How to lower tranny temps while towing

[Perry]

I just got back from my first long distance towing trip from Monterey CA towing my 24' enclosed car trailer, weighing about 6000#. While crossing the mountain passes of 3000' and 4000' in southern oregon and northern california, I was experiencing high tranny temps based on the sensor welded into the pan.

On the way there, I didn't shift into 3 until I started climbing the grade and I had to keep pulling over at rest areas to cool the tranny as it kept going over 250 deg near the tops of the grades. The pryo always stayed below 900.

On the return trip, I kept the tranny in 3 all the time in the mountains going up or down, and the temp never went above 230 at the top of the grade, but it also took a long time to cool while going down hill. The pyro kept peaking around 950.

Short of installing another tranny cooler, what is the proper driving technique for climbing hills while perserving your tranny? Should I have slowed down and shifted to second gear?

Except for the high tranny temps in the mountain passes, the Suburban performed like a champ, easily maintaining 65-70 on the rolling hills in OD and holding 45mph going up the mountains. I averaged 10.5 mpg, except on the return trip tankful through the mountains, where the fillup was 8.5 mpg. And yes, I plan to have the tranny fluid flushed this week.

Perry

[MTTwister]

One option is to search on the "Cheap TCC Lockup " thread - Foools the PCM into thinking the fluid is Hot" and locks up the Torque Converter. ;) Search other threads on this subject to find out how to use it, and how not to use it. redface.gif

[fogg65td]

I don't know on your truck but some trucks have the tranny fluid goint through the radiator and then to an aux cooler. Often times routing the fluid through the radiator causes more of a heating effect than a cooling effect, since coolant temps are often in the 200 degree range and air temps are lower. I did this on my truck but it was before i had gauges. I don't know if it really has an effect but i think im makin sense but might not be.

eric

[markrinker]

Considering what you were asking from your truck, I don't consider the temps you saw to be out of line for a stock setup.

Personally, I'd investigate adding another/larger cooler routed outside the radiator, high capacity finned pan, change fluids regularly, and keep speeds down when in the hills.

[rjwest]

MT Twister resister works locking up the TCC in 3rd gear from 40 mph and up, tran temps WILL stay
much lower, Also will work in 2nd gear from 28mph and up

B&M large Pan droped temps 20-30 degrees.

If you bypass radiator, in town temperatures will run over 200 degrees ( unloaded ) don't know what will happen at very low speeds on hill, with heavy load.

On Hill climbs, in TCC UNLOCKED mode, lowest gear for speed gets lowest temperatures ( less slipage in torque converter)

Down hill ( Idle eng Rpm ) will not cool tran temps.
to much Torque converter eng braking/slippage
Shift to neutral , when safe, will drop temps.

The temperatures you stated are what I have seen
before Mods, up to 275 degrees going to coolers

With deep pan, using TCC lock up sw, I can maintain Tran temps less than 200 degrees most of the time,with 22o degrees max in 1st gear climb.

I have found that in back country, severe hills,
with 3k load, if I use 1st gear and 3000 rpm
tran temps stay much cooler than in 2nd at lower rpm.
Also I down shift to 3rd before PCM commands it,
lock up TCC with Transmission unloaded, than pull
hill in 3rd at 55-60, I believe this is much easier on Eng/transmission.

Thanks MTTwister, Like the TCC sw, wish the
PCM reflash wizards could get the TCC working
in 2nd-4th, Would be a GREAT improvement in truck.

Last Note: if you use TCC lock up switch in 2nd gear, need to unlock it before up shift, or code can be set.

[Chuck1]

rj where can i get a twister resister

[MTTwister]

Chuck1 - I'm working on the patent on that! :D

These instructions apply to '96, (and up I believe)- may
The original thead was back in Dec 9, 03 ( pulled my notes). EDIT ( Ahh - search on TCC Lockup! )

Here's the deal :

Wire a - switched - 50 Ohm resistor ( Radio Shack - 1 pack of 5 100 ohm 1/4 watt resistors, wire 2 in parallel). Place switch in accessible position ( I put mine in the Pillar Pod, with the tranny Temp Gauge).

Connections - are made at the PCM, behind the glove box. There are 3 connectors going to it.

The Yellow Black wire, circuit 1227, goes to Pin C9 middle top row on the BROWN 32 pin connector C1 at the PCM.

The Black ground, circuit 452, goes to pin B12 onthe BROWN 24 pin PCM connector.

I used the plain jane cheapo wire tap.

This setup fools the PCM into thinking that the Tranny temps are "excessive' and locks up the TCC.
Also produces very firm shifts, and if left engaged full time, will eventually cause a wierd engine surging that scares the poop outa ya - see thread =
http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=006481


I believe that the BD Torque Lock triggers a TCC Stuck on mode, and ( for '96 and newer) sets a higher priority DTC code, Type B, and forces the Limp mode.

BTW - the Twister is the project car - 72 Plymouth Duster "Twister".

[Beedee]

Another thing that you can look at doing is conveting over to a synthetic ATF when you do your flush and change. Haven't done it myself yet (it's on my to do list, but since I'm not towing its not a priority), but have heard that it will drop the fluid temp quite a bit.
Good luck.
Brian

[TurboDiverArt]

There's always been a lot of talk about re-routing around the radiator trans cooler. Things to remember, if your engine is reading 195, the radiator is cooler. The transmission line is run through the cool side of the radiator. That 195-degree engine coolant is routed to the driver side of the radiator, it then cools as it flows from driver

[joed]

Something I've noticed is that some stock 454 gassers came with an auxillary electric fan mounted in front of the ac condensor on the passenger side. I saw this and got to wondering if this setup could be retrofitted to the 6.5. I'm not sure it will fit due to the presence of the auxillary trans cooler already being there. Seems like this could provide some benefit, especially if you could switch it on only when needed - it could help lower trans temps as well as coolant temps.

Or would the presence of the fan when not operating block air flow, causing more harm than good?

I think this setup could be retrofitted to manual trans trucks without too much trouble, as the trans cooler is not there. Perhaps it could provide some added ac and coolant cooling.

Any thoughts? Joe.

[jharl@harrelsons.com]

I read all of your posts and to me it sounds like the transmission cooler lines might be backwards. On the 4l80-e the top fitting is the out flow from the transmission this should head to the radiator then out to the transmission cooler and return to the bottom fitting on the transmission. I am not in you part of the country but I have a stock transmission I assed the cooler and I never see temps past 190 degrees.

Just my 2 cents

John
*************************
93 GMC C3500 x-cab,6.5 B-D Exhaust
Compushift PCM
cool AC

[HowieE]

Perry
You have to tell us what speed you were towing at when you saw 230 degrees. If the converter was unlocked, below 50 mph, and pulling for some time in tahe mode 230 is not out of the question for a stock setup.
If however you were running above 50mph, the converter should have been locked these temps are high.
Several things determine trans temp, some of which go unnoticed. My trans runs at 150 degrees F, in the summer,if the converter is locked for a period of time. This temperature is a result of engine heat coming back off the engine and nothing else. I say that because in the winter the trans will run as low a 105 under the same towing conditions.
These results are acheived by removing the trans lines from the radiator, and a secondary fan driven tran cooler set at 165 degrees mounted under the truck. The cooler does not run while traveling at road speeds and the converter is locked but comes on as soon as I get into slower traffic and thus keeps the trans from going above 180 while driving. Under heavy loads at slower speeds I have seen 200, parking in a campground on a hill at very low speeds.

[rjwest]

In Florida, bypassing the radiator cooler causes some pretty high temps in low speed traffic

I installed the Deep pan, Temps run well below 200
degrees, except on long / slow hill climbs.
At cruise ( loaded ) Tran temps running about 170
at 90 degrees outside.

On a very steep hill using the MTTwister switch, Can pull in 2nd gear, 3000rpm ,TCC locked at 50mph, and 12psi ( kennedy Boost fooler ).
Temps well below 200degrees.