[Terry411]

I have a 78 malibu and I went to check the diff fluid and suds started to come out. The people at work sayed that I have water in the rearend. So I figured since I have to take of the rearend cover, I should up grade and go with a posi unit. What is my best rought taking the entire rearend off of a SS Monte Carlo or buying a carrier, ring and pinion. Then what size should I go with 3.43 or 4.11 Every thing is stock with the orginial 305 with I do plan on replacing with a small block 400 and quick shift 350 trans. I will not drive on express way much. And what size rearend do I have up under there now would help also?

[bracketeer]

All toll the Monte SS rear end is not that strong. It would be easier and cheaper to make that swap. You can probably find a complete rear in the junkyard.
If you want to shell out a few bucks. A Moser 9" bolt in is the way to go.
While you have it apart. Replace bushings with Energy Suspension neoprene and box the lower bars. Better yet buy a set of lift bars. See pic.

[Terry411]

What are the purpose for the lift bars is that the same thing as trailer arms

[Triaged]

Originally Posted by Terry411

So I figured since I have to take of the rearend cover, I should up grade and go with a posi unit.

And you are going to get a new engine next time you need an oil change

Is this just your way of talking the wife into it

[Terry411]

Why would I need a new engine next time I change the oil. The powertrain ration will not be correct or somthing?

[lamothe1]

Terry, I think what Triaged is trying to say is if the only thing wrong is that there's water in the RE oil why don't you just spend 20 minutes and change the oil or is this just an excuse to get a posi??

[Terry411]

We'll yes, I was going to add a posi any way, so I figure I should go ahead since I would have the rear cover off. I will be trying it myself. I want to change the ring in pinion also. Should I go with 3:73 or 3:42, I have heard of 3:55 but I do not know if I could get that on my vechicle.

[Triaged]

Originally Posted by Terry411

We'll yes, I was going to add a posi any way, so I figure I should go ahead since I would have the rear cover off. I will be trying it myself. I want to change the ring in pinion also. Should I go with 3:73 or 3:42, I have heard of 3:55 but I do not know if I could get that on my vechicle.

Do you have any clue what you are doing

Swapping out a ring & pinion and carrier isn't an easy thing to do and it requires some specialized tools.

At the very least you need a dial indicator, micrometer, bearing seperator, and a hydraulic press.

This isn't something that the average joe can do in their driveway.

The easiest way to do it would be to find an axle out of a car like yours with the gears & diff you want at a j/y to swap in....

Poping off the cover and changing the diff oil is something anyone can do and something you should have done as soon as you noticed the water in your diff.

[Terry411]

We'll I work at a mechanic shop and they have all the tools I need and I have seen my co-workers reasemble rearends before. But I wanted to try it on my on because they do not like working on old cars. Then I did have a lesson on rebuilding rearends in class but it went over my head because the class was to short for me to remeber all of that stuff.

[Triaged]

Cool. Having someone help you do it is the best way to learn. Nice to have all the tools as well I've watched it been done before but have never done it on my own. I would at least want to have someone check the pattern for me before I put it back on the road.

[Terry411]

what ratio should I go with?