[vertbird]

My 76 TA with 400 is 90% street driven but runs mid 9's at the local 1/8th mile track. I'd like to get to 9.0 or quicker but I'm reading mixed reviews. Some people say the 2.73 is just as quick but it seems those people are often running 455cu+ with 400+hp. I'm running about 220-240hp and figured the 3.42 would help quite a bit and I'd pair that with a 200r4 so I don't lose hwy driveability. A rear end change and 200r4 conversion would probably be $4k but trying to get 400hp out of my engine would be twice that. Any thoughts?

[JB Eng Wis]

200R4 OD ratio is .67 that give you final ratio of 2.29 to 1
Do some math calculator scenarios with your tire height vs RPM's
you may just want a Lower gear ratio set.....

[b-man]

Do the 3.42s.

Puts you right where you want to be on the highway and on the street.

It’s either that or leave the trans and rear gear alone and do a cam and head swap, for about the same outlay you could get close to 400 hp and not end up with the weakest of the OD automatics.

This assumes you have an engine with a solid bottom end already.

[Skip Fix]

My 78 came with 2.56s-3.42s made a BIG difference.

[vertbird]

Yeah b-man I've already done the crower 60240 cam and some head work to the 6x-8's but it's still low compression and the 557 block. I'd love to change blocks, do aluminum heads, roller cam but I'd be in at least $8k.

Thanks JB, you are right....if I did it perhaps 3.73's would be better with the OD.

[Scarebird]

462 / 200-4R / 3.55's were a nice combo in a 3,850 pound car.

[Formulajones]

3.42 with a 200r4 is a sweet setup. People also forget it's just not about the overdrive but you'll gain a 2.74 1st gear that will help launch the car and improve 60 foot times so long as you have a good suspension setup to use it. That alone will help your et.

[steve25]

Do the 3.42 with the 400.
Bedsides the added torque they will allow the motor to gain rpm faster which aids acceleration greatly.
Your mph might not improve much, but your ET certainly will!

[TransAm 474]

I would definiley go with the 3.42. Probably be a completley different car, coming from the 2.73. The 3.42 will be perfect for the street with the 200-4R, for both Performance and Drivability, and still get decent Mileage on a roadtrip when out in Overdrive....

[steve25]

Some info / help.
Sorry I can’t seem to straighten these out like I usually do.

The first chart shows you should pick up a 15% better acceleration rate.

[Cardo]

I'm running a 3:73 with a 200R4 and love it. 27 inch tall tire, probably getting about 20 mpg with a slightly built 389 and the factory Carter AFB. If you already own the 3:42's they'll be fine, but if you're buying gears don't be afraid to go a bit steeper.

[Scarebird]

Originally Posted by Cardo

I'm running a 3:73 with a 200R4 and love it. 27 inch tall tire, probably getting about 20 mpg with a slightly built 389 and the factory Carter AFB. If you already own the 3:42's they'll be fine, but if you're buying gears don't be afraid to go a bit steeper.

3.23's were a bit luggy with a 462 in OD; 3.55's worked quite well.

[Cardo]

By steeper I mean 3:90, or even 4:11. 1st gear is less useful, though. I think the 3:55 - 3:73's are about perfect.

[locomotivebreath]

I have 3.90’s and an M20 with a 28 inch tall tire behind a nice revving 406 and love it ! The motor likes them too . I live in northern Kentucky and it’s mostly 40-60 mph hilly roads with limited freeway however , so they are well suited for the area . Gets about 14mpg with the origional Qjet . Everyone said I that would hate the 3.90s - Don’t be afraid of some gear !