I agree, they only say "It is what it is, deal with it" which isn't very informative. My only understanding of this comes from my background as a mechanical engineer, but I cannot speak for GM! I'm only assuming from my experience with the industry that GM had engineers run an analysis on the bevel gear teeth contact under certain loads (such as a fixed tow weight) and determined that too much heat/stress was generated with the 3.08 vs. the 3.42 gears, therefore reducing tow capacity for the 3.08 no matter what engine is powering it. Less or smaller gear teeth contact with more engine torque can increase stress on the teeth. The 5.3L can probably tow more with the 3.08, but GM needs to cover their butts depending on what their engineers say for warranty purposes I'd assume. Some interesting information would be throwing the 6.2L into the mix. If the 6.2L has the 3.08 rear and still has a super-low tow capacity, we can probably assume the gears are the limiting factor. I can't imagine that the 6.2L would have those gears, but now i'm curious...
Rear-end torque doesn't necessarily matter as much if the 3.08 cannot handle the same towing stresses as the 3.42. So, to answer the question of the first post, that's how GM states the V6 with the 3.42 can tow more than the 5.3L with the 3.08. Both engines can obviously tow more, but when the 3.08 heats up more under higher loads increasing chance of failure, they reduce the max towing recommendation (regardless of engine) Edit: It's a material composition problem of the rear axles (3.08 vs 3.42). The 3.08 under higher loads will heat up more, degrade fluid faster, and break "teeth" sooner than the 3.42 under similar circumstances. Another way to think of it is that under equal loads, each tooth of the 3.08 will see more stress than the 3.42 and has a higher risk of failing sooner. Therefore, GM engineers determined the 3.08 rear axle as the limiting factor (fails first) and lowered the max tow rating to cover their butts.
The 3.08 rear end is simply not designed for towing more and is the limiting factor, mechanically.
Bill Reinhardt replied to Bbaselj's topic in 2014 / 2015 / 2016 / 2017 / 2018 Chevrolet Silverado & GMC Sierra 1500My MPG's dropped when I installed the Diablo MPG tune with a Diablo TCM tune (either firm or hard shifts). Returning the TCM tune to stock fixed this. I hated the canned Diablo TCM tune anyways. Did you apply a Diablo TCM tune by any chance?
Bill Reinhardt replied to sala0288's topic in 2014 / 2015 / 2016 / 2017 / 2018 Chevrolet Silverado & GMC Sierra 1500I'm also curious about the high mileage maintenance and any common problems. Seems like a valve cleaning would be nice at 100k miles At 80k miles, I agree with you getting some new fluids in the differential, maybe on the transmission (if the fluid looks bad). Who knows what the previous owner did, the peace of mind will help in the long term. Oh, brake fluid flush! The fluid is supposed to be clear (easy to check). If it's brown, get it flushed to prevent rusty brake lines. Check again in another 50k miles or 3 years. 2014 Maintenance Schedule
Bill Reinhardt replied to sala0288's topic in 2014 / 2015 / 2016 / 2017 / 2018 Chevrolet Silverado & GMC Sierra 1500Hey OP. I, too, came from a Colorado (2008). Loved that truck. Unfortunately, it had some pretty serious issues at around 90k miles (Valves not seating properly, new cylinder head). I got that fixed and got a diablo tune. Holy cow, made that truck even better. Lightning quick shifts, more power, couldn't go wrong. Recently purchased a 2014 Sierra Work Truck w/50k miles. Apart from the lack of auto mirrors, it has all the same features of my old truck and was dirt cheap, so I cant complain. Love the power and ride quality, though I do notice a slight shimmy at speeds greater than 75 mph. Smooths out with a little weight in the back, however. What bugs me the most with this truck is the transmission. I have a Diablew tune and was expecting the results I had with the Colorado. While the shift quality and speed is a little better than stock, it still lags when you want to simply pass on the highway and need to downshift one gear. I may need to adjust to it... Regardless, when I drive like a normal person, no complaints with the transmission. I too hope to drive this thing for as long as possible!
Bill Reinhardt replied to langston1726's topic in 2014 / 2015 / 2016 / 2017 / 2018 Chevrolet Silverado & GMC Sierra 1500Work truck, as vanilla as it gets 2014 5.3L 4x4 w/ 50,000 mi
Bill Reinhardt replied to jomuehlbauer's topic in 2014 / 2015 / 2016 / 2017 / 2018 Chevrolet Silverado & GMC Sierra 1500Anyone else daily a work truck? 2014 Sierra 1500 5.3L 4x4 w/ 50,000 miles
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Bill Reinhardt replied to Silver space ship's topic in 2014 / 2015 / 2016 / 2017 / 2018 Silverado & Sierra Issues, Troubleshooting, & Recalls/Service BulletinsEDIT: Just got off the phone with my local GMC dealership service center. Stated that shaking at speeds in excess of 75+ mph has been found to be the nature of the fully boxed frame unloaded. He told me he drives a 2015 Sierra 1500 with the same symptoms and searched high and low for a solution when he first got the truck. Found out that placing weight in the back resolves the issue. Has anyone tried this? ORIGINAL MESSAGE: 2014 Sierra 1500 5.3L 4x4 3.42 w/ 49,500 miles Jeeze. Just got my truck a few weeks ago and noticed the shake at speeds in excess of 75mph. Lots of pages on this topic, lots of reading! So far, the only solutions I can find are: Driveshaft balance Spring clamps New shocks (Rear only? Seems to only cover the actual problem) Torque converter (seems to apply to the 8-speed only) I may be missing a few others, but I would love some sort of sticky that summarizes the solutions that have worked, and which engine/transmission/axle combinations it works for. Feel free to PM me your year, engine, drive train, transmission, and axle because I wouldn't mind compiling this info for everyone. Almost at 800 pages of information here, there must be a solution.
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