Hey guys,

I have a gearing question.

Info on my car:

I’ve got a stock AC Delco remanufactured L98 with about 25,000 on it.

For exhaust I’ve got 1 5/8’’ ceramic coated hooker headers & y-pipe, high flow cat, and 3’’ flowmaster cat back.

I’ve got hotchkis boxed lower control arms, track bar, sub-frame connectors.

I just got my new trans and converter installed. It’s a bowtie overdrives 700r4, level 3 with a 2400 rpm stall converter. I had them make the trans with wide open throttle shift points at 5500rpm and allow it to shift in to overdrive at full throttle.

I’m just getting to modifying the intake now. I have a BBK 52mm throttle body, K&N air filters, and I cut out the bellows in the air box. I am also going to get one of hawks TPI intake boxes. Then I am going to get Arizona Speed and Marine intake runners and an aftermarket base. Other than that the intake is stock L98 TPI.

What gears should I get after all the intake mods are done? I am running the stock borg warner 9bolt posi with 2.77 gears. I was thinking about getting 3.27 gears. I don’t take this car to the track at all. It’s a 100% dedicated street car. I have some fun on the highway and on some back roads around where I live.

I’ve heard that some people who have switched from 2.7x gears wished they went to something around 3.4x ratio instead of swapping only to a 3.2x ratio like I was thinking.

 

gas mileage for hwy will be better with numerically lower rear gears, but city mileage will suffer. City mileage with numerically higher rear gears will be better, but hwy will suffer. Acceleration is better with numerically higher gears as well, but you have a lower top speed, just the opposite for numerically lower. Overall it is personal preference, hope this helps!

 

Thanks

 

Since you have a 9-bolt with 2 series gears, you're kind of between a rock and a hard place.

ANY 3 series gears are going tobe impossible to put in that unless you can find a 3 series carrier in workable condition.

Might be best to consider a 4th gen rear, preferably a 98-02 one. Which will also get you VASTLY superior brakes.

IMO 3.4x is about as far as you would ever want to go with the restriction of TPI still in effect. (Runner mfr is irrelevant; LENGTH however, IS) Especially a 350. 3.2x is usually about optimum for those because TPI limits their RPM range so severely.

 

Thanks for the help. Yeah I was worried about that. I know the 9bolt is stronger than the 10bolt but not by a lot. There are so many more parts available for the 10bolt as well.

For the power level that I am at I know I don't need a Ford 9 inch or a chevy style 12 bolt rear end.