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Discussion Starter · #1 ·
hey all new to this page and the diesel world…got an 05 gmc sierra 2500 6.6
normal running temp seems to be around 180ish but lately when I'm on highway and pushing it between 70-80 heats up real quick to 210 now i know thats not high but I've also heard diesels should get that hot as soon as i drop speed a bit it cools right back down been to normal temp.

Also yesterday cruising around 40mph and all of the sudden thing makes this loud humming sort of sound and seems to be not shifting properly let off the gas for a few seconds and returned to normal? transmission? turbo? any answer would help like i said I'm new to this so bare with me. thanks
 

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The noise is the cooling fan engaged-! Normal temp will show almost 210 with 191/195 degree thermostats [GM standard]. The GM temp gauge is not accurate-!
 

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05, so this is a LLY? Theres tons of reading about these trucks & their overheating issues, not saying yours is. Not sure whats done to your truck but if it is a LLY the factory turbo mouthpiece needs to be replaced. The factory one is way too restrictive. Probably change out your coolant & clean the cooling stack (radiator, intercooler) to get rid of any debris. Just throwing ideas out there. How many miles on the truck?
 

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LBZ mouthpiece needs to be put on the truck ASAP!!!! Like you need to do it yesterday. After your replace the mouthpiece do as Robby05 says and fully flush your coolant system and continue to flush the coolant system every 50,000 miles and head gasket issues can be avoided. The LLY's were notorious for this but it's easily avoidable.
 

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Discussion Starter · #5 ·
yes i did and have been reading about the lly and the common problems with it…stock 129,000 bought it about 3 months ago also know about the turbo was looking into upgrading that. my main concern now is not sure if the tranny is slipping with the problem i had yesterday it did seem to run smoothly after that and haven't driven it yet since. i have resources to go to but i figured id ask around on here and see what you guys think.
 

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Hard to say on the trans without more info. When was the last time the fuel filter was changed? Sometime a plugged fuel filter will cause the trans to shift strange
 

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Discussion Starter · #7 ·
Just took truck out for a drive think my problem is the turbo pickup doesn't seem to be there at all
 

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Just took truck out for a drive think my problem is the turbo pickup doesn't seem to be there at all
How old is the fuel filter-?? Diesels need fuel to operate properly. This part of your problem-!!
 

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What exactly is your truck doing? Need more details and maybe we can help.
 
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