speedsecret

I'm thinking of changing my rear 3.36 ratio to something lower.
i got a L-82 equipped with Richmond 4+1 transmission with a final ration of 1:1 in 5Th gear.

I'm looking for better gas mileage on highway but i don't want to kill my acceleration ability. now my engine rev about 2500rpm at 60 mph .
i cant decide if i should change to 3.08 or 2.73 .
3.08 seems like a minor change about 200-300 rpm
2.73 seems like the change i want - around 2100 rpm for 60 mph but I'm afraid its going to be to hard for the engine

the first gears in the gearbox are very short and today I'm barely use them .

what do you say about the change?
what brand of ring and pinion should i get?
what should fit my car 8.5' ? 10 bolt? what size should i buy?

thanks

Tom

joewill

the gear set is only a very minor part of the equation. dropping from a 336 to a 308 will be negligible to the novice. plus it is a pretty big project, especially if you pay someone to do it. while you are under there replace your ujoints, your yokes, while you have it apart might as well replace the bearings and clutch pack, sandblast and paint your carrier and crossmember, new crossmember bushings, gear setup, new seals, rear allignment. might have to cut your exhaust off, so plan on new exhaust. restore your spring, new heavy duty back cover....

i bought a rebuilt pumpkin and did the rest myself and it was about 1 grand.. count on 2500+ if you pay someone to do it.

i bought a 2.73 and I love it. i did have a 4.11 so my end result was much more visible. I can now go on the highway and i actually use 1st gear starting off. Don't care about the loss of accelleration. my engine rarely sees 4000 rpm. I just cruise.

eastltd

Would it be easier to change for final gear in the transmission to an overdrive gear, say .67:1

Talk to a transmission shop to see what they can do.

I run 3:36 in my BB with a 4 speed and see similar RPM's at highway speeds.

speedsecret

thank you for the fast responds

In my country parts are very expensive . {im not living in the US } and to change something inside the gear box will cost fortune.
i already have a quote for changing the rear end ratio and for now it seems like the cheapest way.
i will be in the next month in NYC and i thinking of buying there the parts i need.
i just don't know how the car will run with 2.73 in the rear and what size should i get for the ring and pinion { 10 bolts? , 8.5' , 7.5'?}

gkull

I have a 2.73 in my Camero You also need the power to pull at low rpm in top gear .

TheSkunkWorks

Maths... With the Richmond 4+1's 3.28:1 1st gear and the 3.36:1 FDR you have ~11:1 multiplication. Changing to a 3.08 would be ~10.1:1, which isn't much difference. With the 2.73 you'd have ~8.95:1, which may be a little on the tall side for 1st if your mill doesn't have decent low-end torques, but I'd hesitate to call it unreasonable. On the other end, as gkull points out, pulling top gear is probably going to require some good power. Hope that helps.


TSW

C3 4ME

Am I not correct that the Richmond 4+1 is designed to work with about a 2.73 gear? Isn't the priciple that is has a super low 1st gear, and close ratio gears throughout all 5 gears? I was thinking the design is such that you don't need an overdrive final gear. Anyway, based on what I THINK I know, I would go with a 2.73.

Vette5.5

If you think 2100 rpm @ 60 mph's a strain, check out the current C5 and C6 6 speed set up. 1st gear's a 2.66 ratio which works well the 3.43 axle. 6th gear is a .50 overdrive and 70 mph is at 1500 rpm. I've owned both car's and there's no power in 6th, but seem to cruise ok at 70. Some C5 owner's even claim close to 30 mpg highway.

speedsecret

C3 4ME - as you written the Richmond gear box have close ratio gears with 5th of 1:1 like the stock gear box.
i will like to know if there is somebody that drive a car like mine with the same ratio and how the car run after the change. I'm afraid i will kill my acceleration in all gears.

i know about the long gears in the c5 and c6 but they have much stronger engine then what i have.

Gordonm

Check to see if you actually have a 3.36 rear. The standard rear ratio for an automatic car was 3.55 in 79 and with the L82 and 4 speed it was a 3.70 rear. Not that it really helps what you want but a 3.08 or 2.73 is a very low rear ratio. For performance off the line it is not going to be good unless you have a 1st gear ratio of around 3.00 or close to it. A 5 speed with a deep first gear would be needed.

Vette5.5

Maybe what you're really looking for is a transmission swap. A friend with a 79' L-82 3.73 axle car, fitted a 5 speed Keisler tranny kit. 3.27 1st with .68 od 5th, which figure's to be a 2.54 final for highway cruising. Been in the car several time's, and really drive's nice. Car is stock, but no cat's and dual exhuast. Not sure what the tranny kit cost, but intalled it himself, and has no regret's.

speedsecret

Gordon
first my car came out of the factory as a L-82 with 4 speed stick. then the gearbox changed from the original 4 speed to Richmond 4+1 . {5 speed close ratio gear box with 1:1 ration in 5Th gear}
i also know that the 79 sold with a 3 rear end ratio options - 3.36 /3.55 / 3.70
my car runs on the original wheels {around 27' tall} and with all the rpm and ratio calculator my engine rev around 2500 rpm for 60 MPH and from there it seems that i have 3.36 rear end gears.
it now run with headers , true duals , no cats , magnaflow mufflers.

in the past i have read somewhere in the forum about the ratio in the Richmond 4+1 i will try to find it again .

I don't want to invest fortune on gear change right now us i already have 5 speed gear box i prefer to change the rear end only and keep the

speedsecret

i found the old post on the forum about the 4+1

http://forums.corvetteforum.com/c3-t...y-options.html


from the post there the ratios in my transmission -3.28, 2.13, 1.57, 1.24 and 1.00 to 1

and the guy recommended for 2.73 on the rear.
now when we have the ratio of the gear box what are you think ? is it still going to be hard to pull on high gears?

gkull

Your tranny came with a 3.27 first gear. That is why it is kind of worthless like you said. If it is gas mileage that you are trying to gain the gearing change would not help very much. My modified L-82 motor got over 20 MPG with 3.55 gearing and the 3 speed automatic. It also had 100+ more hp