Engine brake by forcing TC lockup? - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 17 Old 09-02-2008, 10:06 AM Thread Starter
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Engine brake by forcing TC lockup?

Any thoughts on this? I was having trouble on steep downhills (sliding/rolling on top of rocks) Sunday and was wondering if it was possible to add a switch on the TC inputs to force lockup so I could get some engine braking. Anybody know of any kits out there?

/jl

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post #2 of 17 Old 09-02-2008, 10:17 AM
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I know the kits for like a chevy dodge or ford diesel truck require a computer controlled box that splices in to about 20 wires into the main computer of your vehicle. I am not so sure it is that easy now a days.

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post #3 of 17 Old 09-02-2008, 11:45 AM
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on the older power stroke fords it was as easy as cutting and grounding a wire on one of the tranny plugs.
there was a little hiccup to make the PCM not see it, but it was a pretty easy fix.
it was a lot like our locker mods though,to do it 'right' took a little more effort but the basic control was just grounding a wire.
They do it for engine braking while pulling trailers.

Now with our lovely CANBUS system, who knows whats gonna be involved


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post #4 of 17 Old 09-03-2008, 05:20 AM
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What's your gear ratio, tire size, and trans (etc.)?
With my 3.73's and auto trans I'm doing the same on rocky downhills.

Safety fast,

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post #5 of 17 Old 09-03-2008, 06:20 AM Thread Starter
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Originally Posted by Hilldweller View Post
What's your gear ratio, tire size, and trans (etc.)?
With my 3.73's and auto trans I'm doing the same on rocky downhills.
4.10's, 33's, auto trans.

/jl

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post #6 of 17 Old 09-03-2008, 06:31 AM
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4.10's, 33's, auto trans.
Maybe going to 4.88's would do it. I've been less than impressed by my autotrans when it comes to hills.
I have gears on my "eventual" list...

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post #7 of 17 Old 09-03-2008, 07:56 AM
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Are you allowing enough time for the TC to kick in when you are descending? What I notice with my Jeep, and it was the same with my old XJ, is that when you first start downhill the TC isn't helping much. The vehicle starts to pick up speed and gets to that "uncomfortable" spot. Just about the time I think I need to start using the brakes, the torque converter kicks in and the engine braking increases significantly. I've learned to wait for it to happen before I use the brakes and that's usually all that's required. If I apply a little gas while descending, the same thing happens when I get off the gas. It takes several seconds for the TC to kick in again, but it is very noticeable when it does.
post #8 of 17 Old 09-03-2008, 08:26 AM
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wow , must not be nice having an auto.

Keep it on all 4 when necessary
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post #9 of 17 Old 09-03-2008, 09:05 AM
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If the hill looks nasty, I drop it into 4-Lo and 1st gear. At that point it depends on the surface of the trail whether it gets scary or not. If it's muddy or loose rock, you better have a plan, especially if the ruts are deep. Cause it goes just a scootch too fast...
I think the stock gearing was intended for smaller tires and they compromised for fuel economy.

Safety fast,

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post #10 of 17 Old 09-03-2008, 10:13 AM
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Originally Posted by JKKat View Post
wow , must not be nice having an auto.
x2. 4-LO, 1st gear and you will go so slow down hill you can take a nap, 2nd is a nice crawl down.


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post #11 of 17 Old 09-03-2008, 10:18 AM
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x2. 4-LO, 1st gear and you will go so slow down hill you can take a nap, 2nd is a nice crawl down.
We gotta trade rigs one time going down a hill so you can feel our pain...

Safety fast,

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post #12 of 17 Old 09-03-2008, 10:29 AM
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I use to roll in an Auto JK, i know how it goes and boy I dont miss it!


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post #13 of 17 Old 09-03-2008, 07:34 PM
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Are you talking Rubi T/C at 4:1 or the other at 2.72:1? My Sahara flies downhill which drives me crazy especially when I'm following a Rubi who does not have ride it's brakes all the way down. I've finally ordered an Atlas (5.44:1) so I can drive downhill instead of brake downhill too.

-Then I can get that "Better Than A Rubi" sticker made for my hood.

Would you have to yank the tranny to put in a torque converter brake?

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post #14 of 17 Old 09-04-2008, 04:56 AM Thread Starter
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Quote:
Originally Posted by seer View Post
Are you talking Rubi T/C at 4:1 or the other at 2.72:1? My Sahara flies downhill which drives me crazy especially when I'm following a Rubi who does not have ride it's brakes all the way down. I've finally ordered an Atlas (5.44:1) so I can drive downhill instead of brake downhill too.

-Then I can get that "Better Than A Rubi" sticker made for my hood.

Would you have to yank the tranny to put in a torque converter brake?
I'm running the same case as you, the 2.72. What I want is to be able to manually lock the TC via a switch. The computer normally controls this function. I would think that the computer has to see certain values such as engine load, speed, rpm, etc. before lockup can occur. I want to fool it, like some have with the locker bypass switch mod.

/jl

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post #15 of 17 Old 09-04-2008, 08:18 PM
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John, you have a great way of looking at solving a problem. Does the L part of your handle stand for 'Lectrical?

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post #16 of 17 Old 09-04-2008, 09:52 PM
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Quote:
Originally Posted by John L View Post
I'm running the same case as you, the 2.72. What I want is to be able to manually lock the TC via a switch. The computer normally controls this function. I would think that the computer has to see certain values such as engine load, speed, rpm, etc. before lockup can occur. I want to fool it, like some have with the locker bypass switch mod.
If you are in 4 Low and 1st gear, as soon as you take your foot off the brake the TC does lockup (at least it does on mine). I have the 4:1 transfer case so maybe that does make a big difference.

Once and a while I wish it didn't lockup... sometimes I have given it a little gas and then immediately wanted to stop. Hitting the brakes when the TC is locked like that has an very uncomfortable feeling like there just aren't any brakes...

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post #17 of 17 Old 09-05-2008, 03:40 AM Thread Starter
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Quote:
Originally Posted by seer View Post
John, you have a great way of looking at solving a problem. Does the L part of your handle stand for 'Lectrical?
LOL, never thought of it that way, maybe so.

Quote:
Originally Posted by jdrogers View Post
If you are in 4 Low and 1st gear, as soon as you take your foot off the brake the TC does lockup (at least it does on mine). I have the 4:1 transfer case so maybe that does make a big difference.

Once and a while I wish it didn't lockup... sometimes I have given it a little gas and then immediately wanted to stop. Hitting the brakes when the TC is locked like that has an very uncomfortable feeling like there just aren't any brakes...
Mine rolls to a point to where's it's uncomfortably fast. The trails I run are tight woods with wicked switchbacks, not fun on a surface that definately works against you.

/jl

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