Aux Tranny Cooler Recommendation

[Dennis55]

I tow my fifth-wheel trailer (10,000 lbs empty weight) with a 2001 3500 8.1L. Love my truck!! In the past I towed a travel trailer that was about 3500 lbs lighter and never experienced a tranny temp over 200 degF, even while doing some significant hill climbing out West in 100 degF outside air temps. In June, while towing in Vermont, and with outside air temps in the mid-80s, I noticed my tranny temp running up around 225 degF. This while pulling up gradual (less than 5% grade) incline, but over long distances (I 91 and I 89 in VT). Kept my Allison in T/H mode all the time while towing, and when a downshift occurred I tried to back off on my accelerator to keep the rpms around 2500, no more than 3000. I run Mobil 1 synthethic tranny fluid in the Allison; Mobil 1 synthetic in the crankcase.

 

Should I be investing in a secondary tranny cooler for my tow vehicle, and if so, what would you engine-savvy members of the forum recommend?

 

Thank you in advance.

[masterp2]

You are not doing too bad at 225 for small periods of time. But I would suggest a lower temp thermostat.

 

(What the heck is this guy talking about!)

 

If like the rest, your tranny is first stage cooled in the radiator. If you lower the coolant temp in the cold side of the rad, you are also lowering tranny fluid temps. Of course, you more likely are having increased ECT (engine coolant temps) with the load. So the best way ( and this works for the duramax also) is to invest in airflow for the radiator, the entire cooling stack actually). And I don't mean another fan, don't let anyone talk you into that. Design enhanced kinetic airflow through the cooling stack.

 

 

Your AC will be better than ever also.

[Mattt]

Ive experienced the same thing when towing my 10k trailer. However, the jump in tranny temp is not followed/led by a jump in engine coolant temp. My engine temp stays rock solid(roughly 200), while my tranny temp jumps up, and goes down once Im not working the trans so hard(like going downhill or on flat ground).

 

I dont think changing the t-stat would help much if any in my case.

 

Ive posted this same question in the past about an Aux Aux trans cooler, or swapping in a larger trans cooler than stock, and I got little to no response. Anyone?

[dizzy]

I think ideal range is 180F to 200F. Mine has gotten to 200F on a really hot day (100F+). If you are getting over that I would also look for extra cooling. Once the fluid gets hot enough to turn brown the damage is already done.

 

An external cooler is cheap insurance compared to replacing a tranny. You leave the stock radiator cooler in-line and add the external for extra cooling. Jegs carries quite a few different offerings, I would look at the Perma-Cool, but there is B&M, TCI etc.

[linda]

do a search for "Mike L" tranny cooler over at dieselplace.com. Its a direct replacement for our stock allison aux coolers. I have heard very good things about them.

[Mattt]

Where is the "search" function over at diesel place? Cant find it for the life of me....

[Mattt]

Found the search feature....you have to be registered and signed in to use it.

 

Is the Mike L tranny cooler only an option for the Allison? I have the 4L80E trans.

[linda]

yeah Matt...i was responding to the poster of the thread with the Mike L cooler. It is only for the Allison, sorry. B&M makes a real nice cooler that would work well for the 4L80E. Thats what i used for my engine oil cooler.