Have had some issues with the tranny getting "warm" when towing (7K#). I added a relay and manual switch to the fan on the under bed cooler, since the factory switch only turns on at 270*F , hoping it'd help... :

Gauge is brand new (was 4 months? ago) Isspro tranny temp gauge and sender it came with in the output line (as recommended by *most* of the aftermarket slushbox folk).

I borrowed an IR thermometer tonight to eliminate the simple (cheap) first and here's the low down:

Gauge Read (*F)/Location/IR Read(*F - readings taken from less than 6")
Outbound trip @ turn around in P
220/output line @sensor/200
220/input of rear cooler/195
220/output of rear cooler/180
no readings off the engine mounted oil-oil cooler
200/input of front cooler/140
200/output of front cooler/120

Inbound trip @ home in P
235/output line @sensor/195
235/input of rear cooler/190
230/output of rear cooler/180
no readings off the engine mounted oil-oil cooler
225/input of front cooler/150
225/output of front cooler/140

Idling in Neutral after parking for 7-8 minutes
200/output line @sensor/180

Pan read 180*-200* the entire time

During outbound I was running 65-70 in Drive (OD off) at approx. 3000rpms (matted!)...
Returning, I ran Drive up the hills & OD down them. Seemed to run a bit cooler that way, but shot up as I slowed/enter the development near the house.

The fan on the rear cooler was on HIGH the entire time. Flow is output line>Rear cooler>engine cooler>front cooler>input line.

Potential bad gauge/sensor since it averages being off from the IR by 20+*F ? Thoughts? opcorn:

 

Pulling 10K mine would peg the trans temp.gage at 250* on anything that even looked like a hill and would run about where yours does on the flats. I changed out the stock torque converter and the trans.runs about 180-190* and rairly hits 250*.When it gets up to 90* plus outside the engine gets hot 230 on a hill and the trans.is about the same.

 

Hmmmm........ my under bed flips on @ 180 or so.



Makes me wonder if my guage is accurate.

 

Anyone else? (or did I say something bad above )

 

I'd expect the line to be slightly (say 5 degrees max) cooler than the fluid, but 20 degrees is impossible. The gauge is whacked - but at least it's reading hot and it didn't let you toast the trans. If it was me I'd leave it alone and adjust my "Time to back off" number by 20 degrees.

 

Whats the truck got for mileage on it? Does it have the factorytorque converter in it?

 

My trany was gettin about 240 in the pan and I bought an aux. cooler from a friend. Has it's own fan and everything you need, will reduce temps anywhere from 75-100 degrees cooler!!! Check it out on BD-power.com It's worth the investment! Especially if you're running expensive fluid, you want' burn it up quickly and you can change it a bit less.

 

About 156,000 miles and I'm pretty sure it's the stock convertor...

 

The guy I borrowed the IR from discounts it's accuracy and suggests pulling the sensor (PITB, since that will evacuate all the tranny fluid) and dropping it into a small pot of boiling water (on a campstove under the rig) to check the Isspro for accuracy...

Opinions?

 

Well, if he doesn't trust the IR temp gun I guess that's the only way to know for sure.

 

Well, still haven't had time to mess with it, but have a few more questions...

I did take a 80+ mile roundtrip last weekend (60* ambient & unloaded) and couldn't make the tranny temp go over 180*...

Since the tranny temp seems to be closely coupled with ambient/engine temps, I'm proposing to BYPASS the engine mounted oil(coolant?)-to-oil "cooler". My belief is that IF the air-to-oil coolers are trying to pull the fluid temps down lower than 180*, an engine mounted (or radiator) exchanger is not helping that happen, since the engine oil/coolant is almost always hotter.

Since I live in NC where the temps rarely get below freezing (for longer than a week or 3), do I *really* need the engine mounted exchanger for pre-heating the tranny fluid?

Anyone have any experience bypassing the exchanger? Anyone strongly opposed w/ reasoning?

How do the cooling lines attach to the exchanger? threaded fittings? barbs & clamps?

 

OK, 6-8 months of owning the truck and NOT being to tow finally got the better of me!

Wednesday afternoon, I pulled the return hose from the rear cooler (exchanger inlet) and cut the tube feeding the front cooler (exchanger outlet)... eliminating the "heat exchanger" from the circuit completely! I hated to cut the hardline, but should be able to splice it easily (either compression fitting or hose/clamps) should the outcome not be good... and it was a quick clean operation.

A quick trip w/ 8000# load (trailer/Jeep/gear), rear fan on all the time, & 65* ambient(30* less than earlier test) on the same route netted me this: tranny warmed to about 145* within a couple miles (I was easy on it until warmed) and would NOT go above 180* without prolonged stoplight traffic or slow backing!

I then took an approx. 150 mile trip to wheel with the same results. Across the board, it'd heat up to 180* pulling from a stop and once up to 3rd gear running 55-65mph, would cool down to 150*-160* range while running the flats & go up 5-10 degrees pulling a grade. Running 70mph it stayed closer to 170* (never any higher), but 2800rpms sounded like the CTD was gonna come apart! (no bad sounds, just high RPMs for this engine). I found that manually selecting the gears (1st-3rd) and running up to 2500RPMs before the next gear was better on temps than it short shifting. I also bumped it into OD on the downhills... temps went up to 180*, but dropped when back in 3rd for the uphill sides.

It appears these temps (140*-180*) should be within spec for this tranny, right?

Maybe it's just mine, but it appears in "milder clims" the exchanger only ADDs heat during normal operation! The cooling operation performs like I think it should and cools down MUCH faster w/o the exchanger.

Next plan is to move the switch controlling the rear coolers fan (via relay) into the cab where I can turn it on/off when rolling empty. I'm gonna run a snake thru the exchanger to see if the bottom side of the coils are sludged/partially blocked and possibly why taking it out made such a dramatic change...

BTW, pulled like a dream!

 

Good deal dude.Gimme a call later