By Wish I kept my 2000 Z71
There has been an issue with the suspension on our new 2017 Silverado 4x4 ever since we purchased it, but we were hoping after we put some miles on it would settle down, it didn't. I’m referring to its tendency to almost throw you out of your seat when going over large bumps on the highway at freeway speeds of 65-70mph, like entering or leaving the transition onto and off of freeway overpasses, where the pavement raises up slightly at one end or the other of the over pass. Depending on the severity of the rise in pavement, it almost causes the truck to loose control. We wanted the smoothest ride possible and specifically did not choose the Silverado Z71 4x4 because the suspicion was reported to be stiffer for off road applications, now I hear the suspension on the Silverado Z71 4x4 and on the Silverado LTZ (non-Z71) 4x4 are identical, apparently the only difference in the two trucks is some difference in trim.
Most of the time the ride in our Silverado is very nice, except going over bumps. Also the rear of the vehicle is higher than the front ( and higher than my 2000 GMC Sierra Z71 which rode very smoothly). The taller tailgate on our 2017 Silverado makes it harder loading heavy items into the bed.
Is there anything that can be done to lower the rear of the vehicle level with the front ( I do not want to lift the truck), and allow a smoother ride? Can the suspension or shocks be changed out for something that will absorb the bumps better and still give a comfortable ride?
Well, seeing as how I can't find much on this subject no matter what forum I go to, why not try to start the discussion here and see what kind of following I can get and see where we end up.
If you're reading this thread, chances are you have thought about modifying or swapping out your current transmission in your 2014+ GM truck. In my case, I don't mind my 6L80 in my truck. It does fine for what I do right now and it's holding up just fine, but I think the big issue is when you start to search for big power (like I'm starting to do), that 6L80 is not going to hold very much (or so we think). Now, let's all face it. We've seen posts after posts, comments after comments, photos, videos, etc. of guys with built motors with turbos or prochargers shooting down the quarter mile in search for the best time on these 6L80s. Some say they're completely stock, others have them built, and we all ask ourselves the same question: Reliability. How well are these transmissions going to hold up to the abuse on the track? Especially if you want to make it a fast street/strip truck and drive it back home to the garage afterwords.
We know for a fact that 6L90s can hold quite a bit of power. Even though I've mostly seen it in Camaro ZL1 applications, there is a guy on YouTube (GuitarmaggedonZL1) who is running a stock 6L90 on stock converter making 1000HP (give or take on an unloaded dyno) and the transmission hasn't puked all over the ground just yet. (Exaggeration, I know.) So, needless to say, a 6L90 swap sounds nice, at first... After you figure the extra length and weight (and in my case, relocation of the transfer case and getting custom driveshafts made), it starts to look a bit unpromising, but still not out of the ball park yet since it will be able to handle the power some are seeking, but where these newer transmissions lack significantly if you want to do boosted applications at the track (or even just launch control on N/A), no one has developed a transbrake. Very, very few forums are talking about this, and only one video exists of a guy in his BMW testing out a transbrake on a 6L80/6L90, and who knows how reliable it is.
So, now, you start to think: Well, gee. What can I do now? How about a TH400 or 4L80e swap?
So far, I've seen few posts on that as well. No one is talking about it, and I think the biggest problem people seem to be facing is the new PCM: E92. Also possibly the fact that the TCM on the newer transmissions is inside the transmission and whatnot, but whether that plays a part in this, I don't know yet. Now, adapting a TH400 or 4L80e can be done (most likely with a different bellhousing since the bolt holes are in a slightly different spot), but you run into the issue of getting it to speak/cooperate/communicate with the new E92, which I don't think anyone has tried. The only video I've seen of anything working in this application was on a 1320Videos video with a Nova where they were using an LT4 long block (built motor to 388 C.I.) and twin turbos, and it had a powerglide in it. Don't know if it was a manual valve body or computer-controlled, but what I do know is that they used the factory computer to run the DI injection system and piggybacked the rest to an MS3 Pro. After dealing with some issues, they were able to make that thing boogy to a 9 second pass at 148mph. So, these engines have potential to haul ass, but we just haven't figured out how to crack the system.
So, at this point, I'll just leave what I've discussed here and see where the thread goes from here, and I'm hoping people chime in and vendors are watching/listening. Even though the demand isn't hot for it right now, there's going to be a surge for good transmissions when people can buy these trucks/cars/motors/transmissions for pennies on the dollar. Unfortunately, I feel like we'll have to wait that long in order to see results, but oh well.
Just to give you guys an example: In the next year or two (2019 or 2020), I'd like to go turbo with my truck. (Doing all the supporting mods before going there minus built bottom end until I see where I can get with stock bottom end before sending a rod through the block or oil pan) Ideally, it'd be best to have a transbrake in that application with 2-step, but can't do it on the new transmissions. So, 4L80 seems to be the option, but I can't do that either because no one supports adapters or harnesses to make them work with the new motors/ECUs. That's the boat I'm in. I like to research everything before I go whole hog into something. Risk assessment, I guess.
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