Hello all,

OK so the rear end it howling a bit, not terribly bad, but bad enough to not ignore.
So here is what I am thinking...

(I have 3.08 now (GO4 I think the code is)


Here are the Options::

1) Should I just order gears and have them installed?
-- If so what ratio still 3.42?? I would like to have good acceleration :naughty:, but also be able to drive on the highway :smokin:

2) Is it likely to find 3.42's in a rear end that is compatible with the caprice??
-- What cars likely came with lower gears from the factory that I can just swap the whole rear end??

GU6 is what you're after. Make sure your car has an 8.5" rear diff - you can simply swap the carrier and pinion with a '89-'93 9C1 car to get your 3.42 ratio. It has to be '89 or newer due to axle spline count.

I ran 3.42s in my car for a short time, but took them out as they didn't really contribute to acceleration, but they did negatively impact my fuel economy - more than the ~12% that's reflected in the ratio swap.

I ran 3.42s in my car for a short time

Do you still have them?

Also, on the Gm rear ends the carrier bolts from the rear correct? How complicated is it to put the pinion in?

Also if it is howling, does that mean the gears should be rep[laced, or can they simply be properly adjusted again?

Do you still have them?

Also, on the Gm rear ends the carrier bolts from the rear correct? How complicated is it to put the pinion in?

Also if it is howling, does that mean the gears should be rep[laced, or can they simply be properly adjusted again?

Yes, I still have them, but they have a rust coating on them from sitting out on the balcony of my apartment. They're for an 8.5" axle - most civilian cars have 7.5" diffs.

You can easily tell which one you have by looking at the machine pads on the lower end of the housing, by the diff cover. There is one on each side. In the first picture, you will see the 7.5" one. The machine pad on this has a half-hole drilled in it, so that it looks like a pointy dog ear. The 8.5" one is not machined, and looks squarish. This is in the second picture.

http://www.silicon212.org/diff75.jpg

http://www.silicon212.org/diff85.jpg

The howling noise can be any one of many causes. In my case, it was the spider gears that were totally worn and had metal actually flaking off. Improper lash can also cause the noise.

Well I just ran out to the car with a flash light, and it sure looks square to me. I looked at both tabs (each side) and they both look the same and square.

Tomorrow I will look more closely in the daylight. Also is there a code I can look for to be more sure?

Lastly, if I do only replace the gears, are you interested in selling yours? I think I'd like to go with the lower gears.

Well I just ran out to the car with a flash light, and it sure looks square to me. I looked at both tabs (each side) and they both look the same and square.

Tomorrow I will look more closely in the daylight. Also is there a code I can look for to be more sure?

Lastly, if I do only replace the gears, are you interested in selling yours? I think I'd like to go with the lower gears.

I might be into that, let me know where you are at so we could maybe calculate some shipping (I'm in Mesa AZ 85202).

I'd probably give you the gears for the cost of shipping and a box but do keep in mind that these are steel, and with the carrier it all weighs about 40 pounds. The ring is bolted to its carrier, but the spider and axle gears are gone (donated to my own car).

If you have it on your RPO decal on the underside of your deck lid, G87 means 8.5" and G89 means 7.5". The rear case cover over the differential will be almost a pure ellipse on the 8.5", while on the 7.5" it will look more square with rounded corners (the pics above give this away, too).

So seeing as I actually have a 91, I had a typo in the other post and said 91, so I sure I do have the 8.5, anyways about the gears can't I use the same spider gears I have now? As I recall I would just need to have the carrier installed (shimmed accordingly) and also the pinion installed (again correctly) and the other gears can just be swapped?

Is that right?

Oh and I am in Prescott, so maybe if shipping is more then gas for the 80 miles we are apart (that's got to be the dumbest thing I have said in a while, lol) anyways would you be game for meeting up??

Even with your '91, most civilian cars had 7.5" gears (even with the 5 on 5 wheel pattern). The 8.5s were still mostly the domain of the 9C1s and wagons.

You are welcome to come down here and pick them up if you wish. However, you need to make sure the rear end you have is compatible. You should be able to swap the gears if it is compatible, just keep in mind that setting up those gears is a time consuming process and you will need indigo dye and a crush sleeve (for the pinion). You WILL lose your ABS function with this pinion.