I have a 02 QC with 5.9l, with the factory towing package. When I pull my travel trailer (loaded 6000lbs), and with the OD off, after a while (100km or so, sorry I am in Canada) when I am running around 100km/h the truck's rpm is around 2600, and occationaly rpms go up, 3-400 then setting down. If I speed up or slow down it will not do this. Also, when I get to my destination there will be a loud tic from under the truck. If I put the truck in reverse then back to drive the noise with come and go. If I let the truck sit for even 5 min the noise stops but then comes back when I have driven awhile again. Truck does not do this when I am not pulling the trailer. Any ideas? Has a tranny cooler but maybe still getting hot? Even when the tic is there there doesn't slip. someone mentioned a check valve in the bottom line of the cooler, and that if you have one it shoud be removed. Anyone do this, is so how?

 

The jump in rpm's is the torque convertor locking and unlocking. The noise is more than likely from the tranny being a bit hot.

 

Would the tourqe converter locking and unlocking possibly be do to the tranny getting hot? And if it is getting hot, why is the factory cooler not enough?

 

Nope, the convertor will lock and unlock at certain loads and speeds. That is why it only does it at a certain speed range. It does this to lower the RPM's while cruising and save some fuel, when you hit a small incline or headwind it causes the switch for the extra power. The factory cooler may not be enough with the load you are hauling, do you drive in a hilly area? That will add to the problem.

 

I did notice that when I hit a bump at this rpm range, is when the converter would unlock for a split second, so are you saying this is normal? Can I add a second tranny cooler in series with the factory one, or would I be best to replace with a larger one? Would adding an electric fan to the cooler help?

 

Update, this weekend I changed the tranny fluid, and is was a mess. 140,000 Km and I don't thing it was ever done. When I dropped the pan, you could use your finger and swirl the fluid around and you could see the metalic in the fluid. Fluid was dark and brownish. When I Drained the pan there was so much sludge on the bottom, I could not see the magnet, so I assume that the pump was having a hard time to pic up the fluid through the filter. I also strained the old fluid and found 3-4 small pieces of metal, approx 1/8" round. Would these pieces be small parts of damaged cluch plates? Could this be a sign of a possible future tranny rebuild or is this possibly normal wear? After seeing the condition of the fluid I got a can of DIY tranny flush and disconnected the cooler lines and flushed the lines,cooler, and check valve. Pulling the trailer again this weekend, Will update if clicking/knock is gone.

 

BTW, manual said 4 pints of fluid, for filter change, it actually took 6.