Horsepower gains?

[nvsteve]

99 Yukon denali all stock. How much horsepower could I expect to get with headers duals and cold air intake? Not real happy with towing power 4000 lb.. boat on grades. Recommendations appreciated thanks

 

[liquify33]

For that much $ maybe a tune and transmission kit for towing specifically? Does it hunt gears or just no pull at 2500-3000 rpm?

 

[swathdiver]

What is the axle ratio?

 

[nvsteve]

3.73 posi gear. Yes it hunts gears. No pull below 3000 rpm on long grades. Shifts down to 2nd gear which winds rpms to around 4500 which makes me nervous. Non towing performance is ok for such a heavy vehicle. Engine seems to be good, no oil consumption. Transmission was rebuilt about 5k miles ago and shifts fine. I like the car otherwise but wondering whether I should sell it and get something newer with bigger engine.

 

[swathdiver]

3.73 posi gear. Yes it hunts gears. No pull below 3000 rpm on long grades. Shifts down to 2nd gear which winds rpms to around 4500 which makes me nervous. Non towing performance is ok for such a heavy vehicle. Engine seems to be good, no oil consumption. Transmission was rebuilt about 5k miles ago and shifts fine. I like the car otherwise but wondering whether I should sell it and get something newer with bigger engine.

Ok, what size tires are you running? What motor is in there, the L31 SBC? Ideally, you want the engine to be at the peak of its powerband, torque, when towing. The L31s peak came in at 2,800 RPMs. Of course, too much gear then takes away from daily driving until you add gears to the transmission and or raise the torque band of the engine.

 

[nvsteve]

265x70x16 tires . 5.7 motor no mods.

 

[Mechanic421]

I am pulling up some good grades. I never tow in od. And when I hear it unlock the converter I let off some and let it slow some before it kicks down to second. I don’t like the 4500 pulls either.

 

[swathdiver]

265x70x16 tires . 5.7 motor no mods.

Ok, I think the trans in those is a 4L60 and if so, the truck will be turning about 2800 RPMs @ 69-70 MPH in 3rd gear.

Slow down or get more torque. Shorty Headers might add about 10-15 ftlbs of torque, a camshaft upgrade maybe 15 ftlbs more. Might first do 4.10s which would cost less if it's RWD than the other two. Oh, almost forgot, who does tunes on those older trucks? That's what I would do FIRST!

Finishing my thought on 4.10s: At 70 with them, you'd be turning about 3100 in 3rd or 2200 in 4th, not likely to drop into 2nd anymore which would be over 5100.

 

[OR VietVet]

Time for a Duramax diesel rig with the Allison Transmission. Absolutely the best towing rig I ever owned.

 

[nvsteve]

Yeah I know I had a 07 duramax but sold it when I sold my travel trailer. Thought the Yukon would be okay for towing the boat and didn't need a truck.