Transmission temperature??

[Doomsday]

What temperature should the Allison 5 speeds in these trucks typically run at?? Either my gauge is wrong or 250-275 is normal.
I bought the truck not too long ago and did a full maintenance job on it. Cooling system was very corroded from the previous owner running straight water. Trans cooler had a bunch of sediment, was pretty clogged up and I figured that's why trans was running hot. Cleaned out cooling system, all new hoses and fresh distilled water and coolant. Changed trans fluid and filters but getting it out on freeway today it was again running in the 250-275 range. Isn't that too hot or is that normal?? If its too hot, any ideas what is causing it??

 

[wheelspinner]

Normal is 120-220 deg F. Deadline at 300.

 

[rrrr]

Mine normally runs about 170 when all warmed up. Your cooling system probably still has some garbage in it. I run a coolant filter on mine and after 2000 miles and 3 filter changes its finally starting to look good. Check the deuce forum for the setup. Have you change your tranny over to Dextron 3 ? That might help as well. Also check the external tranny filter on the right side of the motor, by the heater fan, and make sure its not clogged as well.

 

[quickfarms]

Did you have the cooling system rodded out or did you just flush it yourself?

 

[Doomsday]

Jeez, your temps are at 180ish?!? Wish mine ran like that.....
Like i stated, I flushed the cooler and coolant system completely out, used simple green and super hot water. Changed both the pan filter and the spin on. Added fresh fluid which is Amsoil universal ATF, good stuff, basically Amsoil Dex 3.......coolant system seems to flow well as I can feel it thru the hoses. Engine runs normal 180-190. Weird thing too is the trans gets up to 200 just sitting there idling while engine warms up! Could the gauge be wrong or is something inside the trans wrong creating a bunch of heat?? When I originally drained the fluid after I bought it, the fluid looked fine, didn't smell burned or had any debris in it. Pan was clean too......

 

[tractors0130]

Could be a bad or wrong temp. sender on the transmission. Use a hand held temperature gun and check the trans. temp. in several locations, if you can hold your hand on the transmission pan, you know it's not running 250 deg.

 

[Doomsday]

Could be a bad or wrong temp. sender on the transmission. Use a hand held temperature gun and check the trans. temp. in several locations, if you can hold your hand on the transmission pan, you know it's not running 250 deg.

That's what I was thinkin, cuz I can hold my hand on the pan, the cooler and the filter and it for certain didn't feel like 250 cuz that is some hot fluid! I don't have a hand held temp gun but I got a friend who does, guess I will see what that tells me.....thanks for the help guys, I will post back my findings tomorrow.....

 

[juanprado]

Water Temp and transmission sending units are the same part number for m939 nhc250; not sure on A2 8.3L. Redneck test is to reverse them and check your readings again.

 

[rrrr]

Do the touch test. Then pull the instrument panel out a little so you can get at the gauge. Make sure the connections are clean and put silicone grease on the contacts. Do the same with the sending unit. I recently replaced my coolant gauge and sending unit because I was getting odd indications. No issues since.

 

[AMGeneral]

I know you have most likely checked,but make sure the trans is not overfilled,I know on my M915A1 even just 2 quarts overfilled made a 20 to 30 degree difference in the trans temp after I switched it over to Dextron 3.

 

[Doomsday]

Got an update.....I did a fluid level check and it was a bit overfilled. I filled it when it was cold and obviously level went up when it got hot so I took some out down to proper fill level. Grabbed the infrared temperature gun and went for spin. Temps on the gauge were in the 275-300 range when I stopped for a check. The gun was reporting a temp of 171 in various spots on the pan. 180ish aound the tailhousing of the transmission and back around 175ish in areas up by the bellhousing. Forgot to put it on the spin on filter up by the cooler. Will get that temp next time.
So from those readings I would think its running in the 200 range but not 275+ like the gauge is saying. When I drained some fluid out while it was hot to get the correct fill level, got plenty on my fingers and it was hot but not so unbearable that I burned myself.
Seems to shift a little weird from second to third gear but overall it doesn't feel like anything is slipping. Guess I will continue to monitor it.......

 

[ZZ4x4]

Hey Doomsday,
I had the exact same problem with the trans reading 275-300F and finally solved it this weekend!
Per the TM, I went through a lot of maintenance but could have found the issue in about 10 seconds if I looked at it another way.

What I did first according to the TM was to verify there were no restrictions in the trans oil cooling system by replacing the spin-on and pan oil filters. I also did flow and pressure checks through the cooler assembly and flushed the oil twice with trans fluid. Still had the problem.

However ,the engine oil temp sender on the block is the same model sender as the trans temp. Even though the gauges have different ranges, the temperature should read the same on either gauge assuming you are less than 240F. What I finally did was to bring the engine and trans to operating temperature and then shut off the truck. Then I reached up behind the gauge panel and unplugged the right terminal from the trans and engine gauges and swapped them. The left terminals are common so could remain plugged in. The engine temp (when read on the engine temp gauge) had said 180F but sure enough after being swapped to the trans temp gauge said 280F. The trans temp when read on the engine gauge said 170 instead of 250+. So it was the gauge that was the failure ! I replaced the gauge and now the trans temp reads around 170 max.

Hope it helps..
Jeff

 

[Hawkdriver]

That is good to know. I have the same exact problem. Transmission goes right to 270 while idling or driving. Sounds like I may need a gauge as well. Where did you get your gauge?

 

[ZZ4x4]

That is good to know. I have the same exact problem. Transmission goes right to 270 while idling or driving. Sounds like I may need a gauge as well. Where did you get your gauge?

http://www.eriksmilitarysurplus.com/tega10f11.html

I got mine here...