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11/22/2017 10:05:29 PM
Posted: 10/10/2004 9:11:54 AM EST
I'm in the middle of tuning up my vehicle and need some help in the field of differentials as I know absolutely zero about them. I'm trying to identify if I have a positraction rear end but I don't know what it's supposed to look like. It's a 1993 Suburban, 4x4 with a 5.7 liter engine. Could someone refer me to a site that has some pictures to identify through. I've googled it to death and turned up nothing. Maybe someone here knows something. Thanks for the help.
Link Posted: 10/10/2004 9:22:41 AM EST
jack the rear end up spin a tire and if they both turn the same way is a posi if they turn oppisite its open
Link Posted: 10/10/2004 9:23:57 AM EST
There really isn't any way to tell if a rear end has positraction just by looking at it. You can jack up the vehicle and have it in neutral and spin one tire and if the other tire goes the same direction then you would have posi (if it goes the other then is an open differential). I'm not sure if this method is full proof but I know my 72 Chevy has posi and both wheels spin the same way. I would think if your burb came with posi it might have is listed somewhere on the vehicle (door jam,glove box or somewhere when they list GVW ratings and stuff). Also there might be some sort of tag with a number on the differential that could be decoded.
Link Posted: 10/10/2004 9:34:37 AM EST
Buy a Toyota.
Link Posted: 10/10/2004 9:52:04 AM EST
pull the cover and look. Probably could use a gear oil change anyway. If you see a ring and pinion and 4 other gears, spider gears, then you have no posi. If you see a bunch of other shit instead of 4 gears you have posi.
Link Posted: 10/10/2004 9:59:26 AM EST
http://www.turbovan.net/Trans3.html

The only way to be certain is to pull the cover and look. In the link you will find pictures and someone talking about spider gears. Spider gears are in the 3rd pic and are the little gears he is talking about with the pin slipping out.

The jack the car up and turn a wheel is not always right. If you have heavy weight oil in the differential and the thing has some drag here and there it can cause the other wheel to want to turn. A worn out limited slip will sometimes not spin the other wheel either.

If working on the vehicle I would get the diff fluid and the additive and a gasket or some form a gasket goop to reseal the cover. Go ahead and pull the cover and get a nice look inside the rear end, might need to post pics as well since this is the board mantra lately.

A posi traction is a series of discs and stuff and will replace those spider gears. So you either will see spider gears or not.

If you don't need the additive, keep the receipt and return it later.

For a 93 you should have the original rear end, but on some trucks things get broken and junk yard axles are easy to swap in so I don't always trust the stickers and labels unless I know the history of the vehicle.
Link Posted: 10/10/2004 10:03:07 AM EST

Originally Posted By Camaroman:
I'm in the middle of tuning up my vehicle and need some help in the field of differentials as I know absolutely zero about them. I'm trying to identify if I have a positraction rear end but I don't know what it's supposed to look like. It's a 1993 Suburban, 4x4 with a 5.7 liter engine. Could someone refer me to a site that has some pictures to identify through. I've googled it to death and turned up nothing. Maybe someone here knows something. Thanks for the help.



Chances are VERY good that it is an open differential. Again, only true way to know is to pull the cover.
Link Posted: 10/10/2004 10:10:07 AM EST
You otta be able to find out without tearin it apart.

I'm sure you can find a book detailing threse rigs or a site that lists different option codes and how to decode those numbers.

For instance I owned a 92 mustang,bought a book on the vehicle and it had this info...I was interested in whether I had a posi,limited slip,ect. too.

Anyhow,on the Ford rearend there was actually a numbered metal tag that was attatched to one of the diff housing bolts,and on this tag was a code that represented the final drive ratio and indication of whether it was an open or posi rearend.

I'd bet that chevy's have a similar ID process.
Link Posted: 10/10/2004 10:11:22 AM EST
[Last Edit: 10/10/2004 10:21:16 AM EST by lvgunner777]
As said earlier, the sure way to tell is just pull the diff cover and see if there is a clutch pack in there. Turning one wheel doesn't always work because there is no torque load on the unit.

It will look something like this:


Link Posted: 10/10/2004 10:44:22 AM EST
Check the build list in the glove box. Or get the VIN and call a local GM dealer, they can tell you the options that came on the truck. Just an FYI, if its a stock truck, it probably doesnt have a Gov-Lock (GM's "locking" diff) .
Link Posted: 10/10/2004 10:46:31 AM EST

Originally Posted By DeadSled:
jack the rear end up spin a tire and if they both turn the same way is a posi if they turn oppisite its open



GM uses a locking diff called a Gov-Lock... It will act like an open diff with both tires in the air, so this test will not tell you anything. The Gov-Lock needs torque acting upon it in order to work.
Link Posted: 10/10/2004 11:40:44 AM EST

Originally Posted By BlackDog714:
Check the build list in the glove box. Or get the VIN and call a local GM dealer, they can tell you the options that came on the truck. Just an FYI, if its a stock truck, it probably doesnt have a Gov-Lock (GM's "locking" diff) .



+1

The codes are called "RPO" codes and they are all in the glove box on a sticker with a bunch of 4-charachter codes. Then Google for "GM RPO codes" and you will find a number of sources to cross check your RPO codes. On My GM cars I just put together an Excel file with the RPO codes and definitions for each feature.

And I doubt you have a Posi rear end.

GunLvr
Link Posted: 10/10/2004 12:06:29 PM EST
Link Posted: 10/10/2004 12:11:43 PM EST
Thanks all. I had the cover off doing a oil change on it, I just didn't klnow what I was looking for. It does have a positraction rear. In it applies and anyone is ever uncertain the code that says is in the glove box, and the code for posi is G80. Again thanks for all the help.
Link Posted: 10/10/2004 12:16:05 PM EST

Originally Posted By GunLvrPHD:

Originally Posted By BlackDog714:
Check the build list in the glove box. Or get the VIN and call a local GM dealer, they can tell you the options that came on the truck. Just an FYI, if its a stock truck, it probably doesnt have a Gov-Lock (GM's "locking" diff) .



+1

The codes are called "RPO" codes and they are all in the glove box on a sticker with a bunch of 4-charachter codes. Then Google for "GM RPO codes" and you will find a number of sources to cross check your RPO codes. On My GM cars I just put together an Excel file with the RPO codes and definitions for each feature.

And I doubt you have a Posi rear end.

GunLvr



Not trying to say that won't work, but GM doesn't exaclty wait for parts if they don't have one handy when they put trucks together. I am guessing that by '93 they were getting pretty good at putting right parts on, but you never know.
Link Posted: 10/10/2004 12:20:52 PM EST
[Last Edit: 10/10/2004 12:24:43 PM EST by Bob243]
This may be a bit time consuming, but the best way to tell exactly what you have is by the RPO codes (probably located on a sticker in your glove box) and look up what they meen... duzy.8m.com/motherload.htm


This one may be better... www.nastyz28.com/rpomenu.html
Link Posted: 10/10/2004 12:22:54 PM EST

Originally Posted By Camaroman:
Thanks all. I had the cover off doing a oil change on it, I just didn't klnow what I was looking for. It does have a positraction rear. In it applies and anyone is ever uncertain the code that says is in the glove box, and the code for posi is G80. Again thanks for all the help.



if you changed the lube, make sure it doesn't need an additive for the clutch pack. Some makes do, not sure about the GM unit.
Link Posted: 10/10/2004 12:24:49 PM EST

Originally Posted By DeadSled:
jack the rear end up spin a tire and if they both turn the same way is a posi if they turn oppisite its open



Yeah, that's what I'd say. If it's currently drivable, just put it in drive, get on some dirt, and floor it. If there's two tire marks in the dirt, you have posi.
Link Posted: 10/10/2004 12:29:20 PM EST
Start truck, Apply brake, Floor it. Release brake. 1 rubber stripe = non posi. 2 stripes = posi.....Or go find some gravel, and punch it there.
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