Waht options do I have to install a limited slip differential in my 89 RS coupe.

Thanks Ringo

 

What rear do you have 9 bolt Borg-Warner or the GM 10 bolt?
Also go to the Transmissions and drivetrain threads on this site.

 

Sorry I have the GM 10 bolt.

 

The Eaton Posi unit and the Moroso "brute strength"are high quality and have a good reputation these are available from summit for about $450.

 

slp still has the brand new take out units for $99

http://www.slponline.com/view_produc...TNUMBER=64501T

 

Can you please explain how the take out posi differs from the other posi units?

Why does it only cost $99?

How difficult is a posi unit to install?

 

I too would also like to know the answer to John's last question.

 

Here you go
https://www.thirdgen.org/techbb2/sho...hreadid=222817

 

you could also go with a powertrax locker. if you want to keep your current gearset, this might be easiest. from what ive heard its only like a 30 minute install. i think thats whats goin in my 91 rs.

 

A guy I work with has a 63 falcom and put the locker in it from powertrax and he loves it. He said it is rather noisy at times though around corners but it dont really bother him because he knows that its normal and his exhaust overtakes the clicking sound most of the time. Ive been thinkin about doing this with my car as well.

 

Eaton is the best all around unit hands down. You can get very good deals on brand new units on ebay.

 

take outs are brand new parts slp takes out of factory fresh cars to install their own products or a different product. my buddy got a whole set of shocks/struts/springs from slp for 80 bucks. im guessing they took them out to put the bilstens in them like on the firehawks or something...

 

So if I picked up one of these take out units for my 1990 formula I would need new gears as well? How much should that run me for some 3.23s or 3.42s? I'm on a budget but I'd hate to miss a good deal.

 

it should come with it if its a unit your buying. ask before you buy

 

i was reading around on the internet and found a place where a guy was talking about the different differential possibilities and he said that the powertrax causes understeering because when cornering the powertrax applies too much power to the inner wheel and causes the front end to want to push out....and also they stated that in rain and whatnot its really hard to keep the car straight.....i would still like to go with a powertrax for my car but i dunno if i want one anymore if that guy is right....

 

most of the people I have seen that got powertrax cant get it to "unloc" half the time it acts like a spool

 

yeah the powertrax unit will do that, its more for a straight line car. what it does is truly lock the two axles together where there is NO slip whatsoever unlike a posi which uses clutches that always have some small amount of slip to them.

 

I am using the SLP Heavy Duty Zexel Torison diff. It's WAY
better than the take off ones for $99. Of course, the heavy
duty one is more money. Like $500! Ouch. But, I am
expecting about 300+ RWHP coming soon, so I didn't want
to take any chances. It was easy to install ( if you've had experience already). I bought everything heavy duty for my
10 bolt rear. If if does blow apart, I am switching to a Currie
9" rear. Although, I don't think 310 RWHP/345 RWHTRQ should
blow it up.

 

people call it a "posi" unit when infact the proper name is limited slip defferential. it unlocks when cornering and locks when in strights. posi is locked all the time and hops when cornoring. so dont get confused when people say posi and mean limited slip

 

posi, sure-grip, equi-lok, and posi-loc are trademark names used for limited slip by ford, gm, and dodge.

dont confuse "limited slip" as the name for an "open" carrier, also known as: a one-legger, one-tire-fire, non-limited slip, or open-diff.

what you just described is a spool, they come in many forms and in many materials. it is simply a solid piece connecting both axles allowing for no differential slip ever.

 

always thought it was the same damn thing

 

no theres more yet, limited slips are broken down into 3 groups

1: frictional; using either a set of clutches or a cone

2: non frictional or gear type like the heavy duty torsen

3: locker (i.e. detroit-locker) which is a ratcheting system very much like the power-trax (only it actually unlocks more often but not always)

the OEM particularly GM has even used a combination of ratcheting frictional. In my opinion they are the worse because of all of the internal parts needed to be fit into the packaging the result was a weak case and internal parts. I have only personally seen these in some trucks in the 10 bolt 7.5" GM and 8.5" GM

this is a picture I made for helping people identify posi's for purchasing the one on the left is a 7.5" ratcheting frictional (bad), the one on the right is a eaton "style" or regular clutch style (good)

 

i knew there was different types. everytime ive been to gm they always called it a limited slip diff, thats why i refer to it as such. eaton posi units are nasty...

 

So no one ever answered the question, how difficult is it to install a posi unit?

 

thats something i would leave to a shop that has the tools to do it with. unless it can be installed without touching the gears...

 

It's not difficult to swap out the parts, it's the specs involved.
For ANY rear end repairs/replacing parts, you should have
some really good experience on how to do that! It's not
like doing an oil change, or an alternater swap! You need
to know about backlash specs, torque specs, stuff like that.
since you are asking that question, it's obvious that you
should have an auto tech whos well trained to do rear end
work. Also, NEVER buy an EATON posi unit. Go with either
Powertrax ( some people I know use them, and work mint!)
or SLP ( I have one now, works mint!). Auburn is ok, that's
what was in the 98-up LS1s. Not the greatest limited slip
unit, but still works good. Powertrax is more of a locker unit.
Careful though! Some make "ratcheting" noises when turning.
That's normal operation of those units. the "geared" SLP H.D.
units are quiet. They are worth their weight, if you ask me! They
are capable of up to 400 RWHP. But, who knows if the rest of the 10 bolt will hold???? :lala:

 

care to explain why? The Eaton units are the best hands down.

 

strongly agreed. i also believe aburn came in the 3rd gens as well as the 4th. could be wrong. i heard those are junkers though...

i have never heard anything bad about eaton units untill now

 

i would also like to why you dislike the eaton units, they are strong, consistant, rebuildable, and you can tune the torque bias. not a bad combination.

 

When you buy a posi unit doesn't it come with the gears already in it?

 

I used to have to work on customers cars and set up a gear based solely on patterning. I always had a perfect pattern but I always got mixed results. This is not acceptable when dealing with customers. Then I read a article in drag racing usa (an old magazine that is no more) put out by a group of gear manufacturers showing a group of odd ball patterns that didnt look anywhere near what would be considered acceptable by the instructions and books I had read previously. At the end of the article the information I gleaned was that if you used 3 tools to check your rearend for proper setup you would never have problems. You wouldnt even need to check the pattern. the pinion depth is etched on to the pinion head and the amount of backlash for new/used gears is shown in a manual for any kind of car. The pinion bearing drag or "preload" for new/used gears is also shown there.

These 3 tools were:

PINION DEPTH GAUGE for setting pinion depth. I also recommend buying a spare pinion bearing and using a brake hone to open it up until it slides on off easy for quickly checking/changing the pinion shims until you get it right so that you dont ruin your bearings on a press working them over and over.

Dial type inch pound torque wrench for checking to see if the crush sleeve is far enough or if you use a solid spacer to see if you have the right amount of shim in it. this is for checking the "drag" of the bearings.

extra dial indicator

and stand

I like to have a separate gauge and stand for checking backlash because the one included with the pinion depth gauge is nice and I like to use it as little as possible. It also comes in handy for checking crank endplay and cam button shimming.

For the record, by the time I set up two cars, half of the labor for the second job I did with these tools paid for them. I also have never had a set of ruined, wasted, or whining gears since. I have done GM 7.5"/7.62" 8.2" 8.5" 10 bolts, truck and car 12 bolts, Ford 7.5" 8" 8.8" 9", Dana 44, 60 rear ends with these tools.

The one thing not listed here you will likely need, especially if you are doing a crush sleeve equiped rear, is either a powerful 1/2" impact wrench, or a special longbar tool for holding the pinion yoke and a huge breaker bar (niether of which fits well under a car on jackstands.

 

:hail: I love the new avatar Tom! But I don't think it'll last very long.

 

why does it say that part number is no longer avalible? uh.. i need to order that slp unit soon. now it's saying the part number is no longer avalible?

 

Uh, why don't you contact SLP and ask them directly!

As far as me saying Eaton units are junk, ( here's a surprise!)
I maybe wrong about that. I think I'm getting confused over
the Auburn units being problematic. You guys corrected me.
But, I will be getting a second opinion on the Eaton units
from my friend ( Master tech of 25 years) to help me out
on this. He's the one who actually pointed this out to me.
But, again it could hjave been Auburn that he said, not
Eaton. I get screwed up with brands all the time. Makes
me look like an a$s, I know!

 

no. posi unit is a posi unit, gears are ring and pinion.

 

He's right. You need to separate the ring gear from the
diff. unit when swapping out the posi unit. You may want
to buy a new ring and pinion set anyways since you
have to get in there and take those out. It's a good time
to upgrade to lower gears, like 3.73s or something. If you
want quicker acceleration off the line AND power to BOTH
wheels, get a limited slip unit and new gears at the same
time. Make sure you buy a rear end rebuild kit as well!
If those axle seals are old or original, nows the time to
replace them before they leak all over your rear brakes!
Your axles will have come out anyways during a diff. unit
swap.

 

And Since I probably can't do any of this myself, how much is a shop going to charge me for all this?

I've heard alot of people say that even shops mess this stuff up regularly, is this true?

How strong is the slp take out unit? Is it worth it for only $99 or should I spend a bit more money and get something better? I don't plan on having a motor that makes a huge amount of power, so the slp take out should hold up well for me right?

Sorry about all the questions, but I don't really know anything about rearends.

 

Ok, first off yes, some auto tech that does the work CAN
screw up the installation ( if he doesn't know exactly what he's
doing! ). It's not like a direct swap. Like I said, you need to go to
someone who has A LOT of experience in building rears to do
this properly. OR, at least a Master Tech of 5-10 years (or more)
experience. There's torque specs, backlash, shimming, end play,
wear pattern, blah blah blah involved. If you decide to have a
shop do it, go to one that does it regularly, or a shop that
specializes in "speed" parts installation on hot rods ( aka high performance/custom shop).

You can have a shop that has lesser experience do it and the
rear end is mint! Dead on wear pattern and everything.
But why take a risk from an "average joe" shop? Either way,
ask first if they guarantee a proper installation and how long
of a guarantee it will be.

NOTE: If you buy Richmond gears, chances are they will
make noise! It's a normal sound from them, due to the way
the teeth are meshed tighter than other brand sets. Some
people "complain" about the noise. But, Richmond makes some
of the best gears and transmissions in the world. So, a little
"whine" isn't so bad.

Even a Master Tech of a billion years can screw up. It's
natural human error. Can't be perfect. That's why it's very
important to ask about some kind of warranty on the
installation. I well known shop would provide at least
a 6 month, 6K mile warranty on the labor. Some even
1 year, 12K miles. Places that just do "drivetrain" work
( aka rear ends, transmissions/transaxles) should even
tell you to come back in a short time to recheck the work.
At least, that's what they do for transmission work.

As far as the SLP "take off" units. I can only say this:
you get what you pay for! It's just a stock unit ( Auburn,
most likely!) from a 1998-2002 F body. On the other
hand, if it's durable for a 300+ RWHP LS1, than it's got
to be just as good for a third gen that does the same!

Now, for the right unit. If your making 320 RWHP or under,
and don't expect to go any more, than the take off
units are fine. I am only going to hit about 300 RWHP, but
I bought the heavy duty one anyways. I also bought it
because it's entirely different than the stock ones. It's more
than twice as strong, and it's gear driven. No clutches, no
springs, no friction materials at all. The casing is stronger,
everything is different. This is compared to a stock 1998
LS1 rear end unit ( Auburn). I don't know if the factory
made anything else ( I doubt any stronger!)

Oh, and about the price: est. $75 an hour x 5 hours.
That's on the high side, and is just a guide. Labor rates
and labor times can vary. All of what I wrote here is just
a guide! A factory Auburn unit is sufficient for the mildly
modded cars. They sell them for a reason. For the budget
minded. And to get rid of the factory F body parts just lying
around.

NOTE: I did not see the take offs listed at SLP. Only
ones are available are the Auburn diff. units that are
$500. Might as well but the Zexel Torsen diff for that
price! I don't know why that Auburn unit is so expensive?
Anyone know?

EDIT: The Heavy duty SLP units are on sale still! Instead
of $500, they are $400! Buy that instead of the Auburn
unit for $500. Those are for Firehawks and Camaro SS,
so they may not be direct bolt on to a third gen rear,
you would have to ask SLP about all that.

 

Thanks for all the info, greatly appreciated.:hail:

 

-

 

No problem! I know it was a long post, but I needed to
cover as much info for you as possible. My opinion on
the diff. unit is to get the Heavy Duty SLP ( Zexel Torsen).
If they don't sell the "take off" units anymore, than that's
all you are pretty much stuck with. At least, in that price
range. You can also look into Eaton and Powertrax. Those
can be found at http://www.Summitracing.com or
http://www.jegs.com. They will most likely be in the same
price range as the SLP units ( $400-$500). Any of those
units can EASILY withstand at least 300 RHWP and more!

 

they are zexel torsen, not auburn.

also, if you are going to spend $500 on a torsen diff. get a T2R.

 

It says the Part number does not exist?? can someone else try and reply back, thanks

 

What is T2R? And how come my Friend's posi unit is
Auburn? Came from factory that way in his 1998 T/A.
If the stock one's are a zexel torsen design, I'm assuming
that the Heavy Duty ones have an extra gear for the posi,
plus a stronger casing? Why would the "take off" units
be only $99, when the heavy duty ones are like three
times more.

What is a better design posi unit for the street? I would
assume the zexel torsen design. I am using it now and
and feels better than the Powertrax unit in my friend's
car, especially when turning. Powertrax units "ratchet"
when turning.

 

I believe they are NOT available anymore! Contact SLP
to find out for sure! You are the second person to ask about
this.

 

I figured this would eventually happen. I mean after all, slp is no longer making SS's or firhawks. The "before" cars were the donors for those posi's.

 

It does make sense. Since GM doesn't make F bodies
anymore. ( At least, for now anyways. Who knows about
the future).

So, like the "take off" units, most likely the "take off" suspension
components they sell will probably dry up as well.


Dewey316 says that the "take off"units were a zexel torsen
design. I thought that the stock units were an Auburn unit?
Can anyone clarify this? Did GM have Auburn AND the regular
duty zexel torsen units installed in 98-02 F bodies?

 

the auburns (except the really old ones) were put in by SLP I thought. the $99 Zexel "regular" duty one you see there is just a regular spring and clutch posi. There was a Zexel heavy duty torsen style they sold and maybe equipped the ss's and firhawks with.

 

98 got the auburn I believe and 99+ got the zexel torsen. The SLP cars had the heavy duty zexel torsen. The regular zexel unit is a torsen as well.

 

I believe this is correct! It sounds right to me.