14 bolt gear ratio?

[JohnRod]

I have a 76 Sub. with a 350/350 and a 14 bolt [8 bolt floater] 3.73, with 9.50x16.5's which are about 29". is the next lower ratio 3.21? or is the an in between? I have a big hill to climb between here and town [both ways of course. I dont think it would pull a 3.21 in high, and going into 2nd defeats the gas mileage idea.
Ideas?
thanks Rod in AZ

 

[Nonstop]

Honestly, I would consider larger tires or a gear vendor style od. 3.42 is the next lower ratio, but it is still in a Suburban with a th350.

 

[Bextreme04]

Is this 2wd? I would look at going to a 700R4 before I'd drop the gear ratio for fuel mileage. You likely wont have any increase in mileage due to the nature of the engine unless you are doing LOTS of highway driving. The hills are going to kill any mileage advantage too.

 

[68post]

Keep in mind that spending money to achieve better mileage is very counterproductive until the monies spent is gained back, which takes time, sometimes a lot of time, if ever !

 

[bucket]

Unless you are doing a bunch of interstate driving and only interstate driving, you won't see any difference in economy.

My '78 also has 3.73 gears and had 9.50/16.5's to start with. I then installed 33's. Now I actually have 35's on the rear. My mpg average has not changed with any of them. And that is tracking miles with GPS, not the factory speedo.

 

[JohnRod]

yes, I should have put a 200R, in 2000 when I was thinking about it. at the time I though the ROI would never work. now 22 years later...ugh.
Rod in AZ

 

[scrap--metal]

The 200-4R that you mentioned is becoming harder to find. 700-R4's are much more plentiful. Just something to consider if you do really want the overdrive.

 

[JBswth]

I have a 76 Sub. with a 350/350 and a 14 bolt [8 bolt floater] 3.73, with 9.50x16.5's which are about 29". is the next lower ratio 3.21? or is the an in between? I have a big hill to climb between here and town [both ways of course. I dont think it would pull a 3.21 in high, and going into 2nd defeats the gas mileage idea.
Ideas?
thanks Rod in AZ

I would change to a 4:10 and put in a 700R4 if you want better mileage, that way you will have a gas-saving OD at speed, but shorter gearing at lower speeds for faster acceleration, but keep in mind that if you have to have a shop do the work, it will take you several years to get back the money you spent. I would forget about taller gears, as in city driving, you might actually use MORE gas. Improved mileage would only happen on the open road.

 

[fast 99]

Really doubt there will ever be a return on any conversion. In the late 80's I tried to rationalize lower fuel consumption to pay for the option cost of a 6.5 diesel over a 454. Think the option was in the $2500 area. It took 100k miles! That didn't include any surprise repairs.

Before spending any money, put some hard numbers on what you expect and the projected cost.

 

[68post]

The quick n dirty is a trans swap only.
Small differences in rear gear ratio are hardly noticed unless there's a big jump, and around town - not at all. The .70 overdrive of a 4L60/700R4 makes the 4.56 gear feel like a 3.21 exactly (do the math, 3.192). I wouldn't go with any higher in a truck than that, and if your tires have much height it will likely be counterproductive.

 

[SquareRoot]

Post a pic of the rear hubs. A FF in a sub? Really. For me, it took a 5 speed manual (nv4500) and Edelbrock pf-4 EFI to achieve any noticeable increase in fuel mileage. It probably wasn't cost effective but the driveability factor is off the hook.