Help me pick my gear ratio.

[CO684X4]

I am looking for ideas on a gear ratio for my 69 2wd truck. Has a mostly stock 390, C6 Trans. I will be driving this daily with a 50 city/ 50 highway use. Looking for balance of power/gas mileage. I was thinking of sometheing around 3.50 or 3.73 gears. Is this a good choice? I am going to get a rear axle next week and want to get the best gear ratio.

[AK F100]

A big key in this decision is what size rear tire are you running and do you have any plans to change to a different size in the future.

[basketcase0302]

I am going to get a rear axle next week

What axle you putting under it? Might determine your ratio availability.

[convincor]

3.25 or 3.50. The 3.73 will get old unless you run like a 35" tire.
Here's a calculator to use which takes into concideration tire size. plug in some #'s and set what RPM you'll be running at and if you can live with it.- http://www.ringpinion.com/Calc_RPM.aspx
Even with a 31" tire and 3.50's youd be running 2532 rpm @ 65mph. You not going to set any milage records with that.

[hotrodfeguy]

Agree with what was mentioned, a stock cam would like 3.25 or 3.50 gears

[CO684X4]

Thanks for the info. I am putting in a 8.8 rear axle out of f150 or bronco. The ratios I have at the yard are 3.50 and 3.73. Not sure on tire size. Overall diameter should be around 29". Looks like I will try the 3.50's and see how I like it. I can always change out the gears later.

[convincor]

definatly stay 3.50. them bronco's ran OD trans with gears like that..

[ToughOldFord]

My vote's for the 3.55s too, it's a good compromise gear.

[fordman]

i'd do the 3.50 for the gas mileage. of course alot fo my trucks have 3.25 and the gas mileage is still real low. probably 8 mpg

[CO684X4]

I know gas mileage and the 390 don't belong in the same sentence but every little bit helps.

[bb429power]

I would say the 3.50 because with something like a 4.10 you'll be at 3,000 rpm's going 70 mph. You'll be sucking gas and haulin @$$ with a 4.10 but I would say 3.50.

[1982 flareside]

308 be good

[Redcap]

308 be good

If you don't want to use your truck like a truck. 3.08s don't pull worth a damn.

[gregamorton]

I have never understood people on here suggesting 3.50 gears or higher for highway driving. If this member is going to be driving 50 miles a day or more he needs highway gears. In all my bumps and dents that I have had over the years that were my everyday drivers I have run a 28" tire on the back and 2.47 to 3.00 gears depending on engine. even with 3.00 gears and 28" tires that puts you at 2100-2500rpm at 60-70mph. With 2.50 gears you would be at 1800-2100rpm at 60-70mph. Without overdrive most people need tall gears for drivers. Now with that being said I am not a fan of putting big tires on to change gear ratios. I hate seeing a nice bump or dent with huge rires on the back and the truck sitting way out of wack. Also look at the engine and power and determine if it will pull high gears. I had a 72 longbed f100 when I was younger and it had a 302 4 speed and I put 2.50 gears in it. Got about 14 miles agallon on the highway and run 80 every where. Put a big cam in it later and would not pull it self up a hill. So all the highway gears should work alright for highway driven with good stock engines. I would like to hear what yall think about this.

[Redcap]

I have never understood people on here suggesting 3.50 gears or higher for highway driving. If this member is going to be driving 50 miles a day or more he needs highway gears. In all my bumps and dents that I have had over the years that were my everyday drivers I have run a 28" tire on the back and 2.47 to 3.00 gears depending on engine. even with 3.00 gears and 28" tires that puts you at 2100-2500rpm at 60-70mph. With 2.50 gears you would be at 1800-2100rpm at 60-70mph. Without overdrive most people need tall gears for drivers. Now with that being said I am not a fan of putting big tires on to change gear ratios. I hate seeing a nice bump or dent with huge rires on the back and the truck sitting way out of wack. Also look at the engine and power and determine if it will pull high gears. I had a 72 longbed f100 when I was younger and it had a 302 4 speed and I put 2.50 gears in it. Got about 14 miles agallon on the highway and run 80 every where. Put a big cam in it later and would not pull it self up a hill. So all the highway gears should work alright for highway driven with good stock engines. I would like to hear what yall think about this.

If you want something that cruises the interstate at 80-90mph and gets decent gas milage, get a ricerocket.

If you ever haul things with your truck, high ratio gears are just useless. Since I use my truck, I prefer a ratio with some serious grunt. I also don't drive my F250 with gas mileage in mind...I know it gets 7mpg loaded or unloaded, pulling a trailer or not.