Differential questions
 

I had my car taken to the dealer for unrelated things and they said my differential was leaking. I looked under the car and didn't see anything on the pumpkin and couldn't find any fluid anywhere else. It rained recently so maybe the water washed it off so I will check again. But if there is a leak it is very small. Is this caused by a bushing breaking or something else? Can I leave it for now?

to accurately test for a leak can I put some cardboard under the car and check for fluid that way? or is it possible that it would just stick to the diff?

no fluid was seen under the car from the naked eye

It could be the diff bushing. That is a common problem

I might have caused it by taking it to Lime Rock last week:(... how much is reasonable to replace do you think? Is there a way to check just by looking under the car?

Also is it even necessary if I don't see any fluid?

Check these links:
DIY Whiteline Differential bushings - MyG37
http://www.the370z.com/engine-drivet...l-bushing.html

based on those threads the OEM bushing is a separate thing with fluid. is that correct? So it might be that and not a leak in the actual diff. I am new to this and just paid a bunch of money for a bent wheel and bearing so don't have that much to spare atm. is it OK to drive on this for a while? I don't notice any sort of wheel hop or any symptoms at all regarding this.

For post market diff bushings(replace when diff leaks) there are two options:

White Line and SPL.

Both are good, but if you are tracking the car a lot consider getting the solid SPL's. If you are tracking just here and there the whitelines will be quieter and smoother.

Either way, when you replace the diff bushings, consider doing a new differential and definitely change out the oil. It's the same labor cost.

i'm running energy suspension bushings

I attached a photo of the diff. There is a little bit of dried fluid but could it be a one time thing caused by some hard driving? It seems dried and that no additional fluid has leaked for a while

I am thinking of trading this car in either this year or next year so I don't want to have to do another huge service if necessary

Yep, thats a torn diff bushing. Once its torn, it needs to be replaced. Myself and another member did the whiteline replacement on my car and wrote up a DIY, its in the DIY section somewhere. Its not that bad of a job.

Edit: Found it http://www.the370z.com/diy-section-d...-bushings.html

Thanks for the information. Seems like a large job for me who is fairly new to stuff like this :(

Yeah I had a shop do it. Definitely worth it to do and it isn't that expensive.

How much was it for you?

haha I majored in math I do not want to do those again

btw I cleaned the area so I am going to see if it is still leaking. I drove it for a bit today with some spiritedness and theres nothing on it now. I am going to check the level of the fluid also, if it is up to par I think I am fine right?

IM 99% sure its the diff bushing. you could prob drive on it easy for a month or two (if you are in a pinch) but i wouldnt go past that!!!