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New LLY Owner

ALL 2500/3500 trucks with a DURAMAX got 3.73 gears, even today. Unless somebody changed them out, you have 3.73's. For a 5 speed, I would hesitate to push 750 torque through a stock 5 speed if your towing. Empty you will be fine, but towing you will limp it if you romp on it. LLY's wake up nicely with a good custom tune. As for an intake, whatever way you go go with a new turbo mouthpiece. The stock LLY mouthpiece is a restrictive bottleneck to put it mildly. An LBZ mouthpiece is a good option, but not a direct drop in. S&B and AFE both make drop in mouthpieces for the LLY.
 
Yea I was looking at those mouthpieces yesterday. I don't tow much, every now and then I'll have a pallet of tile in the bed.
 
tanman_2006 said:
4.10's are better off the line and towing.
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It would be more or less a waste with the DURAMAX unless your towing REALLY HEAVY ALOT! For most towing 3.73's are more than adequite, hence why GM used only 3.73's from the factory. So unless somebody did a rearend swap with one from a 6.0L, or a gear swap, it most likely has 3.73's. I know I have 3.42's, but I put them in it. SOmetimes I wish I had 3.73's, but for the most part I am rather happy with the lower gears.
 
I wish I had 4.10's. Actually have a dually axle from a gasser w/ 4.10's, I will get new gears or whole front w/ 4.10's some day and convert to a CCSB dually w/ 4.10's for pulling.
 
Mikedizzle said:
Yea mine has 4.10's in it from the last owner. He had a 5th wheel camper he pulled with it. He was the original owner
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So he paid a shop to have them put in then. Otherwise it has 3.73's. Open the glovebox and bet it has GT4 in the RPO list.
 
Idk, he had a 5th wheel in it before. He hauled his camper around the country, that's all he used the truck for. He was like 70 years old
 
The Allison's don't really like the 4.10's that much, unless he had much bigger tires on the truck. Otherwise, the 3.73's are more than sufficient.
 
Never heard that Allisons dont like 4.10's. I'd like to hear more on that, I always heard lower gears relieve stress on the trans.

I run 33's loaded heavy and run in 4th, I figured 4.10's would allow me to alteast use 5th w/ light loads.
 
It messes with the shifting. That is why they come with 3.73's. If the truck ran better with 4.10's then it would have came with them.
 
I always assumed it was MPG/emission reasons. Mine seems to want to pull better at higher (~2400) rpms, wouldnt tuning help that issue?
 
GM stuck with 3.73's because it better matches the engines power curve to road speed. 4.10's causes the engine to go outside of it's peak power areas in average road speeds. MPG had nothing to do with it since vehicles in this weight class until recently didn't have to meet any MPG requirements. And emissions testing for trucks is simply based on output, not output over a certain distance. I know I talked to somebody else who had 4.10's, and he hated them. Said it was flying through the gears to quick, and ran out of power to soon.
 
If anything it wants lower gears for freeway driving and this is why the 6 speed came out with double overdrive. But for get up and go in town with our hot weather 4.10's are fun.

Towing or not you want to swap the mouthpiece as it gets better MPG and better power unloaded. Then you can work on a real cold air intake like cutting the foil 'snow' plug from the fender and sealing the intake to it although the engine wants more air than the fender holes provide. (Can we say sawsall?) The last thing an LLY wants is to try and cool 220 degree air that gets heated up more by the turbo.
 
Sometimes I wish I had 4.10's just to keep from gear hunting on back roads. I dont hit 6th until ~60mph and 5th at 50-55, I cruise 50-55 alot on rolling hills and my truck hovers 50-60 and shifts between 3 different gears (PITA IMO). I dont spend much time over 62mph/1400-1500rpm.
 
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