Torque converter lock up question?

QWIKWHIP · 08-07-2006, 02:52 PM

OK, I've been towing with this truck for almost two years now. The last few months have been while lifted on 35's but it's done the same thing since new. Just a little more noticeable now with the bigger tires. A quick back round, it's an 04 with the 2.94 gears, and my travel trailer is no more than 4k pounds loaded up. I'm looking for thoughts or opinions on what I experience while towing. I always tow in 4th gear with tow mode on. The issue is when the torque converter locks up. It will not lock unless I'm doing 60mph or more. And with my speedo being off about 3-5mph now from the tires, that means I'm actually cruising at least 65mph in order for the tranny to even lock up. If I want to "take it easy" and cruise at 55-60 mph the tranny will never lock and continuously revs and just feels generally not good for the tranny. Now again I don't have the Big Tow, so I can't monitor the tranny temp and this is what concerns me. Now while not towing and in 5th gear, the tranny will then lock at any speed. Is it normal to not lock up under 60mph in 4th gear or is something wrong? I find my mileage is actually worse under 60 then it is at 70. Because when the tranny is unlocked at 55 I'm at about 2200-2500 RPM's and if I'm locked at 70 I'm at about 1900-2100 RPM. I've never heard this mentioned before so now I'm wondering why?

Burly · 08-07-2006, 03:25 PM

Quote:

Originally Posted by QWIKWHIP

OK, I've been towing with this truck for almost two years now. The last few months have been while lifted on 35's but it's done the same thing since new. Just a little more noticeable now with the bigger tires. A quick back round, it's an 04 with the 2.94 gears, and my travel trailer is no more than 4k pounds loaded up. I'm looking for thoughts or opinions on what I experience while towing. I always tow in 4th gear with tow mode on. The issue is when the torque converter locks up. It will not lock unless I'm doing 60mph or more. And with my speedo being off about 3-5mph now from the tires, that means I'm actually cruising at least 65mph in order for the tranny to even lock up. If I want to "take it easy" and cruise at 55-60 mph the tranny will never lock and continuously revs and just feels generally not good for the tranny. Now again I don't have the Big Tow, so I can't monitor the tranny temp and this is what concerns me. Now while not towing and in 5th gear, the tranny will then lock at any speed. Is it normal to not lock up under 60mph in 4th gear or is something wrong? I find my mileage is actually worse under 60 then it is at 70. Because when the tranny is unlocked at 55 I'm at about 2200-2500 RPM's and if I'm locked at 70 I'm at about 1900-2100 RPM. I've never heard this mentioned before so now I'm wondering why?

Sorry to sound so dumb, but what exactly does the torque converter do, and how can you tell when the tranny locks up?

bestatchess · 08-07-2006, 05:24 PM

http://auto.howstuffworks.com/torque-converter.htm

The foregoing is a general description. A specific description can be found in the Titan service manual. From my prior perusal of the service manual, the Titan does some fancy stuff relative to lockup, the details of which I don't recall at the moment.

**loufish** · 08-07-2006, 06:34 PM

Mine does pretty much the same. When towing at lower speeds, 50-60 it just doesn't seem to lock up, even not towing at 50 it sounds like the trans is slipping. If I'm towing and it starts that, I'll drop down to 3rd, the rpm does go up, but you can feel the lock up, and the engine sounds happier.
I had 35"s for awhile, but it got much worse, so I'm back down to 33"s...I've posted simular stories, but others say their Titan will tow 7000lbs in 4th gear and no issues..??

QWIKWHIP · 08-07-2006, 07:04 PM

Quote:

Originally Posted by loufish

Mine does pretty much the same. When towing at lower speeds, 50-60 it just doesn't seem to lock up, even not towing at 50 it sounds like the trans is slipping. If I'm towing and it starts that, I'll drop down to 3rd, the rpm does go up, but you can feel the lock up, and the engine sounds happier.
I had 35"s for awhile, but it got much worse, so I'm back down to 33"s...I've posted simular stories, but others say their Titan will tow 7000lbs in 4th gear and no issues..??

I've tried downshifting, but that just brings the R's up more than they need to be.

I just don't understand why it's designed like that? I have tried towing in 5th before, but with the taller gears it just won't stay there. This is were a manual tranny is nice. You can hold whatever gear you want for however long you want to.

**Carbeaux** · 08-07-2006, 08:49 PM

I haven't been driving mine nearly as long as you guys, but mine does take quite a while to lock up. Once locked though, it does seem to hold that pretty far down the speedo. I can see that it would really suck not being able to get it locked while towing though. Hmm, my first test run tow will be in October. We'll see. Maybe a trutrac with the lower gears are in order?

Yellomantis · 08-07-2006, 08:56 PM

Do our trucks have electronic locking torque convertors? If so, cant we just bypass whatever sensor tells it to lock up and put a manual switch to lock it? I have a friend that has a cummins dodge that did just that.

**Carbeaux** · 08-07-2006, 09:04 PM

That's actually a great thought. I'm sure they are electronically controlled. It'd be a pretty sohpisticated mod, but one I'm sure someone on here can figure it out.

electricjohn · 08-09-2006, 09:47 AM

Your computer looks at numerous things to decide when to let the TCC lock, some being engine temp, engine speed, vehicle speed, manifold vacumm, throttle position, and gear selection. There are probally more, but this is what I remember from 1989 technology (OBD-1).

ptgarcia · 08-09-2006, 04:01 PM

Adding a manual locking switch on the Dodge its a piece of cake. You just tap into one wire at the tranny and ground it with a switch in between. Virtually any electronically controlled tranny could be fooled into doing the same. I'm not certain but it could probably be done to the Titan.

QWIKWHIP,

If you get it to lock-up at the higher speed then back off of the throttle to your desired speed will it stay locked?

electricjohn · 08-10-2006, 05:41 AM

If a TCC stays locked up below a desired RPM, pressures can build up in your trans. that could be damaging. The TCM is doing it pre-programed job.

QWIKWHIP · 08-10-2006, 06:05 AM

Quote:

Originally Posted by ptgarcia

QWIKWHIP,

If you get it to lock-up at the higher speed then back off of the throttle to your desired speed will it stay locked?

Nope, It will unlock when my speedo says 60mph no matter what.

SWAMech · 08-10-2006, 12:25 PM

I think that is what it is programmed to do. I am towing a 7000 lb travel trailer and mine locks or unlocks at 58 mph regardless of throttle position. Even when increasing throttle going up a hill it wont unlock until 58. If I push the throttle enough it will just shift to 3rd.

mopar · 08-10-2006, 01:53 PM

I just took a long trip to PA and noticed some weirdness in my tranny. When driving around 70or so when I get on the gas to get to 80 or 85 the tranny doesn't seem shift back up when I let on the gas I have to take it to the higher RPM limit and then kicks the gear up. This doesn't happen when driving say 60 to 70 or so shift points seem fine. Is this related?? It was on the return of a 700 mile trip and I haddidn't notice it till the way back??Is this my TC staying locked?? I have BT gears.

Shane06fl · 08-11-2006, 10:22 PM

in manual 4th gear your TQ converter should not be locking up. The 5th gear is actually over drive when the TQC locks up making the tranny spin at the same speed as the engine. My TQC does not lock up in 4th gear manual. I hope mine isn't broken but Then again your not suppose to tow in OD so while in 4th I don't want my TQC locking.