arthurchapin

Hi all, I have a 02 g500 I’ve had for a while, several years ago I had larger/wider tires put on and did have them calibrate the computer to as close to the new size as they could. Lately I’ve been having the issue where it says TC stuck in N, according to the mechanic the oversized tires wear out the transfer case motor, is that true? Should I drop back down to something more oem sized?

also does it make sense that the diffs won’t lock (pump just runs) if the tc motor is out?

thanks
ac

The Butcher

Oversized tires would not wear out the transfer case. They might increase overall wear and tear on the truck, but not at an appreciable degree. Your mechanic just has no other explanation, so he picked what seemed most obvious to him for an explanation as to why it might fail. I'd rule out an electrical gremlin (bad sensor, wire, etc.). How many miles on the truck? It's a 20 year old truck. Wouldn't be surprised if it's just a sensor, but it's also not impossible the transfer case has an actual mechanical issue.

arthurchapin

Thanks, that makes sense, I didn’t understand how tire size could affect it. I have about 160k miles on the truck so may just have been a failure, he did look at the sensor first but said the motor wasn’t operating. I’ve had very little issues with it over 20 years other than the front windows which I know is a known issue.

Tires I’m running are 325/60R18

does it make sense the locking diffs wouldn’t work if the tc motor was bad and had shown as a malfunction in the ecu?

Floobydust

TC motor wear has nothing to do with tire size. TC motors are a well known failure item because they have nylon gears that wear out easily (the TC motor is actuated at each start-up to confirm position). On an '02, I'm surprised that you haven't had to replace it at least once or twice by now.

Also, the TC motor controller modules were problematic on the '02s and '03s MB has updated this module a couple of times, so if you still have the original, that may be an issue also.

Replace the TC motor and enjoy those larger tires.

knowbenz

Motor has nothing to do with the diff locks. TC lock needs to engage before anything else. Need vacuum supply at switchover valve on firewall, make sure there is vacuum output to lock, leaking diaphragm would cause lock to not engage. There is a vacuum reservoir under drivers headlight that leak at the fitting also. Take it to a different shop.