What kind of posi unit is this?

[72seeten]

I counted 30 splines...bought it off of craigslist here locally, supposedly the owner bought it off someone off this board and decided he didn't want to use it. How well do these work? TIA.

[72dually]

The famous powerlock..........no comment

[69TowRig]

Gov-Lock, it's an Eaton unit. The Power Lok is a Precision Gear unit and the Powr-Lok is a Dana unit.

It has a centrifugal weight system that engages a ratcheting dog-clutch that locks the axle shafts to the carrier when a significant amount of wheelspin occurs (one wheel relative to the other). Over a certain carrier RPM the unit will disengage, or when the applied torque is removed (take your foot out of it).

Visit http://traction.eaton.com/prod2.htm and click the link halfway down to see an animation.

The Gov-Lock is a mechanical locking differential that is OEM on a ton of GM vehicles. For a street rig it's fine but not a limited-slip, so the operation is not seamless, it's either locked or it's not, and it takes some wheelspin to make it lock. The others mentioned above are clutch-type limited-slip differentials.

Personally I wouldn't run one in a street rig with a decent engine nor in an offroad rig. Normal locking differentials handle big input torque by keeping the shafts locked to the carrier under normal drive conditions, and only unlock when a wheel overspeeds the carrier like in a turn. Detroits are like this. The Gov-Loc works backwards, only locking when the torque is applied heavily, which lends itself to more breakage and the nickname "Gov-Bomb". For a street rig I'd run an Eaton Posi, for an offroad rig I'd run a Detroit or a drop-in locker.

[72seeten]

Thanks, I think I will still use it, the truck has a mild 327, and I really don't plan anything further than that. I was just wondering how well it worked.

My 2000 z71 is equipped w/ the factory locking diff (or whatever they call it), I assume this one will peform about the same way? It doesn't really work all that well, but it' better than an open diff.

[69TowRig]

Originally Posted by 72seeten

Thanks, I think I will still use it, the truck has a mild 327, and I really don't plan anything further than that. I was just wondering how well it worked.

My 2000 z71 is equipped w/ the factory locking diff (or whatever they call it), I assume this one will peform about the same way? It doesn't really work all that well, but it' better than an open diff.

Same exact design as the one in your Silverado.

[jeffspower]

The 14 bolt rear I put in my '88 came with one. I hate it. I should have known better (from previous experience) & took it out. But I thought in a 6000lb+ truck it would behave decent, especially since I never drive it in deep mud or bad weather. Grass or loose gravel makes it chatter and wheelhop, no mater if you sissy- foot it or floor it.

The Detroit Locker in my '72 is very mild- mannered in comparison. I never thought of a DL as smooth- but in this comparison...

[woodridge]

To add to 69TowRigs statement that they are not seamless in operation, a transmission shop I used to work in was rack checking a tranny in a pickup on a drive on lift. They would set a jack stand under one side of the diff housing and run the tranny through the gears. The tech had run it up to about 50-55 which means the one wheel was doing about a 100 when the gov-lock decided to do it's thing. It sounded like an explosion when the axle snapped and by the time I got to the back of the shop from the office there was not a soul around and there was a madly spinning wheel creeping out of the axle housing on what was left of the axle, I made a quick exit myself. Fortunately the axle stayed in the housing and the wheel did not go on a rampage. It took over two hours to get the axle gear unramped so we could get the pin out and the c-clip off the replace the axle. So they are not smooth and if used much do not live long.

[1969 GMC]

Originally Posted by woodridge

To add to 69TowRigs statement that they are not seamless in operation, -snip-

Haha, at my old job they had a '96 or '97 C3500 dually dump. Brought it in for a brake job, even though the rear brakes weren't old enough to warrant one (iirc less than 1 year old). Long story short, the gov-lock in that truck's 14 bolt FF had literally lived up to the moniker "gov-bomb." however, the dumbass that drives the truck told us that he heard a BANG about a month ago and never thought anything of it

He drove it long enough for the little metal fragments of the carrier to travel down the axletubes and destroy the wheel seals and bearings. The carrier and pinion bearings were also toast. Gear lube leaked out the ends and ruined the perfectly good pads. We had to send it to a dealership b/c we didn't have the tools to set up gears (and didn't want to mess with it). The only parts they reused was the housing, the hubs, and drums. It was on the low side of $3k, and guess what? Put in a brand new from GM gov-lock. Glad I don't work there any more.

[Skip Greaney]

That is a limited slip out of a late model full size truck. It is a govenor type that "grabs" after 1 wheel loses traction. Been around for quite awhile.

[72dually]

[QUOTE=69TowRig;1994092]Gov-Lock, it's an Eaton unit. The Power Lok is a Precision Gear unit and the Powr-Lok is a Dana unit.

Thanks for correcting me

I guess I have a hard time just typing that word

[72seeten]

You all are starting to scare me w/ all these horror stories, maybe I shouldn't use it.

I have yet another question, I have heard different things about this. The truck has a 700r4, and the lockup converter is not hooked up. From the numbers on the side of the case, I've identified it as an 85 model. Will it eventually burn up w/ out the lockup? The truck has 3.07 or something "highway", cause it is barely above idle at 50 or so in OD. I'd rather just go w/out hooking it up if I don't need to. Some say you have to have it, others say it will work just fine.

[masterbeavis]

Hookup the lockup. It will keep the heat genereated by the torque converter down to a minimum.

[jeffspower]

If you don't want to go thru the work of controlling it electrically, put a checkball in the lockup solenoid. I forget the size needed, any trans. shop should have one. You just have to drop the pan, pull out the control solenoid & put the ball on top of it. It will act a little differently than when controlled by the OEM setup. You will have lockup right as it goes into 3rd. And 4th, of course.

[masterbeavis]

You could also just hook up a switch, lockup the TQ,forget about it, and wonder WTF is going on when your truck is actin funny :P

[72seeten]

I had a 700r4 that was modified w/ the check ball trick in a truck I used to own. It did not work very well at all. It lugged and had a rough operation. Then it broke. Had another tranny that I tried the vac switch/brakelight switch mod on the same truck, and it didn't work very well either. I finally ended up hooking it up through the ECM and it worked perfectly. (It was a 90 GMC that I converted from a 5spd to an auto) Since this one doesn't have an ECM (yet, I'm thinking about a TBI conversion) I was wondering if I could get away without it. I've heard different opinions, from numerous tranny shops, I was wondering if it is really necessary.

[jimfulco]

I'm not going to say a mumblin word.

[FarmTruk]

Wow...that "Gov-Lock" animation http://traction.eaton.com/prodvid4.htm is pretty scary. Looks awful fragile.

[CMars45000]

Originally Posted by jimfulco

I'm not going to say a mumblin word.

Lol, in the four wheeling world we call Gov-Locs "Gov-Bombs" for that very reason. I have seen them hold up to some serious abuse, but then again I have seen the gernade backing out a driveway.

[72seeten]

So.....what kind of posi unit is this one? Any good? Found it here locally, although it has 6 lug axles. Can I take my 5 lug axles and swap them into it?

Thanks,

Steve

[72seeten]

Sorry, here is the pic.

[Beefcake]

currious about the dana 60 that comes in our 72 gmcs.... how strong are those???

[CMars45000]

Originally Posted by 72seeten

Sorry, here is the pic.

That is an Eaton clutch-style limited slip. That is the same one that my 71 had from the factory and I am replacing it with on that has carbon fiber clutches instead of the steel ones. The NIce thing about that style is that are fully rebuildable for about $175 and you can change the springs in them from 200# springs all the way up to 800# springs for more clutch-plate pressure...

[72seeten]

If anybody is interested in a 3.73 posi rearend here is a link to the ad. I just did a search and found out that the 6lug to 5lug swap is pretty involved w/ the brakes so I won't be buying this.

http://austin.craigslist.org/pts/271737991.html

[1969 GMC]

Originally Posted by jimfulco

I'm not going to say a mumblin word.

There's the one I was talking about. This was as it came out of the diff, we did not disassemble it. Everything just sorta fell out.

[jimfulco]

So THAT'S where they went!