rusty vango

my 86 camaro has the "gu2" 2.73 open axle,and im wanting to keep the gear ratio but add a posi unit. the car is not gonna see any track time .and im making less than 300 lbs. ft torque. what posi unit would you guys suggest??

big gear head

With that gear you are going to be limited to the Auburn (yuck) or the Torsen. You can probably find a used 2 series Torsen on ebay cheap because most people don't want the 2 series units.

If you go to a 3.23 to 4.56 then you can use the Eaton Posi, which would be my first choice.

InfernalVortex

iTrader: (4)

Why do you prefer the eaton to the torsen?

Orr89RocZ

iTrader: (20)

Gm 4th gen torsen style. They are awesome. I bought a detroit trutrac for my 12 bolt which is worm gear type posi like gm torsen because i like them so much

Pat Hall

iTrader: (31)

While the Eaton is a wonderful unit, you can pick up a used, 2 series Torsen on Ebay for a fraction of the price for an Eaton. One thing you'll need to do though is switch to 28 spline axles. Your stock 86 rear uses 26 spline axles, and you have to use 28 spline axles with the Torsens. Any 90-92 3rd gen rear will have the 28 spline axles. While you can buy new ones, going to a junkyard for a set of 90-92 axles would be the cheapest option.

Burnout91

Orr,

Could / would you describe the characteristics of the (Eaton) trutrac, vs. the (Eaton) 'posi?'

The trutrac lists for about $120 less than the posi (+++)... on Jeg's site anyway.

Thanks, and sorry if I butted in.

bestracing

The cheapest route would be to find a complete used posi rear end that already has the 2.73 gears in them and in good condition. Go to the home page here and look up the rear end options data and you will see that there are a lot of 2.73 posi options out there. The RPO code on the option list will be G80 for Posi.

If you bought a new or used carrier you will still need to buy a new gear set, bearings, crush sleeve, shim kit, cover gasket and gear oil. You should never re-use your old gears because you won't be able to get them aligned to the old wear pattern and they will be noisy.

I don't know what kind of budget you have so the choice is yours.

Just remember that you don't have to be racing to break these small 7.5" rear ends. Spinning your tires at high rpms and have them grab suddenly can also cause destruction. Replacing the bearing caps with stronger ones and getting a rear cover with the bearing cap brace in it also helps in making the rear end last longer.

Orr89RocZ

iTrader: (20)

The truetrac is just like the zexel torsen with rotating worm gears around the center section. Allows both tires to spin independently when needed and when traction is needed it locks up transfering power to both. The eaton posi has springs and a clutch pack that locks up for power to both wheels. Disengages when not under power to allow differential action. They make a few different eatons from what i have seen. Some with around 400 lb spring packs and some heavy duty ones which could be 600-800 lb for serious hp. They are much more expensive, and can eventually wear out the clutches. The truetrac shouldnt wear out, but run risk of cracking chipping worm gears. Broke a torsen in my turbo car by chipping a worm gear tooth

Burnout91

Yeah, I understand the function aspect; just wondered if there is some performance / driveabilty / effectiveness benefit to the worm-gear type of unit.

big gear head

The Truetrac is my choice for a auto cross or road race car. For most street/strip use I prefer the Eaton Posi. The Posi can be tuned for your needs if you are doing serious drag racing. You can replace the clutches and springs to make it lock up better, and you can shim it to tighten up the clutches. If you don't want it to lock up that well then you can use lighter springs and another clutch set. This is just my preference and I know that others have a different opinion.

As far as the clutches wearing out, I know of many '60 and early '70s Chevelles, Novas, Corvettes and Camaros that are still using the original clutches in the factory installed Eaton Posi. Clutch wear should not be a problem for many years. The Truetrac will wear, just like any other mechanical part will wear. It just doesn't have replaceable clutch plates.

Burnout91

Thank you!

Ron U.S.M.C.

Best (10 Bolt)Posi for street use =
For my car its 28 spline Eaton with 3.42's and support cover.

waynek

Hey guys how you doing? Right to the point, does anyone know why my Torsen 3 series will not fit in my 92 Camaro with the 10 bolt housing? I am baffled.

articwhiteZ

iTrader: (56)

has long has your HP is under 300. you can get your 7.5 to live..with all the aftermarket up grade parts they make.. anything more then 300. and 1 maby 2 good hook ups..kiss it goodby...pinon gear is always the first thing to let go....

Guest

Get the WHOLE rear end rebuilt!!! and use the thickest gear fluid on the shelf!!!!

bmorgil

It depends on how well you can hook it up and how much power you can input. With hard compound skinny tires, only wheel hop will break a stocker or a torsen style (worm gear) with the kind of torque you are talking (and 300 lbs.ft. of torque is not bad). That said there is nothing stronger than a Detroit Locker but a spool. A locker is a little noisy and loose on corners at first but it will quiet down and tighten up with some miles as you get used to it. They take a little getting used to but if you like oversteer punch it on a corner! A total blast. The factory Eaton posi with shimmed clutch packs to eliminate excessive diff gear separation will work well on a dry road and is smooth as silk till you hit it. They are limited however. I wouldn't put it in a clutch car. Do not cram in excess shims or plates in the stock Eaton or Dana. You should still be able to spin one wheel while one is held with the car in the air but, you should feel some drag. To much and you will have trouble putting it back together and it will lock up if it gets hot and wears in dirtying the lube. Do not use Possi lube!!! Not if you modified the diff and eliminated springs. Possi lube is there to keep the plates from sticking and giving you that familiar bang when they break lose and grab and break loose and grab when you turn. My tech guys (before I retired a few years ago) put together a nice hopped up 44 for testing. If the clutches drag to much the axle temp soars every time you make a long sharp turn and anything can break in the housing then. The springs are only in there to apply some load (the springs) to the spinning low traction wheel. Our Dana used a Belleville washer instead of a spring. Not a big difference. As the spinning wheel begins to get load the pinion spiders in the diff climb the axle spiders. This forces them apart and compresses the clutch packs. On dry pavement with both wheels, it will come within 95% of a pure lock up (providing you are not using synthetics or possi lube of any kind). The amount the spiders are able to force the diff spiders out causes less and less tooth contact (this is why you should shim them up) no sloppy diff gears allowed. As the clutch packs compress. That is why they eat diff gears and then drop the parts into your ring and pinion and bearings and I think you know the rest. I could talk diff's all night so I won't. I have 30 years of axle and driveshaft tech experience including 5 years of teaching crews and working as a suppler to NASCAR, tractor pullers and John Force mobiles and on and on. As the Motorsports technical director I was into all facets of racing. Hard work but fun! I had a very large resource base working for me and we could test anything. We had our own 2 mile oval fenced in track and a technical center that was unreal. A Detroit Locker can take abuse like nothing we ever built or saw. We tested the hell out of em. They wont break until you have them at about 3 times the specified torque in! Ford put a ton of them in our Dana axles as special orders for 3/4 to 1 ton trucks. Basically the Dana 60 and 70 series. A Dana 44 was put into production for Chuck Jenks and the SLP project. Nice axle disk brakes and all. I still see these from time to time and SLP might still sell them. If you have a third gen and you spot a Dana 44 for it buy quickly. While testing at MIS we lost the other manufacturers 12 bolt fixed it and then threw the driveshaft (not a large enough Driveshaft diameter for the RPM) the 12 bolt just is not that beefy. It is a pass car axle. Those of you with big power stick to a Ford 9" or a Dana 44. They won all testing. I have seen lots of wheel stands with model 44's. With the power you have, take out all the guts of a stocker 7.5 posi and reassemble with just the diff gears and clutches. Lose the Governor totally. Shim up the clutch packs to eliminate movement of the diff gears and make up for any loss because of parts removal of springs or spacers, spring washers and governor locks. It will act just like an open diff till you get a little smoke to come off the tires. Then it will lock solid. The slippery it is under one tire the less torque you will split and vice versa. It makes for a really quiet smooth diff but it acts just like an open diff until there is resistance from BOTH tires.

Bob

Ron U.S.M.C.

bmorgil,
Wouldn't this be a good choice for his application, that is if he decides to go to a performance gear ratio (3.42 or higher)as opposed to the IMO sorry but worthless 2.73 ratio ?
Posi LSD Differentials

The Eaton Posi LSD prevents wheel slip before it can get started. To do that, carbon disc clutch packs, preloaded by a central spring assembly, are located behind each differential side gear. When torque input increases the clamping load on the clutch packs increases. That causes the chatter-free clutch packs to grab and transfer power to the other wheel.

Muscle cars, hot rods and mild off-road vehicles should look to Eaton's limited-slip differential for their traction answers. And the fact is, Eaton's Posi units are virtually bullet proof.

85 ZXX

iTrader: (1)

You may be able to find online a good used complete 9 bolt rear with a series 2 posi carier with close to the same gear ratio. I've seen them on some Firebirds.

bmorgil

Yes I think a properly set up Eaton of the size in the 3rd Gens can hold it to lbs.ft. in but in the order they fail in testing, The Auburn Gear Cone Style (they are awful). The Trak-Right. A big jump to the Tor-sen Worm gear style (My favorite recommendation at engineering meetings), and then the Detroit is how they rank right off the test lab's torque motors and absorbers. Detroit's are really good at the impact test. The Tor-sen is much stronger, quieter and less warranty prone than the Track - Lok conversion. The case eventually brakes at the cross pin. The conventional case isn't designed for much torque transfer at all. They both (Detroit , Tor-sen) hold up forever. The Detroit was very very strong. We should do a PM or a phone call. Id love to talk axles and driveshafts with ya. I can share a few things you wouldn't believe.

Pat Hall

iTrader: (31)

While the 9 bolt rears are marginally stronger than the 10 bolt, you couldn't PAY me to use one in my car. Reason being is the posi unit in them is a piece of junk, and when they go bad there's no aftermarket replacement available for them. While the 10 bolts are slightly weaker, the big advantage to them is there's more aftermarket parts than you can shake a stick at available for them.

bmorgil

Truly the answer here is you have a lot of choices. You smacked the 9 bolt pretty hard there. I agree it is not for performance usage. Though No removable center section (Banjo style A.K.A. Pumpkin) is strong in a critical area, the Ford 9" style will take sustained 750hp for 500 miles without much trouble. There are a lot of good guys out there who sell 9" Ford's. Being a Chevy guy I hate the 9" also but to be fair..... The issue is under load a few things happen that are important. 1st the ring gear tries to climb the pinion if you have something to transfer that motion to the chassis the lift and vehicle roll center moves back and she'll do her best to stick the tires down. The pinion tries to force itself away from the ring gear. This will break teeth if the differential side bearing support is weak. Finally, the entire diff case pushes against the caps and tries to break outward on the pass side (correctly made and installed a cap /cover girdle with ARP stud's will help a lot here. The 9" Ford is not a bad way to go. There are all three diff's we just spoke of that have models that fit them. With a Detroit locker they are strong and simple (the 9"). Eventually under high sustained racing, that style axle will break teeth on the ring gear do to the lack of Carrier Bearing support allowing the pinion to push the ring gear over when loaded. This is fixed by the great builders specifically Mark Williams Enterprise and Moser. They use an adjustable rubbing block right next to pinion contact on the back side of the ring gear. Usually a bronze tip is used. That ends the problem.

The "Salisbury Style" axle (no removable diff ring and pinion) center section. Completely eliminates the concern over carrier bearing support. In general the weak spot is the difficulty in set up and, on models other than Dana you have a weak point with the crush sleeve. ALL collapsible spacer design pinion preload devices must go. The pinion will collapse the sleeve and you will lose you pinion bearing preload completely. The warranty fractures looked like this. #1 cause - improper carrier or pinion bearing preload allowing too much movement. #2 - Posi clutch pack setting to high causing high heat and failure of heat treated parts spider and or cross and axle gears. The heat can get so high from clutch style diffs they will spontaneously combust into a fire that just keeps getting hotter. And, finally Lack of lube (usually do to a leak. Now day’s people simply don't expect to have to touch their car for 100,000 miles. It gets easy to lose too much lube. I drove a few experimental Firebirds around with Dana 44's and disc brakes. They are not real quite but they are very strong when properly set up.

Ron U.S.M.C.

I did some reading on another site and it was mentioned that the Eaton Posi can come with Green springs = 200 lbs, yellow = 400, red or bare mettel = 800 lbs. My question is about the bare springs. I have a Eaton Posi part #19599 with bare metal springs. I guess that means its rated at 800 lbs. Correct ?

bmorgil

Man Rusty a 2.73 is awfully low numerically for performance usage. Changing to a 3.73 puts you in the right spot for several better parts choices. For every .25 +/- step lower in ratio NUMERICALY rpm's will go up about 200 at 60 mph (this is just an approximation it will vary but not much). I would say if you sprayed a lot of "blower in a bottle" in there and you could go for a land speed record! Just picking on you there Rusty but man that 2.73 is killing you. Even a nice tourqy 350 would act like a 4 banger until you get that baby moving. Also not many parts out there for that ratio diff. If you look most Firebirds came with a 3.55 or a 3.73. With a 3.73 and a locking 3500 rpm torque converter in a 700r4 or a 4L60E You won't be in that 3.06 first gear for long before ya gotta grab second. Big change in ratio step from 1st to 2nd. A 3.73 gear would wake that car up and it would respond very differently. You would think you dropped a rat in it! This should be your first nice bang for your buck. Cam it so max torque is around 70 mph and you are above the stall speed of the converter, locked up solid when engine vacume is high and it will run nice.

Keep after it and Painted Side Up,
Bob

bmorgil

Yes but it is accumulative. If there are four of them it would be the INSTALED load pressure of the sum of all. If you want a great posi for some icy driving use the lightest springs. Otherwise if this is a fair weather car, lose them. I can't tell you how much trouble we have with clutch type diffs. They work great as an inexpensive quiet and fairly strong unit if you take out all springs shim it up and go. I ran quite a few 12 bolts that way. Increasing spring pressure makes those clutch type diffs break. Between the chatter and the diff gears climbing and losing contact they break way before they should. I always finished when we ran them (no springs and shimed) that way in classes that would not allow aftermarket diffs.

Hope this helps you,
Bob

big gear head

If you have a new Eaton Posi in a 7.5 rear end then it has the 400 pound springs with the carbon fiber clutches. The 800 pound springs were used in the heavy duty Eaton Posi and Moroso Bruit Strength differentials (also a Eaton Posi). The factory installed Eaton Posi that was used in the 10 and 12 bolt Chevy rear ends in the '60s and early '70s had the 200 pound springs.

Ron U.S.M.C.

Stomp on it around a corner and you have to be prepared for when it hooks while sliding.You can tell when the posi is working on strait launches as well.
Totally different driving style when adjusting to the posi unit.

Yes, I did build a 10 bolt . And here it is =
Eaton 28 spline posi, new 28 spline axles ,3.42 ring and pinion and LPW Ultimate cover. Here's a link to the Eaton posi unit. = http://www.eaton.com/EatonCom/Produc...iteId=EatonCom and here's a link for the LPW cover.= http://www.jegs.com/i/L.P.W./619/301-7.5G/10002/-1 .

$700.00 for master bearing kit , axle bearing and seals, 28 spline axles, including 3.42 ring and pinion, and labor ,$535.00 for Eaton 28 spline Posi.,$169.00 for LPW Ultimate support cover.. 3 year warranty on parts and labor. Total = $1,404.00.
Two more photos. All done at " The Rear End Shop" Thats all they do.

RWB____s

With the Eaton posi, it is totally rebuildable and tuneable to what ever use you are using it for. I have been running a eaton in my 12 bolt that was custom built and tuned for autocrossing . I have NO spring packs and the clutches can be changed out for different types for racing use. They can also be shimmed to adjust the preload on the unit. www.tomsdifferentials.com <- he has youtube vids on rebulding the eaton posi, how to shim and adjust the preload. This guy builds awesome rearends. been in business long before mosar, strange and other rearend companys. He was west coast based till he relocated to Idaho.

big gear head

I learned how to build the Eaton Posi from Tom about 30 years ago. I still install the springs, but in most cases they are not that important. Some customers notice that the springs are missing and don't feel good about it.

bmorgil

Yah I know what you mean. But if the posi is going to be used as most consumers think it should be i.e. a better grip in the snow and ice, it has to have some clutch pressure or it is not going to do anything as far as help with that kind of traction (ice and snow). I couldn't believe your reference to the "Moroso Brute Strength". You gave away your age on that one man! That was introduced in the early 70's. They had larger Pinion Spider gears in the diff with better Side gears. They had about 25% more tooth contact in the diff system. Those were originally specified by the big truck builders for extreme northern climates (Alaska). The springs were indeed 800+. They looked like valve springs out of an 8 grand motor. We would rip the springs and plates out of them and on dry pavement they locked at nearly 100%. Good clutches. Here's a number that will help with what the springs do for ya. We rejected any model 44 with a spring clutching posi that dropped below a 7% bias right to left. That is nothing. It got there because customers would complain about hammering noise from the rear axle. The only way to fix it was to keep backing off the pre-load or I would get warranty.... Definitely customer perception. I learned the spring trick from a guy in LA in the early 70's. I can't remember much but I know we all took our axles to him. I think his last lame was Estrada. I also think that was part of the name of his shop. It was fun testing his theory in the Lab 30 years later. We now know why it worked!

big gear head

The Moroso unit was suppose to have the 22 disc steel clutch set, but I've disassemlbed them and found the 18 disc fan (or flower) clutches in some of them. They had the 17 tooth axle gears which were stronger and heat treated a little different than the 18 tooth gears. They also had the heat treated cross shaft instead of the chrome plated shaft. The 12 bolt heavy duty Eaton was first used in the COPO Camaros and Chevelles in '69 because the standard Eaton wouldn't hold up to the 427 in those cars. As far as I know this is where the Moroso unit came from.

This is one of the things that I like so much about the Eaton. You can set it up for many different uses. You can't do that with a lot of the other LSDs.

Guest

Eaton FTW.

RWB____s

the last time I talk to Tom, he was still in paramount , Ca. I was concerned about not having srings in my unit. (Toms BOA) he said I did not need them but would install them if I still wanted them. Again this posi was not a stock relacement Posi. It was set u "TIGHT". I have never had a issue with it, ever, and has been in the car since I purchased the complete 12 bolt rearend for my 3rd gen from him I purchased it in 1986.

abray1

Someone was telling me that there is a posi kit that you install in an open carrier and it is supposed to be very good. I don't remember the name of it but you have to have a factory open carrier for it to fit. It is supposed to be very cheap as well. A lot of the 4 wheel drive guys use them.

big gear head

Power Trax Lock Right. I've had one in my 4X4 S10 for about 15 years and put about 140,000 miles on it.

abray1

Power Trax Lock Right; We have a winner. Do you reccomend them? Have you had good success with it? All the 4WD guys really seem to like them. They talk about them a lot about being easy to install and not to expensive.

big gear head

It workes very well for what it is designed to do. Mine has always worked. It has got me out of a lot of sticky places. Most people would probably not like the way that they pop and jerk on the street. All lockers do that some. It's a lot more noticable with a manual transmission. Some people with automatics say that they don't even notice it at all. They are easy to install, but not much cheaper than other LSDs. I think they are around $350 to $380 now. It's been a while since I sold one, but I know that the price was going up on them.

Burnout91

Does Tom's still offer the "Happiness is a Tight Posi" T-Shirt?

RWB____s

Well at one time he did, I use to have one along with the yellow stickers that i still have on my trailer. Maybe you should call him and find out. Last time I talk to tom, he was glad to be out of California and the EPA ****'s that make it hard to have any type of mfg business in the state. Tom use to mix his own special rear diff fluid and sell it. The EPA realy did not like that and he had to discontinue making and selling it.

Pat Hall

iTrader: (31)

I ran one of the Powertrax locker units a long time ago in my 12 bolt, and my personal experience is I absolutely HATED it!! Of course I'm running a manual trans too, and mostly drive on the street. Maybe it is less noticeable with an auto trans. I ended up replacing it with the Eaton unit if that tells you anything! That Powertrax jerked and banged like crazy, not to mention when turning sharply in a parking lot or something, it'd be clacking like mad! Pretty embarrasing on cruise night when you're turning around in Denny's parking lot! I remember lots of people telling me something must be broken on my car. Lol. Oh, and wait til it suddenly catches halfway through a turn on wet pavement! If you were half asleep, you won't be after that happens! The only reason I bought one of those at the time was I didn't want to spend the cash for a whole posi carrier, plus Summit made it sound like the greatest thing since you just slap it in your existing open carrier. Yeah, it was cake to install, but I hated it. The one thing I will say in defense of them is they are tough as nails. I took mine out after almost 10 years of use, and it didn't have a flaw or blemish any where. It had the "zytanium" cross shaft and everything. I agree with Bmorgil on the crush sleeves in a salisbury axle. Every one I've set up for hard use, I always use a solid pinion spacer instead of a crush sleeve.

TA-Rocks

I have a posi with 3.08 gear set. I am looking for a change to 3.42. So, I am saying that if you want that one, I will be selling it as soon as I find the other.

waynek

I just bought a 96 firebird rear end and put a Zexel Torsen with 3.73 gears and I have never been happier in my life with the perfect performance. This is in a 92 RS with a 355 cu.in. and a 700r4. Smash the gas and it leaves 2 perfectly even marks about 30 feet. What I am trying to say is I am completely sold on the Zexel Torsen 3 series.

TA-Rocks

Did you rebuild it yourself? Am I able to change the rear gears in mine to a 3.42 or higher? I read about it long ago, but dont know how it works. I guess it is easier to buy the whole thing and change the rear anyway compared to changing the gears in it.
Is that right?

waynek

I actually bought the rear end and had a mechanic put the 3.73 in for me. All I did was installed the rear end myself. I didn't have the confidence to change the gears myself. If your not sure what your doing putting new gears in, sleep on it and let a mechanic do it. You should be able to go as high as 4.11s. I would recommend not going above 3.73s. I am running 3100 RPMs at 70-75 on the highway. It feels weird, but I love the extra ummph it has. Good Luck!