Hey Guys, Your opinions please. I have a 2005 G35 Sedan A/T with 256,000 miles. I had the tranny rebuilt at 200,000 miles so the rebuilt has approx. 56,000 miles. Frankly the guys who did the rebuilt I don't think did a good job and I don't trust them as I had issues early on. Each time they say it's the valve body and each time it isn't.


The problem: sometimes typically the first start up of the day, when I put the car in Drive it seems like the transmission is not engaging and all I get is the engine rev. I let the rpms drop and hit the gas again and it engages and goes. The other day when I did it and it just revved, I put the car back in Park and then Drive and it was fine. Fluid level is fine and red. Of course when I questioned the guy who rebuilt it he says its the valve body. I guess one of these times he will be right. Btw the first thing I do is backup with no issues and then try to go forward. Your ideas to the issue??

 

When checking the fluid level did you drive the vehicle until the transmission is up to temperature, park the vehicle and go through EACH GEAR letting it it fully engage each gear R-N-D-N-R then park, leave the engine running and NOW check the oil level multiple times?

If you turn off the engine you have to do it all over again including driving, preferrably at highway speeds so it goes through EACH gear properly.

If the fluid level is correct check the transmission ground wire, it's located on the timing chain cover at the very top, there will be TWO wires with crimped on ring terminal lugs under the top middle bolts of the timing cover, remove the bolts, clean the lug, bolt, timing cover with a metal brush, apply electrical anti-oxidation grease and reinstall the bolt.

You might as well clean the entire ground path while you're at it, next it goes from the passenger side of the timing cover to under the coolant reservoir (take off the single 10mm bolt for the coolant reservoir and lift it straight up, leave the hose attached there is enough slack) under the reservoir is a 2 bolt lug. From there go into the battery compartment, remove the negative battery terminal and the 2 bolt lug where it attaches to the chassis next to it, brush, de-ox, reinstall all that stuff.

The transmission is basically just a fancy computer and electrical resistance will definitely cause problems, I think you probably just have a low fluid problem but you might as well rule out electrical ground issues.

 

Cleric,
Thanks for the reply. As far as checking the fluid level, yes I did it as you described same as the repair manual. I also did it cold too. If anything I believe it to be a bit high. Not high enough however to cause foaming. Its red and smells okay.

Interesting info on the ground wire. I'll check that. Fingers crossed that it's disconnected.

 

So it's been a week so far with this fix: I heard that some people were using the product SeaFoam in transmissions and I found out they make a product called Hydra Trans Tune. I had the garage remove 16 ounces of transmission fluid because I was high in the first place and put in the bottle of Hydra Trans Tune. I drove 30 miles up to a friends place because I needed to change a spark plug coil. While the car cooled down for a few hours I went to a used car lot to check on Q50s. Got back to the house and changed the coil. Test drove the car and found that the transmission is no longer slipping. It's been a week. Not only that but when I had the transmission rebuilt 60k miles ago the manual shifting of gears wasn't working, and now that is even working. So $3,000 for a rebuilt tranny or a $12 bottle of Hydra Trans Tune? In my case it was worth trying the $12 bottle!!

 

That makes me think you have a torque converter problem or something. I would call the shop that did the rebuild and ask if they put in a new torque.converter or reused the original one.