Northern Collector

A couple of months ago I acquired a 2013 Suburban 2500. It was a former government vehicle, although I don't know what type of service it was involved in. It's in good shape, 200,000 KM's and no rust, but it is the low spec commercial model. I have detailed it, added the chrome door handles, refinished the rims and swapped the roof rack for the rack off my 04 Z71. During the full fluid changes the transmission fluid looked good, and the pan was clean. The car shifts cleanly and runs well, however the engine noise experienced in the cabin is excessive. It's many times what I experience in my 04 Z71 with the 5.3, hence the question about shift points. Warm or cold the truck wants to shift at about 2000 RPM. If you feather foot it when it's warm you can get it to shift at 1800. This is for an unloaded vehicle. These RPM's translate to the excessive engine (primarily fan) noise I experience in the cabin, so a couple of questions:

• Are these shift points normal for the 6.0 2500? If not I may have a tune as a result of the service it was in.
• If it's normal then can it be related to less sound deadening in the low spec 2500 model versus the older Z71 I have experience with?
• While the viscous fan clutch seems fine, perhaps it's not slipping enough and creating the noise.

Any comments would be appreciated.
Thanks,

intheburbs

I've got an 08 2500. It's a 3LT, so pretty much top-of-the-line for the 2500s. Franky, I've never noticed the engine noise, nor the shift points. My engine is very quiet and smooth, and I frankly couldn't even say what the shift points are under light throttle.

I expected this was a thread about WOT shift points and the lack of a redline on the tach.

My guess would be that because it's a fleet-spec truck, it has little or no sound deadening material, so everything seems louder. Especially if you have no carpeting on the floor. You might want to look into dynamatting the truck, if your engine shift point investigation yields nothing. You might also want to look into a custom tune, like Blackbear. They can change the shift points and fan parameters to whatever you want.

Northern Collector

Thanks, I have read some of the threads relating to transmission tunes and as would be expected most are focused on speed/performance improvements which my use of the truck does not require. Maybe we will get some shift point comments from those with stock configurations. I have already sound treated the doors, but have put off tackling the firewall for now.

repairman54

I would expect a 2500 fleet build to have slightly high shift points over a 1500 spec. truck. Heavier rated truck would be programmed that way.
Fleet build is below LS level so minimal sound deadening.
I'm surprised it has a clutch fan and not electric ones. Must be an extended idle fleet thing for positive cooling with dependability.

Northern Collector

Interesting point about the fan, as that is the source of most of the noise. It would be interesting to hear from other 2500 owners as to the type of fan they have. Also on a specification point my 6.0 has a smooth valley pan which means it is a non AFM engine. Is that true for all 6.0's of this era or another spec change for the commercial trim level?

Still looking for specific experience with the shift points for this configuration.

Thanks

repairman54

I believe only the 5.3 in that gen. were the only AFM motors.
After reading your posts I took notice of when my 5.3 shifts on light throttle and it's around 18-1900 on the 1-2 shift. 2-3 shift is lower rpm.
Research the RPO codes on the glove box label and you will know exactly what options/features it was built with.

intheburbs

All the 2500 trucks have clutch fans and no AFM. Trucks with a GVWR of 8600 or higher are exempt from CAFE regs, so there's no incentive for GM to put it in.

Check the engine hours in the DIC. Typical hours compared to miles should work out to be around 30-35 MPH. So, in other words, your truck should have around 3600-4200 hours. Lower hours than that means the truck has a lot of highway driving and less idle time. You might see that the hours are much higher, and perhaps the fan clutch needs to be replaced.

My cooling fan generally is not on at idle or low speeds. In really hot conditions, with the A/C running, and usually when I'm towing, I get more of a roar from the fan off idle, but again, that's very infrequent and only when I've been idling in hot weather.

HDSuburban

I have a 2013 Suburban 2500 LT also. I am a little surprised that you found the shift point of 2000 RPM too high for a stock tune. My experience was the opposite. I felt the vehicle really lacked low end torque with the stock shift points. It was very annoying driving around trying to merge onto the highway or whenever acceleration was needed. Blackbear tuning solved most of the problems in addition to giving the engine a noticeable power boost. The improvement helps in towing as well which I do very often with a 8000 - 9000 lbs trailer.

As for the engine noise, I definitely feel that the 6.0L engine is noisier than a 5.3L. I don't think it's all coming from the mechanical fan. When the weather is really hot and after a long idle, the fan can be heard for sure, but even under normal operations the engine is noisy by modern standard. I've thought about adding sound deadening material, but not sure where to add or if it's going to be effective.

Overall, I am very happy with the vehicle as it's truly an amazingly versatile workhorse. I'd like to upgrade to a new HD Suburban if GM is ever going to make one...