauge move as you are driving. More suited for a truck that is going to do pulling or hauling a trailer at a lower speed.
Duane

3JsVette

With no overdrive transmission 3:70s will be more than enough. I would rather see an overdrive transmission especially for a daily driver.

c3_dk

I agree, 3.70 with a M20/21 or TH400/350 would be fine.
With a 4.11 a TH2004R/TH700 or 5 speed manual is needed.

Maybe the first choice would be best, if it was a new transmission.

Ryan Menzies

For my 2 cents and what it's worth.:
I have 3.08 gears and an M21 in my 72. I find myself in 4th quite often in town to keep the rpm down and not **** off the neighborhood.
I honestly couldn't imagine going anything lower geared than my 3.08 but this is just my opinion.

Tim 1973

Here is a calculator to play around with. Put your tire size in your transmission info in and you can see your RPM at a selected speed with different gear ratios

http://www.crawlpedia.com/rpm_gear_calculator.htm

Tim