OK, I just replaced all the bearings/races/seals in my 9-Bolt and it seems to be working. I never opened up the carrier while I was in there - so my bad!

My question is this....

In the service manual they describe the POSI Test Procedure something like this:

1.) Jack up both rear tires
2.) Put transmission in Park (Standard in 1st)
3.) Attempt to rotate wheel. Force required should be >35 ft/lbs.

That's all it says.

Well, I can't get mine to turn even with 100 ft/lbs. Is mine frozen (bad) or is mine really tight (good)??? I drove in some circles in a parking lot and there were no issues - the tires turned without jumping or without chatter, so the POSI has got to be slipping when its necessary for it to do so.

Please don't tell me I'll never know unless I open it up!

Sounds to me like you have a good posi unit, don't worry about it.

Woo-hoo!

My original 9-bolt posi carrier seems to be holding after 172K. So much for it being designed to fail. Well, I did have to replace all the bearings, posi-cone dust could have contributed to their failure - maybe/maybe-not.

Of course, now that I said this it will blow out at lunchtime today for sure!


- joe

Glad yours still works. The previous owners of my car NEVER changed the fluid, and it occasionally won't lock up when I step on the gas in a turn. Sometimes it does, sometimes not.

However, it always locks up in a straight line. It needs to be rebuilt though. And I'm dreading that job.

After doing my rebuild (minus POSI) - I know you are right to dread it. I guess it gets easier after you have done it a few times, but having insufficient spare parts, equipment, etc... It makes it hard. Get an extra pinion seal and crush collars just in case, if you do the job. I tore one seal and it cost me another parts order cycle.

I had all my bearings pressed at the machine shop, so that helped a lot.

1-1/8" socket for yoke nut.
1-1/16" socket for the new yoke nut.
Pipe for leverage
Pipe wrenches or other tool to hold yoke.
Big hammer to get yoke off. (Or big steering wheel puller)
Slide hammer for axle shafts (Or big hammer again)
Dial caliper to check backlash (do it before you tear it apart)
0-60 in/lb torque wrench. (I used something with higher range - but its not as easy)
Full set of carrier shims - in case you do end up needing to shim the rear.

I also found once I cleaned the housing and parts with brake cleaner the job became a LOT more enjoyable.

I thought you had to put the transmission in neutral and block one wheel from rotating... it should take at least 35 lbs-ft to rotate the other.

the torque numbers vary with the type of rear. my brothers car had a govlock and you could turn i wheel with no effort. it always worked great in a turn or strait line though.

According to http://www.9bolt.com/ "If torque is less than 35 lb ft unit should be replaced or rebuilt", so looks like you're good to go. 9bolt.com is a great website with a lot of info.

OK....

I did previously read the Posi Test instructions at www.9-bolt.com... I have a problem with these instructions.... Since someone has brought it up.

There it says:

--
The following procedure is used to test the Borg Warner 9 bolt posi unit.

1. Place transmission in Park (or low gear for manual transmission).

2. Raise rear tires from the ground.

3. Lock one wheel from rotating.

4. Measure torque required to rotate opposite wheel.

5. If torque is less than 35 lb ft unit should be replaced or rebuilt.
--

Well, if you lock the driveshaft (step 1) and you lock one wheel from rotating (step 3). You'd have a really hard time rotating the opposite wheel as everything is locked up. I think step 3 should be skipped.

I'm not sure how accurate the burn-out tests are. Its not a locking rear. If your not going straight - how is the limited-slip mechanism supposed to know if you are turning to park or burning out? I think there will probably be some amount of slip but its still not entirely free. I would expect a tight unit to allow less slippage than a loose one though.

FruityOne: Have you tried this test? I'd be curious to see what your results are. Maybe yours would pass this test, but would be closer to 35 ft lbs... I couldn't get mine to turn no matter what I tried!

I know this is an old post but I had my 9 bolt go 1 legged for 1 of 3- (5 mph) launches so I wanted to test it. 2 dark tire marks on the first 2 rolling burnouts and 1 dark tire mark on last rolling burnout.
So as per the 9 bolt test above I put a torque wrench on a lug after jacking up both rear tires in transmission in PARK. The test said the unit was good if it took >35 ft./lbs. of torque to make the tire spin. So I tested on both rear tires in both directions and it always took between 55-60 ft./lbs. to make the tires rotate. The rear only has around 650-700 miles on rebuild.
I'm hoping it going 1 legged was just a fluke.

EDIT***
After going to get instructions directly from http://www.9bolt.com/technical.html
I see that I did need to have the transmission in NEUTRAL, one wheel on ground- not in park with both wheels in the air as stated above.
So I did the test over following the correct direction and the rear failed the brake away torque test of >35 ft/lbs.
Torque numbers spinning wheel forward were 27 ft/lbs and 39ft/lbs spinning wheel backward.
Not so happy being the guy I brought this from said it was a complete fresh rebuild with pictures of the build.

It probably wasn't... I rebuilt my rearend 5-6k miles ago... If you drive it hard, it will fail, especially if it is Auto... Much easier to get it to lock if you have a 5 speed. I have noticed the 9 bolts with 5 speeds stock usually last quite a bit longer. I don't think the Auto's put enough pressure on them all the time to get them to engage, so I think it prematurely wears them out.

Mine is toast again... Works great 85% of the time at the track, but it only locks like 40% of the time going around a left turn and 75% going around a right turn. Lol... I am going to a 9" soon... I spent too much money rebuilding mine, wish I had put the money towards a better rear.

https://www.thirdgen.org/forums/faq-...now-about.html
Post#2 shows the testing method with the transmission in park(not Neutral like on 9 bolt.com) So with the car in park my rear passed the test and with it in neutral it fails the test as I stated my results in post #10 above.
I jumped on the car 3 more times over the wkend and it left duel tire marks all 3 times, last time one set of tire marks had one tire leaving a longer mark then the other tire. It was under similar circumstances as last week when it went one legged(the one tire was more in sand on side of road.)
Think I'm going to add the limited slip additive and see what happens?

Let me know how that goes! If it helps, I will go grab some and see what it does for me.. I am planning on going 9" soon though, so it doesn't really matter. As long as I don't blow up the rear when I am home on leave I will be happy... I might do it anyway just for a study sake for future people...

Gear oil only required for 9 bolt, no limited slip additive needed since they don't use clutches.

The limited slip additive makes it slip easier, it does not make it lock up better. The additive makes it slip easier so that it doesn't pop and jerk when turning corners. If you want to try to get it to lock up better then change the oil and leave the additive out of it completely. Or you could fix it right by taking it out and shimming the gears.

The 9 bolt has a Borg Warner cone type differential which does require the additive. The Auburn cone type differential usually requires 2 bottles of the additive to get it to stop popping and jerking when turning.

+1.

Measuring the amount of toque off a a lug nut is NOT the best way to get an accurate reading. I say this simply because your not turning the wheel at the center of the rotation. There's a good change that your readings will be different based on the position of the lug and position / throw of the axle turning tool. If you look at the shop manuals they show a picture of the tool needed - it measures the tourqe when the tool is turning the axle FROM THE CENTER of the axle hub.

Brake drag is also a significant variable to consider when checking a rear end while it's fully mounted.

I've used several different 9-bolts over the years and IIRC all of them have lost POSI traction when starting a burn-out WHILE cornering,..... as if pulling from a sidestreet. ( Pull into the street a bit , then light-up the tires while in the turn.) However; If the same car is in a parking lot and the wheels start Spinning BEFORE starting to corner - POSI will often hold thru the corner.

I've noticed this in a general way while driving on several different 9-bolts. Some were original 'used' units and 1 was a completely rebuilt rear ( new carrier, gears, cones, bearings, ect.) Every rear end is different and some are obviously more worn that others, so they will all act a little different.

ok guys I'll skip the additive.

I'm still loosing posi sometimes on this freshly rebuilt 9 bolt...I seemed to be a little low when testing the torque to turn turn the wheels. I brought this rear from a guy who rebuilt it, had 0 miles on it after complete rebuild. Has new friction cones ect..
At this point I assume I need to shim the rear more...Can someone explain the shim process in full detail to me please..Thanks

Post #10 above shows my testing results