Gear Ratio Help
 

I have a '72 SWB GMC that I am currently swapping out the old 350 for an LS1.

I have a 700R4 Tranny that I am keeping. I don't plan on tacking the truck to track but want it to come off the line but will also see some good highway miles.

I plan to replace the current rally wheels for 20'' US Mags in the coming months.

What gear ratio would everyone recommend given my set up and how I plan to drive.

I'm currently thinking 3.73 but would love everyone's advice.

Re: Gear Ratio Help
 

3.42 would make it run about 1500 RPM at 65-70.

Re: Gear Ratio Help
 

With the 3.73 and the 700r your final drive in 4th will be comparable to a 2.68 rear gear ratio. The 3.42 = 2.66


I'd go for the 3.73. It's been used numerous times here on the board and there are plenty of testimonials backing that up. A quick search would have produced those results

Re: Gear Ratio Help
 

I have 3.42 with the 700r4 and I am going to change it to 3.73. 3.42 are little too tall for my set up.

Re: Gear Ratio Help
 

Tire height plays a part in the equation as well.

Re: Gear Ratio Help
 

3.73 + 700r4 ( MPH is off by ~10 so actual is about 90 in pic )

Re: Gear Ratio Help
 

Agreed I would figure what tire size you were going with then figure the gear ratio based on the 700 r4 overdrive ratio and what rpm you want to be driving around at.

Re: Gear Ratio Help
 

I vote 3.73, but pick your poison! 4 ratios and 4 tire diameters to compare.

Re: Gear Ratio Help
 

Running 3.73 behind my 700r4 with 29" tires and love it. Runs about 2200rpm at 70, and get's about 16/17mpg on the highway. And you'll love 1st gear.
:gmc2:

Re: Gear Ratio Help
 

First gear with posi is indeed a lot of fun!

-klb