I missed this earlier. If he was legit able to hot wire the lockup then the solenoid was working, as was the hydraulic circuit all the way to the TC. But this was also over a year ago, so lots could have gone wrong between then and now.
32RH P0740 Code
- Thread starter Ken G Ford
- Start date
I missed this earlier. If he was legit able to hot wire the lockup then the solenoid was working, as was the hydraulic circuit all the way to the TC. But this was also over a year ago, so lots could have gone wrong between then and now.
Well, drove it this evening after putting it all back together. Its very hard to tell when TQ is locked up but after listening very closely and counting the gears going into 3rd at 43MPH and 2000 RPM, I did see/feel a 200 RPM drop on the Tachometer. Total trip was about 12 to 15 miles and no CEL on Dash. Speeds anywhere from 35mph to 75mph and no CEL. Will drive it again on Sunday and hopefully, a bad TQ Lock Up Solenoid was the issue. Its funny but every time I work on this TJ, I realize there isn't a bolt or part that I haven't replaced or fixed and yet still, she puts a smile on my face 
Just want to thank all the guidance from everyone here on the Forum. Really appreciate everyone taking the time to reply and give me guidance on possible issue, as well as giving me feedback on my understanding of the TQ Solenoid and how it worked. All the wiring diagrams, Videos, etc. were all GREATLY Appreciated!
Just want to thank all the guidance from everyone here on the Forum. Really appreciate everyone taking the time to reply and give me guidance on possible issue, as well as giving me feedback on my understanding of the TQ Solenoid and how it worked. All the wiring diagrams, Videos, etc. were all GREATLY Appreciated!
The best test is just unplug it at the back of the trans and watch for the CEL. Get it to like 40-45 on level pavement and just ease off the gas ever so slightly. Nothing should change if it’s unplugged. If it’s plugged and working, you’ll see the drop.
And also if you’re cruising at like 50, stomp the gas like a downshift. It won’t kick down at that speed, but you’ll see the RPM go up but your speed won’t change (at first obviously). That’s how you know it’s working.
And also if you’re cruising at like 50, stomp the gas like a downshift. It won’t kick down at that speed, but you’ll see the RPM go up but your speed won’t change (at first obviously). That’s how you know it’s working.
I’ll video my TC lockup tomorrow, it’s quite obvious.
I guess it’s possible the TC itself doesn’t lock up well, and that wouldn’t throw a code since there are no speed sensors. The computer only knows if the solenoid works, not if the hydraulics etc are doing their job.
I guess it’s possible the TC itself doesn’t lock up well, and that wouldn’t throw a code since there are no speed sensors. The computer only knows if the solenoid works, not if the hydraulics etc are doing their job.
200ish sounds right, but to say it’s barely noticeable…that’s an odd way to describe what I experience, anyway.
Snaps for technology. The 1-2 (@ 17 seconds) & 2-3 (@ 27 seconds) shifts are obvious. I'm at 50% throttle (yellow line), speed is increasing steadily (red line), and the RPMs (green line) drop in a predictable sawtooth. It is left as an exercise to the reader to determine the transmission ratios and axle ratio from the graph. The astute observer will recognize that I need to regear, and badly.
The TC lockup is evident around the 33 second mark, where I let off the throttle and the RPM drops again. The major divisions on the Y axis are 500RPM, the green blocks show that the RPM ∆ is roughly -200 RPM. Then at the 40 second mark & around 48 mph I jam the throttle and you see the RPMs bump up again. Clearly not a downshift based on the RPM jump, and the vehicle speed didn't change like you'd expect with a downshift either. Then I let back off the throttle and it locks back up. I should've manually put it into 2 at that point to show the difference in an unlock vs a downshift. Maybe I'll do that later today.
For reference, one minor tick on your Jeep tachometer is 250 RPM, so you should see your RPMs drop by about one tick on the tach when it locks up.
What do you wish it had more of? I found a replacement planet & ring set that can give a better 1st & 2nd gear ratio, but I guess I didn't save that page because I can't find it now. Would love to investigate that further.
wouldn't that require that it slips more when it's not locked up? I mean, there's a lower bound on lockup RPM, and that will be whatever the engine RPM is. The fact that it isn't 1:1 with the engine RPM until lock is because of TC slippage. So to get a bigger drop you'd have to start with more slip.
TC's are real black magic though.
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