Converter lock-up
 

I just discovered something I'd like to share, but it's probably something you guys already know. Driving down a country road at 45 mph and starting up a hill, the engine will sometimes start to lug a bit. Add enough gas and it will downshift to 3rd, but if you just need a little more torque, tap the brake with your left foot and it will drop out of lock-up and give you more torque instead of downshifting. I discovered this myself and think I'm cool. What do you think?

I think it doesn't make sense. If you drop the transmission out of coupling phase and into acceleration phase and maintain the same RPM, the resultant slippage will result in a significant loss of torque.

When mine lugs on hills i've been pulling it into 3rd and letting the TC lock back up. I'll try out your method.

However, if RPM increases you will eventually make up the difference (until you hit about 2900 RPM anyway):

https://encrypted-tbn0.gstatic.com/i...C-Rm1OuyFCjjT4

If the increased torque produced from the higher RPM is more than the torque lost through the inefficiency of the unlocked convertor - the net result would be slightly more torque. So I can believe it. However, the benefit of the increased torque (if any) is also being payed for by a huge increase in heat in the convertor/transmission.

Personally, in hills/mountains, I simply stay in 3rd (direct drive). The XJ is a mountain goat on hills when left in this gear.

I put a switch in my console to interrupt the power to the converter lock up.
Torque, no torque, RPM etc isn't a factor. It' like a 1/2 gear downshift and the engine pulls more readily. Works like a "trailer tow" mode. I like it.

On which vehicle?

90 MJ and 88 XJ

Oh right, the old Power-Comfort Mode.

I thought you got rid of that because the Comfort Mode sucked?

https://www.jeepforum.com/forum/f11/...89-xj-3047369/

Although Power-Comfort Mode and Torque Converter Lockup are 2 different functions.

Not just mentioning that to get to 500 posts.

Well actually, yeah.

correct. 2 different functions.

I thought about adding a switch, but haven't gotten to that yet. My WJ has a button on the shifter that shuts off O/D and I use that quite often. Also I'm not talking about giant hills, just short ones where downshifting is just too much RPM to be necessary. Funny thing. The lock-up in my WJ hasn't worked in 6 years, but started working after the engine got tired and didn't have the power it needed to take the load. At 40 or 45, I sometimes run in 3rd gear because of that. Because she's still basically rust free, I'm putting a new shortblock and transmission in her. I won't buy anything newer because these electronics I still understand and can work with.

Yep. Back when I was commuting every day, going over the Blue Ridge Mountains I started staying in 3rd. I picked up 2 MPG due to not spending so much time hunting between 3rd and 4th. Yes, TWO MPG. I am very careful about keeping track of mileage, and the difference was real. (I use aCar, BTW. Excellent app!)


Less wear and tear on the brakes, too.

Yeah But! My 2000 XJ will lockup the converter in 3rd gear as well. Anything over 40 or 45 mph.

Yeah, my mountain route is at 40 mph. Converter locked up, both the 94 and the 97.