Trans Overheating, lack of Cooling, or ??

[Ernie n Tara]

I have a weird problem

The Data    2011 Winnebego Journey towing Jeep Rubicon
                    6.7L Cummins, 350 HP, Allison Transmission
Problem      Overheats under high load
A. First observed at about 70 mph driving over rolling hills. Hit the first temp warning
Driving gently (slower) kept temps under control.
B. Proceeded to Freightliner Gaffney for diagnosis/repair
They replaced fan clutch and pronounced fixed. $1, 000 plus
C. Proceeded to Ft. Myers FL. Ok during cool day. Overheated again
Spent the winter in Ft. Myers. Cleaned radiator there.
D. Departed for Dallas. Still overheating. Water Pump failed.
Replaced the pump. Noted that this engine uses the low volume pump.
E. Proceeded. Still overheating. Experimented:
  *Water temp well regulated at 190+/-4 deg F- thermostat o.k?
  *Trans temp at idle about 150 deg. F
  *Trans temp stabilizes 140 to 165 at 60 to 65 mph (depending on OAT)
    Water temp still well regulated
  *Trans temp starts rising at 70 mph and continues rising.
    Water temp starts rising at about 180 deg. Trans temp
    Both temps then continue to rise until overheated (about 230+ water temp)
    Reduced load will bring water down quickly; trans much more slowly
F. Diagnosis:
  *Fan clutch - already replaced once
  *Possible pinched trans line?
  *Trans defective?

Your better idea??
? What is normal trans fluid temp?

TIA,

Ernie

 

[dan680fl]

What is the age of the fluid and total miles on the transmission? When the transmission temp raised to 230f, what was the water/coolant temp? Generally, normal transmission temp is 176f. Consider 160-180f as reasonable. At 257f seals break down. The higher temps above 176f will dramatically shorten the life of the fluid. Did they change the fluid when the first repair (fan clutch) was done? If not, This would be high on my list as the next step.

 

[Gary RV_Wizard]

What tranny do you have, Ernie? Allison 3000 or the lessor 2500? The Journey Express model uses the 2500, but the regular Journey uses the 3000.

With the 3000 or 4000, Allison is happy as long as their transmissions stay under about 215. The synthetic fluid remains healthy and the tranny doesn't mind the heat at all. Not sure if the 2000 series tranny are also happy at that range, but a call to Allison would get an answer.

Given that you have replaced both pump and fan control, my bet would be on the tranny cooler. It could be externally clogged with road dirt and/or spilled oil, or internally clogged somehow.

 

[Ernie n Tara]

I expect its a 2500 transmission.
The weird thing is that the radiator overheats worse than the trans. For example, when the trans reaches 180F, the radiator starts up (from its usual190+/-4). At about 194Trans temp, the water temp will be well over 204 and climbing rapidly. It reached 230F water temp with the trans still below 200F.

Slow down and the water will drop below 194F while the trans is waiting to start dropping. Trans is always slow to change temp, either way.

Ernie

Note that I suggested to the Gaffney mechanic that the radiator might be plugged up.

 

[SargeW]

If it used to run cooler under the same conditions, it suggests that something has changed.  I know that seems obvious, but some hungry mechanic may suggest putting in a bigger radiator.  If I was guessing, I would say clogged radiator fins, or clogged tubes in the radiator.  Check the temp on the radiator while it's running and heated up with a laser IR temp gun. Cold spots on the radiator suggest fluid is not circulating freely through the radiator tubes.

My previous rig was a 2010 Journey 34Y. I really hated the Allison 2500, and always felt that it was under sized for that big of a rig. Mine never shifted right under load, and I too saw temps that were right on the hairy edge of the red zone. I even had to turn  the AC off on some of the longer grades to avoid getting the over temp radiator buzzer going off.

My current rig has the Cummins ISC, 8.3 liter, and the Allison 3000.  Even though I am 5000# heavier in this rig, I have never had a temp issue and I am a cruise control driver. 

As far as the trans heat, the Transynd is some pretty good fluid. It is slower to absorb heat, and slower to shed it as well. Has the transmission been serviced recently?  Check the fluid and make sure that the levels are correct. On the 2500 trans there is no on board diagnostic so you will have to pull the dip stick.

 

[8Muddypaws]

Have you ever had the radiator & CAC cleaned?  5 years is plenty of time to accumulate some crud.  Check the space between them too.  Squirrels & birds, birds & squirrels.....

If there's a bypass valve that routs transmission fluid around the OTW cooler that would be my third suspect.

Second would be a dirty radiator and CAC.    5 years is plenty of time to get dust sticking to the fins due to oil misting.  Speaking of which, where does the crankcase vent dump oil smoke?  If it goes anywhere near the air stream that goes through the radiator move it.  (Mine exits under the trailer hitch)

Third would be critters building nests between the radiator & CAC.  Birds & squirrels - squirrels & birds....

 

[Ernie n Tara]

Trans was serviced at Gaffney (25, 000 miles) when the clutch was replaced. I'm about convinced that the radiator iscrudded up. Else I got a bad clutch. Since it running in a good temps band,  I may just baby it until I get back to Gaffney and let them fix it under warranty.

Thanks all,

Ernie

 

[William52]

Heres a way to confirm the problem run it to the overheating event and then take a water hose to the radiator/condenser and see if the temp drops. Water absorbs heat a lot faster. You should be able to watch it on the water temp/Trans gauges.