I’ve got an 01 7.3 CCLB 4x4 with some upgrades: intake, exhaust, Hydra tuner, and a mildly built transmission (triple-disc billet converter, TransGo kit, upgraded valve body, and a few other things). I mainly use it for towing, and right now, it’s pulling a 94 Lance Squire 8000 camper for ski trips in Colorado.
The problem I’m running into is with the torque converter lockup. It locks up at the usual speed (around 40-45 mph), but it’s causing trouble on mountain passes with tight switchbacks, like Berthoud Pass. I have to slow down for the turns, and when the converter unlocks, I end up generating a lot of heat trying to get back up to speed.
I’m wondering what the best way to handle this is. Would a Jelibuilt tune for towing (strenuous or performance tow) help with lockup at lower speeds and in 2nd gear? Or should I just go with a lockup switch? I’m still new to towing and automatics in general, so I don’t want to risk damaging the transmission. Any advice would be greatly appreciated!
How hot is it getting, and what fluid are you running? Locking up too early can put a strain on the engine. The 7.3s don’t really like being under heavy load below 2000 RPM.
Uma said:
How hot is it getting, and what fluid are you running? Locking up too early can put a strain on the engine. The 7.3s don’t really like being under heavy load below 2000 RPM.
Last time I went over Berthoud Pass, the transmission temp got up to 195. I know that’s not terrible, but it was below freezing outside, so it feels like it shouldn’t have gotten that hot. I’m still running the stock cooler, but I’ve got a 6.0 cooler sitting in the garage that I need to install. I’m mainly worried about the amount of slippage happening—am I overthinking it?
As for EGTs, I’ve never had an issue. The highest I’ve seen is around 1150-1200 towing up steep passes.
@Ren
195 is fine for the 4R100. I’d start being cautious around 210 and worried at 220. Adding the 6.0 cooler is definitely a good move. Slippage isn’t terrible as long as it’s not creating excessive heat. Your EGTs sound fine, but you don’t want to push much past 1200 for long periods.
If the unlocking on tight passes is really bothering you, a Jelibuilt tow tune could help with lockup. I’ve had good luck with Brian’s tunes for similar setups.
@Vesper
Do you think the constant in-and-out of lockup on twisty passes is okay? It just feels like the slippage might hurt the transmission, especially with my Hydra tow tune. I’m not super familiar with automatics since this is my first one. Do you know which Jeli tune would work best for me? I’m towing a lighter camper, but the steep grades make it feel like a heavier load.
@Ren
As long as it’s not overheating, it should be fine. Your converter and transmission upgrades are handling the weak points already. Just avoid running with overdrive on unless it’s flat, and manually shift to keep things under control.
I’d reach out to Brian and explain your setup and towing needs. He can recommend the best tune for you, probably something like a 40-60 HP tow tune. If needed, he can customize it to match your setup.
For example, I tow around 10k with an 80 HP street tune on flat terrain, but I switch to a 40 HP tow tune for steep hills. My setup includes a 4" exhaust, Mishimoto cooler, built transmission with a low-stall converter, billet wheel, 6637 filter, and a few other mods.
@Vesper
That makes sense. I guess I’ve just been thinking that slippage is inherently bad because I’m so used to driving manuals where clutch slip is a big no-no. If heat is the main issue, then that’s something I can manage more easily, especially with the 6.0 cooler and possibly a more aggressive lockup tune.
@Ren
Yeah, slippage is fine—it’s doing what it’s supposed to do. The main thing is to manage the heat. Too much slippage can cause problems, but you don’t need it locked 24/7.
If you want to dive deeper into the 4R100, look up Mike Kovalsky on the Ford-Trucks forum. He was a Ford transmission engineer and shared a ton of info, especially about heat management. His posts are a goldmine for this kind of stuff.