83 WS6 T/A

I recently bought a 1986 Trans Am with a cammed 305, Edelbrock performer intake and a 600 cfm Edelbrock performer carb. The motor itself is built for high acceleration because the guy was building it for a drag car. But it has 2.73s in the rear end. Should I swap these out or will 2.73s give me a much higher top speed? It still gets up and goes even with the airplane gears in it. If you're lucky you can even get it to spin but I'm torn between wheather I should keep them or swap them. Suggestions would be appreciated.

big gear head

How fast do you want to go? If you have enough room then the 2.73 will allow you to go faster, but it will take longer to get up to speed. A 3.42 is usually just about perfect for most of these cars with an overdrive transmission.

Formula 305

3.42s are a MAJOR improvement. The 2.73s are nice highway gears but seriously lacking in the get up & go department. It is important to note that in stock trim the 700R4 will lock out overdrive at WOT, leaving you with a "top gear" ratio of about 1:1 (I'm not 100% sure if 3rd in the 700 is 1:1, but I believe it is close.)

http://www.f-body.org/gears/

I used this calculator for my data, assuming stock tire size of 245/50R16 and a redline of 5,000 RPM.

Theoretical top speed (gear limited) with 2.73s in 3rd: 140MPH

Theoretical top speed (gear limited) with 3.42s in 3rd: 112MPH

I've heard there are ways of modding the 700R to shift into 4th at WOT, but I have no experience in this department.

big gear head

Yes, 3rd is 1:1

Ron U.S.M.C.

2.73 to a 3.42 with a new L.S.D. and it will "NOT" be the same car.


Fun factor = 100% improvement.

Phenom-1

3.23 posi I believe to be the best of both worlds.

You get great tire smoking throw your neck back acceleration and run good Rpms on the freeway @ 70mph and mpg stays around 16 city 23 hwy... When you baby it

83 WS6 T/A

I want to be able to hit about 130 and still accelerate pretty fast during low rpms. I took this car for a ride the other day and went up a steep hill, It stalled twice. I had to take it really easy and gradually press the throttle. I want gears that will let me light the tires up a hill. I have a 1983 junk Trans Am WS6 laying around with a posi rear in it. what gearing do you think would be in that? I know for sure it has more than 2.73 so I'll probably take it out, clean it up and swap it over.

Formula 305

If it stalled twice trying to climb a steep hill you have a problem. I'd address that and re-evaluate your acceleration before you decide what to do with the rear.

Also, why on earth do you need to go 130 mph, is this a race car?

big gear head

Sounds like you have more problems than a gear. I'd be checking the ignition timing curve and get it worked out. You should be able to floor it with no hesitation or stall no matter what gear is in the rear end.

Phenom-1

'82-'83 Trans Ams usually came with 3.23s.

But unless you have a manual transmission with bad clutch & gas footwork, there's no reason why you should be stalling uphill.

83 WS6 T/A

It has a 600 cfm Edelbrock on it and that's too much for the engine. It needs a 500. That's the main reason it stalls but it also doesn't accelerate fast enough for me. It won't spin the tires to save it's life unless you're on gravel. I took the other rear end out of the 83 trans am and from what I saw it seems to have 3.08 gears in it.

83 WS6 T/A

It needs carb work that's why it stalled, 600 cfm is too much for the 305. But once you get past the low rpms that the carb screws up on, it still doesnt accelerate nearly fast enough. Also, 130 is not that fast at all. That's the minimum speed I want this thing to go.

redneckjoe

sounds like you need a tune-up. you might check for vacuum leaks too. a 600cfm carb is not too big for a 305.

big gear head

I agree, a 600 is not too big. The Edelbrock carb is set up so that it only allows as much air to pass through as the engine needs. You could put a 750 Edelbrock on it and it would still run fine if everything was set up correctly. I think you have a problem with your ignition timing. I would start by checking the timing advance with a light and see where it is at and work on getting it right.

Ozz1967

iTrader: (4)

Also, gearing is all relative. I have 3.73's with my 5.7 and I can tell you, I ruined that theoretical top limit mentioned above. I was at 130 on the autobahn running about 4500rpm in OD. I was getting to the limit though where it was going to downshift to third and that would have possibly been ugly.

With a good kit in your trans, you can change how the trans reacts to overdrive at 75% throttle or more.

Ozz1967

iTrader: (4)

It needs a properly tuned Quadrajet is what it needs!!

skyscrappin1

Hi what LDS

skyscrappin1

[QUOTE=skyscrappin1;5872893]Hi whats L.D.S. never heard of such...

big gear head

It's LSD, not lds. LSD is limited slip differential (posi).

Ozz1967

iTrader: (4)

[QUOTE=skyscrappin1;5872894]LOL.

LDS is "Latter Day Saints", as in the Mormons.

Big Gear Head has the answer.

2005Impalla

I believe I have 2.73s in the back of my car it feels like I am taking off in 2nd gear. I have had 3.23 rear gears in a stock 305 Camaro once and loved them. This time I want to go with 3.42s There was a big difference between the 2.73 and my 3.23 gears. I am running a 28" tire with the 2.73s though and my 3.23 had stock rears on it so that is another factor. I would check if there is a tag on the SW6 rear and see if it tells you want gears it came form the factory with. If you want top speed I would look at making it so you can grab 4th gear. Also you will not hit top calculated speed due to your stall converter slipping a little and not delivering full engine speed to the transmission so factor that in to your top speed when choosing a rear gear. A 3.23 might be your best choice with a modified throttle valve.

Ozz1967

iTrader: (4)

Your RPO codes I believe indicates what gearing it came with if you have them.

83 WS6 T/A

Hey guys, I apologize for my stupidity, I went to time the car and the guy who sold it to me didn't even have the distributor tightened down and it was way out of time, It's good now and will fishtail on dry roads when you put the throttle to the floor no problem without hesitation. I don't know why I didn't think to check that.

RS Chris

It happens. Sometimes we get caught up in looking for big problems we forget the little or simple ones.

big gear head

I was pretty sure that you were going to find a problem with the timing (post 9 and 14). Glad you found it.