what gears in 1980? 3.55 or 3.73? thx!

[tsingh]

hey people. i'm new to the forum and to the world of hotrodding sbc. so here's what i've gotten done to my 80 vette:
- rebuilt engine (9.5:1 CR), comp.cams xtreme energy 268 cam, speedpro flat-top pistons, new cranks, the heads are from a 71 vette and it's well ported (by the guy before me).
- msd ignition module, new plugs, wires etc
- k&n filter and cleaner
- holley 750cfm carb
- edelbrock eps intake
- hooker competition headers (black)
- cat's out - converted to true duals
- performance mufflers.
- b&m shift improver kit on the stock th-350 tranny.
- my front and rear tires are 255/60/15 goodyear GTII

- i (an amateur!! by all means) estimate 325hp, 390lbs/ft torque.

aside: this is a regular summer car, will see the 1/4 mile only to see how much quicker it is. i lke driving aggresively, but besides that, it's gonna do regular city and highway driving.

- i haven't gotten my vette back yet, but was thinking of changing my rear gears: questions i have:

1. i don't wanna invest in a positraction system, so can i just change the gears IF other parts of the differential are in good working order? --- if so, what exactly do i need to buy? thanks.

2. from my driving habits, which one is best (in terms of performance/price), a 3.55 or 3.73? gas prices in toronto are ridiculous anyway, but i'm also considering the longeviity of the car life when i consider performance (since 3.73 runs the engine higher on the highway etc etc).

3. lastly, what can i expect if i change my rear tires: to say a 295/50/15 or 275/60/15?

thanks, your thoughts would be invaluable!!

cheers, tsingh.

 

[mmvette80]

what gears in 1980

I just installed a 700R4 in mine. It is equal to having 3.73 gears but i still have the 3.08. 700R4.com. I can cruise @ 70mph and @ 1700rpms. Cross country hear I come!

 

[lytemup]

do you race it? if so go w/the 3.73 and biggest rear tires you can. if not, consider the driveability - high rpm on the highway gets old after not very many miles, and the milage will be worse with the 3.73 and wider tires (rolling resistance). i guess u just need to decide what most important to you or find a compromise! :s

 

[mmvette80]

I just test drove my car with my new 700R4. For the first time since I own the car (7yrs) I can fry the tires off the line. I cat tell yo how godd that felt. Tomorrow i'll take her out on the highway and check out the new overdrive.

 

[Evolution1980]

lastly, what can i expect if i change my rear tires: to say a 295/50/15 or 275/60/15?

I have 255/60/15 on the rear. Any more than that and you will be outside your wheel wells (Re: tossing road debris at your fenders.)

I thought that the TH350 was a positraction tranny. I know that when I jump on mine, they both lock up all the way until I'm done lighting the tires.

As for your carb, not sure why you went with a Holley 750 when the Q-jet is a 750cfm as well. Properly adjusted, it can perform just as well as the Holley. They both have their pros & cons. I believe the Q-jet is the better carb for daily driving. And it still works as well at WOT. (But this is all discussed in a diferent post )

 

[Big Fish]

You could change your ring and pinion gears, but keep in mind your rear end is shimmed and gear replacement will change the shim requirements. I would suggest leaving the rear end work to the pro's who have the correct tools to properly mesh those gears. Otherwise your rear end will self destruct or be noisy. The 3:55 gear is a good all around use gear, same ratio that came standard on the L-82's. You will most likely lose some top end going to the 3:73. If both your wheels are not hooking up at this time you must have a problem in the rear end with the clutch pack.