1976 K20 - Factory front Posi?

[BILT4ME]

Not factory, but I had a 1960 frame that I installed a 1975 3/4T front axle that WAS a 3/4T, then swapped hubs with a 1/2T to get back to 6 bolt wheels, then I installed an Eaton LSD in the front.

I also had an Eaton LSD in the rear in a 1979 GM 12 bolt rear axle

I had a 350, bored 0.060", ported, polished, balanced, about 375 HP with a 4 speed.

I ran 33 x 12.50 x 15 tires with factory Rally rims.

The LSD in the rear was very nice, except with the 4 speed and bigger tires, I kept eating spiders in the rear LSD and I was in the city most of the time driving on paved roads. I would come around a corner and accelerate in an area with water from a sprinkler, catch one tire and start to spin and not get out of it soon enough and munch the rear when it got dry pavement .

The one in the front was great as long as I wasn't on a slick surface. The first time using it all locked up, I was in the mud and I discovered I could not turn a corner and about pegged a tree. Because everything was turning the same speed, I couldn't turn! I had to burp the throttle hard to get it to turn.

I typically did not drive it with the hubs locked in unless I had a good chance of getting into some bad stuff. If it was snowing, I would lock the front hubs, but run in 2WD unless I was almost stuck.

If I were to do it all over again, I would do a selectable locker in the front (ARB / Harrop) before I would do an LSD.

We are building a 1970 GMC K2500 for my son and we've installed a Detroit Locker in the rear and it behaves MUCH differently than the LSD I had in the rear of my truck from years ago. Much tighter and NO slip!