captainmorgan

I have a 4 speed with 3.73 gears and at 70 MPH and 27" tires I'm running about 3300RPM. I want to change to a OD trans but can't afford it right now. The 3.73 gears are fun in town but not at highway speeds for longer distances. I'm thinking about changing to a higher gear until I can afford an OD trans.

Has anyone changed from a 3.70 to a 3.08 or 3.36 gear? Did you like the change? Does the car seem sluggish in town?

Thanks,

jnb5101

a quick look at your engine profile indicates that you have a high rpm engine. i'd stick with the 3:70. i think driving the car in town wouldn't be much fun-by the time you got into the power band, you'd be at the next stop-light.

7T1vette

If you want to reduce highway speed rpm's, swap to a 3.08 instead of a 3.36. A 3.08 will drop the rpm's by about 20%; 3.36 will only drop it 10% [300 rpm].

Your best approach would be to install a 5-speed, overdrive tranny. That would match up really well with a 3.73 rear gear. But, if that's not in the 'cards' right now, go with the 3.08.

joewill

swapping gears is not cheap, there is gear purchase, gear setup, the 'while you are at it' disease will set in after you get it all apart and discover the hundreds more that you will have to spend after you get the rear end all torn apart. ujoints, crossmember bushings, gaskets, bearings, side yokes, heavy duty cover, new clutch packs and more will escalate your cost. add shipping of these parts and paying someone to put it in, you are halfway spent to ward your OD Tranny. if your ultimate goal is to put a OD tranny in, let the money you will spend swapping gears be your down payment money on a new tranny..

i did the same thing, swapped a 4.56 for a 2.73 because the low highway and cruising rpm was more important to me than neck snapping torque off the line.

72ls5fla

I had a friend in town do a 3.73 -> 3.08 swap.

Said it made a BUNCH of difference. He can now cruise 80 MPH and turn close to 3100 RPM. At 70 MPH you will turn around 2550-2650 RPM.

Makes a big difference in gas consumption too!!!

His is a 1970 w/454 4spd (M21) - says it pulls nicely too. But lost it's neck breaking launches at traffic lights.....

Benjy

I just swapped my 3.73 gears to 3.08 on my 1960 Vette. At 80 mph an hour I was doing 2900-3000 rpms, 60 ish about 2200. Have not seen much of a power loss on street driving. Although I need to find the correct gear for my speedometer, my readings are off by 7-9 mph.

cagotzmann

have a 78 with 3.08 gears plus I have a 6 speed. ZZ383 Engine and is fun to drive anywhere street or track days and I get 27.4 MPG (23.4 MPG US) on the highway @ 73.5 MPH .1800 RPM.

City driving is 1-4th gear , main high traffic roads 5th, highway 5th and 6th. Great everywhere. At the road course track days I use 2nd & 3rd gears which covers 60 km/h - 165 km/h