How hard is it to replace the clutches in a posi 9" rear by one's self?

SadbutTrue

SadbutTrue

Founding Member
May 1, 2002
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Granada Hills, California
#1
My clutches seem to be worn out on my posi. Its fairly new, and when I bought it almost everythign else was replaced, except the clutches (which supposedly were inspected and were supposed to be fine as they were, but they weren't replaced). However, it never worked more than sporadically at best, and now doesn't work at all under load. My dad and I are considering taking it a part and installing new clutches by ourselves. How involved is this? What do we need ot be careful of? What special tools are required (for example, is a press required to put the clutches in place?) How much should it cost us to do? If I were to have a shop do it, how much should it be? Are there any tests or things I should do to ensure the clutches are whats wrong? (we have added posi fluid, before that comes up, a bunch of it)

Thanks for any help you can provide.
 
#2
simple repair. check and record backlash before you remove the carrier. mark the carrier halves before splitting them. you may want to get a posi kit that includes the springs, plate, clutch spacers and new clutch pack. there should be one washer behind the clutch hub. lube the new clutches with ford XL3 friction modifer before assembly, use latex gloves.
 
#3
fastback brian said:
simple repair. check and record backlash before you remove the carrier. mark the carrier halves before splitting them. you may want to get a posi kit that includes the springs, plate, clutch spacers and new clutch pack. there should be one washer behind the clutch hub. lube the new clutches with ford XL3 friction modifer before assembly, use latex gloves.
Click to expand...

will i need a press to get the clutches in? I heard I might. Any estimate on cost/good kit recommendations from Summit or wherever? Thanks.

Oh, and being that I've never done anything like this, if you could elaborate more on the process, I'd appreciate it. I'd hate to miss a small but critical step, though we do have a shop manual to go with whatever info I get here. Thanks again.
 
#5
IDK about summit carring them, you can try to go to a ford dealer or search through a mustang and fords mag and maybe find someone that specializes in 9" rears. There is a guy every year at the huge all ford swap meet that I get all my 9: stuff from. Don't forget to get the 4 little springs for the cross pin block.

Soak the clutch discs in friction modifier for at least overnight, or a full day before installing them. No press needed, just alternate them clutch,steel,clutch steel etc.

It's been awhile since I rebuilt one (5+ years, so I'm going off of memory). Most people say that once you rebuild a 9" T-lok, it never acts like it did when it was new. I never had too much of a problem in mine on the street, but I eventually upgraded to a Detroit Locker as it didn't last too long launching at 5K on slicks!
 
#6
Just to be sure, am I right that the clutches seem to be worn? Like I said, when I bought it, the guy specifically said he replaced all the little things (including the springs) but not the clutches. In addition to not spinning the driver's side wheel, the rearend makes a popping noise on turns. I added 10 ounces (2.5 little bottles) worth of friction modifier. This helped the popping, but did not eliminate it. If it matters at all, I reused some 8" 28 spline axles to save some money. Am I right to suspect the clutches are gone?

So there are no reputable online sources for new kits?

Thanks again
 
#7
it makes me wonder a couple things here...

1), why would some take the time to "rebuild" it and tear it down not to replace the clutches...

2) Why you car is not spinning the D/S. Nature of the differential says that will be the first one to spin...

you are right in thinking it is the clutch discs. just make sure you replace the steel shims too. New clutches wont be any good without a good surface on the steels.

The stock 9" shouldn't make any noise around a turn. However it is quite common on many aftermarket units like the Detroit lockers. That thing is noisy. it is also possible that whoever had it torn apart put extra clutch discs in there to tighten it up more. this is very common in the 8.8 axles. I have rebuilt a bunch of those and had similair "popping" sounds while going around corners. it is the price to pay if you don't want a one wheeler peeler.

I don't know online, just search and see what you come up with. When I bought my rebuilt kit, I think it was around 100 bucks for all the shims, clutches springs, etc. But that was over 5 years ago to.
 
#8
i was under the impression that the limited slip differentials worked by spinning the passenger side first, and then, if that couldn't achieve traction, spinning the drivers side too. Is this backwards?

Could there be anything I'm completely missing?
 
#9
the passenger side is always more likely to spin because of the way torque is transferred through the drivetrain/suspension. The drivers side rear wheel is pushed in the ground, whereas the pass. side is not. Ever notice how the drivers side of the car tends to lift? Thats becuase its planting the drivers side tire. The body lifts on that side, which makes the car squat on the other side, which unloads the suspension on the passenger side, leading to the infamous "one tire fire" in open diff equipped vehicles. With a perfect chassis setup, an open rear will spin both tires under straight ahead acceleration, but its easier to add a posi or locker type device.
 
#11
sounds about right if you ask me....either that or a combination of that and worn out springs. honestly as long as you take it apart slowly and pay attention how it all goes back. Honestly once you get a handle on it, it is really a fast and easy thing. Its harder to resetup the rearends lash than to take apart and rebuild the traction loc.
 
#12
SadbutTrue said:
Just to be sure, am I right that the clutches seem to be worn? Like I said, when I bought it, the guy specifically said he replaced all the little things (including the springs) but not the clutches. In addition to not spinning the driver's side wheel, the rearend makes a popping noise on turns. I added 10 ounces (2.5 little bottles) worth of friction modifier. This helped the popping, but did not eliminate it. If it matters at all, I reused some 8" 28 spline axles to save some money. Am I right to suspect the clutches are gone?

So there are no reputable online sources for new kits?

Thanks again
Click to expand...

I thought it only required one bottle of friction modifier per rear end? That's why they packaged it the way they did. More is not better in this case. Are you running "MobileOne" synthetic gear oil. I was for a while and found it effected the clutches some what from locking up. You might try flushing and refilling with the correct amount of fiction modifier and gear oil before rebuilding.
 
#13
I wouldnt use synthetic fluid, good quality 80w90 and one bottle of ford XL3. The best clutches to get are the ford/motorsport set but some of the aftermarket stuff will work just fine.

the stock posi has a preload so there is no delay in action, both wheels get power and will spin the same. currie has a torque sensitive posi that uses the spider gears natural foce of seperation to add pressure to tyhe clutch pack and can act like a open carrier under low load conditions..

You really dont need a press to rebuild the posi, there are few counter sunk screws that hold the carrier case halves toghether. you may be able to use them to pull the case closed after rebuild.
 
#14
thehueypilot said:
I thought it only required one bottle of friction modifier per rear end? That's why they packaged it the way they did. More is not better in this case. Are you running "MobileOne" synthetic gear oil. I was for a while and found it effected the clutches some what from locking up. You might try flushing and refilling with the correct amount of fiction modifier and gear oil before rebuilding.
Click to expand...

actually, thats what i did the first time (pennzoil posi 85w90 with 1 friction adder), but it was making the popping. a local shop advised me to add more friction modifier, specifically gm stuff (and i did tell him it was a ford rearend, he said the gm modifier was better, or something), and I did. Like I said, it helped, but did not solve the problem.

If I were to do this myself would I have to reset the lash and preload for the rearend? I don't really know what i'm talking about here, so please enlighten me :)
 
#17
how hard is it to put one of those posi units in, instead of messing around with replacing the clutches and refurbishing the rearend? Paying 350 for a new posi sure beats paying twice that to have someone rebuild mine or install a new posi on their own.

What would be involved with this (list everything, assume I'm a moron :) )
 
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