TCC towing changes

[Spartus]

Hi guys.

I have a 2005 Tahoe with 5.3l that I'm using to tow a 4000lb 19ft travel trailer. I tow in 3rd gear with Tow/haul button on at 2500 rpm / 65mph. It tows really well on small to mid sized hills and I can maintain 60-65 mph.

However, the TCC never ever seems to unlock when going up these hills. Some of the big huge hills I slow down to 50mph and the engine makes horrible moaning/chugging sounds. Once I mash the throttle to the floor the TCC will unlock, but then it downshifts to 2nd gear and soars to 4000 rpm so that I can climb the rest of the hill.


Questions. Should the TCC stay locked while under load for better efficiency? Wouldn't unlocking it while under massive load help the moaning/chugging that I'm experiencing? I'd think that after 60% throttle or so that the TCC should unlock, but don't want to overheat the transmission.

Basically, should I take the TCC apply/release for 3rd gear and lower the mph numbers?

HPtuners.com won't let me upload my tune, so any input would be appreciated... thanks.

[Nick 2K2 SS]

You might want to try and scan the truck while driving with the trailer on it to see where your TPS%'s are at so you can use that as a guide when adjusting your TCC apply/release speeds. Yes keeping the TCC locked increases overall drive train efficiency and it keeps the tranny fluid cooler by not allowing the converter to slip. But you might need to actually raise the mph numbers at higher tps% in the TCC apply/release table for tow/haul mode. If you lower the mph then it will lock the converter sooner and keep it locked longer.

[jimmyblue]

Probably better to downshift and relock, than run up
hills in high slip. You have to learn how you like things,
and chip away at it incrementally.

[Spartus]

Thanks for the input guys.

I'm trying to avoid a downshift though. The engine lugs down to 50-55mph on the big hills, and if I push it too hard it does downshift, but the RPM's fly up to 4k. Maybe it's me, but I don't like towing with the engine revving that high.

I need to do a scan next week on our next trip and log what the trans temps are to figure out if I need an extra trans cooler. The idiot gauge tells me the engine is at about 205 degrees when towing, with fan temps set at 195. Hopefully the transmission is close to that.

Another reason why I thought it would be a good idea to unlock the TCC is that I'm worried about damaging either it or the transmission due to the extreme lugging of the engine.