I think i got it figured out

[85 Cutlass Brougham]

You do not need the adapter if you are using the matched set of those gears and the diff they were installed on. You do, however, need a pinion depth gauge, and a few other pieces to properly set up gears. A shop usually charges $150-200 to do it, which is about what the tools cost. Plus, you would need a pinion bearing that is honed out so that you can remove and replace it without a press, plus another pinion bearing that will be the final part that actually gets installed. You also want to change the axle bearings at this time as well as all the seals, so you would need a rebuild kit. If you are going to have it done professionally, I would bring them both axles and let them do the tear down so that you reduce the chance of contamination. I will also note that the S trucks used gov lok diffs that are not the best design for strength.

 

[canucksfan1]

but it would be strong enough for a basically stock 305 right??? I don't plan on building a crazy engine for this car maybe one day something like a 300hp 350 but it will be a street car maybe an occasional drag race for fun.

The gears will be going into the matched gears will be installed into the cutlass diff which as far as i can tell is the same as the s-10 diff the new gears came out of except themounts of course so no adapter then???

(O and i can probably get one of the other techs at my work to do it for a case of beer and a few bucks so i am thinkin of going that route)

 

[85 Cutlass Brougham]

It should be OK with a mild engine so long as you don't run slicks. I would check the spider gears in the carrier and make sure they are not chipped. If they are, don't use it because it will fail. The gears will not fit the Cutlass's 2 series diff. They will fit the 3 series S10 diff which fits in the Cutlass axle housing. So, just run the gears from the S-10 and the Diff from the S-10 and all will be well.

 

[canucksfan1]

so i would have to weld brackets on the s-10 diff and bolt it into the cutlass???

 

[canucksfan1]

or do i just gut the hole rear from the s10 and put everything into the cutlass housing after i gut it??????

sorry i am having trouble seeing this in my head right now, i should understand i know

 

[85 Cutlass Brougham]

The differential is not the axle housing. It is the carrier, which is what the ring gear bolts to and the axles slide in to that connects it all up. Differential refers to a device that allows the wheels to move at different speeds going around a corner to compensate for the dissimilar arcs the inside and outside wheels scribe. The whole reason for the GM case breaks is to compensate for the pinion gear diameters which get smaller as you go numerically higher. Ford does not do this, as they vary the thickness of the ring gear, so the carrier remains a constant. The posi unit is a differential, and so is the open diff that came in your car. Positraction was a Chevrolet marketing term for a Limited Slip Differential, or LSD for short. A limited slip generally uses a series of clutches, cones, springs or gears to reduce the slippage of one wheel versus the other. The Gov Lok is a bit different in that it uses a governor to lock the wheels together when it detects slippage. It requires one full turn of the wheels in order to hit the lock point, where it violently locks them together. This works OK in an off road application, but can be bad in a moderately powerful street application.

 

[canucksfan1]

Ah i understand now, do u think it would be a good unit to use in my car??? I don't plan on haveing anything more then the stock engine in it maybe once that goes do up an average 350 for it.

O and i apologies for all the questions, i am just having a dumb day today and couldn't seem to figure it out.

 

[85 Cutlass Brougham]

I have an average 350 in mine and run a 7.5. However, I only spent $65 for it, with the right gearing already installed. I have a posi I will be installing along with a ring gear spacer, so mine will be under $200 when done. If I were going to spend any more than that, I would just hunt down an 8.5 because it is way better. I am still looking for one now, even though I have the gearing I want. Because, if I ever want more power ( 150 shot?) , I will break the 7.5 very easily.

 

[canucksfan1]

well mine would be free cuz it is out of my old truck, well except the case of beer to get my buddy to put it in for me

 

[85 Cutlass Brougham]

That, and you would want to get new seals and bearings while you are in there.