[Half-Inch Stud]

Has anyone run a 2:56:1 Posi into the 11s. Asking for me.

[Bruce Meyer]

I knew a guy that dipped into the 11,s with a 2:73 gear. It was a 77 or 78 T/A. 455 with ported D ports a big cam and high compression. Had to run race gas. Cam duration if I remember correctly was 240 ish @ .050. The car was hard on converters.

[77 TRASHCAN]

I think Ernie’s (TA man) car could get into the 11’s with his combo. Considering the fact that he’s run 10.70’s. Not sure how well a 2 series gear set would hold up...

[Stan Weiss]

Originally Posted by Half-Inch Stud

Has anyone run a 2:56:1 Posi into the 11s. Asking for me.

Mark,
What are you running for a trans?

Stan

[ta man]

Originally Posted by 77 TRASHCAN

I think Ernie’s (TA man) car could get into the 11’s with his combo. Considering the fact that he’s run 10.70’s. Not sure how well a 2 series gear set would hold up...

I think there are a few others that could do it easily. The torque convertor selection would be vital.

[Formulajones]

It's not as bad to do if you run the low 1-2 gear setup in the trans like most do. That helps with the converter issue a bit as well.

Usually a 3.08 gear with the low gear set in the trans is a good compromise, it leaves and acts like it has 3.42's in it.

Going with a 2.73 wouldn't be much of a change, I would expect 3-4 tenths difference at most.

A 2.56 however, I'd definitely want the low gear set in the trans, if for nothing else to help the converter along a little bit. Quite frankly though, I wouldn't even be interested in hitting the drag strip with a set of gears like that, lol. Too much compromise. If I were taking it to that extreme I'd just look at other methods to get the cruise rpm down.

[Slick]

Originally Posted by Stan Weiss

Mark,
What are you running for a trans?

Stan

Mark runs the 4L80E Stan.

[i82much]

Easy, just run a 20 inch tall tire.

[Formulajones]

Wait what??? A 4L80E overdrive and we are worried about keeping a 2.56 gear in the car?

Put some 3.73's in that thing and let it eat.

[Formulajones]

Originally Posted by i82much

Easy, just run a 20 inch tall tire.

lol

[RocktimusPryme]

Ive done some minimal research into the low gearset in the transmission. I think I read that the low gearset gives up some strength. Any truth to that? Ive got 3.08s myself outback.

[Mr Anonymous]

buddy and I got his 81 formula into the mid 12s on a 3.08 - but about everything you would think to make it go faster didn't. Went to 4.10 and the catapult into the middle 11s seemed like space travel.

[Formulajones]

Originally Posted by RocktimusPryme

Ive done some minimal research into the low gearset in the transmission. I think I read that the low gearset gives up some strength. Any truth to that? Ive got 3.08s myself outback.

There are a couple brands. I'd have to look at which one was more favorable as I don't remember off hand. TAman uses them with success, he could give you a quicker answer.

[ta man]

I've had my low gear set for a few years no issues.

[ta man]

Originally Posted by Mr Anonymous

buddy and I got his 81 formula into the mid 12s on a 3.08 - but about everything you would think to make it go faster didn't. Went to 4.10 and the catapult into the middle 11s seemed like space travel.

He picked up 1 second with a gear change? Any more details?

[Navy Horn 16]

Originally Posted by Formulajones

Wait what??? A 4L80E overdrive and we are worried about keeping a 2.56 gear in the car?

Put some 3.73's in that thing and let it eat.

Or enter some standing mile competitions. That car must have a 230mph top speed with 2.56 gear and .75 overdrive.

The Texas Mile in Victoria, Texas is pretty cool!
https://www.theusmileracing.com/the-...stration-info/

[amcmike]

Originally Posted by Formulajones

Wait what??? A 4L80E overdrive and we are worried about keeping a 2.56 gear in the car?

Put some 3.73's in that thing and let it eat.

Well high 11s would be in the 115mph range. If he had a 6-6.2k rpm redline, theoretically he'd be able to cross the finish in 2nd gear (assuming 26" tall tires and stock 4L80E gears). That would eliminate time loss normally to shifting into 3rd (maybe .25 to .5s?).

[geeteeohguy]

Originally Posted by RocktimusPryme

Ive done some minimal research into the low gearset in the transmission. I think I read that the low gearset gives up some strength. Any truth to that? Ive got 3.08s myself outback.

I'm running a 2.56 safety track in my '67 GTO behind a TH400. Compared to a 3.36-3.55 gear, the ring gear on the 2.56 is super thin, and the pinion gear is a huge diameter. The 3.55 ring gear is a LOT beefier. While I love the 2.56 gear on my street car with it's low highway rpm and high fuel mileage, it would not be a choice for dragstrip operation at all.

[Slick]

Mark (HIS) is a very, very smart guy, and a very nice guy.

Please don't try and figure out the why of 4L80E AND 2.56 gears. Nor figure out the need to run 87 octane. It makes my head hurt trying to understand.

If I guessed that his design goals are maximum fuel economy, longevity (revolutions/mile) and performance, it would still probably be wrong.

Did Mark mention that he is running a Dominator?

Add that up!

[Skip Fix]

Having 2.56s in my 78 TA when new it can sure cruise at a lower rom and feel like it has reasonable pickup. But convertor choice is a big deal.The shop run by a Pontiac SS racer that freshened the stock motor put a convertor in also. Was so loose with the 2.56s it never really locked up and actual the heat generated was raising the radiator temp until I had them swap in a different one.