What damage could have been done if...
 

The axle boots were replaced and excess grease was used in the repair process. This happened to my sister on my nephew's car. The next day my brother-in-law was brought in for emergency open heart surgery. So I am trying to investigate this for her. As my nephew was driving it home the CEL and Transmission lights came on, the car started smoking and he felt it dragging and heard it making noise. They towed it back and they cleaned out the grease and re-packed it with new grease. It seems ok now but I am concerned there may have been collateral damage. Could this have stressed the front diff or the tranny to the point of decreasing its life expectancy? The tranny light coming on is concerning, in particular.

Re: What damage could have been done if...
 

I couldn't imagine that it would cause any sort of problems. I don't really think there is such a thing as too much grease in the cv joint. I tend to suspect the transmission issue was unrelated.

Re: What damage could have been done if...
 

No one else has anything to add?

Re: What damage could have been done if...
 

I agree with Mike.

The only effect of too much grease is that it could force some out of the boot and cause some smoke.

Re: What damage could have been done if...
 

That is what they claimed happened and what was causing the smoke. But that doesn't explain the CEL and tranny lights coming on the drivability issues. It was a little unclear as to what exactly the issues were but it sounded like something was dragging or holding the car back.

Re: What damage could have been done if...
 

Maybe the boot was so over-full that it was pressing against something? What kind of car was this?

Re: What damage could have been done if...
 

no, too much grease in the cv axle cause any form of driveability issues. It might smoke a lil because grease got squeezed out onto the exhaust but other than that there is NO possible way it could hurt anything. Its a rubber boot that would be pressing against metal every direction it could go. The boot would pop before anything else could happen.

Now if they didnt put the knuckle/cage back on the axle shaft correctly, the CV joint itself would start to lock up (or if they lost one of the balls inside the knuckle joint)

you may have 2 issues going on, might be a front diff side bearing starting to seize up and it just happened to occur right after you had the axle boots replaced.