Allison Heat Issue

[HavasuRed]

I have a 2005 Allure with a Cat C9 hooked up to a Allison 6 speed. Everything works well and engine temps are good. Problem that I have just discovered is that the trans temp gauge climbs very high when I am stopped and in gear. As soon as I move, it starts to come down. If I take it out of gear when I am at a stop, it will not overheat. If I come into a traffic jam where I have to go slow, it climbs, and of course, if the traffic is moving, I can't take it out of gear so it climbs and I sweat hoping the traffic will start moving and the temp will go down. Anyone have an idea as to what is going on?

[Skip426]

Allison says 5mins MAX for idle in gear to prevent over heating.
Also , for driving in slow traffic to select the highest gear you expect to achieve for the speed , 3rd for 30 , 4th for 40 to stop excessive shifting and the higher RPM keeps the fluid moving and cooling faster.
If traffic is crawling use first.
From my manual , trans fluid is considered overheated when the sump temp exceeds 250 , I believe this is an ATF temp , transynd is higher . Your coach should have Transynd. I've seen the temp spec, here in the forums I'll see if I can find it.
Looks like Transynd gives another 30 degrees over regular ATF.
But my old manual lists an Trans ECU , shift inhibit feature at 262.
If you don't have a complete operators manual for your trans , they are a free download from the Allison web page.
http://www.allisontransmission.com

Also on the page under " Related Benefits " download " Allison Electronic Controls Package" pdf file , for all the info on codes and retrieving them for WTEC III and IV systems.

[dons2346]

What do you consider "very high"? Mine runs right at 195 and will climb when in slow traffic. I have never seen it over 220.

What you are experiencing is normal from what I have read here and on other forums

[Steve Ownby]

Originally Posted by HavasuRed

I have a 2005 Allure with a Cat C9 hooked up to a Allison 6 speed. Everything works well and engine temps are good. Problem that I have just discovered is that the trans temp gauge climbs very high when I am stopped and in gear. As soon as I move, it starts to come down. If I take it out of gear when I am at a stop, it will not overheat. If I come into a traffic jam where I have to go slow, it climbs, and of course, if the traffic is moving, I can't take it out of gear so it climbs and I sweat hoping the traffic will start moving and the temp will go down. Anyone have an idea as to what is going on?

When the torque converter is unlocked in 1st or 2nd gear the temp will rise as the torque converter slippage will cause the fluid to heat. If stopped in traffic shift to neutral. If stuck in very slow traffic try to lag back and then get enough speed to get the transmission to lock up. It should lock toward to top of 2nd gear. Then it will stay locked to a lower speed if you don't apply too much throttle.

[HavasuRed]

Thanks for the input. I haven't had this coach for very long so i don't have too much of a track record, only about 2500 miles. It has fairly new transynd. The trans runs at between 210 and 230 pretty regularly even when climbing hills. I have not thought that to be too much of an issue since that is only a little past the mid range point on the gauge. The rig has a brand new radiator, so engine temps don't vary much from mid-range on gauge. I have never seen how high the trans will get if I leave it in gear at a stop, but when I get off of the highway after traveling and the engine and trans are pretty heat soaked from travel, the trans temp starts to climb up beyond 240 real fast until I put it in neutral. It kinda sounds like this behavior might be fairly normal and mine seems to be a bit more sensitive than most. Which is too be expected because so far everything on this coach is more sensitive than most!!!

[smlranger]

Perhaps I have not been paying close attention to it, but my tranny temps (per the Silverleaf display) have never approached 200F. I believe on our most recent trip, the most was 185. However, we've not pulled any real tough grades yet or been stuck in traffic with coach idling in gear.

[Steve Ownby]

Originally Posted by smlranger

Perhaps I have not been paying close attention to it, but my tranny temps (per the Silverleaf display) have never approached 200F. I believe on our most recent trip, the most was 185. However, we've not pulled any real tough grades yet or been stuck in traffic with coach idling in gear.

Typically idling in gear will heat it up the most. Pulling a long grade with heat up the engine coolant and that heats up the transmission fluid some because most transmission coolers are internal to the radiator.

[terry735001]

The rig has a brand new radiator hummm

i am sure your transmission coolers is not in the radiator

i think the Cat C9 transmission coolers is like more out side off the radiator

if they installed a new radiator over trash in the system then your transmission cooler could have trash in the small holes in it but if the cat is not running hot then i think your ok


soon you well be a pro at this in no time soon

[Skip426]

My coach has only an trans fluid to coolant , oil cooler, mounted in the lower rad hose, and attached to the frame rail, no oil to air cooler like a pick up , so the trans runs a little cooler than the engine because it gets the benefit of the coolant being through the rad before the engine does.
Probably not the perfect set up, but it seems to work just fine.

HavasuRed; I listed fluid temps for a sensor in the transmission sump, because that's where mine is. If by any chance your sensor is in the fluid line from the trans to the cooler, or your trans is equipped with a hydraulic retarder. The chart I have lists higher max temps allowed.

[dons2346]

The gauge and the sender unit can have 10% error each which could give temps in the range the OP states.

I am surprised that CC didn't install Silverleaf in the coach

[HavasuRed]

I really wished that it did have Silverleaf, but it doesn't, so I'm stuck with analog gauges.

[Mr_D]

Originally Posted by Steve Ownby

If stuck in very slow traffic try to lag back and then get enough speed to get the transmission to lock up.

Try leaving extra space, like 4 car lengths and you'll have 5 cars try and stuff themselves into it!
Really bad in the ice and snow! Leave a safe stopping distance and get continually cut off.
With TranSynd and good cooling you should never get an overheat. Today in 60° weather at 62 mph I saw 147° trans temp. However, in heavy traffic it does go somewhat higher, even so I have a hard time getting it hot enough to use the onboard level sensor.

[HicksRA]

Have you checked your fluid level?
If it is overfilled, that can cause overheating.

[HavasuRed]

I will check that, I recently had that wet PTO installed and they topped off the Transynd that was lost when they did the work.