I started noticing that I am having only one burnout mark when I turn my tires over- on the passenger side. I just got through doing a break job and while the car was on jackstands I turned the rotor on the back and the one on the other side was turning the same way. I don't have any funny noises coming from the rear. This is on a 1992 z28 with some mods. Gears are 3.23. I just boiled the tires in my driveway and it was the same deal. I'm running about 32 psi in my rear tires. The rear tires are Kumho Supra 712, size is 255-50/16. Other than this the car runs perfect. Is this normal? Thanks for any help in this matter.

 

if the posi is working as it should you'd have 2 tire marks. are you sure you have posi or do you think you have?

 

If both wheels turned the same direction you should have a posi. My guess is that the clutches are shot and it's slipping instead of "distributing power equally to both the rigth and left tires."

 

The "turn the wheel" thing is inconclusive. If there's more friction in the side gears and spider gears than in the pinion bearings at the instant you make the so-called "test", the other tire will turn the same way.

Most likely the car doesn't have posi. The only way to know for sure is to take off the cover and look. Which should be the first thing you should do anyway, if you suspect rear end problems.

If it is equipped with a posi carrier but it doesn't work, then the end result is the same; the car doesn't have the benefit of a limited-slip rear.

 

When I replaced the carrier a little over a year ago and the new-used carrier came out of a 1992 z28 that had a 5 speed. This carrier looked to be more heavy duty than mine that had gone bad. But, it did have the little clutches and springs that went between the gears. If I remember correctly, the car used to leave two skid marks. I'll be pulling the cover off one day this week and check it out. I'm running synthetic oil in this rearend with the GM posi additive. You don't think the synthetic oil had anything to do with it do you? If I do need to replace the clutch, does anyone have any suggestions on a good replacement?

 

No, the synthetic tends to make them hook up too well, if anything.... the "friction modifier" additive is necessary to let them slip smoothly around corners. They tend to groan and chatter without it.

The stock posi units in these cars were mostly Auburn, after they quit using the Gov-Lock in the early 80s. They are rebuildable in theory but Auburn doesn't supply the parts any more.

If you're looking to just replace it, a good alternative is the stock unit out of a LS1 car. It's the Zexel "torsen" type. SLP used to sell those for $99 but they ran out some time ago. You can pick them up on ebay and wherever, though; they're closer to $200 now. Or, you can get an Eaton heavy-duty one.

 

RB I looked on ebay and found one of the Zexel carriers. It had three pictures of it and on the side view I noticed these don't have the little clutch with the little yellow springs like mine had. I called a salvage yard not far from my house and he asked me what gear ratio I was looking for. I told him I already had a set of 3.23 gears and I just needed the carrier. Should I just get the whole deal or just the carrier? He told me $100 for the carrier. I assume just the carrier, because he told me $100 after I told him I just needed the carrier. What do you think. BTW Thanks for the feedback. Just so I'll know is there any way I can tell I'm getting the Zexel unit. Do I just need to make sure it looks like the one pictured on ebay?

 

The Zexel doesn't use clutches. Here's how it's built. http://www.torsen.com/products/T-2.htm So whatever you get, should look somewhat like this, if it's supposed to be a Torsen. These came in 98-up F cars with LS1.

 

Another decent and fairly cheap option is a new Auburn. They are only about $375 brand new from Randy'd Ring & Pinion. The Auburn is a tough unit, though different in operation than the Torsen.

 

What would be the best oil to use with the Zexel torsen?

 

Amsoil synthetic gear lube. That's what I run in everything. You won't need posi addative with the Zexel either.

If the rear is freshly rebuilt I would break it in with conventional 80w90 gear lube. You will need to change the lube after the first 500 miles, so using synthetic at that point is a waste of money. Follow the gear manufacturers recommended break-in procedure.

 

I just got back with my rearend. It is the Torsen with a set of 3.23 ring and pinion bolted to it. They told me it came off of a 99 or 2000 Trans am. The housing had a sensor on the top of it and when I took the cover off, on the backside of the ring gear, there was a piece that looked like a big sprocket. Something to do with the sensor, I guess. Anyone know if this will seperate from the gear? This unit looks like the T2. Will I need any special instructions to get this thing going or is it just pull the old carrier out and bolt my gears to the T2 and install it? He charged me $100 for the whole rear axle housing and its guts minus the axles. Did I get ripped or get a good deal?

 

The gear is a reluctor wheel for the ABS/traction control system. The sensor reads the motion of the wheel and uses that information to determine is slip or brake lockup is happening. You should be able to just leave the wheel on the differential and stick it in the factory 3rd gen housing with no ill effect.

You should just be able to swap your ring gear onto the Zexel differential and bolt it all back together using the factory side shims. I would run the pattern on the gears just to be safe, and check the backlash too, but it should be fine, unless the new differential has too much runout, or was somehow damaged (very unlikey, but I have seen it before).

Did you get ripped off? Did you get the brakes with it? $100 seems a bit steep, but the parts are from a relatively rare (in junkyards anyway) newer car, so probably not. I can usually score a complete axel drum to drum for $100-$150 from a 3rd gen. Disc brake rears fetch about $50 more. Keep in mind that the newest 3rd gen rear is now 13 years old though.

 

No, I didn't get the brakes with it. One side of the axle housing is cracked, I guess from the wreck, but the guts look good. The ring gear on the torsen is a 3.23 and I have a 3.23 in my car, but I guess it wouldn't be a good idea to leave that gear on there and try to match it up to my pinion gear that is already in the car, would it?

 

No! Use your ring gear. Gears are matched sets. They are actually put in a fixture and lapped with compound at the factory to ensure perfect engagement. Just like a valve and valveseat in a cylinder head.

 

Right; use your gears, just put your existing ring on that carrier; put new bearings on the carrier if you didn't get the outer races of the ones that are on it (might have to get a machine shop to do that if you don't have a puller that will pull them), and put it back in your rear (well, your car's rear, anyway) using its existing shims. Check the backlash between your existing ring & pinion before you take it out, with a narrow feeler gauge if you don't have a dial indicator; should be around .008", plus or minus about .004". Then check it when you put in the other, it shouldn't change by more than a few .001"s.

 

Where do you insert the feeler gauge to check for backlash? Where the gears mesh together?

 

Yup, between the gear teeth. You're trying to see how much free space there is between them. You're looking for a very precise amount: some, but not too much. Gears "grow" when they get hot, so if there's too little, they destructively smash together; but if there's to much, they misalign, and wear fast for that reason. Look for about .005" - .012".

 

I don't have Amsoil around my area without ordering it. Any other recommendations on the oil I need? I guess I still need the GM additive, don't I?

 

Valvoline makes a good seveere duty 75w90 weight oil that is very good. I run it in all my 4X4 stuff, because with water crossings and mud I change the oil too often to justify the expense of synthetic.

Red Line synthetic also has a good rep.

 

You said that you used a synthetic gear oil in your rearend. That is what did your posi in. I destroyed a BRAND NEW auburn within a few days by running synthetic gear oil. It was one tire fire within 48 hours because of the synthetic. Auburn says right in the installation instructions (who reads that???) NOT to use a synthetic gear oil, its just too slick.

The same goes with transmissions. Synthetic in both manuals and automatics is a bad idea. Mobil 1 in the ol' crankcase is a great idea, but thats about the only place for synthitics.

(Let the flaming begin)

 

If a manufacturer specifically recommends not to use synthetic then I would have to advise anyone to follow their instructions. Every rear that leaves my shop has regular mineral oil in it, and I tell the customer to change the oil after 500 miles of normal driving.

There is nothing wrong with running synthetic in manual or automatic transmissions. Synthetics reduce friction and handle heat much better than conventional oils. The service life of the oil can also be extended. I run Amsoil synthetic ATF in my T56 and love it. The shifts are smooth, and the trans is quiet. I've torn down broken transmissions that ran Amsoil ATF, and even after thousands of miles the bearings looked brand new. That's very uncommon on a manual trans that runs ATF. Typically the bearings are showing wear after only a few thousand miles. In automatics synthetic provides higher heat handling, which is the number one killer of automatics transmissions. Synthetic ATF from Amsoil is formulated to allow smooth and clean clutch engagement, and minimize wear, but there is no chance that it will cause the trans to slip more than conventional oil. It is slippery stuff, but it's also sticky. It's hard to get it off of stuff. Usually you need to use brake clean or some other solvent. You won't get it all off with a rag like regular ATF. That's a great trait for ATF oil to have. It ensures that everything stays lubricated and that the clutches stay soaked with oil. I personally don't run synthetic in my automatic, but that's because the trans is in my 4X4, and I change the fluid often to avoid contamination. At nearly $8 per quart it's just cost prohibitive (my trans takes about 15 quarts). I actually run a mix of half ATF and half Catapillar 30 weight hydrostatic drive fluid. This mixture came from Dana at Pro Built, and I have to say that the heat handling is excellent, though the smell is terrible! I can get the cat fluid in 5 gallon buckets fairly cheaply, and the ATF I buy by the case, so it really helps keep the cost of 4-wheeling down.

In differentials I run Amsoil synthetic of the Valvoline product I mentioned above. I don't run an aftermarket posi in anything, so I can't really comment about that. My Camaro has a Lock Rite in the rear and I run Amsoil synthetic, and my 4X4 runs a Detroit out back and an ARB in the front with the Valvoline (again, due to the frequent change intervals). My Jeep's still got open diffs front and rear, and it's a beater so it just gets the Valvoline. I've got Amsoil synthetic in the transaxel and rear differential in my WRX. It really improved the synchro action on the trans, which is slow due to the lack of multi cone synchros. I've got 25,000 miles on the stuff and have had no problems from the rear either. I occassionally drag race the car and autocross, so I'd know if traction had been compromised by a damaged differential. My Mustang has Amsoil syntetic in it with the stock Ford Traction-Lock (that's posi in Ford-speak). It still leaves two tire marks of equal length and color. I don't put many miles on the car, and keep the synthetic in it mainly to keep everything coated with oil since the car sits for long periods inbetween use. I've seen rears that accumulated a lot of surface rust on the gear teeth that were out of the oil, and when the vehcile started to be driven again the rust flaked off the gearset and destroyed the bearings, and consequently the gearset too. An expensive mistake that I'd like to avoid.

BTW, I'm not a fan of Mobil 1. I know plenty of people who swear by it, but I've had problems with seal leakage over the years on a variety of different vehicles. I don't think they put enough seal protection addative in the oil. It seems to be fine in new vehciles with fresh seals, but older vehicles with some mileage always seem to spring leaks. That was what promted me to research and consequently start using the Amsoil product line. I've never had a seal leak with Amsoil from any component. Additionally, from the research that I've done Amsoil is the best synthetic around that isn't mega expensive (there's stuff that they use in Ferraris, but it's $50 a quart!). The heat handling is exceptional, the filmstrength unmatched, and the addative package is properly formulated for extended service life, and seal lubrication. Royal Purple and Red Line both have excellent reputations in the racing community, but I've been so hapy with Amsoil that I've seen no need to try anything else.

 

I've taken the chunk and pinion gear out of the salvage yard housing. However I don't think this is s 3.23 gear set. I've got 41 teeth on the ring gear and 12 teeth on the pinion gear. One other thing I'm not sure of, maybe somebody can enlighten me, is how do you install the C- clips that holds the axles in the Torsen unit. Not a whole lot of opening there.

 

41 / 12 = 3.4166666 or 3.42

 

There's never much room to install the c-clips. I put them on the end of a magnet, slide them in place, and then pull the axel to seat them against the side gear.

 

I have a TA aluminum rearend girdle/cover with the bearing cap preload bolts, and I switch over to synthetics, now all the bolts/plugs on the cover leak. I cranked everything down, but the preload bolts only take like 5 ft-lbs of torque. Plus I have an Auburn posi in there, but it was broken in with conventional oil like 4+ years ago. I think I'll switch back to coventional oil come this spring. I also put Mobil-1 in the T-5 and noticed it leaking more but that was from the shifter. A new Hurst solved that problem so I'll probably stick with the M-1 in there.

 

The aluminum girdle covers all leak regardless of the oil used, unless you take the time to remove the pre-load bolts and coat the threads with liquid Teflon. That's sealed everyone I've ever done and I've never had a leak.

 

TKO, you have a PM