BlackC3vette

The spec's for my comp cam call for 3.23 to 3.73 gears in my 80. It's a 383 with the original 4 speed. It still has the original rear with the 3.08 gears. My plan calls for a 3.73 setup, but just for the heck of it, I know plenty of guys here on the forum run the 3.73. So, if you run 3.73/4spd are you happy with that or do you wish you selected another ratio?
No, I like the 4 speed, so no overdrive is in the near future.

mvette76

the freeway gets kind of old with the with 3.73 gear 2800@60 other than that its a blast and right now I have a 350 with about 400hp

Go Vette Go

Personally, I like the 3:36 for just cruising.

My 69 had a 4:11 and did not like to pass by any gas station.

The 76 with a 3:36 cruises down the highway and gets pretty good gas mileage.

OMF

If you put in 373's and do any amount of freeway driving, you'll be begging for a 5 speed.
I have 3.36's in mine and 60 mph @2700 gets old fast....thats why I put in the 5 speed.

TheSkunkWorks

IMOE the 3.55:1 is very hard to beat for a multi-purpose performance ratio, but even with that I have to agree that an OD would much improve highway cruising. 2651 RPM at 60 MPH (assuming 27" tire and 1:1 4th).

FWIW, a 3.36:1 ought to be turning 2509 at 60.

scottyp99

So, I guess the question we need the answer to is: Do you drive it much on the highway?

Scott

Alwyn678

To a 700R4 and could not be happier!

BlackC3vette

Well, at (3.73)2800@60 I guess I won't want to do that for very long! It's not my daily driver, but its highway driving if I take it to work.
It looks like the 3.55 ration is a good compromise with 3.36 being a better one. I really would like to move away from the 3.08 to take advantage of this 383. True, the 383 can spin the tires off the line, but moving to at least the 3.23 is a priority.
I would like to thank all who posted rpm@mph, it's a big help. There was a really good post (last summer?) about overdrive trannys and rear ratios, I just couldn't find it.

hugie82

but if your gonna do a gear change go with the 3:23
I did 3:55 and I was reving a lot higher than 2800 rpm at 60mph. I would say it was closer to 3300 rpm but I had an auto trans

BlackC3vette

This is a four speed manual which I like.

BlackC3vette

Hopefully somebody with the 4 speed/3.23 combo will post what his 60mph rpm is (hopefully).

hugie82

I had a 4 speed with the 3:42 in a chevelle and it sucked also but I like cruising fast on the highway here in NJ . Everyone is doing 80mph and trying to do 60 is suicide.
My 82 has the 700R4 and it's a dream to drive on the street. The first gear is much lower than your 4 speed and I can launch with 2:78 gears. With the overdrive I'm doing 80mph at 2000rpm ! No exaggeration at all.
Think about what the rear will cost that price the trans swap. It's not much more and with 3:08 ,it will boogie!

scottyp99

There is only .16 difference between 3.07 and 3.23, I doubt you'd even notice a difference. The overdrive tranny with a low first gear is the real solution here.

Scott

Postal123

I know you're content with the 4spd manual, but if it were me...assuming you're going to do a gear swap anyways, I'd select something that will give you some performance and tolerable highway driving in the short term, but also work well with a 5 or 6spd manual down the road. I say this because with only 4 gears you will always need to compromise. With 5 and especially 6 you can have the best of all worlds. I have a TKO 600, but now wishing I'd waited and gone with a 6spd. Remember all the ODs have a much higher numeric 1st gear so something in the 3.36 to 3.55 range is similar to 4.11s with your 4spd off the line. With 5 gears you have to choose between 1)performance and THEN a highway tranny OR 2) performance through 5 gears with a little RPM buzz on the highway. With a 6spd you can have your cake and eat it too. I say this only because I'd assume the bug will hit you at some point...

BlackC3vette

My son and I went for a short cruise today and without the wheel to hold onto I realized how much I was being pushed back into the seat. So would I feel the difference between the 3.08 and the 3.23? Who knows.

Anyway, I just got this thing back on the road again and I just want to enjoy it for awhile. After doing the engine, resealing the tranny, converting this 80 to dual exhaust, all the wiring/harnesses, fixing the steering, etc.., it just feels great to run the gears again!

Moving to the overdrive sound great, but I really think this needs to be planned out. I don't want to incur all the time and money for an OD tranny to find out my rpm at 60 mph is too low and it lugs because I didn't want to change out the 3.08!

LS4 PILOT

Need to use a M21 the 2.20 first helps tame the RPM some.with those high numeric axles

My M21 and 3.36 is actually decent on the highway under 65 is no bother.
First is actually a bit fast , no a creeper at all. I can drive around in first and second most of the time in the city.

These gearings were common before the mid 70's gas crisis....I don't remember them be annoying really. It's just the way trucks and many cars were . Big land yacht were different There was no lugging along at 1200rpm doing 55 mph performance cars.

I grew up riding with the windows down , no AC and the engine spinning , so when you needed to pass. RPMs were already up there , just mash the pedal and go .....gas was cheap ....you just let her rip ..no overdrive was needed.

Big Block Dave

An M21 trans would create less response off the line, and maintain the same highway rpm as any other non over drive trans; We want to tame the RPM on the highway and take advantage of the ratio out of the hole. The one advantage it has is the ability to downshift from 4th to 3rd at higher speeds without creating a drastic change in rpm.

I think there is a t10 that has a 2.4 something 1st gear and a close ratio between 3rd and fourth. If this is the box already in the OP's car, Id say thats a win.

Alwyn678

Then install a 6 speed Manual.

71454Chevelle

An M21 with its 2.20 1st gear with a 3.08 rear gear is the last transmission you want in there. That first gear/rear gear combination is a pitiful 6.77 SLR (staring line ratio). No good for any off-the-line performance My 2nd gear combo (trans gear ratio x rear gear ratio) of 8.12 has more gear ratio than that 1st combo.

It doesn't matter which Muncie or Borg Warner 4 speed you use, 4th gear has the same 1:1 ratio which means interstate rpm would be the same between all of them. An M20 Muncie with its 2.52 first or Borg Warner Super T10's 2.64 or if you can find one 2.88 first gear tranny would be the best non-OD transmission when using a 3.08 rear gear.

BlackC3vette

According to Corvette by the Numbers this 80 has the 2.88 first gear. As far as I can tell, this is the original tranny and rear end, the case numbers match.