The code is.... 5JGC1191

I know the last 4 numbers stands for Jan, 19. 1st shift

Looks like all the "JG" stands for 3.08 gear

I can't find a "5" listed any where. All the charts I have found shows 2, 4, 6, 8, etc

And YES i'm 100% sure it's a "5".. I looked twice and so did my dad. We used one of those 500,000 candle power spot lights, wd-40, and a brush to clean off and see the numbers

 

The "code" is pretty much useless, for all of the above reasons, and more.

If you really want to know what rear end you'v egot, take off the cover and look. Have you changed the fluid lately? Then it needs it, and you need to take the cover off anyway. While you're catching up on the overdue basic maintenance, make a point of looking at the parts.

 

RB83L69... How can I tell the diff in a 7.5" and 7.625" ring gear by taking the cover off and looking???

Here's the deal... My dad bought an 82 firebird. It came out as a 6 cyl car, had a v-8 swapped in, use to have a "lincon locker" rear (welded spider gears) the guy broke that rear, then went to a junkyard and got one to replace it. He didn't know what year car he got the junkyard rear from

I know by pulling the cover off you can tell gear ratio.. Look at the face of the ring gear while you turn the axles, you'll see numbers stamped on ring gear. It's the amount of teeth on ring and pinion, then just divide the two numbers and you got the ratio

 

There is no difference between those 2 "sizes". They're the same thing.

Go look up some gears in catalogs; you'll see that they're all the same for that rear in all the chassis that they've used it in over all these years, 77-current. That includes A, B, F, and G cars; S trucks; Astro vans; even Monzas from the late 70s. They all use the same gears and the same internals, in any given year.

2 things in the rear end have actually been changed over the lifetime of it. In about 80 or 81, they changed the head bearing on the pinion (the pinion itself remained the same) to a larger one; and in 89, they changed from 26-spline axles, to larger ones with 28 splines. Neither of those has anything to do with the supposed difference in the ring gear diameter, or whether a given carrier or gear set will fit in a given housing.

Since all of these cars were later than 81, they all have the larger pinion bearing; so you don't have to worry about that. The only thing you have to identify, is which axles (and therefore which carrier and side gears) you now have. You can put any carrier and axles into any housing, as a set; but, a 26-spline (early) carrier will not accommodate the larger axles, because the hole they have to go through, is too small. So just count the axle splines, and note the gear ratio (3.08 or lower, or 3.23 or higher) you'll know everything you need to know in order to get the right parts.

Make sense?

 

Thanks... That cleared up alot. Makes good sense to me. You seem to know a good bit about these 10 bolts, so I have 1 more question.

I understand what your talking about with the sizes but why is it that theres diff part numbers for the 7.5 and 7.625"

Like with mine. I just ordered and installed a power trax lock right in my 88. The lockright #1930 says for 7.5" 26 spline, the lockright #1932 says for 7.625" 26 spline

 

It's because the internal size of parts inside the carrier is different.

The carriers are completely interchangeable with each other, as complete units; but their internal parts (which the Lock-Right replaces) are different.