Help with gears

Going to 3.42 rears is going backwards. You're going to get less torque to the wheels. Meaning you'll need to drop another gear to make it pull the same as now.

You want up the hill faster, gotta make more ponies. Rear end ratio will make no difference in how fast you make it up a hill.

 

If you need more power someone will point you in the right direction for a good tune. Read through these threads

Borg Warner 171702 or 177287 on a 14L Detroit???

Diesel Doctor.....OMFG!!!

 

Not many series 60 performed well with a dpf . Those years were very bad all around it seemed.. Low power Low mpg and in the shop often .

 

I used to run a 12.7 Detroit with a 10 speed and 435 hp and the slowest I ever went uphill,at 80K was 28Mph.

you have a power issue, and are not making 480 HP. Find that issue, and you’ll fix your problem.

it may well be that DPF, not my area of expertise.

 

Has your fuel mileage tanked too, even on flat land?

 

Hand, reread these two posts.

3.42 gears would be a higher gear ratio than 3.70s. How so? Well, 3.42 is actually an abbreviation of 3.42:1. I may be wrong, but the way it would work would be that your driveshaft would turn 3.42 revolutions for every 1 revolution that the tires make. It's actually a leverage thing. The more revolutions that the driveshaft makes compared to the tires, the easier time the less the engine has to work to get the load up the hill, but the slower the truck will be on top end AND the higher the rpm the engine runs when cruising. For general freight loads, 80000lbs and under, you don't want to go to a gear lower than your 3.73. So, what's wrong?

Like @Accidental Trucker said, you have a power issue. If the engine is idling smoothly but can't pull for crap, that's a sign of breathing issues. It would be like you breathing through a straw. If you're sitting relaxed, it's a bit of a strain, but no major issues. However, if you had to fight someone while breathing through a straw, you're toast.You said that you have a new turbo. Can you hear the turbo whirring? Yes? Good. So either you have a restriction on the exhaust side or a boost leak. Boost leaks come from either the boost hoses or perhaps a small crack in the air to air intercooler. I don't know much about that DPF stuff either, so I can't help you. A boost leak test, however, is a simple process.

Luck in battle.

 

sorry.

 

The truck has Coronavirus. Seek help immediately.

Was the truck pulling the hills better before the turbo was replaced? If yes, I'd start with that.

 

Whens the last time it had a fuel filter? Check any rubber lines on the suction side of the pump for age. Theyre multilayered and often internally delaminate. The hose jacket can look good but the liner can unbond from the jacket and pinch shut from suction. Or theyre often cracked and sucking air. The egt and boost pressure will drop and the exhaust will get a rumbly note when fuel supply is insufficient.

Theres probably no need to change rearend gears for hill climbs. You have a shifter, move that to suit. Your rearend gear only needs changed if your top gear cruise rpm and speed arent suitable.. Or maybe if you cant take off uphill in low hole fully loaded. Bottom gear and top gear are where you look to evaluate ring and pinion ratio. Everything between is just shifting the trans. If it wont climb the hill fast enough for you thats a HP issue. Or a patience issue. Truckin in the hills takes as long as it takes.

One should decide not to let the rpms fall BELOW say 1500 or so on a hard pull. And not let the EGT climb over say 900+/- a bit. The rest is variable. What gear and what speed DONT MATTER. What rpm and what EGT do. For boost you want all you can get. It is air conditioning for the combustion chamber. Pour on the fuel and drop some boost out of leaky pipes... Youll be pegging high EGTs. Compressed air COOLS the exhaust gas. Fuel without enough compressed air raises it.

High rpm provides more fan flow, more water and oil volume and more hands to do the work per unit time. Lugging up the hill beats the oil out of the bearing clearance space and kills engines. Its called oil wedge pressure. Much much better to over rev at light throttle and ease on up at 19mph than to blast up it going 60 growling the whole way and boooom.. Head gasket lets 3000 psi or so into the water jacket which explodes the radiator because it cant vent out the 3/16" vent cap fast enough. BTDT. Broken trucks are slower than 19mph and cost more to do it.

 

I'm having a little trouble with this statement but the rest is SPOT ON.
IMO of course.