I have the stock 3.42 locking rear in my truck. What gears would you suggest for an upgrade and what part number/ spline would I need? I'm looking at an eaton posi unit. I like to spin my tires and cut up a little, I'm just waiting for it to go out, that or the tranny. I'm planning on trying to make around 300-350 whp later on but this is and will be my towing truck and daily driver. I was thinking somewhere around 3.73- 3.90 gears. Dont really want 4.10's or higher.

 

i would get:

3.73 gears
Eaton Posi
Yank 3000

you should be able to have some fun then.

for the Posi, you want:

8.5"
10 bolt
30 spline

 

If your not driving coast to coast every week get 4.10's
You'll be glad you did.

 

Do the 4.10's, you will be happy. A 3.73 would be a difference, but a smaller one. As long as you dont plan on going with a shorter tire you wont mind the 4.10. You would only be looking at about a 10% increase in cruising rpm in overdrive, so it wouldnt be as bad as most think on the highway.

 

Right now at about 60mph I think I'm pulling around 2k rpm's. So I'b be looking at around 2200 with 4.10's? How is gas mileage? I've been noticing my rear end feels like its slipping almost. Almost like I'm spinning the tires but not really going anywhere. Also a slight clunk sound that I've narrowed down to the rear. How hard is the install on the eaton unit and about how much do they go for? Also for those track days how much of a difference will I notice between the 3.73's and 4.10's? One more question, on the torque converter, 3k isn't too much? I run a 2500 on my th400 sitting behind a 428 and its not enough but I know how it acts and I'd think 3k would be pretty noticeable in my truck and might cause problems for others trying to drive it, like the gf.

 

if u change the gears its gonna have annoying whine, and the 4.10s kills about 1.5-2mpg

 

Now I know that with a locker you'll have an annoying knocking but why a whine? Would I still get it with the 3.73's or is it just 4.10's or larger? I've had posi on my 76 and 79 trans am's, one with 3.23 and the other has 4.10's and I dont really notice a whine. Of course with the cut outs open you dont notice much at all except a tooth rattling rumble.

 

the eaton install is not that bad. i did it myself for the 1st time last year. if i can do it, most people who like working on trucks can.

the yank 3000 is a perfect stall. not too high, not too low. i even tow with it. 4.10's and a TC would be too much. go with 3.73, eaton, and TC.

or put in the eaton and TC, then see if you want to swap gears. i am sure you can still get whiplash with a 3000 stall and 3.42.

 

BTW, the yank 3000 has great driveability. you don't even know it is there unless you punch it to the floor from a complete stop. the G/F won't even know.

 

If the gears are set up right and you use GM gears they will not whine. Your city mileage will suffer more than your highway mileage, but both will suffer some.
On these engines I would say a stall would do more than a small gear change. If it had 3.08, then I would say a gear. With 3.42 you might want a stall first and a gear later. You will like both and a 4.10 will make a big difference, but stall first might be better.