rearend ratios


Junior Member
my son is working on his 78 chev, he took out a rearend that is 3.73 and is putting one in that is 3.07, he wants to know if the 3.07is going to help or hurt is fuel economy..he doesnt care I do.


Junior Member
well, it will help fuel econmy but make it somewhat of a dog. i have an 86 chevy 4x4 with a 3.08 ratio and my acceleration/power kinda sucks. i would like to put a 3.73 in it. this is from my experiences, I`m not saying I`m right. is his truck a 4x4, because bigger tires reduces your gear ratio too, about 10% for every inch taller than stock. so the just of it is......if he is planning on a performance truck i would just leave in the 3.93.<p>frahmie


Senior Member
It all depends on how the truck is driven, if he spends a lot of time on the E-way it will be a help. as long as he is not trying to pull a trailer. But it will decrease the take off power.


How can I find out what ratio I have in my suburban? I heard that it can be done without pulling the covers & counting teeth- anyone know how?


Junior Member
Gordo,<br>Normally your sub will have a sticker on the inside of the glove box. But, if the gears have been changed you'll probly have to take off the cover, count the ring gear teeth and divide the pinion teeth by it. <br><p>----------<br>Bill Herz<br>


Senior Member
hey there-<br>I have an 87 Silverado 4x4 with junk 305 & 3.42 gears. It's not bad, but I pull a 20 landscape trailer loaded with commercial mowers & it's a dog; esp. in the spring when I still have my 32&quot; mud tires on.<br>I'd leave the gears alone; it'll take more gas to get the engine to lug the truck up to speed, esp. if stop-&-go driving.<br>If it's a 2wd, ok. If it's a 4x4, you'll have to swap front & back axles to get the same gears in both. That's lotsa bucks.<br>One solution is taller tires; 3&quot; lift in the back & extra spring in the front of my truck totalled me about $175. That's cheap, & a 3&quot; lift looks good without having to alter driveline angles, lengthen drive shafts or brake lines, etc. With a 3&quot; lift , you could fit 33's without cutting your fenders; any taller & front tires will barely catch on corners of wheelwells. Good luck.<p>----------<br>Smitty ô¿ô<br>