Locking up the torque converter - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-18-2000, 01:28 PM Thread Starter
 
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Locking up the torque converter

Wondering if anyone has come up with a means for locking up the torque converter on auto trans equipped CJ/YJ/TJ's for those nasty downhill stretches where it doesn't want to lock up and you come careening down trying not to lock up your brakes. I seem to recall there being a converter control relay on the firewall of CJ's and YJ's (I'd imagine TJ's have it as well) which could probably be triggered with a switch. I started thinking about this after I went to bed, so I didn't have a manual handy. Probably have to plumb in some diodes to keep from frying the PCM, but I never forayed that far into electronics to determine exactly what would need to go where. Has anyone rigged up something that works, or should I start looking for someone who knows their electronics to help me put together something?

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post #2 of (permalink) Old 12-18-2000, 02:52 PM
 
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Re: Locking up the torque converter

Yes there is a way to have a switch to lock up the torque converter but I have know idea what it is. One of the guys in my club has a lock up converter and he also has this feature on it. I might be able to call him to night and get some info for you. He runs a 350 chevy in his CJ5 with this set up and it works real well.
GP'n

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post #3 of (permalink) Old 12-18-2000, 02:53 PM
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Re: Locking up the torque converter

[img]/wwwthreads_images/icons/tongue.gif[/img] If I were you, I would pose this question to Larry Van Every.....his posts are under LEVE. Larry is pretty good at automatic transmissions and has a good grasp of electronics as well.[img]/wwwthreads_images/icons/smile.gif[/img]

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post #4 of (permalink) Old 12-18-2000, 05:56 PM
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Re: Locking up the torque converter

Sorry Rod, Bad news! The 70's to late 80's Torquflite series automatics only lock up in direct drive. That means only after 3rd gear has been engaged. There is no way to force the lock up as it's hydraulic controlled and the EMC's don't have a thing to do with the lock up.

JCWhitney and Summit Racing both sell valve body modificaitons that will modify the shift positions for better response, and this does have an affect on the lock up. Newer electonic generations of the T999 (sorry, can't remember it's number) can be controlled by throwing a switch and engaging lock up.

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post #5 of (permalink) Old 12-18-2000, 07:08 PM
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Re: Locking up the torque converter

Jeepskate-
Been there - tried to done that. Great idea! I did some serious FSM recon work and determined that yes it would work. Quick rigged an simple toggle switch and took off down the road. (By the way, the PCM isn't in danger as what you are doing is simply switching a relay.) What I found out is that LEVE is exactly right. Third gear only. In order to make it work like you and I want it, there will have to be modifications to the hydralic circuitry in the TorqueFlite. It is on my list of things to do. (It just won't get done real soon, if you know what I mean.)

But I'm here to tell you this, in low range, third gear, it will pull the beast down to a stall. It willl nearly stall the motor before it downshifts. The problem is, of course, that you are still going too fast since you are in third. There is enough there, though, to make me realize that I want it. I just haven't a clue how to go about it.

Does anybody else?

It would take away the last objection to an automatic for wheeling if it was something relatively doable.

sln

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post #6 of (permalink) Old 12-18-2000, 08:56 PM
 
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Re: Locking up the torque converter

not quite the answer to the converter question, BUT you can rig a hand control on that kickdown linkage inside the truck, to tighten it all the way up when you wish, and it will hold it in 1st gear a little better if you doint have a manual valve body ( or modified valve body).

ive done this by accident before while re installing the mechanism, and it has pretty good engine braking qualities, but bear in mind I was testing it on the road, so you would have to test it further.

I wouldnt think it would be hard to tap into that pipe on top of the valve body and give it full pressure the whole time, and then ad an electric solenoid/valve to it, so that you could achieve full lock up in any gear, the downfall would be, it woudl stall the motor if the rolling resistance overcame the drivetrains torque, you would have to be careful with the usage, maybe even a momentary switch.

good luck with it

OzarkJeep

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post #7 of (permalink) Old 12-18-2000, 08:58 PM Thread Starter
 
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Re: Locking up the torque converter

Not all that bad. The unit I really want it for is a 1995 32RH (the late-model T-999 designation), so there is perhaps some hope.

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post #8 of (permalink) Old 12-18-2000, 10:09 PM Thread Starter
 
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Re: Locking up the torque converter

Cool. I was hoping someone else had poked around this a bit. Did you disconnect the wire from the PCM to the relay? My concern was that if you left the wire hooked up for normal functionality, the PCM might not like the voltage from the added switch bleeding back down that wire.
Next question, since this seems like it needs quite a bit of R&D and some tranny mods to work...would using a converter with a lower stall speed help?

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post #9 of (permalink) Old 12-19-2000, 07:53 AM
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Re: Locking up the torque converter

Are you pulling the shifter all the way down to manual low? If you start out in manual low the rear band is engaged for engine braking. if you start in a higher gear, or it shifts up, it will not engage the low band until you pull it back to low and get to a low enough speed to downshift to low. with 4wd in low and trans in low it shouldn't get over 5mph or less before the converter spins the engine up pretty good.

CJeep

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post #10 of (permalink) Old 12-19-2000, 11:37 AM
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Re: Locking up the torque converter

[img]/wwwthreads_images/icons/smile.gif[/img] In the midst of all this I feel like I must interject this one thought: The lockup in autos is actually not locking up the converter? Is that right? It is simply clutching a shaft that is driven by the DRIVE side of the converter and runs through the tranny to the rear. Like it is a mechanical freeway for the power with no offramps; it just runs through the tranny front to rear. Is that right? The OBJECT of lockup being twofold1) it bypasses the tranny and avoids the losses from the machinery; (2) it takes the load off the converter itself and enables the converter to be smaller (and therefore cheaper to make). Increased fuel economy is a by-product of the by-passing and the loss-avoidance. THE PROBLEM IS.....the enguin-ears at the fack-tree only made the lockup for low-torque situations like cruising, as evidence by the fact that it will only hook up in high gear. Will this flimsy mechanism hold up to the sort of duty that you are contemplating?[img]/wwwthreads_images/icons/tongue.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img][img]/wwwthreads_images/icons/wink.gif[/img] Our '97 ZJ has a three speed auto with .69:1 overdrive on top of that, and we have the highest rear axle gearing that you can get(3.55:1). Many times when climbing grades in direct, I wish that I could kick out the lockup and gain that 200-300 RPM for a little more power. Sometimes I tap the brake and kick it out momentarily to help the engine, but I KNOW that when I do that, my tranny fluid temp is going to pop up due to the extra slip in the tiny converter.[img]/wwwthreads_images/icons/tongue.gif[/img]If I had my wish, I would have a switch on the gear selector to DISABLE lockup. I just don't have nerve enough to install one without being a little more cognizant of what the rest of the ramifications might be. We get fantastic fuel mileage on the flat ground....about 25...from that 4.0 engine, even using the A/C.[img]/wwwthreads_images/icons/smile.gif[/img]

CJDave
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