thanks for the support guys,
I put a lot of time into my posts and it's nice to be appreciated
gp02a0083 said:
I got an 84
H/O 8.5 with the 3.73's. The gears look like they are in mint condition. I found that strange engineering sells the coil spring type clutch pack differential unit. Im curious besides the carrier needing replacement, should i get a installation package that is the basic kit or the complete kit as you described? I plan on reusing the gear set (i think it will work well with my 307 / 2004r combo for now) so I would imagine i would only have to re-shim the carrier left/right and not worry about the pinion depth setting.
gears are very hard to ruin, unless you're pushing huge power or you're very careless, it's hard to damage gears. They can wear quickly tho if the pre-loads & backlash are not set properly. Strange, Eaton, Auburn, pretty much everyone has similar 4 coil clutch pack setup now in their posi units, but you pay more for rebuild-able ones like the Eatons. They also provide a better pressure transition and are customize-able depending how aggressive you need.
you are wondering which installation kit you need... lets see if I can explain this
as a rule of thumb, whenever you change the geometry or the position of the carrier inside the housing, you need to do a full re-setup of the carrier (measuring backlash and pre-loads, etc...)
what does this mean?
if you are installing new parts like bigger or different gears, pinion bearings or crush sleeves, or even a whole new carrier, you are working with new geometry, you need to perform a full setup. This takes trial & error, you have to install and re-install trying different combinations of shims until you achieve the proper backlash, pre-load, and contact pattern on the gears.
but let's say your clutches are warn, or you wanna replace your carrier bearings... You can take it all apart, keeping track of the arrangement of the shim stacks; and just put it back together with the same shim arrangement, and you will not have changed the geometry.
Even with new bearings and new shims, you just have to copy what came out, and put it back together the same way.
However, using a new crush sleeve on the pinion gear does upset the geometry and will require a setup. Many people just re-use their old crush sleeve, making sure the new shim arrangement is as same as before.
So, which kit do you need?
well, it depends on what you want to replace. I strongly doubt your carrier is bad, these differentials are bullet proof... If the posi is slipping, replacing the clutch pack is the cheapest option.
http://www.gbodyparts.com/product_info. ... 0debb3b51c
Unless you are planning for heavy race use, the components in your diff are beyond sufficient. I recommend replacing the clutch pack & S-spring, carrier & pinion & axle bearings, and it'll be like new!
Jegs's "Deluxe" rebuild kit has all the components you need, even new bolts and gaskets
http://www.jegs.com/i/JEGS-Performance- ... Id=1176762
and like I said, since you're planning to keep your gears, keep the carrier; the rebuild is simple, just copy the shim arrangement that comes out, and re-use the crush sleeve.
Bweavy said:
Khan we just came out with these in the U.S. They will be available just before May/2013.
http://www.gbodyparts.com/product_info. ... 0debb3b51c
The S-spring we bought up about 5 years ago from GM. We are getting low on them but mainatined a good price.
Nice write up your doing. Glad some one took the time. I will probably do a link back from my site to your post.
Bweay, this is great news!
I was so upset to learn the GM no longer produced these; I think I called every major Drivetrain parts place, and no-one had or made any. In my above post to 1987GN "Stewart", I posted an email of someone on the V8Buick.com forum who started producing his own. Poor guy had to fork up alot of $$$ to produce them in numbers.
I wonder if you know him?
and thanks for the props on my thread, it's very appreciated
G-Body_Vet said:
Good write-up! I don't know why, but differentials have always seemed like the mysterious part of the car that only a handful of people and places are knowledgeable about. I plan to rebuild my 8.5" and go to a lower numerical gear when the time comes. I've subscribed!
yeah, I've done alot of digging to find decent information, and much of it is pieced together. I found much of it on 4x4 / off-roading forums... I guess those guys are good at somethin
thanks for the subscription! I hope it helps you out
Blue86Monte said:
When should one think of converting to a spool instead of a posi. What's a power range that a posi will not hold? I want to convert to a posi, but do not want to be replacing clutches all the time. 8.5 under the car right now with a spool, but it sucks on the street :|
I've never seen a posi not hold to big power. Maybe it's me, but I've encountered this dis-trust from many people. There's a few guys around here running 10 to 9 second GNs on their factory 8.5 posi units.
The Eatons last longer than the factory S-spring units for a few reasons... The 4 spring setup provides alot more load on the clutches than the flimbsy S-spring, better pressure distribution as well. And the Eatons also use better clutch material, you can get them with carbon-fiber clutches as well.
I think duration/durability of a posi unit comes down to a few things
- a quality carrier... don't ever trust a gov-lock. And Auburns are cheap, but you can't rebuild them when they die. A good quality setup like Strange, Eaton, etc... is worth the extra cash.
- the 8.5 10bolt is based off the GM 12bolt design. Except the 28 spline axles, both differentials are comparable in durability. And in a recent hotrod article, a 12bolt & Ford 9inch were compared, and they determined the 12bolt stronger. So I don't think you have much to worry about in terms of strength.
- the posi wears depending on the amount of street use. If you drive the car in tight bends (at slow speeds where the clutches are forced to slip) many times a week, it will wear sooner than a car with primary straight track use. But I think even in bad cases, you've got a good 5 years of hard use before you start to notice unreasonable slip... And with a rebuild-able unit, it's not as big a hassle.
