Posi-trac issues
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Senior User
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From: Heart of Dixie
Posi-trac issues
Somebody tell me what is wrong here. No matter what my speed is or if I have my foot on the gas or not, whenever I am turning left my differential (I'm guessing) is making my truck jerk like something is locking up. Its loud and it sounds very bad. I know its coming from the rear end because the differential is the only thing that could make this happen since it only happens when I turn left. It sounds like if i keep driving it like this its going to end up completely breaking on me and I wont have any way of driving at all. Does anybody know what this might be? Help please I can't be stranded for long. 
Lead Driver
Joined: Jul 2003
Posts: 7,406
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From: Wheatland, Mo
Could be a lot of things but first things first. If you are sure it is your rear diff...then place it up on stands and remove the cover. Take a look and see if you can find the prob part. May be able to get a decent replacement gear(s) or whatever is needed from a salvage yard. And correct me if I am wrong, but don't our trucks have the limited slip on the rears and not the posi?
Another thing to check, and only if you have 4 wheel drive, is to make sure you are completely out of 4x4. If in 4x4, and on dry pavement, you will get a binding feeling in a turn, especially when going slower and in a sharper turn. If no 4x4, then go back to the rear diff. if the rear diff is not the issue, then start looking att he fornt suspension when it is turned. Have someone crank the wheels back and forth while you are looking to see if you notice anything binding or not working properly.
Another thing to check, and only if you have 4 wheel drive, is to make sure you are completely out of 4x4. If in 4x4, and on dry pavement, you will get a binding feeling in a turn, especially when going slower and in a sharper turn. If no 4x4, then go back to the rear diff. if the rear diff is not the issue, then start looking att he fornt suspension when it is turned. Have someone crank the wheels back and forth while you are looking to see if you notice anything binding or not working properly.
Fleet Mechanic
Joined: Sep 2002
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From: okla
My experience says get ready to spend some big bucks to overhaul your third member. Had a late 80"s Ford 1/2 ton van with exact same scenario. It did function for longer than I expected, but required expensive repair.
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Joined: Mar 2005
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From: Cornelius, Oregon
Originally Posted by BillyBob69
And correct me if I am wrong, but don't our trucks have the limited slip on the rears and not the posi?
Elder User
Joined: Mar 2005
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From: Cornelius, Oregon
You are mistaking POSI for a locker. In a limited slip rear (whether it's positraction, or any other name) there are either gears or clutch packs that limit the difference in speed of the two axle shafts until a certain criteria is met that will allow them to "slip".
In a locked rear-end both axle shafts are physically locked together and do not allow any slipping. Certain locker units (such as Detroit lockers) automatically engage and disengage to allow for turns, while others are manual (such as ARBs Air-Locker) requiring the driver to engage and disengage them.
From an online dictionary:
Posi (or Positraction):
GM's designation for their various Limited Slip Differentials. Became almost generic and was applied to different technologies.
In a locked rear-end both axle shafts are physically locked together and do not allow any slipping. Certain locker units (such as Detroit lockers) automatically engage and disengage to allow for turns, while others are manual (such as ARBs Air-Locker) requiring the driver to engage and disengage them.
From an online dictionary:
Posi (or Positraction):
GM's designation for their various Limited Slip Differentials. Became almost generic and was applied to different technologies.
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From: Heart of Dixie
Yes posi-trac and limited slip are the same thing. Different names but both are open differentials until one wheel spins fast enough for the differential to lock both of them to travel the same speed. Now for my rear end, my truck's I mean. I got it towed to my Ford dealer this morning and it turns out that my spider gear has been stripped to pieces, literally. There were metal pieces all over the inside of my differential and they claim its going to run me about 2+ grand to repair which I think is a complete ripoff, but I think I'm going to have to give in to it because I dont have the time to order another set. Does anyone else here think that 2 grand is a ripoff?
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Elder User
Joined: Mar 2005
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From: Cornelius, Oregon
2 Grand is a little excessive imho. My brother spun the carrier bearing in his '96 Dodge Ram a couple months ago. The chunks caused quite a bit of damage and involved replacing the carrier, ring and pinion gears and machining the casing. He got it done for under $1300. Luckily he didn't screw up any of the anti-lock stuff otherwise it could have been a lot more expensive.
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New User
Joined: Jun 2005
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From: TN
Bummer man. 2k is a lot but thats a dealer for u man. Are u mechanically inclined? If so scavanging a new chunk(gear assembly) from a junkyard and getting a repair manual and renting tools from Autozone to do the job would be a inexpensive option, maybe $100-$300. Or even easier and less headache a salvaged rearend $200 from a yard or recovery company. Just match up the numbers(gears, model, ect.). Good luck!
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Joined: Jun 2005
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From: TN
Originally Posted by pitrow
Certain locker units (such as Detroit lockers) automatically engage and disengage to allow for turns,
Mountain Pass
Joined: Mar 2004
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From: Jackson
Originally Posted by pitrow
Limited slip and posi are the same thing. Posi is short for Positraction which is like a brand name for a limited slip diff. Kind of like "Bondo" vs. "Plastic body filler". Technically it's a brand, but people use it universally.
Limited slip and (posi) positraction arn't the same thing. When you turn left or right with limited slip one wheel spins slower them the other. With ture posi when you turn the rear wheels with squeel or the rear end will jump beacuse the rear wheels are turning the same speed.
Logistics Pro
Joined: Jan 2002
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From: GANS
$2000 is probably what it will run you. Not good, but if you do it yourself, you could probably get a used axle for $400 and swap them.. a couple days under the shade tree and $50 in parts will do it.
I swapped the rear axle in my '85 in 20 degree weather.. would have had it done in a couple hours more if the rear leaf hadn't fell apart..
I swapped the rear axle in my '85 in 20 degree weather.. would have had it done in a couple hours more if the rear leaf hadn't fell apart..
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Joined: Mar 2005
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From: Cornelius, Oregon
Originally Posted by AAALeadFoot
>LOL actually detroits engage when traction is lost and cannot be disengaged until u shift to reverse and back up a few yards, this is why ARB's are popular they don't lock up on the street ad spin u around on the freeway.
Tractech’s locking differentials are the NoSPIN® and Detroit Locker® brands (same product, different market segments), the Detroit E-Z Locker™ and Detroit Gearless Locker™ brands. They keep the wheels locked together (except when turning) so that together the left and right wheels, always deliver maximum traction to the ground; neither wheel can spin out.
They allow different wheel speeds in a turn by disconnecting the faster - moving wheel (usually the outside wheel - driven faster throughout the turn), driving the vehicle with the other (inside) wheel.
They allow different wheel speeds in a turn by disconnecting the faster - moving wheel (usually the outside wheel - driven faster throughout the turn), driving the vehicle with the other (inside) wheel.
Trust me guys, I KNOW what I'm talking about here.
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Joined: Mar 2005
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From: Cornelius, Oregon
Originally Posted by solidpwder
Limited slip and (posi) positraction arn't the same thing. When you turn left or right with limited slip one wheel spins slower them the other. With ture posi when you turn the rear wheels with squeel or the rear end will jump beacuse the rear wheels are turning the same speed.