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flatbed56

Hot transmission

14 posts in this topic

Came back from a 1900 mile vacation with the 30ft trailer. Weight w/truck approx 17000lbs to 18000. Part of the trip from Dubious, WY, to about Moran WY, 5 % and a 6 % grades pulls, at 2 to 10 mph for approx. 20 miles , 6900 ft to 9600 ft. This was all road construction, mud, holes, no pavement and a pilot car. The transmission, hit 240+ and the truck at 220. I am running syn. in everything. I pulled over were I could and cooled off at the summit. For 1800 miles the truck ran great. My question would a fan on the transmission cooler help or ad a fan and extra cooler help and which one. I will be going again. Sorry for the long post. Thanks

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You probably need some sort of aux cooler, and/or the ability to lock the tq converter in 1st (if thats even an option)...The engine was most likely getting hot from the trans and the trans is cooled with the main radiator, so you were heating the coolant in the rad. We have had the trans overheat dad's 454 Burb several times, its the main reason my dad now drives an 06 Cummins with a G56.

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thanks for the reply. Were would you locate the aux cooler or replace the current one in its spot.

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Came back from a 1900 mile vacation with the 30ft trailer. Weight w/truck approx 17000lbs to 18000. Part of the trip from Dubious, WY, to about Moran WY, 5 % and a 6 % grades pulls, at 2 to 10 mph for approx. 20 miles , 6900 ft to 9600 ft. This was all road construction, mud, holes, no pavement and a pilot car. The transmission, hit 240+ and the truck at 220. I am running syn. in everything. I pulled over were I could and cooled off at the summit. For 1800 miles the truck ran great. My question would a fan on the transmission cooler help or ad a fan and extra cooler help and which one. I will be going again. Sorry for the long post. Thanks

Ok... Just lookingh at this a bit closer and thinking about it for a moment you got a radiator and/or thermostat problem. (Doing a bit of assuming...)

Now I would start out and look at both side of the radiator and I bet your going to find it all gunked up with oily residue (Cause by the stock crankcase vent) or mud (caused from offroad operation) possibly. The trans can't cool any more than the radiator can so since your slow rolling and not moving air very well the radiator start heating the trans fluid like in your case.

Posted Image

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So if your radiator looks like this then you not moving air through any of the coolers hence the aux cooler won't do much anyways. So it might be time to look into a bit of inspection. Even mine look like...

http://forum.mopar1973man.com/attachment.php?attachmentid=1597&d=1282528988

You won't want to come out to Idaho then you could drive up to Seven Devil Summit as a test run. :tongue: Start at 1,800 feet in Riggins, ID and drive 17 miles up a very steep single lane dirt road for 17 miles till you reach Heavens Gate at 9,000+ feet. Average speed up or down this road is about 10 MPH...

http://en.wikipedia.org/wiki/Seven_Devils_Mountains

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Agree with Mike to check the radiator for cleanliness & the fans for correct operation. I added an aux transmission cooler on my towing built 454 C30. I think I would disconnect & cap the in-radiator cooler & go with a separate unit. The one I bought snaked the trans fluid though a good size unit. I think the most awesome cooler I ever saw used an AC evaporator... but there was lots of room under that hood, more than a Dodge offers. Russ

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There are pros and cons to bypassing the factory cooler..Pros: The trans run cooler; trans wont heat coolant (thou this is a much smaller effect with an aux trans cooler)Cons: aux cooler becomes primary and needs to be much larger; the trans takes longer to warm-up.If you only tow with the truck a bypass may be a good idea, but if you still DD the truck I wouldn't bypass the OE cooler.

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On a previously owned Suburban, the factory radiator trans cooler was routed into an auxiliary transmission oil cooler mounted in front of the A/C condenser. Not always the best place to mount a trans oil cooler due to A/C condenser heat. I would suggest diverting the return to the transmission of the factory trans. oil cooler and route it to the auxiliary cooler and then route back to the transmission oil return line. That way you are using both oil coolers. I would definitely inspect/clean the radiator as mentioned but when a transmission over heats, it can sometimes cause the engine to over heat as well due to the extreme amount of heat the radiator is absorbing. I would try to find a place in front of the radiator but away from the A/C condenser to mount the auxiliary trans oil cooler. That way is will get plenty of cool air, at least as much as is possible. Another item you may want to consider adding is a Mag Hytec Double Deeper transmission oil pan. They are expensive but they double the amount of oil your trans pan holds as well as increase cooling surface area in addition to cooling fins. http://www.mag-hytec.com/store/index.php?main_page=product_info&cPath=1_8&products_id=7&zenid=eb112aebace261c01d5ebab70930df83 Be sure to ask about crossmember clearance and any other issues that may affect pan clearance. This is a BIG pan but it makes a HUGE difference. I had a 4L80E that continuously over heated when towing heavy, I installed one of these pans and it made a HUGE difference and improvement.

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There are pros and cons to bypassing the factory cooler.. Pros: The trans run cooler; trans wont heat coolant (thou this is a much smaller effect with an aux trans cooler) Cons: aux cooler becomes primary and needs to be much larger; the trans takes longer to warm-up. If you only tow with the truck a bypass may be a good idea, but if you still DD the truck I wouldn't bypass the OE cooler.

Kinda lost me here (i know i know easy to do) Why does he need to bypass - why can't he just add AUX between the OE cooler and the tranny on the return line. Only reason I ask is thats what I plan to start hooking up next week. http://www.summitracing.com/parts/DER-15950/ oh ..... I just re-read - I think your pretty much saying to use AUX and not bypass unless it has enough capacity. In terms of hooking up - I asked jimbowie and he sent me some pics of his install - he has it mounted on drivers side between frame and real wheel driveshaft ........ with the frame and the cross member as anchor points. thats what I am gonna do also.

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oh ..... I just re-read - I think your pretty much saying to use AUX and not bypass unless it has enough capacity.

Correct. If you only tow heavy, or only drive heavy below 30 mph then bypassing the OE cooler may be for you, otherwise a good aux cooler between the OE cooler return and the trans is the best bet. You still want the aux cooler in good airflow, even if it gets some hotter air from the a/c its okay.. Consider my a/c condensor is in front of my intercooler, and my IAT's are only +40ish from ambient at 30-35 psi boost, a/c full, 95* day, and the air coming out of a HE351 at 35 psi is HOT, HOT, HOT.. much hotter than anything your trans will put out... so they key is flow then temp. I would rather have 50 mph of 150* air than 20 mph of 95* air. Make sense?

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Sure - but I assume thats for an AUX cooler relying on the truck moving for airflow - eg having up front ? The tranny cooler (AUX ) that I was planning to use was a 12V switched fan that would be under the bed somewhere - so pretty much ambient temps. I don't see why you would use an AUX cooler up front - unless it was a bigger capacity than OE. The whole point for me with the 12V switched FAN was during stop/start traffic. During highway driving/lockup I am barely over engine temps (180) in the HOT line out of the tranny. But much start/stop traffic and I quickly hit 220 in the hot line.. So with a 12V switch fan - when basically not moving and no airflow up front - I hope this will supply enough flow to keep my temps in check. So I guess 2 different options - but having DUAL coolers (OE + AUX) and having the AUX with its own air supply seems to make the most sense to me to cover all situations (towing, not locked up, stop/start). Can't give any figures as won't be starting till this week, but I know jimbowie mentioned around 50degree drop on his setup. So hoping for something similar.:thumb1:

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I've used a trans cooler alone on the C 30, and swapped in a big flex fan. I also ran a aux trans cooler on the return line on a 84 GMC 1500 with a poor 305cid that I towed a heavy steel stock trailer with. Even after I swapped in a big flex fan, I could watch the engine temps climb on a good grade & drop back on the down hill. My ex got that truck in the divorce & wrecked it soon after. I kept the C30.

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Why not have a fanned cooler up front? You would get more airflow with vehicle speed, and the fan.. Then when towing hard on the fwy the fan doesn't need to run.

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Why not have a fanned cooler up front? You would get more airflow with vehicle speed, and the fan.. Then when towing hard on the fwy the fan doesn't need to run.

Dunno - good question :shrug: - for me right now its mainly space- Even those these things aren't that big - there's only limited places to put them :):thumbup2:

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