I have a 2006 G35 AT with 109 K miles on it. It recently had a Service Engine Soon light. I had it diagnosed it at infiniti showroom and they told me it needed a valve body in the transmission and it would cost $2.3 k to fix it.The diagnosis took a little less than 2 hrs to make at the dealer. I then took it to a reliable Auto shop i have used previously. This guy had fixed my car for far lower prices than the infiniti had quoted previously on multiple occasions. He took a day and informed me that my car has transmission fluids and anti freeze mix up and running and so the transmission needs to be rebuilt with some changes made to clutches and sensors. The valve body will also be replaced as part of this.
The auto shop guy informed me that he will have 2 yrs -24,000 warranty for the rebuilt transmission and it would cost me around 5.5k. Has anyone had a similar experience with the g35 AT? I appreciate your suggestions.

Thanks

 

as far as I know the only place where coolant and transmission fluid come in contact are in the radiator. There are two hoses that come from transmission into the radiator for cooling transmission.

So if coolant got into the transmission that means you got a radiator issue as well.

As far as the rebuilt, just buy a used one, they are well under $1k. Much better option IMO than rebuilding the old one.
What's more important is that you have to consider fixing the coolant leak issue. If coolant got into the transmission, that means trans fluid got into coolant.

 

I think the radiator will also be fixed during the repair. Are there any reputable online websites or stores that sell used transmissions for G35? How much does it typically take to replace a transmission ?

Thanks

 

You can get them off Ebay. Several people here have bought Ebay trans and transfer cases and such. How well they work....different story.

Transmission replacement, on a lift, with a trans jack....3-4 hours or so? Just guessing. I've never replaced a G35 trans. I've done it in other cars and it took about that long doing it on my back on jackstands

 

with proper equipment it's not a difficult of a job. To rebuild a transmission your shop will have to take it off anyways, might as well make it easier and slap a new one on.
You can use car-part.com to find a transmission at a junk yard, or search local junk yards for one. .