Positraction vrs Locking Diff?

[azmikep]

Hi again Guys.
1990 GMC C1500 Shortbed mild 5.7 motor
4 speed auto tranny
I’ve got a 10 bolt with 3.42 gears.
I am looking for advice on either a locking differential or a posi rear install.
I am currently in Florida where it seems to rain once a day for 15 mins.
Is this something I can do myself in a garage?
What do you guys think of swapping gear ratios at the same time? If so what gears would you recommend?
Are any installs easier then others? Should I buy a kit vrs parts loose?
Fastest I go is 70 mph on freeway. I get 13 mpg now. So mpg isn’t too much of a concern.
Thanks again I appreciate everybody’s advice

 

[Supercharged111]

For a 2wd in FL, I wouldn't consider a locker, just get a Truetrac. 3.42 is a good gear for a C1500 with TBI. I had that in my C1500, later went 3.73 when those gears got eaten by an exploding sun gear. The 3.73 was a bit much on the highway for a motor with no legs, but back then all I had close to home were 55 roads so it worked well for me. Doing 70+ it just didn't seem as happy as it did with the 3.42. Do you have a cam or anything to make it want to rev more than 4000?

 

[PlayingWithTBI]

I have 4.11s with 275/60R15s on my 88 C1500. It does ~2800 RPM at 80 MPH with the 700R4 trans (.7 ratio in OD). I had 3.42s originally and gained 3/10ths of a second on 0-60 and 1/4 mile with the gear change. It's still an open diff and I've been debating what I wanna do with it. The lunch box locker is an easy instal, you don't even have to mess with the pinion depth or backlash, unless you change gears. It'll make popping sounds when taking a turn though. The Detroit TrueTrac is completely mechanical with no ctutches so, it'll hold up longer than a posi with clutches. It's just costs twice as much as the locker.

 

[Silverado1994]

I have 4.11s with 275/60R15s on my 88 C1500. It does ~2800 RPM at 80 MPH with the 700R4 trans (.7 ratio in OD). I had 3.42s originally and gained 3/10ths of a second on 0-60 and 1/4 mile with the gear change. It's still an open diff and I've been debating what I wanna do with it. The lunch box locker is an easy instal, you don't even have to mess with the pinion depth or backlash, unless you change gears. It'll make popping sounds when taking a turn though. The Detroit TrueTrac is completely mechanical with no ctutches so, it'll hold up longer than a posi with clutches. It's just costs twice as much as the locker.

What's that jewel run in the 1/4?

I've got a lunch box locker in mine as well with 4.10's and don't really mind the clicking on turns and with the traction bar set up it no longer has the spring wrap up and takes off nice'n straight.

To azmikes point ...the Lock Right lunch box locker is a good and viable option to go with. I've had no trouble with it in the last 2 years I've been running it.

 

[Supercharged111]

I have 4.11s with 275/60R15s on my 88 C1500. It does ~2800 RPM at 80 MPH with the 700R4 trans (.7 ratio in OD). I had 3.42s originally and gained 3/10ths of a second on 0-60 and 1/4 mile with the gear change. It's still an open diff and I've been debating what I wanna do with it. The lunch box locker is an easy instal, you don't even have to mess with the pinion depth or backlash, unless you change gears. It'll make popping sounds when taking a turn though. The Detroit TrueTrac is completely mechanical with no ctutches so, it'll hold up longer than a posi with clutches. It's just costs twice as much as the locker.

What's that jewel run in the 1/4?

I've got a lunch box locker in mine as well with 4.10's and don't really mind the clicking on turns and with the traction bar set up it no longer has the spring wrap up and takes off nice'n straight.

To azmikes point ...the Lock Right lunch box locker is a good and viable option to go with. I've had no trouble with it in the last 2 years I've been running it.

Are you guys getting a quick 1 wheel peel before it locks?

 

[Silverado1994]

Are you guys getting a quick 1 wheel peel before it locks?

None of that. As soon as you straighten up from a turn the splined halves mesh together thus "locking". It's not like that centrifugal locker that GM had for a while (I don't know if they are still using that or not.)

 

[PlayingWithTBI]

What's that jewel run in the 1/4?

Well IDK since I can't get it to hook with the 1 tire fryer and I don't wanna make any claims until I can. 1/2 throttle from a stop and it breaks free.

 

[Silverado1994]

Well IDK since I can't get it to hook with the 1 tire fryer and I don't wanna make any claims until I can. 1/2 throttle from a stop and it breaks free.

I hear ya. Been there and done that.

 

[Silverado1994]

The only real Achilles heel to the lunch box locker is all dependability / longevity stops past 450 hp (or so they say). God only knows how well mine is gonna hold up to the 406 that I just installed in my truck. I guess time's gonna tell. lol

 

[Stringer]

For a 2wd in FL, I wouldn't consider a locker, just get a Truetrac. 3.42 is a good gear for a C1500 with TBI. I had that in my C1500, later went 3.73 when those gears got eaten by an exploding sun gear. The 3.73 was a bit much on the highway for a motor with no legs, but back then all I had close to home were 55 roads so it worked well for me. Doing 70+ it just didn't seem as happy as it did with the 3.42.

really good advice here and def what i would do