gears 308 to 373

[Buddy]

OK I have a 85 with a 305 and a 700r tranny. I am running 35's on the 308 now and the truck is LAZY! i have a chance to get a entire axle and the guy tells me it is a posi and 373. What is involved in switching these housing out. I am just going to swap the entire rear ends. Is it worth the swap... how hard will it be. Also how do i tell if it is a posi and what are the benefits of that. also how do I tell if they are 373 if they are still in the rear end?

[Irish_Alley]

yes it would be worth it. yes its a easy swap unbolt u bolts, brake lines drive shaft and swap. use new u bolts. there are numbers on the ring you can divide them and get the ratio or take the ring teeth number divide by the pinion teeth and thats the same. bout the posi unit best i can say is post a pic while you’re in there

[Blazin]

He has the matching front end too?
If yours is original it will be a 10 bolt. Is the new one a 10 bolt? Or is it an older 12 bolt?
If its a 12 bolt you will need a cross over U joint. As the 12 bolt uses a shorter cross, and a smaller diameter cap.

[Buddy]

they are both 12 bolt

[Buddy]

I did the switch butI just changed the gears inside the axl and kept everything else. wasnt that bad or hard thanks to you tube.... time will tell if it done right. I have about 200 miles on so far and no problems. there was a fair change but I think i could of went with the 411's and noticed a bigger change. truck is still a little lazy but i think it might be that little old 305 should have put in the 35o when i had the chance.

[beastie_3]

Just remember that your RPMs will be higher, especially on the freeway. So if you do a lot of freeway driving, MPGs will drop too and engine will turn faster.