rear diff (non-4X4 also applies)

[Knanthrup]

Hey, I just confused myself a little. According to the RPO tag in my glovebox, I\'m supposed to have a 3.73 rear end (code GT4) and a locking differential (code G80). I have my 4X4 project up on the stands right now and I was just looking and messing with the rear and from what I was told, if you turn one wheel, with a posi rear end the other one should turn the same way. I also tried holding one tire and spinning the driveshaft while in nuetral and it didn\'t seem to lock and hold the other one.



Is there something I\'m missing here or is it not acting like a locking rear diff? I got the truck from my dad who got the truck from my grandpa who bought it new so I know they didn\'t change the rear axle, I\'m just a bit confused and I want to make sure I have a 3.73 locking diff.



Any input?





On a second note... I\'m half tempted to use this rear on my 2wd with the swap, but I figure it\'ll probably go to better use in the 4X4.

[my454s10]

what year is it...how old...it may be that the clutch\'s are wore out and it will not apply the friction force to lock the two axle\'s ...maybe it\'s a limited slip...

[eurekarobert]

I just did the the same to my \'85 4x4 and the same thing both tires rotate in opposite directions!! what the heck?

[Knanthrup]

It\'s an \'84. It\'s been through it\'s work but never abused. I don\'t think it\'s gotten to the point of wearing out the clutches bu tI could be wrong.



I don\'t know if it\'s limited slip or locked or what, I\'m just going by the code on the RPO sheet. It says locking, maybe it means limited slip... does that mean that it still wouldn\'t lock the other wheel when I\'m testing it?



Blah, I don\'t know... I\'m confused and I don\'t know much about rear ends... I was hoping someone else would.. http://www.s10v8.com/images/smilies/icon_biggrin.gif

[my454s10]

i think a true posi will turn when you spin one tire..the other tire turn in the same direction...a limted will turn on way and the other whell will turn the opp...put the truck in netural..with the back wheel in the air...make sure you do it safe ..use jack stands..and turn the drive shaft...if it\'s a limited slip it will make a few turns and then both tires will lock..

[rudedogg]

remove the cover check the #\'s on the ring gear and look in the center of the carrier to see if it has 4 springs or a little metal piece that looks like two r\'s,if it has either of the two get a new gasket,gear oil pref. synthetic,limited slip additive and bolt it back together.......

[ZZ4Blazer]

I thought that the factory limiteds slip in the s-series were lockers. No clutches or the need for special lube?



If thats so, it probably won\'t \"lock\" into posi unless your driving it and it has some load on it.

[eurekarobert]

OK I called the local dealership and talk to a guy and he said that the rear end needed to be under load to \"lock\" as zz4blazer said.

[Knanthrup]

oh sweet. in that case im probably ok. it just made me wonder and a little nervous when it didn\'t lock from my little test. im sure it will then under load...



on another note, is there a code on the diff itself outside to tell what kind of rear it is? if not is the code inside the cover the same as the RPO code? the reason i ask is that on my 2wd, there is no RPO sticker in the glovebox and so I\'m not sure what rear I have. i would like to hope it may be a limited slip but i cant tell without a running engine... plus gearing is a mystery so far. thanks-

[s15laynrubba]

Look on the passenger side, front side of the axle tube.I had to scrap the dirt off to find it.Worse case scenerio,drop the cover and look on the large ring gear.You will see several numbers stamped onto that gear.Hope that helps

[speeder]

I had the same rearend. they lock under load, but never on a wet pavement, which is stupid, since with the V8 and auto, it will almost spin out when it downshifts in the rain. I had to go to an 88 4WD locker rearend to get the posi. Yours probably has a spirng loaded plate between the spider gears.