'05 Auto Transmission issues unresolved with "LubeGard"

After searching this forum for advice on resolving my '05 Tacoma Pre-Runner Auto Transmission "shudder" issues, I found several posts swearing by the use of "Lube-Gard" transmission additive. Well, I've changed my transmission fluid following the product directions and weeks later there the problem persists. A friend/mechanic recommended bringing it to a transmission shop to have the entire transmission system flushed and replacing the ATM filter as well. One shop I talked to said that this may cause more issues. Another option is rebuilding it but I've just reached 300k miles. Any advice is welcome!
Thanks John

 

Describe when the shutter occurs.

Does it feel like driving over rumble strips while in OD going up hills or hauling a load with 3/4-full throttle applied?

if so it’s probably your torque converter. The lubeguard shutter fix is to be used as a diagnostic tool only. If you added it and the shutter stopped for a period of time, it’s probably torque converter.

If the shutter fix did nothing, then it’s most likely deeper in the transmission.

 

Thanks for your reply. The shuddering seems to occur when I'm driving at low speeds around 32-38 mph. It never occurs while accelerating. I've cleaned intake & sensor and changed plugs. If it's a Torque converter issue, is there a recommendation?

 

Does it feel like going over rumble strips? One way to test is drive it until the shutter is happening, then with your left foot apply pressure to the brake pedal lightly. If the shutter goes away it’s probably torque converter

 

yes, I guess I could compare it top running over rumble strips. If it appears to be the torque converter is that an expensive fix?

 

Did it stop for a bit after you added the lubeguard?

 

no

 

Also, doesn't occur if I drive in 4 gear instead of D

 

Have you looked at your rear driveshaft to see if there’s any play from the u joint? There’s 3 of them. Just something else to check

 

will do!

 

So it happens only in 5th, shift to 4th same speed goes away? If that’s the case, sounds more and more like your TC

 

correct. How easy is the TC to fix?

 

Or should I ask, how expensive?

 

You have to drop the transmission out pull the old TC off and slide the new one on. Drain all the fluid of course.

I would say it should be around 2grand to have a shop do it, with a quality converter

Take it somewhere that knows transmissions and have them run codes, it could be throwing some.

 

I really appreciate your advice!

 

No worries, hard to say the TC is exactly the problem here but sure sounds like it. Try the brake trick to see if that can tell you anything.

I would have a tranny shop run codes to see if anything pops

 

is it a shudder or a vibration? I had a similar scenario where LubeGard didnt do anything. It only happened in 5th lockup, low RMP, slight throttle input. Turns out it was the engine lugging. I got around it by using HPTuners to adjust the lockup timing. These are very hard to describe and diagnose over a computer, so it could be this, could be TC, could be something else.

 

I've been having the same issue, especially in hot weather 100°+ with the A/C on. Pre-ignition - pinging - detonation (whatever term you desire) is occurring. If I get it tuned is there a specific tune/map that I should ask for?

 

With that many miles, it will not hurt to at least replace the ATF filter with a drain/refill if it has never been done. Lets see if transmission guru @gearcruncher is available to provide an opinion.

 

hop over in the HP Tuners thread here https://www.tacomaworld.com/threads/hp-tuners-for-2005-2015.600793/
JustDSM was the main contact for tunes, but I think the process has changed. There's info in that thread tho.