Will the 4L80E shudder at highway speed

[THEFERMANATOR]

If the problem is the tcc being commanded to lock/unlock/lockunoock etc- the. Yes the brake switch test would show it. Simply unplugging the brake swith- you don’t have to try riding brakes and smoking pads/rotors.
But it it is something internal causing it- brakes applied it won’t stop it. So your still at the point of seeing it on a scanner.

It would be astonishing if the $20 thing from wally world shows it. I would wager against it- but hopefully am wrong. Just make sure you can get it returned if it doesn’t.

Just because it's cheap doesn't mean it won't do the job. I have a $20 SX cable that I use to read & write to p01 & p59 PCM's. The $20 tool is just the gateway, it's the software that you use that dictates what it can do.

@THEFERMANATOR I was unaware of this issue! Please do share more info on this. I remember seeing mine on GMTDscan only showing about 50-60% while in lockup. my slippage would show upwards around 100+rpm under light acceleration and would go 500+ when heavy footing it. I always thought my converter clutches were gone. could this be an issue. only ever got the PCM code that one time a while back. I will have to reconnect the laptop and verify the numbers I mentioned.

@96GMC7.4l/454 I apoligize if I sound like I'm hijacking your thread. I'm just reading and learning on these tranny's myself

The PCM can vary PWM depending on load to help jeep trans temps down, but as far as I know, all 4l80e's are a pwm lockup meaning they are pulsed on for a soft engagement, but they should lockup and stay locked when engaged(less than 20 rom's slip when engaged). It was the 98+ 4l60e that got EC3 lockup where it never fully engages lockup and constantly slips.

 

[96GMC7.4l/454]

WHOOAAA HORSEY! “...think it’s the front passenger wheel area”
This thread started with the assumption you were feeling it from transmission actions. Kinda how you titled the thread.

Absolutely wheel/ suspension/ steering components can create high speed shudder.
Have you tried rotating tires front to back to see if the feel changes (moves location)?
Out of balance tire, tire separation, bent rim, is highly possible and normally occurs at specific speeds.

Bad shock absorber will have one wheel going down the road like dribbling a basketball while the rest of the truck is stable. That is a unique sensation I found most people couldn’t identify other than “something is different than usual”.
One wheel knocked out of alignment caster, camber, toe can be an issue, especially a wiled out ball joint in the beginning stages of getting a “death wobble” can all send a shutter through the truck.
4wd? I have seen cv joints without grease from torn boot binding create an oddball feeling at high speed.

I’m gonna go back to WarWagon’s suggestion- get it up on jackstands. Start by dojng a drive and noting what speed and exactly how it feels with a helper. Then onto the stands, Make sure if it comes off it can’t crash into anything. Have someone “drive” it up to the speed where you notice the issue the worst and you go around the outside of it -SAFELY AWAY FROM IT- and watch wheels, drivlines, etc.
If you see nothing, swap front and rear tire positions and drive it again, same road same speed and see if anything changed.

Having someone drive along side of you and signal them when to start video recording focusing on tires one at a time, driveshaft, and if they can get good angle from small car, from front end also. Zooming in and out to study it. Post the video on YouTube, bitchute, whatever and put a link here.

You might get an old phone, go-pro, etc. and mount it underneath for same thing. This is a legit way to find problems that otherwise never get found until the crash investigation or the one bad part has destroyed multiple other items and it all gets swapped.

Ok so I’m sure you haven’t a site dry thing I’ve posted so I’ve rebuilt this frint end from the frame out put totally different wheels and tires on it and nothing has changed so I’ve started with tranny mount motor mounts and what felt to me like a possible trans shudder and yes it feels like a passenger front area however if it is tranny the direction of torque would feel like passenger front area aswell