Hey guys i have a 87 t/a gta with a 350 tpi, th350, 3.73 gears
The car is a weekend car and I like to go faster on the highway.

at 3000rpm i am going 60mph

i want to put in 2.73 gears what do you guys think about this?
is it a good or bad way to go and what will happen?

 

Welcome to TGO. After the 3.73's, the 2.73's are going to be a disappointment, I'd think. You might consider something between, say, 3.23's.

JamesC

 

Thank you
So you think the 3.23's is a good idea

Do you know how much more of a top end will I get?

 

I have the same setup. TH350 and 3.73 gear.

If you are running a 26" tall tire, you could go up to a 28" tire and take some rpm out of it. It should be cheaper and easier than a gear swap.

 

Enough to get you in some hot water . IIRC, the L69, equipped with 3.73's, had a top end of 138. Do you want to go faster than that? Or is the question one of mpg?

JamesC

 

lets try this. at 85 mph, using a 700R-4 with working converter lockup, and 245/50R16 tires, your rpm is: 2900 with 3.73:1, 2650 with 3.42:1, 2500 with 3.23:1, 2400 with 3.08:1, and 2100 with 2.73:1. I suggest stopping at 3.08:1, forget 2.73:1 even exists.

 

You should be able to swap the complete rear end with someone. There are more people who want to go from a 3.08 or 2.73 to a 3.73 than people who want to go the other way.

 

why is the 2.73's a bad idea what makes it so bad?

 

I've owned and drive more than a half dozen f-cars that came with 2.73:1, and in every one except the '95 Z28, I actually got better gas mileage going to a 3.08:1 gear. Most of those cars later got gear-swapped again, to a more serious gear, but when a 3.08 gives both better mileage and better acceleration, than the 2.73, then why consider a 2.73?

 

put a 700 back in....i do 2400rpm at 60 with 3.73s...its right in its sweet spot lol

 

2400 @ 60 with 3.73s? Something's way wrong. Either your speedometer is way off, or your tach is way off, or your converter isn't locking, or your tires are extremely short. My '88, on new 235/60R15s, was 2170 rpm @ 65 mph, locked. Gotta love aftermarket digital tachs and electronic speedometers. The calculator says it should be 2171, so I had it dead-nuts perfect!

 

I'd go with 3.23 or 3.42 for a car that is used on the
highway often-i had 3.42s with a th 350 for a couple
years and didn't mind them,engine would turn over
3000 rpm cruising on the highway,but didn't bother
the engine any or affect mileage to any noticable
degree. had a 2.77 9 bolt in car for a short time and
did not like them-car was a dog at low speeds.
In my much lighter '69 camaro though i had 2.73
peg leg and that car was actually very quick off the
line and hooked well!, had mild 4bbl 350/th350-
so if your car is light and has lots of torque you
might not do too bad with 2.73s