Back in a XJ

So last night I traded my 89 Bronco for a 92 XJ. Has the 4.0 but has a auto. The guy put a 4in lift on it and 33's. He also took out the Dana 35 rear and put in the 8.25 with a locker. He clams it has 5.38 gears but what I wanna know is what would be the best gears for this set up. My speedo is also off by 10 to 15 mph and gas mileage is pretty bad. Going to use it as a daily driver and a toy so I want a set of gears that will be good for both. I also got to fix the oil leak it has too. Guess its leaking from the rear main on the pan. How easy will it be to change out. Never done it while the engine was in the car. All I know is glad to be back in a XJ. been 3 years to long

I could be wrong, but 5.38s in a C8.25? That doesn't sound right. I didn't even think that was possible. I thought 4.88 was the max in the c8.25.

4.56 seems to be the consensus popular choice.
I've also heard/read that an oil leak from the back of the valve cover can look like an RMS leak.

4.88 is the biggest you can fit in a 8.25. Like dsdtdemon said, 4.56 is a popular choice for street rigs on 33's.

Checking for oil leaks you should start at the top of the motor and work your way down. That way you don't replace seals on the bottom when they aren't leaking and still have a leak from the valve cover or oil filter adapter.

You should pop off the cover of the axle and see what ratio is in them. It should be stamped on the ring gear. If not, jack it up and spin the driveshaft and count to get the ratio. It will be hard to get it exact, but with popular gear choices being 3.55/3.56, 3.73, 4.10/4.11, 4.55/4.56, and 4.88 you should be able to figure out which one it is.

After you figure out what gears you have, find which speedometer gear is the correct one and swap that out with whatever is in there right now. Quadratec has a chart to figure this out. Its pretty much impossible to check your gas mileage if your speedometer is off.

Ok ya I figured he didnt know what he was talking about cause the bronco I traded had 5.38s on 35s but did better on gas haha. But I know the valve cover is leaking and I made a 65 mile run last night and lost 3quarts of oil. I did stop and add oil so I wouldnt mess the engine up. Ya I got to do a few things to it so when the snow melts Ill jack it up and check the gearing and try to pin point the leak.

Ok so I am trying to change the oil pan gasket because it is messed up on the rear main. Went and picked up a new gasket it and it has 2 extra holes in it then my block and pan. Been told that all the 4.0s are the same block and oil pan but why do I have the wrong gasket. Its the one piece gasket from Fel Pro

Ok so I meant it was leaking from the back of the oil pan gasket. Wasnt set right but fixed it and test drove it and now for sure the rear main is leaking but the leak isnt that bad but enough to were I wont drive it tell its fixed.