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kenwyatt · 09-13-2021, 07:29 PM

On a trip and have a couple things happen I haven’t experienced yet.

1) This started yesterday, driving along normally and engine temps normal around 190. Noticed the digital readout would drop to 188 and in a few seconds to maybe 1 minute goes back to normal, always 188. Oil levels normal and changed less then a year ago as well as the coolant. Wires on the sender not loose.

2) Trans temps have always tracked the engine temps fairly close. Driving along on flat land with everything looking normal around 190 to 196 and noticed just the trans temp went to 201 then 203. Parked overnight and today noticed the engine temps normal around 190 but trans temps running about 12 to 15 degrees under under the engine temps. When I shut down today I checked everything I could with a thermal gun and that agreed with the readings I got from the Aladdin. Know what would cause cold readings as well as hot but haven’t seen temps separating like this. Any ideas appreciated

8.3Oilbuner · 09-13-2021, 09:48 PM

Good evening Kenwyatt; In my 01 Windsor with the Cummin's ISC and an Allison MH3000, my transmission temp is always 10 to 20 degrees lower than my engine temp. Only time the trans. temp gets close to engine temp. is if I am in slow traffic and doing a lot of idling. A lot of that temp in the trans. come from the torque converter building heat. If I am stopped too long I put the trans. into natural. I don't have an explanation of why yours spiked in temp.in the transmission. I would just keep an eye on it to see what happens!

jacwjames · 09-14-2021, 06:58 AM

Watching,

I watch my temps, engine and transmission, and I've noticed mine starting to climb a little. In the past the transmission would always be lower then engine unless climbing hills.

My recent trip it seemed like my transmission temps climbed quite a bit. I was stuck in traffic near Detroit, stop and go, transmission temp climbed above 200. I monitored and like Oilburner I shifted to neutral when possible.

Finally, last week I changed my transmission filters, did not find any problems, old filters were clean, oil looked good. After the change I took the rig for a drive to get it temp and check oil level. Checked for any codes also. All good.

But I have to back my rig into my garage up a slight grade, as I did this the temps started to climb, I had an alarm set at 220, it went to 228F. This is still well within the temp range of the transmission. Not sure what is going on.

I am going to check the cooler, I did wash it out a couple weeks ago.

jacwjames · 09-14-2021, 07:05 AM

Watching,

I watch my temps, engine and transmission, and I've noticed mine starting to climb a little. In the past the transmission would always be lower then engine unless climbing hills.

My recent trip it seemed like my transmission temps climbed quite a bit. I was stuck in traffic near Detroit, stop and go, transmission temp climbed above 200. I monitored and like Oilburner I shifted to neutral when possible.

Finally, last week I changed my transmission filters, did not find any problems, old filters were clean, oil looked good. After the change I took the rig for a drive to get it temp and check oil level. Checked for any codes also. All good.

But I have to back my rig into my garage up a slight grade, as I did this the temps started to climb, I had an alarm set at 220, it went to 228F. This is still well within the temp range of the transmission. Not sure what is going on.

I am going to check the cooler, I did wash it out a couple weeks ago.

kenwyatt · 09-14-2021, 07:39 AM

Thanks for the replies. Next leg is 250 miles in a couple days so we will see how it runs. Cooler is always better than overheated.

jacwjames · 09-14-2021, 12:24 PM

I washed my cooling stack out again, this time from both directions with a pressure washer and oscillating head. Took the AC condensor loose and swung it out of the way. Could not see any significant amount of dirt/debris.

Took it for another test drive, the same route I took the other day and then backed it into the garage, temp got to ~209, a little better then before but not much.

When I was crawling underneath I check the wire on the temp fitting and it was barely on, not sure if that might change the temp reading or not.

Outbound · 09-14-2021, 12:46 PM

Wonder if backing up your driveway has your trans fluid migrating to one end of trans leaving parts without fluid.

jacwjames · 09-14-2021, 12:52 PM

The access to the garage is not that steep, I've had spots at campgrounds steeper.

I don't know if I'm just paranoid or not. I have had a Silverleaf VMSpc for ~8 years and don't recall the transmission temps getting that high.

I noticed on my last trip that the temps were creeping up and now have my eye glued to the display. I just got a new tablet for display and took the time to set up an alarm for the transmission temp, initially I set it at 220 but as I was backing in last week it started to alarm. I now have it set to 230.

Wondering what everyone else is see for high temps.

jbrinsfi · 09-14-2021, 01:02 PM

Climbing up a steep long grade at altitude on a hot day my trans temp will get up to 210 to 220. I have noticed that it tracks engine coolant temp and that it takes longer to go up (and come down) than the engine coolant temps. I am not sure but I think the trans cooler has engine coolant circulating through it.

I have a 39' Fleetwood DP running a CAT 350

kenwyatt · 09-14-2021, 01:32 PM

JB, Not sure on yours but believe your trans cooler is built into the radiator so the transmission fluid is circulating thru the engine coolant. At least that’s how my C13 works as far as I know.

dfb101 · 09-14-2021, 01:59 PM

I live in AZ in the desert where the ambient summer temperature is 110+. I have Cummins ISC with Allison 3000, I use a scanD for my coolant and trans temp and when climbing I see temps as high as 220. I have a local big rig mechanic that says on average trans temp is ambient temp + 100.

jacwjames · 09-16-2021, 07:58 AM

I took the time to pressure wash my radiator, CAC, and condensor. I used a low pressure with a osculating spray and didn't get too close to the fins. Could not see any significant amount of dirt come out. I crawled underneath the coach and spray the radiator from the inside, trying to hit as much of it as possible working around the fan and shroud.

I then took the coach for another run, following the same path as before and then backed into the garage as before. The road coming to the subdivision has a fairly steep entrance followed by some 90 degree turns.As I pulled into my driveway I was at ~205F! Backing into the garage I got it on the first try this time with no back and forth. The transmission temp still climbed to ~220F, slightly lower then before.

Not sure what else I can check. Not sure if I'm just paranoid or if I really have a problem.

I have ordered an oil analysis kit and will send a sample off. I checked and I have ~35K miles on the fluid since the last change with multiple filter changes. As stated before, when I changed the filters recently the oil looked good and no signs of contamination in the oil or filters.

Is there a chance that the transmission cooler, which is integrated into the radiator could be partially blocked? How could I test other then disconnecting the hoses and putting air on one side.
The coolant side of the radiator is working, temps of the engine are where they should be, during my drive the engine temp was 183F.

Vamoose · 09-16-2021, 01:07 PM

I'm not an expert on any of this, but I recently talked with someone whose name comes up on these boards quite often as the best of the best - Tom at Massey Diesel in Phoenix, AZ.

I have a Detroit Series 60 engine (500 hp) paired to an Allison 4000 transmission in my 43' HR Navigator. After I bought it, I was concerned about driveline temps and whether or not the Aladdin readings were accurate - the Aladdin says the engine is running about 190-195 F, and the trans between 220-227 F. These are temps consistent, when running on flat highway, regardless of exterior temp (104 in Phoenix or 85 in Flagstaff). The engine temps climb to 208 on a steep hill, the trans temp never goes over 227.

Tom didn't even hesitate to say that all of this is perfectly normal. He told me to look at the gauges and I'd see that the engine temp range is substantially lower than the trans temp range, supporting the idea that the trans should be hotter. I looked - he's right.

His expertise made me feel much better - I hope you find it useful.

Judd

Analyte · 09-16-2021, 01:55 PM

It's possible you could benefit from an additional auxiliary trans cooler that you could place in clean air.

I've had trans coolers plug before requiring replacement so that's not out of the question if the increase is only recently