Best all around gear ratio, street and hwy

Opinions as to the best gearing for a mild 350 build that bridges the gap between street and highway.

 

It will depend on several things. For instance, your motor and your tires will come into play. Also your mix of driving will affect it, too!

If you are running a pure stock motor with short 14" tires, I'd say got with 2.73 or 3.08 but if you have a stout motor that doesn't reach high vacuum until 2500 RPM and 275-60R-15 tires, I'd say go with 3.23 or 3.42. If you have an overdrive tranny, you could go with 3.42 or 3.73 with not much downside.

What RPM do you want to turn and what is your top cruise speed? I generally like my top highway speed to be no more than 1/2 my redline and no less than the stall of my converter or where my cam produces the most vacuum.

Currently, I cruise 3300 at 70 with 3.73 and 275-60R-15s. A little tight but then I am having an overdrive built and it will drop it to 2200 at 70, which is above my stall by a little and will be locked up at any rate.

Your mileage may vary.

 

3.23 for a stock 1968-70 8.2 rear and 3.08 for a 8.5 1971-72 rear.

 

I second this
as for 71-72 if you have a 255-60 and smaller i'd go 3.08 if you have a 275-60 in the rear, 3.23 is great
as for gear brands, either u.s gears, motive performance, or yukon

 

3.08 or 3.42

 

best thing to do is figure out what speed and what rpm you want to see on the hi-way @ the givin speed by using this

http://www.ringpinion.com/Calc_RPM.aspx

 

Thanks for all the input. I currently running a 3.08 set up that was installed before my engine rebuild. Now that all is done I think my top end is great but I feel I could use a little more bite off the line. However, I am extremely satisfied with the RPM's at highway speeds. Hope you guys can see my dilemma.

 

Hi Steve. I'm running 255x60x15 tires with a 3.23 posi rear (stock 350 4bbl) which has a nice take off on the street and no problems on the highway. I'm running 3,000 RPM at 70mph.

 

Overdrive time.... lol ou:

 

Are you saying an overdrive tranny would allow me increase the gear ratio and have lower RPM's at highway speed?

Just got my turbo 350 where I want it with a shift kit and all.

PS: I'm running 14 inch not 15 inch tires and rims.

 

I can absolutely relate.

Sounds like the 3.42 might be right for you.

 

That is why we all are doing the overdrive trannies. You can have 3.42 and drive the final ratio with 3.08. 200r4 700r4 4L60 and 4L80 etc.

Jim

 

Thanks for the info Jim. Just finished dumping funds into the motor which came out great but cost some $$ to do it right. Probably gonna stick with what I have for now until I have the funds and time for a different tranny or gear change. I was concerned in the beginning about the ratio when I went posi, but since I like the highway I compromised not knowing how much additional power I was gonna get out of my rebuild.

Boy does experimenting get expensive! However, its all good as I love my Buick and this site for the information available! :TU:

 

If funds are tight, you should have enough torque to enjoy it, just maybe not enough to be the fastest off the line every time. Stick with what you have if it is reliable and working.

 

Another possible solution

If you're happy with the 3.08 rear gear at hi-way speed, you could keep it and try a higher stall torque converter. A "loose" converter can really make the car feel a lot stronger off the line. The "cost" (due to increased slippage in all gears) is slightly higher rpm's at cruise, slightly higher fuel consumption, and more heat in the trans fluid. As long as you don't get carried away, the pro's outweigh the con's, IMHO. Something around 2000-2500 rpm stall works fine on a street car, and shouldn't be too expensive.

 

Any idea what would something like that run?

 

I have a friend here in Michigan who builds convertors and is very reasonable with prices as compared to other well known builders. His convertors are very high quality and will not have excessive slippage when driving normally, but when you hit the loud pedal it will have the higher stall speed. His name is Mike Ridings and number is 586-255-3426, tell him I recommended you to him.

I run his convertor in my 200-4R and it works very nicely. You will still need an external trans cooler,but it wont build as much heat as a cheaper stall convertor.

If you do a lot of highway driving and want to keep the RPM's down but still have great off the line performance with a lower rear gear ratio save up for an overdrive trans. I built mine with some good hard parts and other stuff from CK Performance and love it. With my TH-350, 3.31 gears and 245/60/15 tires I was turning 3200 to 3400 and still being passed by everything on the freeway. One day while driving my Buick back from the Frankenmuth Autofest on I-75 and was passed by a late 40's sedan with an overdrive,( I could tell by the exhaust note), I said that's it I'm building an overdrive. I now pass everything while turning about 2300 rpm with the lock-up conv. on. Wish I would have done this years ago! Anyway just my .02 worth.

 

Good advice!

Thanks

 

I am guessing 3.42's... only b/c that is what is being put in my old 2.73 rear end at present and I hope it is. ;-)

 

Another way to go is to install a lower first gear in the tranny you are using now..if you have a T400 you put a 3.0 first gear in it which with your 3.08's makes first seem like 3.73's..it also affect second gear a little bit..you will still have 3.08's for highway use etc. The T350 also has a lower first gear available but not sure if its a 3.0..might be a 2.75 gear?