grimesjm1

OK... It seems everywhere I go I get a different answer. I have an '87 Coupe with the 2.8 automatic. The car feels like it is geared WAYYYYY to high. I've had it since October and I've been picked up for speed 4 times in the thing, my first ticket was the first one in a year and a half. Unless I a consciously staring at the speedo and letting off the gas, I can't drive 55! The thing wants to cruise at 80 mph and at 55 it feels like 40. It revs at less then 2000 at 55 mph. I am best friends with the previous owner of the car who tells me that the car is bone-stock. His brother has an '85 with th 2.8 auto and he says it drives the same.

So I a putting gears in it. Thing is, everyone on here recommends getting a 3.42 or 3.73. Problem is, my car comes stock with the 3.42's, and I doubt just going to a 3.73 is going to make that big a difference. What do you guys think? Everyone says 4.1`0 will kill fuel mileage on the highway, but is it really that much lower then the 3.42?

BTW... I can't put pics of my car in my signature ye, here's a pic in case anyone was interested.....

grimesjm1

oh yeah....no i don't drive it in the snow...pulled it out of the garage to take pics cause i am thinking of selling it on eBay

Berlyn0963

iTrader: (4)

theres nothing wrong with it
my car tachs real low at 55 also ( i have 3.23 )
dont worry about it and i wouldnt change nuthin if i was U
just watch your speed more often and U'll be fine or U'll end up like me with a reckless 101mph

:lala: :lala: :lala: :lala: :lala: :lala:

grimesjm1

I know there isn't anything wrong with it, I just wondered how low I can go. I drive it on the highway but I want fastr take-off power. I feel I can go lower and not sacrifice too much because it feels so high now. I have no idea how low I should try to get awaywith though....I hear so much about the 4.10's being too low, but those same people recommend 3.42's which is what i have already, it seems too high. Thanks for the help tho

TomP

Yep; that's the beauty of the 4-speed automatic (700r4 trans) with a lockup convertor- your rpm's at highway speeds drop dramatically. You can feel an increase in rpm's (while doing 55) by keeping your right foot "constant" on the gas, and pressing your left foot on the brake- just enough to turn the brake lights on, but not enough to slow the car down. This disengages the TCC (torque convertor clutch), which means your torque convertor comes out of lockup, and your RPM's raise.

Just drive around in 3rd (D) instead of 4th (OD).

I have 3.73's in my car... I swapped on a 3.73/posi/disc axle from an '84 trans am. I didn't notice a drop in gas mileage- but then again, I never pay attention to mileage. I could definately feel an increase in "performance" tho.

In fact, with the 3.73 rear, and the B&M 4-3 kickdown kit (prevents part-throttle kickdown from OD into D when you're flooring the gas), I can now go even faster in overdrive.

grimesjm1

TomP--so you think 4.10's would be too low too?

KED85

Do you realize you could be spending up to a grand to install these gears, proper?
Do you realize you can buy a complete axle for way less?
Do you realize how may of these 4:10 axles exist?
That's why you may economically end up going to just 3:73 or leaving what ya got alone.
I've got 3:42 and I love them.
I've got the torque of my 3.4 (200ft lbs) and it makes this Firebird-SING!
I have no problem getting off the line nor highway speed. I can normally cruise at 80-85 & get 27MPG in return. Works by me!
I can also cruise higher, but, not worth it for the engine wear. My 3.4 loves 70+. The slippery Firebird body makes 80+ also very enjoyable, too. Seems to settle in, just right.
You need a bigger engine! Try installing a used 3.4 for your dollars.

TomP

Actually; my swap was far from economical! By the time you add up the axle rebuild (bearings/seals), POR-15 paint, the brake rebuild parts (new hoses & ebrake lines & caliper mounting bolts & slides & bushings & one rebuild kit), the one store-bought rebuilt caliper, the master cylinder, and brake fluid, I had spent about $600. Then came my "fight" to get a hard pedal- the master cylinder rebuild kit, another rebuilt master cylinder, and the gallons & gallons of brake fluid. THEN, the final "winning" fight- add up the price of the Phoenix V12 injector, caliper repair (recall) kit, and another bottle of brake fluid. I'm sure I spent over $1000 by now.

Gears cost $200. Installation costs $200-$300. Oh well; at least I have rear discs now!

You can also change your rear tire size. If you go to a "shorter" tire, your "effective" gear ratio is lowered. "effective" gear ratio is how the gear ratio is "felt". Formula is (old tire height) divided by (new tire height), then take that number, and multiply it by your gear ratio.

For example, my old rear tires were P255/70r15's. Stock size was P215/65r15. The P255's were 29.28 inches tall, the P215's were 26.18 inches tall. (26/29)*3.42 = 3.07. I had an effective rear gear ratio of 3.07.

Say I went to P255/40r15's (is that a real size?) instead. That tire height is 23.16. (26/23)*3.42 = 3.86 ratio.

My current rear tires are P275/60r15's. They're 28.2 inches tall. (26.18/28.2)*3.73 = 3.46 effective.

Just something else to think about...

KED85

Thanks for the real world cost breakdown, Tom.
When I bought my 1967 RS/SS Camaro Convertible 4-speed-350 (1984), the guy kept the original axle. I asked why.
"I spent over a grand making it right for racing".
I was given a 10 bolt from a a lesser car.
I have the right 12 bolt, now.
Got one for free & I paid $300 for one.
Both highway gears and non posi's (3:07).
Posi installed in a 12 bolt was an option. Mine are 12 bolt non-posi for F bodies.
No biggie, I do have to rebuild them, tho. I add posi unit. And gears and..... Yep, $1k easy. And I'm using old tech axle, but new prices. BUT, will be adding Corvette rear disc brake on one axle. These are 11" drums on a light car, ya know. Acceptable.