Thread: Help with rear end ratio

Tweet

I have a 1978 pontiace firebird with 350 small block with 350 horse and 400 foot lbs tourque. I have a TH350 3 speed trans with 25.5 tires. I'm looking for a good street/strip rear end gear ratio. Something i can drive back and fourth to work and take to the strip on friday nights. I need something better than the 273 in it. before my engine upgrade to the current specs i was running mid 16's at the track with a stock 350. I need a good ratio that will work well with my current power and not eat me alive in gas and not sound like a air plane going down the road. I've thought about the 3:55 or 3:73 but thats just my unexpereinced guess. Any thoughts on the subject would help.

Well, we need more info, was the 25.5 tire used when you ran 16's? If so, then 3.73's would be good, if not a 4.10 ratio would be better because the bigger tire than a stock tire, will decrease the final ratio, the 4.10 would compensate for the raito loss and end up being around a 3.73 or so, to get a true 4.10 which I doubt you would need or want because of some streetability issues on interstates and such, you would need a 4.27 raito.

I'm running basically the same combo as your car...
I run a 3.55 rear gear and like it a lot, except on long trips...
Seems the engine combo I have is 'happy at 3100 to 3300 rpm and that equates to about 72 mph... I ran a 125 mile trip Sunday to a car show
(see pic's at:
http://community.webshots.com/album/384945224IqjTtC

Got 16.8 mpg.... Not too bad...

4.11's were fun...in town only...

Hope the info helps...
Jeff

I ran 4:10 in the panel truck. Drove it al over the country. Longest trip was 2 days each way........ pullin' a camper no less. It was great ............. Little hearing loss, but other than that it was great.