torque converter

[digglesworth]

So when does the torque converter lock up? I've noticed that since I've had my scangauge and installed the external cooler that the truck won't shift into overdrive until the trans reaches 68deg. The trans runs pretty cool all the time. I've got a thermal bypass valve in but it's only gotten above 180deg a few times. It's not summer yet so maybe that'll change. I'm just trying to get an idea of how the torque converter works and the role it plays when the trans is cold vs warm. Thanks.

 

[USMC_TOP]

It locks while your in 4th gear heading down the hwy driving normal without your foot in the peddle, you should feel it lock and see the rpm's drop. Almost feels like it drops into 5th gear. I want to say it won't lock up if you put it n 3rd when your towing something heavy but maybe they do now days? Fourth gear has the least amount of bands and its weak compared to the other 3. I was never aware of temp having anything to do with it.

 

[Best4x4]

It acted strange on my 07 when I added the external cooler. It wouldn't shift into what seemed like OD until the transmission was warmed up, so basically for the first 5-8 miles of driving the H3 had higher RPM's and then all of the sudden it would go back down to normal once warmed up. My wife didn't like how it acted vs before with the OEM cooler setup so when the radiator blew and I installed the Silla Replacement I went back to the OEM setup. Shifts fine now, and the coolant/trans temps are just about even with each other. The trans hasn't gone over 215F, 180-203F seems to be the norm.

 

[digglesworth]

My engine temp is steady between 198-202.... My trans has never gotten anywhere close to that. I have a 180 degree bypass valve in it but it hardly ever gets up that high so the cooler is doing absolutely nothing. My mpg took a huge dump after the trans cooler, 35s and pcm tune. I understand I was loosing some with 35s but the pcm tune was supposed to get a little back. I haven't gotten above 15mpg on the highway with the cruise set at 60. It's been windy as hell here lately (steady 20-30mph) so maybe that plays into it. But this is HORRIBLE. Maybe it's the roof rack? Brushguard? I dunno.

 

[alrock]

I haven't seen 15 mpg in a couple of years. Many of your mods - leveling, roof rack, larger tires, sliders/UCP, brushguard - decrease mpg due to resistance and/or weight. The tires are the biggest culprit with the unsprung weight and the extra torque required to get them moving. I've dropped nearly 1 mpg recently due the move from 35s to 33s.

My trans cooler didn't affect mpg, but I didn't expect it to either. I lost .5-1 mpg for each of the following mods: leveling, roof rack, tires from 32-33, tires from 33-35. I haven't hit 13 yet on my last two tanks.

 

[digglesworth]

Good to know Alex. I figured that's the consequences we suffer in the name of modding. I wanna find some extra hp though. It's bad enough I have a 3.5. I could really use the extra 22hp of the 3.7... Might look into a header, cat back and maybe the e-fan kit. But in the end, it is what it is. I love my truck but I'll just have to increase the fuel budget. Or take the girlfriends cobalt.... Lol

 

[poncho1965]

Weighed my '3 the other day, 5420 lbs. Still on 33's, no roof rack, 3.5 motor. Was surprised at the weight.


Mike

 

[digglesworth]

With the cruise set on 65 on a flat highway, I'm sitting at 1990rpm. Is this normal?

 

[Best4x4]

I think it's like 2100RPM on my stock 07 with the stock tire size.

 

[digglesworth]

Thank you sir. I just drove about 45 min to the climbing gym. About 95% highway. Scangauge said 17.5 when I pulled in. I'm ok with that.

 

[digglesworth]

when I left I made a conscious effort to pay attention to feel the torque converter locking up. I definitely felt the extra little kick down after it shifted into overdrive.

 

[USMC_TOP]

Sweet!

 

[MaxPF]

It locks while your in 4th gear heading down the hwy driving normal without your foot in the peddle, you should feel it lock and see the rpm's drop. Almost feels like it drops into 5th gear. I want to say it won't lock up if you put it n 3rd when your towing something heavy but maybe they do now days? Fourth gear has the least amount of bands and its weak compared to the other 3. I was never aware of temp having anything to do with it.

There's only one band in a 4L60, and it actuates in second and fourth. All other functions are done with clutches.

 

[USMC_TOP]

Bands, clutches;........... I was just trying to say the higher gears are weaker than the lower. Thanks for the correction.....................