Longtime Duramax owner finally registered

kken12

New member
May 27, 2020
17
3
3
Temecula, CA
Hey all, I’ve read so much information from all your posts I figured it was time to sign up. Located in SoCal, I have an lly that I’ve owned since ‘08. About 180,000 miles and I don’t plan on getting rid of her anytime soon. I’ve done the lbz mp mod, cold air intake, exhaust, banks economind, and it’s got a 6” lift on 35’s along with other misc. upgrades. Tows my toyhauler (12k lbs) all winter and occasional camping trips in the summer. I replaced the front end and shocks last summer. My main issues now are with the tranny and the engine running hot. Glad I found this forum, so far it’s been a wealth of knowledge. Thanks guys
 
  • Like
Reactions: rmallen30

darkness

Active member
Jul 15, 2009
959
69
28
45
vegas
Welcome. Does it only overheat climbing? Might be time for a fan clutch and a cooling stack cleansing.
 

kken12

New member
May 27, 2020
17
3
3
Temecula, CA
Trans isn’t overheating, it’s the engine that runs hot. Reading some threads though makes it sound like 235 isn’t bad. I completely back off when the temp gets there and that with me already babying her because of the trans issues.

Definitely going to look into those suggestions. Thanks fellas
 

Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
2,887
279
83
Neenah, Wisconsin
Like said above, it wouldn't be a bad idea to change the cooling fan clutch (Hayden or Kennedy), clean the cooling stack, and maybe put some new thermostats in. What kind of RPM were you at?
 

kken12

New member
May 27, 2020
17
3
3
Temecula, CA
RPMs were around 2k, I don’t get on it due to limped trans a few times in the past. Planning on getting both issues addressed this summer.

I first suspected the fan clutch because the fan wasn’t kicking on at around 217 where it used to. It wasn’t kicking on till almost 230. Just randomly too. I’ve read a bunch about that being due to the outside temp or temp coming through radiator? But as of now the plan is to clean the cooling stack, new thermos, and new fan clutch. Big ticket item will be the tranny.
 

Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
2,887
279
83
Neenah, Wisconsin
RPMs were around 2k, I don’t get on it due to limped trans a few times in the past. Planning on getting both issues addressed this summer.

I first suspected the fan clutch because the fan wasn’t kicking on at around 217 where it used to. It wasn’t kicking on till almost 230. Just randomly too. I’ve read a bunch about that being due to the outside temp or temp coming through radiator? But as of now the plan is to clean the cooling stack, new thermos, and new fan clutch. Big ticket item will be the tranny.

If your fan isn't kicking on until almost 230 then that is a major red flag. My LB7 with new radiator/Kennedy fan clutch/mishimoto thermostats ran around 195-200f the entire 2200mi round trip to Denver Colorado and back in 85-95f ambient temps with the AC on full blast.
 
  • Like
Reactions: RMJ_LB7

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
18,931
1,311
113
Phoenix Az
stock fan wont come on till 210-220. running the kennedy clutch, that drops down to 190ish for it to come on. Hayden 2886 is off a kodiak and has a deeper off set into the fan shroud. it works in a light duty truck but insetting the fan into the shroud more hurts cfm some. There has been good ones and bad ones of the hayden as well. i really like the kennedy clutch. very well built piece for the cost.
 

kken12

New member
May 27, 2020
17
3
3
Temecula, CA
I’ll take a look at that Kennedy one. I had read somewhere it was built by Hayden but with some slight differences. Coming on at 190 I would think that fan would be running constantly? Either way ,I’d like the truck to be running cooler when I’m hitting those grades with my toy hauler loaded.

Sounds like I’ve got a good starting point to address my running hot issues. I already know what I’ll be doing with the trans haha
 

kken12

New member
May 27, 2020
17
3
3
Temecula, CA
Just wanted to follow up with how the truck is doing after the suggestions. I hate when I research an issue on a forum where I’m reading the thread and at the end it just stops and the person didn’t follow up with if the suggestions fixed the problem or not.
Added the Kennedy fan clutch, replaced the thermostats, and cleaned out the cooling stacks. I’ve towed heavy (just under 12k) a few times now. Each time up to Johnson valley (king of the hammers location) which you so cal guys know they have some decent grades (6-8%). Truck ran so much cooler. Granted it isn’t hot out but it did run noticeably cooler and when the fan would kick on my ect dropped very quickly. Thanks to all of you who pointed me in the right direction. The fan still kicks in a little later than I anticipated but it does not let the truck get above 225 so far. And that’s only been the steepest/longest grades. Like I said, when the fan kicked out those temps dropped quick. The thing I didn’t get around too was the transmission. Thanks again for the help. And if anyone reads this thread, those suggestion will work.
 
  • Like
Reactions: RMJ_LB7

RMJ_LB7

Member
Feb 25, 2020
201
15
18
25
California
Two of the biggest upgrades I have seen people do for towing is the Dmax store transmission cooler and also the banks intercooler setup. I had a guy local to me that was pulling a huge boat up over the passes and after he installed the banks intercooler it ran so much cooler.
 
  • Like
Reactions: Bdsankey

kken12

New member
May 27, 2020
17
3
3
Temecula, CA
Trans temps haven’t been an issue. I’ll look into the intercooler. I’ve done the LLY tricks to help it not run as hot as they are known for. I’m gonna have to have the trans rebuilt at some point.