Search the Community

Hey guys, I did the thermal bypass conversion to active by pass on my 2018 8L90. Did a step by step video because I hadn’t seen anybody do an actual full replacement video nor had I seen one on a 8 speed. Trans runs about 45 degrees cooler now. Check it out and let me know what you think. It’s the exact same procedure on 6 speeds just mounts different on the transmission.

I recently bought a used 2016 Sierra Denali 5.3L 4x4 in March with 48k miles. Truck has been great until yesterday (now 52k miles) when I ease into the gas it shudders and shakes like crazy until i punch it. The tach is bouncing up and down and it doesn't matter if it's in v8 or v4. It almost feels like it's a misfire but it's weird that it only does it when I'm easing into the throttle or going uphill. The truck has the 8 speed transmission. Has anyone else ran into something like this and would the manufacturer warranty cover the fix for this?

Is this how most dealers do a trans service on MQE 8 speed? See link below. I would like to order some fluid from Black02Silverado and then test it. I am too crippled to do a pan drop anymore and since the filters on these things are screen doors on submarines I would like to do the fluid exchange by machine pump. Is this the procedure a dealer will do from the stand pipe fixture and trans oil cooler block assembly with adapter. No dipstick on this 2022 LTD Trail Boss. https://static.nhtsa.gov/odi/tsbs/2019/MC-10163890-9999.pdf

So I've tuned my truck with and it has made a difference from what I can tell. A couple of questions, however. 1. Is there any way to truly fix the hard downshift from 3-2 and what I call lagging going from 2-3 under acceleration? I installed the 91 octane tune, disabled AFM, speed limiter and changed the shift points from 2-3. It seems like the shift point pressure is too much. The RPM's spike when i'm easy on the throttle after a stop. 2. There is an option to change the axle ratio via the tuner which I thought was impossible because the axle is ratio is mechanically fixed, yes? I think I have the 3.23 but I am not 100% sure 3. Side note, I have an Air Raid intake tube, k&n filter, installed a catch can and did a muffler delete. I took out the flapper valve out as well. Truck runs and performs better (sounds awesome too). When I go to pass cars on the highway, I can easily break 100 and you can tell the engine still has a lot left. I truly believe that this truck's engine life has been extended greatly after disabling AFM. Thanks guys.

I have a 2017 Chevy Silverado 4x4 5.3l V8 with the 8 speed transmission. I already flushed out my transmission and filled it back up with the Mobil 1™ Synthetic LV ATF HP blue label. The question is, do i also use the HP fluid for my transfer case? Or do i need to use just a standard ATF fluid instead. I cant seem to find a straight answer on this. The owners manual states to use DEXRON®-VI Automatic Transmission Fluid. Would using regular ATF in the transfer case and HP ATF in the transmission cause any issues? Thanks in advance!

So I finally gave up on waiting for a fix for the 8 speed and its many mis-behaviors and had my truck tuned by a local custom tuner that has been working with LS/LT motors and transmission tuning for many years. He plugged in his laptop and rode with me for over two hours. The truck is a new animal. Great at shifting and the engine acts like the beast it should be. My truck is a 2015, 6.2L 8 Speed, 23,000 miles. It has always had the low speed clunk and recently developed the shudder, especially in 8th at steady state highway speeds. Here is some of what was done. AFM shut off, Torque Management shut off, Variable cam timing adjusted to performance lift, 1st gear set to hold until 11 mph, higher shift pressure for next few gears, torque converter set to 0% slip, raised speeds for converter lockup especially in 8th. Other parameters were adjusted, but these were the main ones. Some of what was learned. The TC was slipping too much when trying to lock at light load (half in half out) causing the shudder. It was also trying to lock at too low of a speed/RPM almost lugging the engine (again most pronounced in 8th). No more shudder in any gear. It does take a decent speed (over 60-65 to lock up in 8th, but once locked it will stay locked below 60 unless I kick it in the pants or the load increases). As most of you experience, 1st gear was trying to get to third as quickly as possible. Now I can move through parking lots without trying to throw a U joint. There were more learnings but these 2 are the big ones. I will probably lose a bit of MPG in town driving (I am fine with that) but the 60 mile trip home at freeway speeds netted 20.1 MPG ... not enough loss to consider if any. Performance is incredible. I floored it from a stop a couple days later, and had to back off to preserve the tires as it started roasting them. Shifting at full throttle was impeccable. Longevity (as long as I dont drive it live a sports car) theoretically will be better than it was with all the clunks and shudders. I am thrilled with the results. If any of you live near Van Buren Arkansas, and are interested I will pass on the contact info.

Looking at crew cab short bed 4x4’s with the V8’s. I just can’t wrap my head around not having low range so it’ll either be a Z71 or a Trail Boss. Been watching prices and I’m seeing Custom Trail Boss trucks starting to get close to the prices of the LT. As in within a grand or even less. Anyone bought a Custom and regret it? I have a 2011 Silverado 1500 4x4 and my wife has a 2017 Yukon 4x4. Both have the 6L80 transmission and hers has the Ecotec 5.3 V8. Very happy with that engine and transmission combo and even with less power my ‘11 moves and drives well with the 3.42 gears. Will I miss anything with a Custom instead of a regular LT Z71? 6 spd vs 8 spd? Gas mileage? Something else?