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Taxman · 06-30-2007, 06:20 AM

I installed my new transmission temperature gauge yesterday. Got the shock of my lifetemp stabilized at 220!

I think that is too hot.

My question: What temperature should I expect to see in an 18,500 lb mh with a 454/Turbo 400 powertrain?

I am using Mobil 1 synthetic trans fluid and running, in addition to stock trans cooler a large air to air external cooler.

Do I need more cooling capacity.

BTW, OAT was low 90s, and engine water temp was 190 - 200, depending on speed.

Taxman · 06-30-2007, 06:20 AM

I installed my new transmission temperature gauge yesterday. Got the shock of my lifetemp stabilized at 220!

I think that is too hot.

My question: What temperature should I expect to see in an 18,500 lb mh with a 454/Turbo 400 powertrain?

I am using Mobil 1 synthetic trans fluid and running, in addition to stock trans cooler a large air to air external cooler.

Do I need more cooling capacity.

BTW, OAT was low 90s, and engine water temp was 190 - 200, depending on speed.

Bob (WA0MQE) · 06-30-2007, 06:32 AM

I'm not sure about the Turbo 400, but on my previous moho which was also a 18,000 lb rig, had the 8.1 GM engine and 4L80E GM transmission under normal driving conditions (level road) temperature no more then 80 or 85 the temperature would be right on 180 degrees which is what the manual said was normal operating temperature. At 90 or higher outside temp. it wouldn't surprise me if it went higher, although I don't recall. Climbing long hills it would easily run over 220.

If your's is running 220 all the time I'd think you should look into it a little closer. Have you changed the fluid lately? If not it wouldn't hurt to have it flushed thoroughly (including the cooler), change the filter, etc. You didn't mention what year and type chassis. Mine was a 2001 and also had two twin electric fans that cooled the transmission cooler when the fluid would start warming up. If you don't have something like this you might look at after market kits for same.

DriVer · 06-30-2007, 07:15 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Taxman:
I installed my new transmission temperature gauge yesterday. Got the shock of my lifetemp stabilized at 220! </div></BLOCKQUOTE>Here is a transmission fluid temperature vs expected service interval chart:

TRANSMISSION FLUID – LIFE EXPECTANCY vs. TEMPERATURE
DEGREES F? // MILES
175 100,000
195 50,000
212 25,000
235 12,000
255 6,000
275 3,000
295 1,500
315 750
335 325
355 160
375 80
390 40
415 Less then 30 Min.

OIL TEMPERATURE MEASURE AT CONVERTER OUTLET TO COOLER
350 degrees F is the maximum temperature. This is the normal place to install a temperature
gauge or signal. The temperature in this location will vary significantly with each vehicle startup
or hill. If the temperature reaches 350 degrees F, reduce throttle. To lower the transmission
temperature with the transmission in NEUTRAL, run the engine at 1,200 RPM for 2-3 minutes
to cool the oil. DO NOT allow the converter outlet temperature to exceed 350 degrees F.

OIL TEMPERATURE MEASURED IN THE SUMP OR OIL PAN
"¢ 150 degrees F – Minimum operating temperature for continuous operation.
"¢ 180–200 degrees F – Proper oil level checking temperature
"¢ 200 degrees F – Maximum oil level checking temperature.
"¢ 285 degrees F – Maximum sump/oil pan temperature for short duration, such as a long hill climb.
"¢ 300 degrees F – Metal parts inside transmission begin to warp and distort in varying degrees, seals melt rapidly and transmission fluid life is extremely short due to oxidation and distress.

Taxman · 06-30-2007, 07:53 AM

Driver,

Thanks. That is good info -- I'll keep it for reference.

I'm going to be aggressive about lowering the temp -- probe is in an external oil filter before the coolers. Gonna replumb it and put on an external fan.

Taxman · 06-30-2007, 10:34 AM

Bob,

Thanks. I'm running Mobile 1 synthetic and it is fresh.

I believe I'm taking the temperature before the cooler -- gonna check the plumbing Monday and ensure that I get temp after the coolers have done their job.

Safe travels,

Frank

Gary RVRoamer · 06-30-2007, 12:28 PM

Where are you measuring the temperature? The tranny sump or one of the lines to/from the cooler? All will be different. 220 is not unusual for fluid going out to the cooler. That line often comes right out of the torque converter and is about as hot as it gets inside the tranny. The tranny's sump is usually less if it is cooling enough and the return line ought to be close to the radiator temp or even less if you have a big tranny cooler.

Taxman · 07-01-2007, 09:05 AM

RV Roamer,

Thanks. I have double checked my aux cooler installation, and have determined that I am measuring trans temp FRom the TC to the cooler.

Will re-route lines to get trans temp after it has been through the coolers, and will put a fan on the air-to-air trans cooler to get even better cooling.

I really, really do not want to abuse this transmission in any way!

Safe travels,

FRank

Taxman · 07-02-2007, 01:23 PM

Bob, Driver, RVRoamer,

Replumbed oil cooler lines this AM: Fluid flows FRom transmission to air-to-air cooler to external filter to radiator cooler to transmission. Temp probe is in the external filter and the trans temp stabilized at 180. Engine water temp was 180 to 190.

Based on my experience FRiday, the air to air cooler (with full time fan) is good for a 40 to 50 degree temp reduction.

I'm a happy camper!

Safe travels,

FRank

DriVer · 07-02-2007, 02:37 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Taxman:
I'm a happy camper! </div></BLOCKQUOTE>

Taxman · 10-24-2007, 04:12 AM

Follow up -- Trans temps are just fine. Appreciate all the help and advice.

Digital Boy · 10-24-2007, 10:25 AM

I haven't read the entire thread. So, I'm sorry if this is a repeat . . .

I have an Allison MD3060 6 speed tranny. I bought the rig with 54k miles. It now has over 80k.

The tranny temp gauge ALWAYS read 240 degrees when hot. Owners of other similar RVs reported temps of about 170 degrees.

The Ocala Allison shop put their computer on it and verified the 240 degrees. They told me that it was well within specs. I then took the rig across the street to the Cummins shop for service. While up on the lift I asked the tech to locate the Tranny temp sender.

He came to me and was surprised to report that my sender was mounted after the torque converter. It is supposed to be mounted after the tranny cooler!

Allison then told me that the cooler was probably bringing the temp down to the 170-180 degree range and that 240 degrees coming out of the converter was just about right.

Since then I haven't given it another thought.

Where is your sending unit mounted?