[wheelsquad]

What year and model ATV do you have? Just curious

It's a 2004 TRX400FA (Rancher 400 AT). Having the Hondamatic probably makes it more sensitive than others.

This thing has always been like having cheat mode on hills. Climbs anything. But not yesterday. I got stuck on a rocks going up a hill a few times. It wasn't fun.

I'm assuming it's the oil because I changed it Saturday and it was fine before that.

Rustler, I'm one of the few remaining regulars with the 400AT. Been running Rotella T6 now since I put a new clutch in 3 years back. I also mix in at 5% Lucas Heavy Duty Synthetic oil stabilizer. I picked that idea up from Melsman a while back. The added zinc helps cushion the pistons on the swash plate. Last thing I did was make my fan controlled by manual switch, so I can run it as soon as engine gets warm. These 400AT's run the oil really hot and without the fan running they can get too hot way too easily, which is how I smoked my original clutch, fan didn't turn on cause the oil temp sensor stopped working.

EDIT: There were a couple years where I ran the Valvoline oil. I don't remember it ever being any different than any other kind, because I think for quite a few years my auto tranny wouldn't shift properly because of a slightly slipping clutch. But when the clutch really went out was when the oil temp sensor stopped turning the fan on. To be safe, I would just run Honda oil or Rotella T6. Ever since my new clutch and running good oil, I've had zero issues whatsoever with the autoshifting.

 

[wheelsquad]

I didn't realize these 400ATs had such a bad rap until reading this board the last few days. Makes me worried about mine.

How hard was the clutch swap?

Funny you mention the oil temp not working. Mine stopped working a couple years ago so I rigged up a switch to turn it on manually myself.

I did the diagnosis on it last weekend by jumpering a couple of the terminals on the 34P ECM plug. The light came on so according to the manual I have a bad ECM?

Not sure on the ECM, but if everything else is working well I wouldn't touch the ECM. Sounds to me like a bad oil temp sensor like mine. If the sensor is bad you won't get the fan to come on on its own, and the oil temp warning light will also never come on at extreme hot.

I'm able to be the technical advisor to my brothers on most things, but getting them to tackle the centrifugal clutch was not something I succeeded in convincing them of trying. So I had a reputable dealer do it. Based on what I saw in the service manual, I'd say it's a one day job or less if you're a good wrencher.

 

[wheelsquad]

I'm still running 5W-40 Rotella T6 in my 14 Rancher and lately I've been getting a lot of ticking sounds from the engine. I installed this oil back in February and have only put 50 miles on it since then. I also checked the valve specs when I changed the oil and they were still good. Oil still looks as clean as it did when I installed it. This thing specs a 10W-30 as the preferred viscosity so I don't know if the heavier weight in this colder weather is causing the increased noise.

Wayne

At cold startup temps, the 5w40 will actually be THINNER than the 10w30. The T6 is not likely your problem. But you could try a different 0wXX or 5wXX synthetic to eliminate the oil as a cause, it won't hurt anything.

Valves might need to be adjusted.....

Yep, I agree and would check valves again.