Q: I change the axle on my car and now when I put it into gear it does not go in gear and it makes a grinding sound

When a CV axle is removed some transmission fluid will leak out. The first thing to check is the transmission fluid level. If the fluid level is too low that will cause difficulty in shifting gears and possibly noise. Also, it is possible for the output shaft seal to leak if a used seal is used with a new axle. Check for leaks at the seal area. The best practice is to replace any seal that is disturbed when replacing an axle. Replacement of the seal is the only guaranteed way to prevent transmission fluids leaks at that point in the assembly. Other than those possibilities, mere replacement of the axle cannot cause the present problem you are describing. If low fluid is not the issue, you may have a shift linkage adjustment fault and/or internal transmission damage. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a transmission leak/noise diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.