I drove my truck (while towing a 5000 lb boat with AC on and the outside temp reading 110 in Las Vegas) up a 6% grade for about 3 miles at 60 mph. My engine temp went to 250 and my tranny temp went to 290. I pulled over right away and shut the motor off, and the antifreeze came pouring out of my overflow. What should I do and is this normal.

We've been having a discussion about overheating LLY's since last August IIRC. Do a search to gain some intel on this issue. Your truck burped because it was shut down too early and not allowed sufficient time to dissipate the heat before shutting it down. Did your truck give you an "overheat" read on the DIC? :o:

Towing at higher elevations at higher RPM's seems to be the wrong prescription for the LLY's. Your experience is right in line with others. 290* on the Ally is enough to scorch the tranny fluid IIRC. You might want to have it checked and replaced if necessary. :rolleyes: Sounds like you were in 4th gear, did you have tow/haul engaged?

You will find on the other overheating post that one of the DP members is in discussions with GM about this issue. We're trying to get GM to step up to the plate and provide a fix instead of having to pursue them through litigation. Sorry to hear of your problems. You should be able to tow 5k lbs on a 6% grade, just back the RPM's down. Later. JJ :)

Thanks for the input, no I didn't have the tow haul engaged (should I have) and no the overheat light didn't come on and I was in fourth gear:)

Always best to use tow/haul when towing IMHO. ;) The Ally is one smart tranny, let er' do the job. I would still have the tranny fluid checked. IIRC above 230* the fluid can lose some of its lubricating properties. You might go on the Allison forum and see what the tranny boyz think.

The overheating thread I mentioned is active on this forum right now. 80+ pages. You can probably get a good idea of what's going on in the last 10 pages or so versus reading the whole thread.

IIRC the DIC shows an overheat condition at 275* so you likely didn't get that hot. The truck burped because the coolant stopped flowing and the heat from the engine had no where to go but through the coolant. Later. JJ :)

IIRC????

IIRC????


If I Remember Correctly
In My Honest Opinion

Acronym heaven!! ;-)

Since its a diesel the best thing to do would have been to let it idle instead of shutting it off. The manual even says to do this when your running too hot.

Fast Idle; 1000 - 1200 rpm.

Idahofox

If I Remember Correctly
In My Honest Opinion

Acronym heaven!! ;-)

Thanks!!

I'm just curious, can you hear your clutch fan engage??? On mine, I very rarely hear the clutch fan come on. Even with the A/C on.

YES!!!!!!!!!!!!!!!
It soulds like you have an airplane under the hood. You will also clearly here it turn off.

Thanks for the input, no I didn't have the tow haul engaged (should I have) and no the overheat light didn't come on and I was in fourth gear:)

Curious, did your clutch fan come on?

YES!!!!!!!!!!!!!!!
It soulds like you have an airplane under the hood. You will also clearly here it turn off.
Yes, thats what it is. This past saturday I drove out to Fontana, CA where it was 100 degrees. Had the A/C on at all times. When taking off at a light, i could hear the engine sound lil bit different....my eng temp was about 190 and the tranny was about 200..I noticed my tranny gets hotter than my engine temp. The eng temp never exceeds 190ish. tranny gets up to 200 and past a line or so but never more than that..by the time I see the tranny get up there I hear the fan going on, but not sure if thats the tranny cooler or eng fan? as time goes by I see the tranny temp drop back down to either 200 or a couple lines below 200..I take it this is normal and I dont have a problem?