Best gears for towing on 37s and efans?

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reddot

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Hey guys. Now that im just starting to tow more then ususal I really need to upgrade my gears. Im running ProComp 37x12.5R17 Xtreme ATs. True size im pretty sure is closer to 36. But not sure what gears to go with for the best towing on the interstate? 4.10? 4.56 too much? It seems that most forums would rave about 4.56 but I talked to a dealer just to get an idea on their price but he suggested 4.10s for highway use. I have a 30ft enclosed car hauler 10k capacity and just a small open 10ft open single axle to tow motorcycles and ATVs. Any help would be great. Thanks.

Side note. I have the Flex-a-lite fan setup in my truck. I have no issues unloaded but the slightest load and the coolant temp goes up. I have the ATS dual CPS kit and the upper rad hose is pretty high and makes me wonder if I have an air bubble? What are normal towing temps? Pretty level grade(across North Dakota on I94).

Thanks for any possible help.
 

Graygoose

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well R/T's have 4.10's and 33" inch tires, I'd do 4.56's, your talking minimal RPM's difference at highway speeds between 4.10 and 4.56.
 

Redtruck-VA

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Being a diesel. I think tou might upgrade the cooling system then look at some engine upgrades. Gears are geat for our gas trucks, but I'm not sure it is the way to go for a diesel.
 
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yeah im going with 4.10 gears. Not much that can be done with the cooling system. Guess the issue is the efans are only good when the truck in unloaded. If I want to keep temps down when towing imma going to have to go back to the stock clutch fan. ****!
 

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I run 4.56 on my truck with 34.7 tires and it is about 2200 at 70mph. With 37's I think you would really like 4.56 gears. RPM's would be close to stock 3.92 I think. Towing is where 4.56 gears rock I don't have the constant downshifting the 3.55's allowed. I can tow in tow/haul and 5th gear all the time highway. Almost never downshifts even on hills.
Oh and normal temps for me are trans under 160 and coolant temp around 197 hottest I remember when towing.

$miley
 
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reddot

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trans does not seem to be too bad just the coolant temps that are getting out of hand. time for the clutch fan. At least when its time to tow the two chevys back to fargo.
 

Redtruck-VA

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Not sure why you are using electric fans. But if that is what you want to use I'm sure there are units that will work well. Off road I can understand wanting to turn off the fans if in deep water or if running in cold temperatures. But as a diesel performance mod I don't see an advantage. Maybe check on a diesel forum to see what is working for other diesel owners. Gas performance mods aren't the same for diesels.
 

Stangshcky12

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Electric fans free up a good bit of power on diesels when removing the pretty heavy duty clutch fan.
4.56 with 37s would be similar to a stock setup with 3.73s, if you weren't running a large tire I would never recommend 4.56 in a diesel

The fan definitely seems to be the culprit though, pulling 12k lbs with 3.73 and 35s I never really notice high coolant temps
 
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well the tire is closer to 36in in real life then 37. So a 36in tire with the 48RE 4.10 gears going 70 I should be at 1875rpm. That seems good to me so I think im going to stick with 4.10 gears and getting the clutch fan in before the first two. Gawd im so disappointed in these efans....

And yeah the efans are amazing except when your towing. The clutch fan is heavy and I gained almost two MPG from just that mod. So I would not say efans and a diesel is a pointless gas only mod.
 
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