I am looking at a car with a rearend from a 98' camaro z28. This is a 95. Is there any difference in gearing?

 

They made 3 different gear ratios for these cars. 2.73's, 3.23's and 3.42's. The 3.42's only came in 6 spd cars. So it really depends on what the car originally had and which got put in the car. The brakes could be different but will work if he swapped the brakes off the 98 rear.

 

What gears would a 98' automatic have? 3.42 i'm guessing....How easy is it to swap out those gears? How much would a 4.10 or a 3.78 be? And how about install?

 

98 auto would have had 2.73:1 std.and 3.23:1 as factory option hi-performance axle package.

 

As above, you are looking at 2.73 or 3.23 gears. As for how easy it is to swap them into another axle housing on a scale of 1 to 10. You are looking at an 8.5. Spacing the pinion and matching the ring gear is a tedious task that has to be done with patience and some background knowledge. Don't misunderstand, everyone has to have a first time experience. Installing a gear set is difficult. If you don't get the crushed sleeve for the pinion correct, you can try it again unless you have pulled it back too far. In which case you have to remove the crushed sleeve and try it again with another one. This is why nearly everyone advises having an experienced mechanic do the job. They have the tools, spare parts and experience.

The pinion depth from the ring gear edge is stamped on the end of the pinion. This requires a depth micrometer reading from the edge of the ring gear and usually an impact gun to pull the pinion back against the resistance of the sleeve that is continually crushing as it gets drawn back with the pinion gear. Spacing the carrier and checking for backlash requires a dial indicator. Even if the backlash is correct and the pinion depth appears to be right the gears still must be checked and adjusted using marking compound to determine if the gears are meshing correctly. If not, then pinion depth and subsequent carrier side spacing has to be adjusted. It can be a back and forth thing....

Gears run about $200 new. Doing it at home will require an install kit which includes shims, marking compound, crush sleeve etc.

Having it done usually costs $300 + but you will not need to buy an installation kit.

 

Without any signature info, I think I follow you but just want to make sure.

{1} You are "looking at", to buy? a 95 car that someone has installed a complete rear axle assembly from a 98 Z28 into?
or
{2} You already have a 95 and am asking about installing the gears from that
98 rearend onto the carrier in your present rear axle assembly in your 95 car?
or
{3} 2 except use the carrier from the 98.
If {1}, you may want to look to see that the ABS / Traction Control system is configured the same {as far as wheel / axle speed sensors} between the two. {95 car / 98 rear axle housing.}
If the car is Traction Control equipped, and someone has installed a non TC axle housing, they likely did not install reluctor equipped axle shafts nor the speed sensors for those. This will cause the ABS, TCS to not funtion and an SES light
If {2}, and you install the gears yourself, and your 95 car is not TC equipped, then you may want to plan on purchasing a reluctor ring in addition to the parts already mentioned. The problem is going to be getting the ring gear off the original carrier without a press and you cannot get to the backside off the original gear to press it off without removing the ABS reluctor ring from the carrier first. Unless your luck is better than mine, the original reluctor ring will break before you get it pressed off.
Look at the second picture on the right on page 10 of my cardomain site and you'll see how the ring is a larger diameter than the gear.
The second picture on the left is the press configuration I used to press the new reluctor ring onto the carrier which was no problem.
If {3}
If you use the carrier from the 98 axle, and that car was not TCS equipped, you won't have this issue but you will need to set the pinion depth on the pinion gear before installing that carrier and ring gear {as already mentioned}.
If the 98 was not TCS equipped and your car is, the reluctor ring on the carrier can be left in place but removing it would be better since it's just going to be dead weight only just a few ounces.
I know that's kinda confusing. I can give a simpler answer if you post more information.

 

I would recommend 3.73's for an Automatic tranny car. I installed Strange gears on a {3-Series} Zexel carrier. My car had 3.23 gears on a 3 series {cone-style} carrier from the factory.
If the carrier your going to use came from a 2.73 gear ratio car, it will be a 2 series carrier and in order to install a gear ratio of higher {numeric} ratio than 2.73, you'll need a special design gear which is not available from GM or use ring gear-to-carrier spacer which is a weak configuration if your putting a lot of power to the rear.
Have fun!!!