I read in a post that the out line to the cooler on the transmission has a valve that sometimes sticks and prevents fluid from circulating. My tranny temps are running to 200* with truck empty and no load. The only recent change is a Jody Tipton DP-Tuner, 4 pos. chip. I haven't been running this high temp until recently. I'm waiting on a tru-cool to arrive soon and will install right away. In meantime will check filters, valves and flow through of OEM cooler. Any other suggestions? Last thing I need is a burned out tranny.

 

How many miles? Have you changed the fluid and filter?
You may also want to consider an external filter.
It should be lower after your Tru-Cool install if nothing is plugged up.

 

You have a serious problem that needs to be addressed BEFORE you add any thing to that tranny, adding any thing like a cooler will just cover up the symptoms and not address the real source of the problem.

With the 90-100F heat that was pounding my area, I only 160F max unloaded at 75mph, and once the temps dip down to 70F, the needle points to 140F. All I have is the stock tranny cooler.

If you haven't been following a 30K mi ATF flush interval, you should.

200F is getting pretty close to the border of temp range of the ATF, so the good news is that you haven't toasted the fluid.

If you haven't yet, I'd suggest that either you or a reputable shop flush and replace the filter on that tranny.

I've done it both ways, and I've found that I can get a complete chemical cleaning, fresh Mobil ATF and a Filter for $150. The time I did it my self, I spent about $80( including filter), 3 hrs of my time and had a huge mess.

My time is worth more than that nowadays, so I just take it down to the local Transmission Pros shop. This way, if something looks fishy, they let me know, other wise I leave happy with a crisp shifting 4r100.

 

sorry to say... i think superrangerman is right... i was up over 200* with the stock setup.. but that was towing 10k lbs in 94* heat and humidity with the ac on... stock setup in that heat empty was just over 140* after riding around for a long time with the ac on and sitting in some traffic...

 

There is a bypass on that transmission that opens to circulate cold oil back to the transmission rather than to the OEM coolers till the oil heats up. Maybe the bypass is stuck open, so the coolers are defeated. Take it to a tranny shop, OR, find the coolant return line from the coolers, disconnect it, and check the flow rate of the fluid (with the tranny warmed up). I believe I heard you should get about a quart in 15 seconds. If the bypass appears to be stuck and the coolant return flow is very low, the bypasses are cheap and easy to replace.

Warren

 

Warren,
He plans to get a Tru-Cool.
I know they have the option of coming with a bypass or without, would that be the same bypass you are speaking of?
If so, he MAY be able to knock down two ducks with one chevy.
IF and MAY.....

 

Thanks for the help. Today I did a chemical flush, changed the filter and flushed the cooler. I've only had the truck for about 5000 miles so don't know what's been done. I got a lot of very black fluid out of the lines from the cooler. It did flow well so the cooler is not stopped up and the bypass on the transmission is working. With ambient temps in the mid-90s and humidity in the mid-90s, driving 70 empty the temp was about 170. So, its still a little high but the tranny shifts fine and isn't loud. There is an occasional noise after a shift that I don't know how to describe. It's sort of a sigh. Any more thoughts?

 

that sigh you hear is the turbo. it spools up with rpms and when your tranny shifts the rpms drop off and you'll hear a PSSSSSshhhhh as the tubo spools back down. its more noticable if you have an after market air filter, or an air cleaner setup like Kwik did.

Just an idea....
another thing you may want to check is the exhaust back pressure sensor. it is on the front side of your motor, there is a small tube that runs from the exhaust up to the sensor. what it does is senses the load you're putting on the truck and adjusts the shifting parameters... these are known to COKE up and stop working... unplug and remove, start it up, hit the pedal, and you should see it blowing exhaust up, if not replace tube and sensor or get the kit... if it does blow exhaust, look up inside the sensor if it is gummed up... if so, you'll either need to replace it or look for one of those aftermarket kits that plug into the sensor line and fools the computer. Mine works so I dont know much about the aftermarket kits

 

Thanks for the suggestion. Is the Exhaust back pressure sensor near the coolant temp sensor by the fuel pump? My Haynes manual doesn't even show or list it? I'm headed out of town so will have to watch the temps until I get back.

Thanks again.

 

look at front of motor, look down at fan, just to the left of the cooling line going into the water pump, you'll see the sensor and the metal tube running down under motor.

safe trip!

 

LMAO
Cool - I like it.

 

Thanks Technitron, I found it. I didn't know that could cause high temps in tranny. Tranny seems to be shifting fine and quiet, but after two flushes, one with a machine and putting in a good synthetic, I'm still running close to 200*. My guess is low line pressure due or something along those lines. Guess I'll drop the tranny. But, over 700 miles I averaged 22.5-23.5 mpg with AC and traveling 68 to 70 mpg. I'm pumped about that.

 

No. The OE tranny has a bypass pipe with a valve in it which opens to let the fluid circulate back to the tranny rather than the coolers until the temperature warms up. The trucool bypass only bypasses the trucool itself until the temperature warms up. Its probably harmless to have both, but if the valve in the OE bypass is stuck open no amount of added auxiliary cooling will help.
Warren

 

Warren, I flushed the tranny twice and the cooler. Fluid was running through the pipes and cooler. I think I either burned the OD clutches or the TC on vacation. I was towing 8K TT in mountains w/o tranny temp gauge. Anyway, tranny is being rebuilt and upgraded locally, heavier clutches, triple lock TC, etc. Hope to have it back by Monday.

Mike