32RH torque converter doesn't lockup at highway speeds

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Fletcher34

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Jun 27, 2018
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Fayetteville, AR
Just bought a 02 Sahara 4.0 for stupid cheap. CEL was on and PO stated it was for Torque Converter Lockup solenoid???? I know it's a 3 spd and it shifts great. However the torque converter doesn't lockup at highway speeds, at 55mph it's around 2100 rpms. My question is: If change out the switch and it still acts up, is there any harm to just running it like it is? I do mainly in-town driving. Not really looking to do a tranny rebuild unless I have to. Is this something that can go on or is it a precursor to more problems?

Thanks,

Travis
 
I can't speak to whether or not there would be any harm from letting it run like that, but replacing the solenoid is pretty straight forward, and that's the first place I'd start.
 
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Locking the torque converter allows it and the transmission to run cooler, plus it gives better mpg due to the elimination of slippage inside the torque converter.
 
Jerry Bransford said:
Locking the torque converter allows it and the transmission to run cooler, plus it gives better mpg due to the elimination of slippage inside the torque converter.
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I get the transmission running cooler. But is there any difference in running 55 mph at 2100 rpms vs. 70 mph at 2100 rpms? Either way it's the same rpms.
 
Fletcher34 said:
I get the transmission running cooler. But is there any difference in running 55 mph at 2100 rpms vs. 70 mph at 2100 rpms? Either way it's the same rpms.
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You get worse mpg and a hotter transmission when the torque converter is unlocked. Heat is an automatic transmission's worst enemy.
 
pittmansons said:
Going up steep hills my TJ shakes/shutters bad. Driving on flat to rolling hills it drives fine, no symptoms at all. 32RH 3.07 stock everything besides 30inch JK tires 16inch rims w/spidertrac spacers
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The only thing that has helped significantly is tightening the TV Cable to the max, which has increased the RPM's going up steep hills
 
Fletcher34 said:
I get the transmission running cooler. But is there any difference in running 55 mph at 2100 rpms vs. 70 mph at 2100 rpms? Either way it's the same rpms.
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Let's put some numbers on this. Let's say with a properly functioning torque converter it takes 30hp to push aside 70mph of wind as we drive our bricks down the freeway. But because your TC is out that same amount of power (same gear, same throttle position, same RPMs, same everything) only pushes you down the highway at 55mph. That means only 55/70ths of your power is making you move and the remaining 15/70ths is being turned into... you guessed it. Heat.

(15/70) * 30hp = 6.4hp = 4.7kW of heat. That's roughly two of the large burners on my electric range turned on full blast, sitting inside your transmission cooking. Another way to look at it is: a properly functioning TC is like adding a transmission cooler capable of removing nearly 5kW of heat.

Maybe it only takes 20hp to move down the road at 70mph. And maybe the TC doesn't sap that much energy. And maybe the airflow at 55mph is sufficient for removing that much additional heat. Play with the numbers and see what you get.

I'm not trying to start an argument. Just trying to put this into perspective.

Edit: ...aaand I just realized I'm replying to a two year old post 🤦‍♂️
 
pittmansons said:
The only thing that has helped significantly is tightening the TV Cable to the max, which has increased the RPM's going up steep hills
Click to expand...
That is grossly misadjusting it which can cause excessive pressures inside the transmission. It sounds more like you need to regear your axles to a more appropriate ratio. The correct tightness for the TV cable is either barely taut or just a tad tighter than that but never "to the max".
 
Jerry Bransford said:
That is grossly misadjusting it which can cause excessive pressures inside the transmission. It sounds more like you need to regear your axles to a more appropriate ratio. The correct tightness for the TV cable is either barely taut or just a tad tighter than that but never "to the max".
Click to expand...

I will order the Yukon 4.56 & a Detroit Trutrac to put in the rear. I do light off roading up steep rockyish terrain slow speeds. Will the rear Dana 35 be ok or do I should I get a Dana 44. All 4 wheels will never leave the ground
 
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