Allison running too cold

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Allison running too cold

April 09, 2022, 10:29:05 am

So we'll give it a shot here.

Coming home from our last 4K trip trip, I noticed our Allison MD 3050 transmission running about 50 degrees colder then the engine. Thought it to be strange as it always runs at, or slightly above engine temp at 185 degree range (3126 Cat). I worked the retarder a few times, temp came up 10-15 degrees, then went back to like 136 degrees. Shifts fine, fluid looks good and at correct level via the stick, just changed it 4K miles ago.

Got home, checked everything over. Drove it to operating temperature, checked everything with a pyrometer.I have the Blue Fire system, and also my old Silver leaf. I hooked it up also, and it reads the same (136F). I can't check the fluid from the keypad, as code 70 comes up "Too Cold". Trans has no codes.The factory gauge shows like barely 150 (I changed that sensor before) but those aren't very accurate anyway.I never look at that gauge, so don't even know what is correct.

I have the Allison repair manual, my 1st thought was a bad sensor, but that is inside the pan. It honestly seems as though the transmission is actually running 50 degrees colder, because of the pyrometer readings on the outside, which I did all over the trans case.

So I took it to Spokane RWC International, the only authorized Allison place in the area. No Allison trans place in the area. I had the rear trans bearing checked there before, was real happy.

So I get a call, and they said they drove it 10 miles. he reads the techs notes, and it's everything I did, tech say's it's fine, no problem found. Well I'm not comfortable with that. Why would it all of a sudden start running 50 degrees colder? It's not my imagination, because I watch the computer like a hawk. I've driven this coach 30K miles.

A nice problem to have, at least it's not running hotter. But from what I read, if it changes any more, the computer may tell the trans to go into limp mode. Something I don't want to have happen on the road.

At this point, they asked if I wanted them to call Allison, I have yet to hear back, and now it's the weekend. After I slept on it, I'm thinking "Aren't you Allison" Seems like they don't have a clue.

Any input would be helpful
Thanks
Chris

Re: Allison running too cold

Reply #1 – April 09, 2022, 10:33:32 am

Chris,

Can you shoot the bottom or lower side of the transmission with an IR thermostat?

What was ambient temperature when you have this happening? Said another way, was the engine thermostat open?

Re: Allison running too cold

Reply #2 – April 09, 2022, 10:55:00 am

Could your cooling fan controller be stuck on high?

Re: Allison running too cold

Reply #3 – April 09, 2022, 11:50:23 am

Quote from: Doug W. – April 09, 2022, 10:55:00 am

Could your cooling fan controller be stuck on high?

You know Doug, I read that somewhere while searching, but if it did that, wouldn't the engine be running too cold also. I mean the coolant does them both. But this is certainly a possibility. Will check this out.

Brett, I did do that, all over the trans caes with pyrometer. Even pulled trans dipstick, reading oil on stick. So did The tech.
Thermostat is open, engine temp is at operating temp,as the throttle won't work fully untill normal engine temp is reached, which is 185 degrees.Pyrometer on engine block/head, says engine at 180's FH

Anbient was in the 50's, but even in 17 degree weather,has never done this.
Last 400 miles it did this, when it was 65F out.Thanks for input.
Chris

Re: Allison running too cold

Reply #4 – April 09, 2022, 12:14:42 pm

Chris can you take a reading of the water temperature leaving the transmission cooler. May be that the radiator temperature was cooling to that point and engine thermostat is maintaining temp in engine. I thought there was a thermostat in the transmission also, that may of failed in the open position? I reach out to my Allison service friend and ask him. I do know he likes his trans as cool as possible. Since I have stopped excess radiator cooling my trans and retarder run much warmer.
Scott

Re: Allison running too cold

Reply #5 – April 09, 2022, 12:33:45 pm

Quote from: dsd – April 09, 2022, 12:14:42 pm

Chris can you take a reading of the water temperature leaving the transmission cooler. May be that the radiator temperature was cooling to that point and engine thermostat is maintaining temp in engine. I thought there was a thermostat in the transmission also, that may of failed in the open position? I reach out to my Allison service friend and ask him. I do know he likes his trans as cool as possible. Since I have stopped excess radiator cooling my trans and retarder run much warmer.
Scott

Thanks brother
Just got off the phone with Doug brainstorming. We have similar opinions as you. I will talk to RWC monday. I never checked temp at cooler output or actual temp at the radiator, which Doug suggested.

I also have a call into Bob Dale, but he has bad cell right now. He has same engine trans as ours, and mentioned in the past he changed his trans cooler to a upgraded one.

I will finish this post when I find the resolve, meantime any other input would be appreciated.
Thanks All
Chris

Re: Allison running too cold

Reply #6 – April 09, 2022, 12:49:59 pm

AJ has not got back to me but will. Ill post when he does. So when I'm running down hill and are running hot, the trans will open a port and drop temperature for a moment, quickly ramps back up. During that time I am running fans at full speed both for cooling and dynamic braking assistance typically starting to shed speed with service brakes to drop a gear. Higher temps and bigger hill, good fun
Scott

Re: Allison running too cold

Reply #7 – April 09, 2022, 01:13:14 pm

Quote from: dsd – April 09, 2022, 12:49:59 pm

AJ has not got back to me but will. Ill post when he does. So when I'm running down hill and are running hot, the trans will open a port and drop temperature for a moment, quickly ramps back up. During that time I am running fans at full speed both for cooling and dynamic braking assistance typically starting to shed speed with service brakes to drop a gear. Higher temps and bigger hill, good fun
Scott

Thanks Scott
Here is an interesting tidbit I didn't post so as not to confuse things:

So the day I noticed this driving home, we came to Deadmans pass. Hwy 84 drops about 6K feet in 5 miles. I worked the retarder as I always do, with my eye on the computer. Never got above 205FH.Ambient was like 30-40 degree.

We go to the bottom, and parked at Wildhorse casino for the night. Walking around, I noticed we pucked 2 qts of coolant. I had not added any, nor does it ever do this. Having rebuilt the engine I watch the coolant like a hawk. So I cleaned it up, added 2 quarts, drove it home 400 miles with no issues. So something happened, some kind of event.

My theory was, the trans was reading 136, but was really higher, so when we went down the grade getting the trans temp to 205, it really was 255. But over trans over temp light never came on, nor did the retarded stop working. I was thinking the trans cooler was hot, expanded the coolant in it, then puked it out the overflow tank. But now I'm not sure that's what happened, because I'm thinking the trans really is at 136FH, was really at 205.

Our coach never runs hot, even in 100 degree temps with air on, dragging car, or dragging enclosed race car trailer.Never seen more then 210 on a big hill.

I always get the weird stuff going on, never the normal stuff. LOL

Chris

Re: Allison running too cold

Reply #8 – April 09, 2022, 01:54:54 pm

Actually that helps. I think you may be two quarts over full hot full level. With all the weird stuff I added Ive been able to see things a little different. Almost zero background fan speed and increased temps too follow (all) near 200+ all the time. When we had the failed fan control unit everything ran cooler with fans at 100% all the time but at a cost. Being able to hear the fans ramp up from the drivers seat is a nice feeling. I did this chasing fuel economy and left a needle valve inline to easily adjust background speed up if I wanted to, IAT protection. Haven't to date needed it IMO. Low fan speed saves fuel. Less drag. I run the coolant overflow tank at 1/4 to 1/3 from empty. At shutdown I run fans on hi to shed extra heat and it makes a big difference. 20 degs indicated, again all.
Im guessing your shedding too much heat from radiator (background fan speed too hi). Your wax valve is field adjustable, just a messy pain to do. Leaks oils while adjusting. The extra cooled radiator is really nice but it comes with a cost. Our typical trip is 1800 miles or 4400 miles. For me it makes sense. For most it wouldn't. Equally important is its not too hot and the temps can be controlled when needed.
Scott

Re: Allison running too cold

Reply #9 – April 09, 2022, 02:44:04 pm

Quote from: dsd – April 09, 2022, 01:54:54 pm

Actually that helps. I think you may be two quarts over full hot full level. With all the weird stuff I added Ive been able to see things a little different. Almost zero background fan speed and increased temps too follow (all) near 200+ all the time. When we had the failed fan control unit everything ran cooler with fans at 100% all the time but at a cost. Being able to hear the fans ramp up from the drivers seat is a nice feeling. I did this chasing fuel economy and left a needle valve inline to easily adjust background speed up if I wanted to, IAT protection. Haven't to date needed it IMO. Low fan speed saves fuel. Less drag. I run the coolant overflow tank at 1/4 to 1/3 from empty. At shutdown I run fans on hi to shed extra heat and it makes a big difference. 20 degs indicated, again all.
Im guessing your shedding too much heat from radiator (background fan speed too hi). Your wax valve is field adjustable, just a messy pain to do. Leaks oils while adjusting. The extra cooled radiator is really nice but it comes with a cost. Our typical trip is 1800 miles or 4400 miles. For me it makes sense. For most it wouldn't. Equally important is its not too hot and the temps can be controlled when needed.
Scott

Thanks Scott
Nope it's not over full, I have never added, or subtracted any coolant, in 20K miles since I rebuilt the motor. Like I said, I watch it like a hawk. Having to rebuild the engine, kinda makes one anal about everything. More like paranoid!

Engine hot towing in 100 degree temps,or cold, it has never gone above the hot line in the bottle, or below the cold line when engine is cold after sitting. Never added even one teaspoon of liquid, which I thought was pretty cool (pun intended).

But all your other info is very interesting.
Chris

Re: Allison running too cold

Reply #10 – April 12, 2022, 09:06:11 pm

Finally spoke with AJ. Yes there is a oil temperature thermostat. Sorry I neglected tp ask we're it is located.
Scott

Re: Allison running too cold

Reply #11 – April 12, 2022, 09:32:36 pm

Quote from: dsd – April 12, 2022, 09:06:11 pm

Finally spoke with AJ. Yes there is a oil temperature thermostat. Sorry I neglected tp ask we're it is located.
Scott

Thanks Scott for your help. Yup, it's in the pan....I have the manual. That's why I took it in, didn't want to do it myself.

Here is the update:
I picked up the coach today, they didn't charge me.Woo Woo. Good to have drag racing friends in high places.They confirmed trans was truly at lower temp then engine.Just surprised they didn't figure this out. But Doug got me pointed in the right direction, after talking to him on the phone. Just couldn't wrap my mind around how the engine temp could be normal, and trans so cold. But he set me straight! Now I have to talk him into getting his Jeep dirty!

Bruce Bean and I talked a bunch, and he came up with a good idea. I hooked the hydraulic lines together, which puts the fans at low speed. Driving it, everything heated up to normal slowly, but by the time I got home (including slow driving on our road)), trans and engine was at 200. The ambient temperature is 39 degrees, so I think the fans were turning too slow. But mileage came back up noticeably 2-3 MPG. Pyro showed temps backup everywhere, radiator, cooler ETC. Dash gauge went up normal also.

Hooked lines back up, everything is normal except low trans temp.Picture of Blue Fire, was driving home from shop. The Pyrometer is when I got home. That's the trans cooler and radiator temps.

Love my Blue Fire
Chris

190 degree wax thermo valves are out of stock everywhere, and $409.00+ ride!

Re: Allison running too cold

Reply #12 – April 12, 2022, 10:08:09 pm

Okay so the wax valve was failed and running fans too hi. This makes perfect sense. Radiator, trans was max cooled. Glad its resolved. Yes MPG will be better.👍👍 I like being able to run the fans at max for shutdown, the added solenoid is a home run for me. Downside to getting it fixed is reduced retarder capacity.

Re: Allison running too cold

Reply #13 – May 04, 2022, 08:58:50 pm

UPDATE

Thanks Doug W. ....Dsd.... Scott for input. Part's been installed about a week, but couldn't drive the coach, had a OPOC (other pile of crap) in the way fixing the slides.

So the fan control was stuck on high like Doug said. Installed new Controller, it's the English one everyone raves about. Got it from NW trailer Supply. Can't say enough good about them, have had great experiences with them over the years. They are also the HWH parts people to go to. Part was on backorder, they told me to order it, they were getting some in next week. They did as they said, and sent it right out at the end of the following week.$425.00 with the ride.No tax in Oregon.

I had fun with my BFF Bruce Bean, he wanted me to drain everything..Bla Bla Bla. I had the new one ready, wrapped a towel around the fitting, bam, maybe a thimble of fluid came out.Tid Bit, don't leave cap open.

Here are the parts, and a picture of my Blue Fire (highly recommended). Fuel mileage definitely went up.I also listed the fittings sizes, if you want to cap off, or by pass.

As mentioned to test, lines hooked together, fans stay low speed. Capped, they lock to high speed. My understanding is, the defalt is high speed if control fails. But that might be on electronic control.Note that with the side radiator, if the fans are in low speed, as the air passes by (even at low MPH) you may overheat, but it's slow to do that.

I also chose to stay with 190 degree (factory) rather then 200 degrees. I tow a race car, and want the temps to be low when I approach hills, not later. Just my humble opinion.Our mileage is killer, so not worried about that.
Cheers

Link to Northwest trailer supply. Click here:
Northwest RV Supply

Re: Allison running too cold

Reply #14 – May 04, 2022, 10:21:05 pm

Nice write up 👍👍

Re: Allison running too cold

Reply #15 – May 04, 2022, 10:34:04 pm

Quote from: gracerace – May 04, 2022, 08:58:50 pm

UPDATE

Thanks Doug W. ....Dsd.... Scott for input. Part's been installed about a week, but couldn't drive the coach, had a OPOC (other pile of crap) in the way fixing the slides.

So the fan control was stuck on high like Doug said. Installed new Controller, it's the English one everyone raves about. Got it from NW trailer Supply. Can't say enough good about them, have had great experiences with them over the years. They are also the HWH parts people to go to. Part was on backorder, they told me to order it, they were getting some in next week. They did as they said, and sent it right out at the end of the following week.$425.00 with the ride.No tax in Oregon.

I had fun with my BFF Bruce Bean, he wanted me to drain everything..Bla Bla Bla. I had the new one ready, wrapped a towel around the fitting, bam, maybe a thimble of fluid came out.Tid Bit, don't leave cap open.

Here are the parts, and a picture of my Blue Fire (highly recommended). Fuel mileage definitely went up.I also listed the fittings sizes, if you want to cap off, or by pass.

As mentioned to test, lines hooked together, fans stay low speed. Capped, they lock to high speed. My understanding is, the defalt is high speed if control fails. But that might be on electronic control.Note that with the side radiator, if the fans are in low speed, as the air passes by (even at low MPH) you may overheat, but it's slow to do that.

I also chose to stay with 190 degree (factory) rather then 200 degrees. I tow a race car, and want the temps to be low when I approach hills, not later. Just my humble opinion.Our mileage is killer, so not worried about that.
Cheers

Link to Northwest trailer supply. Click here:
Northwest RV Supply

Chris.....could you share the Bluefire dash layout.....I have one
Thx

Re: Allison running too cold

Reply #16 – May 05, 2022, 10:31:57 am

Quote from: Hans&Marjet – May 04, 2022, 10:34:04 pm

Chris.....could you share the Bluefire dash layout.....I have one
Thx

I made it myself. Wanted something simple.I believe it is in the list of their dashes, as I posted it on their web..
PM your email, I will send it to you.
I love this company, constant upgrades, works with Apple, or Microsoft.
Cheers

Re: Allison running too cold

Reply #17 – May 05, 2022, 10:34:20 am

I was told they are not NTP fittings. I just matched them with a graph I have. They matched with that. I will let you all decide.
Cheers
Chris

Re: Allison running too cold

Reply #18 – May 05, 2022, 10:35:37 am

Quote from: bbeane – May 04, 2022, 10:21:05 pm

Nice write up 👍👍

Thanks Brother
I just put the info out to help others in the future.
Talk to you
Chris

Re: Allison running too cold

Reply #19 – May 05, 2022, 04:49:33 pm

Quote from: gracerace – May 05, 2022, 10:31:57 am

I made it myself. Wanted something simple.I believe it is in the list of their dashes, as I posted it on their web..
PM your email, I will send it to you.
I love this company, constant upgrades, works with Apple, or Microsoft.
Cheers

Got it !

It's loaded on my Ipad Mini......going to add Oil Pressure data

Thx Chris

Re: Allison running too cold

Reply #20 – May 07, 2022, 11:15:00 pm

Quote from: Hans&Marjet – May 05, 2022, 04:49:33 pm

Got it !

It's loaded on my Ipad Mini......going to add Oil Pressure data

Thx Chris

Good deal, you could probably dump the "cruise on/off", and put it there. I wish my Cat had oil pressure in the harness. No biggie, enjoy
Cheers
Chris

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