Switched to a 03 6.0 Yukon from 05 5.3 Tahoe, seems sluggish

[Dan Acosta]

Just bought a 03 2500 Yukon XL with the 6.0 and have sold my 05 5.3 Tahoe. The 5.3 had a BB tune, but was the basic 87/89 tune. It also had the factory electric fans. Both vehicles have the 3.73 gears. Today is the first day of driving the Yukon and it seems a little bit more sluggish than I had expected. I know it is heavier, since it is the XL, and the drive train is a bit heavier, I guess I was expecting more from the 6.0.

It also seems to have an almost exhaust leak from the drivers side. I cant spot any carbon, or cracks. Are the 6.0s know for this or faulty exhaust manifold castings? Perhaps it is just the sound they make through the exhaust pipe.

So as far as it being sluggish, is there something I should look for, or is that about right? I am on the lookout for the fans & wiring harness, and will have the tune done as soon as possible. I guess I was just looking for someone that had a similar experience, or could suggest some upgrades that actually make a difference.

 

[about20ninj45]

Your comparing a stocker to a tuned powerplant, not really apples to apples comparison. Weight play a factory and so does torque management. Trans tuning also helps that thing to move out of its way.

 

[bottomline2000]

More weight, drag from the clutch fan and compound that with the 4l80 heavy torque converter and different gearing, it is going to feel and possibly be slower than a tune 5.3 with efans. The 80e 1st is geared like 2nd gear of the 60e.

I have the 2500 drivetrain in my tahoe and 1st is a little noticeable, but I have a lighter high stall aftermarket converter, efans, full exhaust and am tuned so I know you will notice it.

My engine seems louder, but I think I have a cracked weld from a crap ass exhaust shop that needs to be fixed and it's aftermarket. Everything should be similar to a factory tahoe exhaust wise.

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[Dan Acosta]

I didnt think about the gear ratios being different in the trans. I was just thinking about the weight, and converter mass. Good point. It seems like it is taking off in second gear compared to the tahoe. So the fan really does make a difference? I guess I was just expecting more. Probably just got to get used to it. I didnt realize how tight the shifts were on the Tahoe BB tune, until I drove this.
I got this one for towing, so do you think the headers would really make a difference?

 

[bottomline2000]

I didnt think about the gear ratios being different in the trans. I was just thinking about the weight, and converter mass. Good point. It seems like it is taking off in second gear compared to the tahoe. So the fan really does make a difference? I guess I was just expecting more. Probably just got to get used to it. I didnt realize how tight the shifts were on the Tahoe BB tune, until I drove this.
I got this one for towing, so do you think the headers would really make a difference?

A tune with efans would wake it up. My tahoe felt sluggish and anemic before it was tune with the stock engine and trans. If it make u feel better i have 3.42 gears!! The problem with the 80e is first gear is lower and overdrive is taller so it feels sluggish taking off and final drive gear you turn higher rpms in O/D so its a trade off. Yes, that clutch fan felt like a parachute to me and really freed up some power when I did the conversion. Your 03 will operate them just like your 05 did. @ScottyBoy sells the factory harness on here and it's the way to go.

The headers will make a difference in the upper rpm range, not sure how much they help on the low end. I'm also running a cam so my engine breathes a lot better too.

I also wanted to mention Transgo has an HD repoprogramming kit for the 80e. It enables you to dual feed the forward clutches in the transmission which greatly increases it's holding power and you can tailor each shift of the transmission. It gets rid of the mushy shifts. I currently have no torque management in my tune so she can rip thru the gears with no delays. There are some tips to setting this up, but I did it all myself. If u do this mod don't drill your valvebody. Sonnax has a better option that won't ruin your transmission.

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[01FormulaTA]

The 2500 XL prob weighs roughly ~1000lbs more and the LQ4 6.0 doesn't make much more power than the 5.3, its gonna feel slower, that being said it is also a 15 year old vehicle and probably needs a tuneup, i.e. new air filter, new fuel filter, new spark plugs and wires, oil change, flush coolant, replace PCV valve, clean the throttle body and fuel injectors...pull the valve covers and see what it looks like....regarding the exhaust it shouldn't sound much different than your 5.3 did...does the exhaust leak sound like a ticking sound? it could possibly be a blown exhaust manifold gasket, if you do end up replacing it make sure you get an OEM replacement...part number 12617944

 

[Walkercraig01]

interesting , ive always wondered how they stacked up

 

[Dan Acosta]

The 2500 XL prob weighs roughly ~1000lbs more and the LQ4 6.0 doesn't make much more power than the 5.3, its gonna feel slower, that being said it is also a 15 year old vehicle and probably needs a tuneup, i.e. new air filter, new fuel filter, new spark plugs and wires, oil change, flush coolant, replace PCV valve, clean the throttle body and fuel injectors...pull the valve covers and see what it looks like....regarding the exhaust it shouldn't sound much different than your 5.3 did...does the exhaust leak sound like a ticking sound? it could possibly be a blown exhaust manifold gasket, if you do end up replacing it make sure you get an OEM replacement...part number 12617944

Interesting info about the exhaust manifold gasket. Sounds like there may be some history of this on these engines. Usually the factory manifold gaskets are pretty good. I just so happened to be searching (in limited light) and thought there could be a little black around at least 1 of the ports. I will probably have to clean it off and see if it reoccurs. If that is the case, is there also any issues with exhaust bolts? I had a 460 Ford in a class c rv, and about half the bolts broke off in the head - what a nightmare.

 

[Dan Acosta]

A tune with efans would wake it up. My tahoe felt sluggish and anemic before it was tune with the stock engine and trans. If it make u feel better i have 3.42 gears!! The problem with the 80e is first gear is lower and overdrive is taller so it feels sluggish taking off and final drive gear you turn higher rpms in O/D so its a trade off. Yes, that clutch fan felt like a parachute to me and really freed up some power when I did the conversion. Your 03 will operate them just like your 05 did. @ScottyBoy sells the factory harness on here and it's the way to go.

The headers will make a difference in the upper rpm range, not sure how much they help on the low end. I'm also running a cam so my engine breathes a lot better too.

I also wanted to mention Transgo has an HD repoprogramming kit for the 80e. It enables you to dual feed the forward clutches in the transmission which greatly increases it's holding power and you can tailor each shift of the transmission. It gets rid of the mushy shifts. I currently have no torque management in my tune so she can rip thru the gears with no delays. There are some tips to setting this up, but I did it all myself. If u do this mod don't drill your valvebody. Sonnax has a better option that won't ruin your transmission.

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Good to know the Trango site has some good products, I am not sure I want to get that involved. I will have Black Bear do what they can with the tune and go from there. Just got it so I have to $ manage the upgrades, but good to know the fan make a difference. I will be on the look-out. I have a feeling those are hot parts at the salvage yard.

 

[bottomline2000]

Good to know the Trango site has some good products, I am not sure I want to get that involved. I will have Black Bear do what they can with the tune and go from there. Just got it so I have to $ manage the upgrades, but good to know the fan make a difference. I will be on the look-out. I have a feeling those are hot parts at the salvage yard.

Completely understand. The fans were a premium at one time from the yards... I have a set rom an 05 Yukon I paid $250 for like a sucker. Rock auto sells brand new Dorman fans for like $130 which is what I have in my truck and it's a long story why I have 2 sets, but the short is do yourself a favor and use the factory wiring harness. I have the expensive factory ones in a box I need to get rid of, but due to size would be better to sell locally at a big loss lol.

Check the manifolds for broken bolts as we have all had them break and is a known problem. The tune would be a good start with basic maintenance.

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[Dan Acosta]

Completely understand. The fans were a premium at one time from the yards... I have a set rom an 05 Yukon I paid $250 for like a sucker. Rock auto sells brand new Dorman fans for like $130 which is what I have in my truck and it's a long story why I have 2 sets, but the short is do yourself a favor and use the factory wiring harness. I have the expensive factory ones in a box I need to get rid of, but due to size would be better to sell locally at a big loss lol.

Check the manifolds for broken bolts as we have all had them break and is a known problem. The tune would be a good start with basic maintenance.

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Bad scenario, first and last manifold bolts broken on drivers side. I see the front one has a stud sticking out - cant tell about the rear one yet. Do I buy the camps or attempt to remove the rest of them and replace with gasket?

 

[bottomline2000]

Bad scenario, first and last manifold bolts broken on drivers side. I see the front one has a stud sticking out - cant tell about the rear one yet. Do I buy the camps or attempt to remove the rest of them and replace with gasket?

Thats your call. I have a stripped bolt on mine. I was gonna put a helicoil in it and i just broke down and did the quick and ez clamp. It's a permanent fix. You may be able to get the one with the stud out but are probably going to need to pull the manifold off to get a good grip on it.

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[swathdiver]

Your Tahoe's final drive ratio in 1st was 11.41:1 and the 2500s is 9.26:1. 2nd gear is closer and 3rd is the same obviously and then you have the 2500 being about 1,000 pounds heavier unloaded. What is the horsepower spread between the two engines? 30 horsepower?

 

[Dan Acosta]

Your Tahoe's final drive ratio in 1st was 11.41:1 and the 2500s is 9.26:1. 2nd gear is closer and 3rd is the same obviously and then you have the 2500 being about 1,000 pounds heavier unloaded. What is the horsepower spread between the two engines? 30 horsepower?

Trying to wrap my head around the gear ratio thing... So the Tahoe "launches" quicker because the higher ratio - more revolutions of engine to driveshaft rotations. I would have thought the 2500 would of been designed with a lower (higher rotations) first gear ratio, since the assumed intent is for towing. Additionally I would think that since that is the case, the mpg would be better since the rpms are reduced - at least through city driven gears.

 

[Dan Acosta]

The clamps work great! I ended up buying the dorman units from Amazon, They were a little less expensive and the shipping was fast & free. I ordered yesterday morning and had them installed by 7pm (same day).

 

[swathdiver]

Trying to wrap my head around the gear ratio thing... So the Tahoe "launches" quicker because the higher ratio - more revolutions of engine to driveshaft rotations. I would have thought the 2500 would of been designed with a lower (higher rotations) first gear ratio, since the assumed intent is for towing. Additionally I would think that since that is the case, the mpg would be better since the rpms are reduced - at least through city driven gears.

The 4L80 is a computerized Turbo 400, same gearing with an overdrive. It's use is intended for durability. It was the advent of the 6-speeds with their steep 1st gear to get the loads moving and two over drive gears for economy that made them easier to drive.

A 2011 2500 Suburban for example has a final drive in 1st of 15.02:1. That's even steeper than a Duramax with the Allison transmission which is 11.54:1.