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Over heating transmission


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On my 99 executive, M-11 cummins, allison 4060 transmission.  On a recent trip thru Oregon I was noticing my transmission temp on my recently added scan guage. Accesind a long 6-7 mile 6% grade over the Siskiyou mountains, my trans temp went to about 195, 4th gear, outside air temp 50 degrees.  Over the summit and down the grade into Ashland Oregon, Jake brake on low, 4th gear, 50 mph, 10 mile grade @  6%, my transmission went up to 238 degrees.  Normal temp at level cruise is about 170. Dash guage also read about 220, although they are notoriously un-reliable. Transmission is 'pre-selected' to try for 3rd gear when applying Jake brake. Talked to an Allison tech yesterday, who was 'not sure', he thought transmission should not produce heat when 'locked up' going downhill with Jake brake on.  What am I seeing ? No warning lights on dash, no codes produced on transmission. Trans fluid level is good.

Edited by fiat124man
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1 hour ago, fiat124man said:

 

On my 99 executive, M-11 cummins, allison 4060 transmission.  On a recent trip thru Oregon I was noticing my transmission temp on my recently added scan guage. Accesind a long 6-7 mile 6% grade over the Siskiyou mountains, my trans temp went to about 195, 4th gear, outside air temp 50 degrees.  Over the summit and down the grade into Ashland Oregon, Jake brake on low, 4th gear, 50 mph, 10 mile grade @  6%, my transmission went up to 238 degrees.  Normal temp at level cruise is about 170. Dash guage also read about 220, although they are notoriously un-reliable. Transmission is 'pre-selected' to try for 3rd gear when applying Jake brake. Talked to an Allison tech yesterday, who was 'not sure', he thought transmission should not produce heat when 'locked up' going downhill with Jake brake on.  What am I seeing ? No warning lights on dash, no codes produced on transmission. Trans fluid level is good.

Wow! Same summit and same issue. Had my radiator thoroughly cleaned and issue went away. Now I do it regularly myself with simple green non corrosive to aluminum. 

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Transmission fluid O.K., Side radiator.   will clean and inspect.  BUT, Allisons are NOT supposed to produce heat in LOCKUP ! New to me also. Allison tech said MAYBE torque convertor was failing ? Lockup IS working, Jake brake does slow it down bigtime.  Rig is right at 38k lbs with toad. Maybe my fan is not speeding up when hot ? Had it checked/serviced by Source engineering in Oregon last Summer.  Supposed to be the best.    🙁

 

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Interesting.  The engine temp normally runs 175 at cruise, was up to 190 going uphill, but dropped some going down the grade.  Hmmmm.

Also, the shift pad shows that when engaging the Jake brake, the target gear is 3.  I think it only got to 4, but not absolutely positive. However, 3rd gear is also supposed to be lockup. (I think) Former owner was from Texas, so west coast grades were not something he encountered.     😟

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