The TCM in my son's G35 Sedan is shot, and needs to be replaced. Since the transmission has to come out, I want to get his transmission rebuilt/upgraded because we bought the car used. Is there a company that is the best to send a transmission to for rebuild/upgrade?

 

The transmission doesn't need to come out to replace the TCM. Disconnect the battery, drop the transmission fluid pan, remove the valve body which has the TCM bolted to the back side of it. Then replace the TCM and put it all back together.

It's not that difficult really, if it's a new TCM it will need to be programmed by Nissan/Infiniti. If it's a used TCM it's plug-and-play and won't require programming.

You can look up the installation instructions for the TransGo shift kit, it has nice pictures and instructions for removing the valve body.

Note, only the 2004.5-2007 G35 had the internal TCM, the 2003-2004.5 had an external TCM mounted next to the ECM near the glove box. You can look at the left side of the transmission to tell which one you have if you're not sure. The external TCM has a harness coming out of the transmission that has three plugs on it, one black, two green. The newer internal style has a single large grey plug right where the wires go into the transmission. Nevermind just realized you have the V36 chassis with the HR engine, you have the internal TCM. You posted in the V35 chassis subforum.

If you do decide to rebuild the transmission try to find a local reputable transmission shop, there's usually a couple in each town but TYPICALLY you want to stay away from the big box chain tranny shops like AAMCO. Call around to some of your local reputable auto builder specialty shops like hot rod or tuner shops, ask them who THEY recommend for transmission rebuilds. Once you talk to half a dozen different shops you'll start to see a pattern because they typically use the most reputable tranny shop in town.

 

Also, if it's just the solenoids that need to be replaced you can just get a solenoid kit. Sonnax has some nice pictures on their website of which ones are which as well as other stuff pertaining to the RE5R05A transmission.

 

Moving this thread to the appropriate subforum.