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Discussion Starter #1
I have my eye on a roadmaster that lacks the limited slip differential. Is it possible to remove the cover and change the gears inside to make a limited slip?. If so has anyone done this or what is involved. Where can you buy the internals of the gear case?.
 

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There are locker rears that can be inserted in place of the spider gears, but from what I understand, they are not going to make you happy. Jegs and Summit both carry them.

To replace the gear carrier with an LSD, will require that the mesh be reset. Since the carriers and LSD are not always exactly the same, the gear mesh can be off enough to make the gears whine. It can be done, but may not be worth the effort.

If you are going to swap the carriers, you should also consider changing the gear ratio. It is a little more work, but you can get better performance.

Unless you are going to be driving in a lot of snow, or racing, a LSD is not really necessary.
 

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I am also looking at a Roadmaster with an open rear end. The other bummer is the 2.56 gears. I am finding that looking online you can still score used rear ends for these cars with posi and better gears if you look hard enough. Keep in mind that Roadmaster rear ends are slightly narrower than "94-'96 Caprice and Impala SS rear ends. I just learned that on this site last week.
 

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IF you're not changing gears, installing a limited slip is not that difficult and should not have any gear noise issues. You just need to get a good preload on the new carrier bearings and then adjust to the same back lash as you had previously.
 

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I'd at least install new carrier bearings,along with axle bearings/seals.
 

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Discussion Starter #8
G80 limited slip

If i raise the gear ratio up from 2.56 will it hurt my fuel economy?.Both eaton and auburn posi units only work on gear ratios of 2.73 and up. If i change the internal gears to 2.93 or 3.08 will my fuel economy suck. The last g80 equipped car i had got 28 mpg highway given i did not drive like a complete Ahole. I hope by going to a higher gear ratio i would not be sacrificing fuel economy.Will a higher ratio fit in the axle housing? what do i have to do to make sure the speedometer reads accurately?
 

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There have been a number of posts on using the 2.56 axle housing with other ratios. It can be done, but it requires a spacer.

The other housings are compatible with any ratio except 2.56.

Your fuel mileage will not suck with the higher ratios. It will change a little. Sometimes the "in town" mileage will increase, and the "highway" mileage will decrease.

To correct your speedometer, you either have to have a computer tweak (94-96), or change the driven gear for the VSS (91-93).
 

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Discussion Starter #11
G80 limited slip

By raising gear ratio to 2.93 or 3.08 how much will my highway mpg go down?. When i got 28 mpg highway im not 100% sure but i believe i had g80 and 2.56 gears as that was most common on non tow package cars which mine was. I am only finding 3.08 gear ring and pinion gear sets on gm parts websites so thats probably what i will get .I would like to see close to 28 mpg as possible.by the way can i expect any performance advantage to going up to 3.08?.What would need to be done to the cars computer? Thanks
 

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By raising gear ratio to 2.93 or 3.08 how much will my highway mpg go down?. When i got 28 mpg highway im not 100% sure but i believe i had g80 and 2.56 gears as that was most common on non tow package cars which mine was. I am only finding 3.08 gear ring and pinion gear sets on gm parts websites so thats probably what i will get .I would like to see close to 28 mpg as possible.by the way can i expect any performance advantage to going up to 3.08?.What would need to be done to the cars computer? Thanks
Man 28mpg! Im still on 2.56 gears and I get around 20mpg mixed driving. 3.08 will have a noticeable performance advantage vs the 2.56 while still offering good cruising mpg.
 

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Discussion Starter #13
G80 limited slip

When raising gear ratio up to 3.08 are aftermarket ring & pinion sets just as good as oem?.
Oem is between $600-650. Aftermarket sets from nitro gear & axle as well as Yukon gear & axle go from $230-360. Are aftermarkets good or junk?.
 

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From what I have read, the OEM gears may take a little more abuse without breaking. The others may be a little more brittle, but for normal use, they all should work about the same.
 

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While I have put many aftermarket gear sets in and most were quiet with good patterns, they are hit and miss sometimes for finish.

Actual full on sold by GM gear sets, you have a better chance .

The "OEM " gear sets, they elude that they are the same as the manufacturer is a GM supplier.

Just because they come from the same place, does not make them the same!!!.

All this said, Motive , or AAM gears are typically good.
Yukon, said to be good, never personally used them though
Also, the lower numerically ratio gears are less likely to make noise on set up

But, for 3.08 gears, I would buy used factory gears.

There are likely 20 guys on this very forum that have them sitting around ,low miles, out of Impalas.

Hell, I have set right here with reluctor.
Problem, I am on the west coast of Canada.

Do a "wanted to buy" in the parts section.
 

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I changed my gears and carrier in my 94 wagon the an Eaton posi unit and 3.42s. What a difference! If you are worried about gas mileage. Leave the gearing alone.
 

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I think I still have a roadmaster wagon posi rear, and I am also in dutchess county NY. If you are interested let me know, I believe it is a 2:92 gear.
 

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By raising gear ratio to 2.93 or 3.08 how much will my highway MpG go down?
From 2.56 to 2.93 or 3.08, the MpG penalty is barely detectable - and so is the performance improvement.
Upgrading to 3.23 or less is an egregious waste of time, energy, and money; both the performance improvement and the changes in MpG [up or down] are insignificant; that's why it's hardly ever done, and should never be.
The higher your cruising speed, the less discipline your right foot has, and the higher the gear ratio you select, the worse the highway MpG gets.
The collective experiences of the ISSF points toward a loss of 2-3MpG highway for 3.73, with city MpG improving as gearing increases.
When i got 28 MpG highway i'm not 100% sure but i believe i had g80 and 2.56 gears as that was most common on non tow package cars which mine was.
Most 2.56 cars did NOT have G80 limited slip diff; very rare for non tow-pack cars to have a limited-slip diff.
I am only finding 3.08 gear ring and pinion gear sets on gm parts websites so that's probably what i will get.
Don't settle!
[If you only knew how many people were unhappy with upgrading to 3.42 and then went to 3.73 …]
I would like to see close to 28 MpG as possible.
Now you are at cross purposes, you may wish to go 3.42 instead of 3.73.
By the way can i expect any performance advantage to going up to 3.08?
Going up from 2.56 to 3.08 is not going to amount to much additional performance advantage, and without a stopwatch, you may not notice much, if anything at all.

My personal experience involves going from 2.56 to 3.42. Since highway MpG seems very important for you, I very highly recommend:
3.42 instead of 3.73 - unless the terrain where you usually drive has lots of steep and/or long hills and little to no flatness, then you should do 3.73
The tallest tires you can fit - 235/75R15 instead of 235/70R15, 255/60R17 or 235/65R17 instead of 255/50R17
What would need to be done to the cars computer?
Have it reprogrammed by pcmperformance.com, or some other pcm tuner.
When you do, express to them that you would prefer to lose as little highway MpG as possible, despite the gearchange.
 

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Concerned about gas mileage? Man,did you get the wrong car...If I were you,I'd leave it be. Why invest all the time,effort,and money to achieve so little? My around town mileage actually got better with the 3.73's,and that's with a 3000 stall 9.5" converter. Highway mileage dropped a mile,or two at most...
 

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Gear Ratio Upgrade

I installed an Eaton posi with 3.73 Yukon gears in my 94 Caprice wagon. Originally had the 2.56 open gear set. I had to re-learn how to drive the car, the performance improvement was dramatic. In town mileage increased slightly but highway mileage dropped about 2-3 MPG.
 
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