When does Torque Converter Lock?

jg45 · **Posted:** Wed Feb 27, 2008 12:18 am

I have been trying to figure out why my mileage has dropped off from almost 16 to 11.5 MPG. It finally dawned on me that the toque converter isn't locking up when I am in overdrive driving around town. IF I turn off overdrive, I can tell that it is locking in third. Also, when I get on the interstate and get over 60 it locks. I think I recall it locking in 4th when cruising around town at around 45 MPH, but it isn't doing it now. I connected a scan tool and pulled no codes. Should it be locking when cruising at 45 in overdrive?

tjkj2002 · **Posted:** Wed Feb 27, 2008 12:24 am

jg45 wrote:

I have been trying to figure out why my mileage has dropped off from almost 16 to 11.5 MPG. It finally dawned on me that the toque converter isn't locking up when I am in overdrive driving around town. IF I turn off overdrive, I can tell that it is locking in third. Also, when I get on the interstate and get over 60 it locks. I think I recall it locking in 4th when cruising around town at around 45 MPH, but it isn't doing it now. I connected a scan tool and pulled no codes. Should it be locking when cruising at 45 in overdrive?

No,not if all the requirements are met for the TC to lockup.

_UnLiMiTeD_ · **Posted:** Wed Feb 27, 2008 12:37 am

mine will lock up at 40mph all the time

KJ4ME · **Posted:** Wed Feb 27, 2008 1:31 am

30-35MPH with a shift into O/D at 40MPH

jdumont · **Posted:** Wed Feb 27, 2008 5:17 am

Pretty sure your talking about when i feel a little hiccup on the highway at 64 mph. Thats when my revs drop from around 2600 to 2100

tjkoen01 · **Posted:** Wed Feb 27, 2008 9:12 am

Like tjkj2002 said, the condition must be met, however it depends on the tranmission as well.

My 45RFE will only lock up when I hit about 60 on the highway without much load on the engine; with the OD off, it tends to lockup as soon as it can in 3rd regardless of speed.

Not sure when the 42RLE will lockup, looks like it will do it around 40.

tommudd · **Posted:** Wed Feb 27, 2008 9:29 am

all depends on how much throttle is applied, type of streets, level, up/downhill, speed, how you usually drive, how you are holding your mouth, if you kissed your dog before you left home, have had mine lock at 40 at times, and other times it tries to find it, seems like no real reason just works and I never worry about it, course I never kiss my dog either!

jg45 · **Posted:** Wed Feb 27, 2008 11:07 am

I do have the 45RFE and from the sound of it, I am experiencing normal behavior. I guess, the search continues for the missing MPG.

Jeepjeepster · **Posted:** Wed Feb 27, 2008 2:35 pm

Your problem is the tires and the fact that its winter.

All the diffs are cold, tcase is cold, tranny is cold, all adds up to alot more friction than you would have in the summer.

I can 16mpg when I first start out on the hw at 60mph when its 25F out. I can come back through that same area and get 20mph that evening after all the oils have warmed up.

In other words, its normal.

jg45 · **Posted:** Wed Feb 27, 2008 2:56 pm

I am also wondering if the cheap Sam's club gas could be a contributing factor.

indianrefining · **Posted:** Wed Feb 27, 2008 5:03 pm

jg45 wrote:

I am also wondering if the cheap Sam's club gas could be a contributing factor.

That's possible, although the winter blend additive packages which all gasolines have this time of year would probably have more to do with it. I almost always use 87 octane Shell, and see a drop-off in my MPG every winter.

Albert · **Posted:** Wed Feb 27, 2008 5:34 pm

indianrefining wrote:

jg45 wrote:

I am also wondering if the cheap Sam's club gas could be a contributing factor.

That's possible, although the winter blend additive packages which all gasolines have this time of year would probably have more to do with it. I almost always use 87 octane Shell, and see a drop-off in my MPG every winter.

I have been using Sunoco - 87 octaine. I always thought that any name brand gas was better than no-name brands, but I have no proof of that. Maby a better additive package or something??? I don't know. My gas mileage has gone way down. I figure it's the winter gas mostly.

As far as warming up goes, ideling for 10-15 minutes in the driveway does nothing but warm the engine. Then you start driving and your tranny, diffs, etc are still stone cold. I run it for a minute of two, then start driving. Lock out o/d for the first 2 or 3 miles and turn on the bun warmer (seat heater). Everything warms up together. It takes 10 miles or so to warm up a drivetrain in this cold weather. Right or wrong, that's how I do it.

BTT....My torque converter locks up when in o/d at right between 40 and 45 on a level road when I am not giving it a lot of throttle.

jg45 · **Posted:** Wed Feb 27, 2008 6:46 pm

Seems like an interesting trend. The 45RFE doesn't lock up the converter as early as the 42RLE. I wonder if that trend is apparent in real world mileage results. It sure seems like the later models get better mileage.

tjkj2002 · **Posted:** Wed Feb 27, 2008 7:07 pm

jg45 wrote:

Seems like an interesting trend. The 45RFE doesn't lock up the converter as early as the 42RLE. I wonder if that trend is apparent in real world mileage results. It sure seems like the later models get better mileage.

TC lockup is one factor for MPG's but the 45RFE takes alot more power to turn then a 42RLE also,more drag=less MPG's also.But the 45RFE is a stouter tranny then the 42RLE.Just remember that the 45RFE was originally put behind V-8's in RAM pickups and Grands,was put behind the 5.7 HEMI when first introduced,where mpg's was not a real big concern.

tjkoen01 · **Posted:** Thu Feb 28, 2008 2:54 pm

tjkj2002 wrote:

jg45 wrote:

Seems like an interesting trend. The 45RFE doesn't lock up the converter as early as the 42RLE. I wonder if that trend is apparent in real world mileage results. It sure seems like the later models get better mileage.

TC lockup is one factor for MPG's but the 45RFE takes alot more power to turn then a 42RLE also,more drag=less MPG's also.But the 45RFE is a stouter tranny then the 42RLE.Just remember that the 42RLE was originally put behind V-8's in RAM pickups and Grands,was put behind the 5.7 HEMI when first introduced,where mpg's was not a real big concern.

you mean the 45RFE was put behind the v-8's :wink:

tjkj2002 · **Posted:** Thu Feb 28, 2008 3:17 pm

tjkoen01 wrote:

tjkj2002 wrote:

jg45 wrote:

Seems like an interesting trend. The 45RFE doesn't lock up the converter as early as the 42RLE. I wonder if that trend is apparent in real world mileage results. It sure seems like the later models get better mileage.

TC lockup is one factor for MPG's but the 45RFE takes alot more power to turn then a 42RLE also,more drag=less MPG's also.But the 45RFE is a stouter tranny then the 42RLE.Just remember that the 45RFE was originally put behind V-8's in RAM pickups and Grands,was put behind the 5.7 HEMI when first introduced,where mpg's was not a real big concern.

you mean the 45RFE was put behind the v-8's :wink:

Yaw I got a going and didn't realize I typed the wrong numbers,Thanks I fixed it.

When does Torque Converter Lock?

Who is online