lockers

[murraygmc]

i have maby a hard question to ancer.  iv got a 85 gmc with the V6 4 speed ( L,1,2,3,r ) 4x4 what rearend do i have ?  the reason im asking is im looking in to a rear locker and dont know what to get ?   P.S. im going to upgrade to a 350 soon

[VileZambonie]

If it's the stock rear end it's probably a GM 10 bolt. 3.08:1 was a common ratio but the only way to tell for sure is to pop the meatball cover off and check.

[murraygmc]

ok im kinda slow lol  how the heck do you check   

[Captkaos]

All 83-87(91) 1/2T trucks came with 10bolts from the factory.  To tell there are 10 bolts on the inspection cover.
To tell what ratio it is, pull the cover and look for the tooth count stamping on the ring gear
To find out if it is a factory limited slip, there will be a rachet mechanism and a spring on either side of the carrier.

[murraygmc]

ok so how do i come up with that no. ?   what dose it mean if i bought a locker do i got to buy the guts in the rearend too thanks

[Captkaos]

How to come up with what number?  The ratio?
If you buy a locker and like the current ratio, you only need the locker and associated parts.  (I would replace the bearings/seals)
If you are buying a drop in locker that replaces the spider gears, you only need to pull the crosspin and replace the guts of the carrirer.

[murraygmc]

ya the raito no. iv got no clue what kind of locker i want the cheepest probly .   any ideas on what kin of locker to buy im just going to mainly need it 4 snow geting to fire wood (that could b any whare) slight to modret trail riding

[Fishtail8]

You could also try checking RPO codes in the glovebox, as long as no one's switched diffs over time.  A trick that works for approximating gear ratio without pulling the cover is....

1- Make a chalk mark on the side of the driveshaft, and the 12 oclock position on the driver's side tire.
2- Jack the rear end up so both tires are off the ground.
3- With a friends help, rotate both tires at the same time, forward, and at close to the same speed one complete revolution.
4- While making the one complete revolution, count how many times the mark on the driveshaft goes by it's original starting point.

It's not rocket science, or as good as popping the cover. I've used this trick a couple of times, and it gives you a good idea of what you could have. I usually put the chalk mark on the side of the driveshaft facing the tire I marked. Try it and see if it works.

As far as checking for a locker or limited slip in it, rpo's and /or pulling the cover are the only way.  If it's got the G80 rpo it should be a gov-lock.

[Captkaos]

The G80 = A gov-loc is only applicable for late 70's and a beyond.  The early trucks had G80's but had a clutch type limited slip.

If you want to go on the cheap (as in all around) look at lock-rite or ez locker.  They replace the spider gears and you don't have to take the rearend down.

[78 Chevyrado]

Just pull the cover, it doesn't take long and it probably needs an oil change anyway

Gear ratio= (number of teeth on ring gear) divided by (number of teeth on pinion gear).

[KoolerSL2]

or another way would be to find the code on the pass side axle tube and call your local dealer.
they would be able to tell you what gear and such as long as the rear end is the original one.