The CRD has an electric and a mechanical cooling fan. Are there any negative side effects with the electric fan not running?
Mine seems to of died. It is getting power to both the high and low speed at the fan wire connector.

If your electric fan is not working, your air conditioning may not work properly and running during the summer with AC on may cause over heating.

If the fan is getting power but is not spinning then the motor may be bad.
I dont know if the motor can be replaced separately.

Although I have never tried this on my own CRD, sometimes you can disassemble the electric fan motor, file the brushes, clean the contacts, clean out all the crud inside, add a little grease to the bearings, reassemble, and get some more life out of it.

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U.S. Army Retired

Does it have a lot to do with cooling the transmission?

Not a lot.
If your engine driven fan is still working (fan clutch) it should be pulling enough air to cool the transmission.

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U.S. Army Retired

Maybe or maybe not. On the CRD the transmission cooler is in the bottom of the AC condenser not the radiator. The electric fan cycles based on sensors which may or may not include transmission temp and it's main purpose is to push air past the AC condenser when "told" to. The mechanical fan cycles, triggered by a thermal coil in the fan clutch, based on radiator temp and I presume to a lesser extent the temp off the stack of AC condenser, radiator, and intercooler. How well the mechanical fan will or will not work to keep tranny coolant temp ok if the electric fan is dead is open to question.

There is at least one report of the AC not cooling properly at low speeds with the electric fan dead which suggests insufficient air flow across the AC condenser even with the mechanical fan functional.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

I will say that if I sit still long enough the AC will start to blow warmer air.

I also notice that with a lot of start and stop driving when I slow down to stop the transmission make a thud when the overdrive is disengaging.
It does not do this when coming off of a highway run.

Your torque converter is locked over 50mph, and transmission is relatively cool. When tc is not locked, it generates more heat. I would try fixing the electric fan if I were you. Or consider some other alternatives such as a main e-fan to replace the viscous or other e-fan to replace your broken one.

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2005 kj CRD, samco, suncoast tc, provent, Kennedy lift pump, GDE ECO full torque, 2nd gen filter head, 245/70/16 a/t tires, mopar light bar, fumoto oil valve, OEM Skid Plates, ARB Front bumper and HD OME, tru cool LPD47391 40k GVW tranny cooler (stock cooler delete), FF Dynamics e-fan and shroud, rocker arms replaced, HDS2 190F thermostat.