I have a 2008 G35 Sport with 175k miles and the automatic trans is going out. Local shop I go to confirmed engine code and indicated needs to be rebuilt along with replacement of valve body and radiator. They quoted $4k for everything but this would be outsourced to a reputable local transmission shop which includes a 3yr/36k full warranty on the transmission and work. I will be getting additional quotes from other shops as well to see if this is reasonable. I really love this car and am torn between scrapping for whatever I can get for it vs. rebuilding the transmission and keeping for a couple years for my son to drive when he gets his license. I don't think I could find a comparable car for the price to fix the transmission and would love to give it to my son as his first car. If I can convince myself that other major costly issues are reasonably unlikely to happen (mainly engine going out) then I would like to fix it and keep it, but just not sure yet. Any thoughts on this will be appreciated.

Thanks,
Bill

 

Just a thought, but why not buy a used transmission and just swap it in? You can probably find one for around $400. The radiator job will cost around $600. Save some money and get more life out of the car.

 

Soooo... what code EXACTLY ?

 

Great suggestion - I actually ended up going that route and it's being worked on right now. I took it in to a different shop to get a second evaluation and diagnosis was similar. They were able to locate a used transmission in great condition with 78k miles on it and will be adding a stand-alone trans cooler since existing radiator is in great shape. So we'll see how it goes - hopefully will have it back tomorrow.

 

I don't remember the exact code - wrote it down and googled it but lost the paper. Both shops pulled same code and it was definitely related to the transmission. I'll see if I can locate and post later.

 

Ok because there is a sensor on the output tailshaft that is accessible by just removing the valve body that is a common item to go out and it's only about $25 for a new one if you do the work yourself. There are a LOT of components inside a transmission that are replaced individually.

If your car is throwing a check engine light you wouldn't just immediately replace the motor would you?

 

I agree and appreciate your feedback. Based on what I read in these blogs when I searched up the engine code (which I subsequently lost) along with two independent evaluations it appears the trans and valve body were shot enough to merit some serious work. The second shop also confirmed the damage when they opened it up. Hopefully everyone has been honest and the assessment is correct, but if not there's nothing I can do now as the decision has been made to move forward. At least I'll have one with 78k miles on it which will be a great car for my son when he gets his license. Given that I made it to about 180k miles driving it somewhat hard I can't complain. It's just been so much fun to own and drive.

 

Typically by the time you have that kind of miles on the transmission it's got a lot of components ready to go out so I agree that replacing it with a lower mile used unit is a good choice. I doubt that you had multiple shops trying to deceive you, I'm glad you got a second opinion on it though.

The primary cause for valve body failure is simply not changing the fluid often enough, the clutch friction plates wear over time and the microscopic bits of material are not picked up by a filter in this transmission, they just continually wash through the entire system and eventually erode components to the point of failure.

A drain and fill every 30k is definitely worth the time, if you want to make it REALLY easy you can pump out the fluid from the top by removing the dipstick and sticking a section of tygon tubing down the tube and using a pump to pull it all out. it's about 4 quarts so just do it by hand with one of those gear oil pumps that normally go on a bottle of gear oil, all you have to do is use a hose clamp to keep the tygon hose attached to it and another section to go down to a bucket to hold the old fluid. If you buy a liquid transfer pump for gasoline from Amazon it's even easier because it moves more fluid per stroke.

Using this method you also get a really good idea of the actual condition of the fluid since you can accurately see it's color as it's going through the clear hose.

If you do use this method make sure to unroll the tygon and let it straighten out so it doesn't try to curl up once it's inside the transmission, it's some pretty stout stuff though so this usually isn't an issue, you can leave it in the sun for a half hour and it's very pliable if it isn't very straight when you get it.

 

Thanks for these great tips! I have always been good about changing oil every 5k using semi-synthetic for the engine but I do regret not being better about changing trans fluid as often as recommended. Definitely will start to do it every 30k on my vehicles going forward especially if I can do it myself with the steps you shared. I get my car back today or tomorrow so looking forward to driving it again.