Hi guys, I've been asking a few questions in some other threads and thanks to those who've answered some of those questions! But I digress... I figured I'd just put all the questions I have onto one thread.

First off, I'd really like to put a limited slip differential into my '84 Caprice, not so much for performace reasons, but mostly for traction reasons in the rain and snow. I'm also considering changing the gear ratio while im in there. Just to give it a little bit of a higher gearing... not too much maybe 3.42 at the most. Now, I know that in an '89 Civi Caprice, its got a 7.5 inch 10 bolt rear end, with 2.73 gearing. Is that the same on an '84 civi model Caprice? Also what are the splines, and how many comes with the stock rear end. When looking though different gears, there was something about shims necesary for installation... whats that about, moving the differential so the teeth line up right? And last but not least, I've also been hearing about series 1, series 2 and series 3 carriers... what does my car have, and how does that affect my purchasing a different rear end? Thanks so much in advance guys!

~Pete A

A B-Car with a 7.5/7.65 10-bolt? I thought they all came with 8.5" units.

You can look under many GM largeer RWD cars and light trucks and find plenty of compatible units, complete units. You probably won;t have to change anything except possibly the yoke (or use a custom driveshaft). If you purchase a complete axle, you won't have to concern yourself with crush sleeves, pinion depth, carrier series, spline counts or anything like that. If you're lucky, you might find a complete '94-96 Impala or 9C1 axle with a 3.08 posi, disc brakes, and brake cables.

I kinda just wanted to change the innards of the existing rear end to whatever it is I decide to go (clutch based posi, or lockup). I've looked into junkyards, and the only posi rear ends I was able to find were ones from the cop cars. The thing is though, they have a larger bolt pattern, which would require me to have different rims for the back wheels. Oh, and as far as I know the civi Caprices had the 7.5" rear end and the wagons and 9C1's had the 8.5". But I could be wrong.

For the 77-90 models I quite certain only wagons and 9c1s came with an 8.5" 10-bolt. Somewhere along in there the # of splines did change. But I think that may have only been on the 8.5". Best bet would be to call a tech-line for some place like Currie axles or some place like that. They will know for sure.

Do you have the number by any chance??

No I don't. I just remember from years ago when I bought the limited slip unit to put into my 9c1 I had to know when I ordered from Summit. The # splines changed in 88 or 89. From 26 to 28 I think.

So that would mean that odds are I have a 26 spline, right? but then again I have the 7.5" and the 9C1's had the 8.5". oh and I don't mean ta sound stupid, but here goes.... what are the splines? My guess was the teeth that connect the differential to the wheel drive shafts, but I wanna be sure.

You are correct. They are the teeth if you will, which are machined into the end of the axle shaft. This end interlocks with the differential.

Does my '84 have 26 splines? And one last question... what is the difference in the carrier series, and what series do I have. I would assume series 2, but I'd like to be sure. Thanks so much!

With your 2.73 ratio, you should have a 2-Series carrier. The offset for the ring gear is different on the 3-Series to accomodate a smaller pinion gear. You will not be able to simply "swap the innards" without setting the backlash, pinion depth, and checking engagement and contact pattern. And doing that while under the car is possible, but not nearly as easy as on the bench. If you don't have the dial indicators, inch/pound torque wrench, Prussian Blue dye, and yoke tool to hold the pinion while turning the yoke nut, you might want to consider a complete axle swap. You can get a good, used axle for about $100 in many salvage yards, and it may be a good excuse to upgrade to the 8½" axle.

Well, I've went to the three closest junk yard to where I live (the closest one being 20 minutes away) and the cheapest I could find a limited slip/posi rear end was $275.00 and I'd have to find it and remove it from the car myself. If I kept my 2.73 gearing (leaving the pinion shaft alone, and keeping the ring gear) and just swapped the differential only with a 7.5" 10 bolt series 2 carrier equipped with a posi-traction/LSD unit, would that be more "do-able" and less involved than changing everything inside of the differential housing?

Check 80's & 90's Camaro's, Firechickens, Monte Carlos, Cutlass's, etc. I think they only came with 7 1/2 or 7 5/8 carriers after 1981.

Oh, cool... Thanks! Maybe friday I'll use my day off to head over to the junk yard again, and start tearing open rear ends.

Check 80's & 90's Camaro's, Firechickens, Monte Carlos, Cutlass's, etc. I think they only came with 7 1/2 or 7 5/8 carriers after 1981.

...Except for those that were equipped with the 9-bolt Borg-Warner axles (like mine). There were quite a few of those in F-Cars from 1985-89. If you could get one of those to fit, it would be worth $275.

$275 for an axle? They're really proud of their junk...

Yeah, they really are... well at least for specific things I guess. They only charged me $40.00 for a used rust free southern gas tank for my caprice, $30 for a set of emission legal Edelbrock headers. But then again, they wanted almost $300 for an axle, and when I asked about a set of rally rims they had they asked $400. Normal steel rims with tires though are $5 a piece! I dunno how they price their stuff, but whatever I guess.

Hey, I was browsing around ebay, and does anyone know if this'll fit. All the specs seem to match: Check it Out (http://cgi.ebay.com/ebaymotors/82-92-Camaro-Firebird-10-Bolt-Posi-Carrier-low-miles_W0QQitemZ110023913416QQihZ001QQcategoryZ3373 1QQrdZ1QQcmdZViewItem)
Once again, thanks so much guys!

The posi diffs originally came with small tags (about 1" wide x 2" long) attached to the cover. Many time these were lost or not put back on when the oil was changed, so may be missing. So, in my opinion after spending many hours and days in wreckers, here are the easiest ways to check for a posi in an F body by sequence of ease:

1) The tag.
2) Spin the brakes (axles); if both axles spin in the same direction, it's a posi. May not always work as I'm told weak posi's won't spin both axles in the same direction. Don't know if that's a fact, as I've never bothered to pull the cover off a diff where the axles didn't spin in the same direction.
3) Look for rear disc brakes; they usually, but not always, have a posi diff.
4) Pull all the covers you can.

I'm lucky around here, as there's one wrecker that has around 3 to 4 hundred GM's ranging from the 60's to 00's at any given time. They usually turn over the selection every three to four weeks. It's not even a sport to find a posi. They charge ~$45.00 for the posi or ~$90.00 for the whole diff whether it's disc or drum brake, but you do have to remove the parts yourself.

2) Spin the brakes (axles); if both axles spin in the same direction, it's a posi. May not always work as I'm told weak posi's won't spin both axles in the same direction. Don't know if that's a fact, as I've never bothered to pull the cover off a diff where the axles didn't spin in the same direction.


Make sure the transmission is in other than park with the engine off, or the driveshaft removed when you do this - else the wheels will spin either in opposite directions or not at all!

The lever-lock type and Zexel-Torson type posi units don't quite work that way. You'll be able to spin the wheels in opposite directions all day long on a ZT diffy and never know that you may have passed up one of the best posi units ever designed. the old "same direction" trick only really works with the cone-clutch type posi diffys. It's best to either remove the cover or look for the tag.

7.5" was the axle in these cars at least 77-up and if they were civilian and non towing or F41 package

most all b bodies and g bodies and f bodies were 7.5" or 7.625"

some f body were dana 44 although very uncommon and some were 9 bolt borg warner and not that uncommon, and were 88 and up only,

the g bodies wich as the SS and the turbo regals and such had the 3.42 and were th 8.5"

otherwise all the rest were crappy ratio and 7.5"

as were all the s-series trucks through about 94 or so, some started getting the 8.5" finally


if youve never seen a 7.5 under a b or g body then you either dont know what a 7.5 is or you are somewhere where all the cars are HD suspension or ar 9c1(police) or 9c6(taxi)

ive never really seen one yet, and definitely not a g body with 8.5

too rare here, in IL only 30% of the vehicles left in this state- according to the DMV- are 95 and older

so thats why



good luck

...some f body were dana 44 although very uncommon and some were 9 bolt borg warner and not that uncommon, and were 88 and up only,

otherwise all the rest were crappy ratio and 7.5" ... as were all the s-series trucks through about 94 or so, some started getting the 8.5" finally

if youve never seen a 7.5 under a b or g body then you either dont know what a 7.5 is or you are somewhere where all the cars are HD suspension or ar 9c1(police) or 9c6(taxi)


Way up here in the north end of IL the F-Bodies started getting Borg 9-bolts in 1985. I've never seen a Dana 44 in a ThirdGen F-Body, so they must be VERY uncommon, and I've been around a couple of them. The rest of them were indeed 7-5/8 Saginaw axles.

I was basing the B-Body 8½" axles on the three B-cars I've had/have. One was an '85 wagon (which explains the larger axle) and the other two are late Impalas.

Be careful about those all-inclusive categories. I've had a G-Body with a 12-bolt.