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Converter lock-up

Old 04-30-2019, 05:05 AM
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Default 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?
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Old 04-30-2019, 06:57 AM
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Originally Posted by dave1123 View Post
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.
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Old 04-30-2019, 07:17 AM
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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.
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Old 04-30-2019, 07:24 AM
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Originally Posted by Dave51 View Post
...maintain the same RPM, the resultant slippage will result in a significant loss of torque.
However, if RPM increases you will eventually make up the difference (until you hit about 2900 RPM anyway):

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Old 04-30-2019, 07:31 AM
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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.
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Old 04-30-2019, 08:03 AM
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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.
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Old 04-30-2019, 08:22 AM
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Originally Posted by cruiser54 View Post
I put a switch in my console to interrupt the power to the converter lock up.
On which vehicle?
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Old 04-30-2019, 08:30 AM
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90 MJ and 88 XJ
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Old 04-30-2019, 09:23 AM
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Originally Posted by cruiser54 View Post
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/
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Old 04-30-2019, 03:04 PM
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Although Power-Comfort Mode and Torque Converter Lockup are 2 different functions.

Not just mentioning that to get to 500 posts.

Well actually, yeah.
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Old 04-30-2019, 04:58 PM
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Originally Posted by Dave51 View Post
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.
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Old 05-01-2019, 09:00 AM
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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.
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Old 05-02-2019, 02:06 AM
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Originally Posted by jordan96xj View Post
Personally, in hills/mountains, I simply stay in 3rd (direct drive). The XJ is a mountain goat on hills when left in this gear.
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.
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Old 05-02-2019, 03:38 AM
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Yeah But! My 2000 XJ will lockup the converter in 3rd gear as well. Anything over 40 or 45 mph.
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Old 05-02-2019, 07:40 AM
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Yeah, my mountain route is at 40 mph. Converter locked up, both the 94 and the 97.
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