Ok, I have taken the advice from many on this sight and have done a few things to my truck. I installed the 3 gauges:tranny temp, boost, and pyro. I installed 4" exhaust, new engine fan/clutch, deep tranny pan with synthetic fluid and 2 qt temp reducing agent recommended by tranny shop. I find that the tranny still runs the high 230 degrees without load. Temp her in Vegas is 100 degrees. I was hoping to pull the boat to the lake tomarrow (11000 lbs). Any other suggestions.

Where is the guage sender? How about your torque converter? Does it seem to lock up above 50 MPH in 3rd and 4th? It needs to lock to increase flow through the tranny and cooler IIRC. My trans temperature guage sender is in the hot line before the radiator, and my transmission temperature will drop 20-30 degrees in a few minutes when the converter locks.

BTW, my fluid temperature is around 220-230 on a hot day until I get fast enough to lock the converter (50 MPH light throttle, 58 MPH 3/4 to full throttle).

I have gauge in the hot line coming out of the tranny. How do you know when the converter locks? I guess I hear it shift gears, but not she what to notice to a locked converter. Towed boat today for first time. Pulled pretty good. Engine stayed 200degree or less, but tranny ran up around 300. I was towing around 50mph most of the time except in city. I was able to get temp to drop around 220 couple times. Any other suggestions.

In 3rd or 4th gear, between 50 and 58 MPH, you should feel what seems like another shift, and see the rpm's drop 2-300 or so.

300 degrees is quite hot. I have only seen that once, towing 17K or so total, on a huge climb here in CO, varying between 1st and 2nd gear.

Do you know for sure if your temperature gauge is accurate? - those temps are killing your fluid regardless if it is synthetic or not. Synthetic is good for reducing friction over mineral based fluids, but the additives in them will break down too when heated. Synthetic is not the cure all - try getting your temperature problems under control before going the synthetic route. You should be shooting for temperatures below 200 F if you want tranny life. I know there is a difference between pan temps and converter out, but if the fluid gets that hot, it doesn't matter if it is synthetic or not. Additives start leaving the fluid between 230-250F, and by 260 there isn't much to go on.

I didn't add capacity but significantly boosted my cooler size using a 29000 btu cooler from Tru Cool (same company that makes the trans cooler on your truck) which cost about $70 from www.bulkpart.com (http://www.bulkpart.com/). My tranny pan temp has not exceeded 170-175F since I installed it, and I know a cooler is far more effective in reducing heat than adding capacity. High capacity pans are okay if you have already added cooling, but start with cooling what you have before you have a larger volume to try to cool.

I personally don't believe you need to add larger pans to cool these transmissions and mine I have over 200,000 miles on my original (no rebuild yet). Again - work on cooling what you do have and do it with an active cooler - one that sit's up front in the wind. Passive systems such as larger pans won't do much for cooling like the in line variety. I design hydraulic systems at my day job and the trend is to cool what you have, not add more fluid.

Right on, 95Yukon! Cool what you have. The ideal spot for a trans temp sender is in the oil pan. This measures temps of the fluid going through the filter to the pump/trans components. Don't worry about line temps, you need to know what the temps are in the fluid that's about to go to work!

An add-on cooler is the only way to drop temps below the radiator trans cooler's capacity. Pan sump temps should be 165 - 175 under ideal conditions. The towing load, etc. will change this somewhat, but you should be able to maintain this range with proper cooling.

When installing an add-on cooler, follow the instructions for installing it in series with the existing factory radiator cooler. Do NOT remove the factory cooler from the loop. Install the add-on in the return line from the radiator to the trans. This permits the factory heat exchanger to bring the trans up to operating temp faster on cold startup as it's designed to do.

When I bought my truck 4 years ago (113K miles) I added a cooler & tranny temp gage, installed just as Fred482 has described above. Several times a year, I tow an 8000 lb travel trailer, but the rest of the time my '95 K-3500 is my daily commuter, her in central Texas.

Up until last summer, my tranny temps ranged between 185 and 215 as I commuted each day, depending on whether I was stop-and-going or driving at steady 55-65 mph. During those first 3 years, I thought this was normal, as I used synthetic fluid & had added the extra cooler. Then, at 185K, the tranny had what I would call a catastrophic failure (no slipping, just stopped pulling & gave a tremendous "whump" when you put it into gear. I had it overhauled ($ 2000) at AAMCO & asked that they NOT spare any expense - that I intended to keep the truck at least 5 years, or longer.

Now, since the overhaul, the temperature stays between 120 and 160 as I commute, and only an occasional excursion lately to 180, since the ambient temps have reached 98, or so. In retrospect, I can't help but wonder whether I could have overhauled it earlier, for less expense, had I known that the hight temperatures were somehow related to the advanced mileage (wear) ??

Thanks for the feedback. Now you got me nurvous. Do you know what the temps usually are running with stock application (stock coolers) for normal city/hwy driving. Like I said, mine runs 220 going from tranny to cooler and stays there. This almost makes me believe that my gauge may not be reading correctly. Taking her into AAMCO on Wed. to test gauge and install different cooler.

Your numbers may not be off, but you should confirm it. Before I replaced the original "heavy duty factory cooler" which came with my towing package, my transmission pan temps could climb over 200F.

Here's the cooler I used for my tranny:
http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=2&Product_Code=H7B&Category_Code=tru-cool-ind&Product_Count=0

It's and engine cooler with low pressure drop, current price $65.00, so still reasonable. They also do coolers similar with hose barbs attached, I just liked the flexibility of the threaded connectors. Wish you luck with your transmission shop - some will support giving you all the cooling you can get then others seem to resist it, or tell you too much cooler is bad. I've never had a problem and just made sure the cooler lines flow through the radiator cooler first - it warms the oil in the winter, and the plate type coolers allow some bypass when the oil is cold.

I had the factory Heavy Duty cooler on my truck aswell and found it to be less than adequate. Last week put on the heavy duty Long Tru-Cool cooler and seems to be much better already, even though I haven't really pulled anything hard yet. It still hovers just over 150 whereas before with similar driving was around 185. Towing got it up to around 235 before, so I hope it is better now. The cooler is designed to allow the fluid to warm to opperating temp before allowing it to flow through the cooler just like the factory set up, only it is about 2x the size!:ro)

If you have to tow slow, It's better to run higher rpm's of lower gear.
Converter is in stall and heats up less.

You will probably need a Bigger cooler and a bigger pan.

I run a truck camper and use the TCC lock up resister to hold the TCC locked in 2nd and 3rd Gears on hills, Really keeps temps down.

Before I put in the Big Pan I was running 230-250 with TCC locked, Never seee
more than 200 now ,mostly top temps at 185..

Note, You have to clean behind Trans & oil cooler, They get REALLY crudded up.

I ran a lot of dirt roads in Montana and Dakotas, a few years ago, Fine sand was in the condenser, Had to clean each hole, That got my Coolent temps back to normal.

I run with a PML deep pan extra 3 qt fluid plus a Deraile 25,000 Lb rated cooler under the bed, with thermostat controlled electric fan set to come on @ 170F rarely break 190F (sensor in pan) pulling 18K load on 100F/100% humidity day

I run with a PML deep pan extra 3 qt fluid plus a Deraile 25,000 Lb rated cooler under the bed, with thermostat controlled electric fan set to come on @ 170F rarely break 190F (sensor in pan) pulling 18K load on 100F/100% humidity day

Now thats how I would do it IF I could but mine doesn't require cooling.

bowtie, wanna trade???

bowtie, wanna trade???

Trade What? :lol:

Trucks 96 dually , auto

Trucks 96 dually , auto

NAW I'd better keep mine seeing how it goes in for new paint tomorrow

I had same tranny temp problems with temps up to 300* pulling some of the passes in WA, ID & MT. I had a aux, fan cooled, tranny cooler installed and got the temp down some, but just driving in slow conditions (city), even empty, would produce high temps. I installed a BD Torq-Loc and have been better off. My tranny kicks in/out of lock up at 45 mph and the Torq-Loc lets you lock-up in 3/4 at 35 mph. This has solved a lot of my temp problems and it also has helped in down hill runs as well. Even after I got to the top and started down the other side in 3rd for some back off help the tranny would stay up at 240 to 260. Now the down hill runs that are over 35 cool the temps down to the 175/180* range.

I took my truck into tranny last week and had them run some test. They attached an infered gauge right next to the sender unit on the tranny line and found that there gauge read 40 degrees less than what my gauge was reading. The fluid was anilized and found to be as good as new. I'm not sure if it is the sender or the gauge. Waiting to recieve new parts from MFG.

srl520
I have wondered about the sending unit myself. The aux cooler I installed was for vehicles up to 28K weight. The cooler should have brought it down more but I didn't go as far as you did. Let us know what your new gauges do for you.