It’s definitely both, but if I’m of the opinion if we can point to either temps or oil change interval as the main factor for seal hardening then temps are the #1 offender
GX460 P2714 P0761 Ultimate Summary and Hope For A Fix Thread
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It’s definitely both, but if I’m of the opinion if we can point to either temps or oil change interval as the main factor for seal hardening then temps are the #1 offender
Interesting, it is full synthetic (was not aware of that). I'll probably stick MaxLife though as I've been running it for about 5.5 years and 70K now with great results, and it's readily available in the US if I were to need to unexpectedly add in an extra quart or two for some reason.
I'd keep the AT205 experiment going on for some time, then try a pan drop. The clutches naturally wear on the transmission with age, just like brake pads. If the pan has never been dropped, there will be a thick layer of clutch material on the bottom of it (plus potentially some metal). Changing fluid is certainly great, but the layer of gunk on the bottom of the pan will just re-contaminate it. I suspect that frictional clutch material being suspended and continually circulated may also accelerate wear of seals/solenoids/etc.
I am about to copy your general plan - I did a drain & fill yesterday, I'll drive it for a week, then I'll do a pan drop to check what's in there, change the filter, fill it back, up, drive it for another few weeks, and then if that doesn't work I'm going to be adding the AT-205 as a last ditch effort before I go for a full rebuild!
There’s some real automotive engineering jackassery going on right here. There are things bolted to the bell housing that have nothing to do with the transmission. It wouldn’t surprise me if some mechanics pull the engine when pulling the trans. This wiring should have been bracketed to the body. Putting it this close to the exhaust and hot running transmission can’t be good for the life of the wiring.
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I do not recommend this as a DIY. Transmission shops charge what they do for a reason. The trans is finally out. I’m about 11 hours into this project
GX470 long-tube header install took me ~21 or ~22 hours all-in
. That was 5 years ago, so I've had 5 years of enjoying the benefits of the headers and don't really think too much about how much of a PITA the job was . Were you working with the rig on jackstands, on a lift, or something else? I'll eventually need to pull the trans when my rear main seals starts really, truly leaking. My buddy has a lift - I might take over his shop for a weekend.
GX470 long-tube header install took me ~21 or ~22 hours all-in
Were you working with the rig on jackstands, on a lift, or something else? I'll eventually need to pull the trans when my rear main seals starts really, truly leaking. My buddy has a lift - I might take over his shop for a weekend.
I didn’t want it that high. Limited trans jack height. I don’t trust jack stands for rough handling. Light work or tire work is fine, but I don’t want to be under it manhandling a trans if one gives up. Had to slide it off the trans jack to get it out with the bell housing still on. It will go back in without the transfer case attached. Too much weight
Posting this here because you all might find it interesting although it’s a bit of a sidebar. I just updated my AI with how the AT205 treatment has been working now that I’ve put 300 miles on the truck, 7 days, 50+ reverse engagements, and driving only in D for 4 days… and it thought of you 
“At this point the evidence has crossed from “encouraging” to “statistically hard to dismiss.” Think about what your baseline predicts: under the old regime, 50+ reverse attempts should have produced a pile of failures, and four straight days in D — the mode you abandoned two years ago — should have tripped codes within a day or two. The odds of that streak happening by pure luck while nothing changed are vanishingly small. One variable changed, and the two symptoms that both trace to hydraulic sealing improved together, on the timeline the chemistry predicts.
I’d move my odds from that 15-25% band up to something like 70-80% that the seal hypothesis was right and the AT205 is genuinely working. The remaining uncertainty is durability, not diagnosis.
That reframes your open questions. The second bottle: don’t add it — you’re getting a full response at the current concentration, and the only thing more would add is overfill risk to a transmission that’s currently behaving. The seal has absorbed what it needs; more in the fluid doesn’t push more into the rubber that’s already saturated.
The two milestones left are a couple hundred more code-free miles of cold-start D driving, and then the real exam — cool weather. Florida’s version arrives late fall, and that’s when a still-marginal seal would announce itself. If it sails through December mornings, you can call it fixed rather than improved.
One forward-looking thought: once you’re confident, a drain-and-fill with fresh WS is worth doing not just for fluid health but because this transmission spent a year slipping in and out of limp mode, and clean fluid plus a look at the pan magnets would tell you how much clutch material that era cost you.
And seriously — write this up on that IH8MUD thread. A $10 bottle resolving the symptom set that’s been sending people to $8k transmission replacements is exactly the data point that community has been hunting for years.”
“At this point the evidence has crossed from “encouraging” to “statistically hard to dismiss.” Think about what your baseline predicts: under the old regime, 50+ reverse attempts should have produced a pile of failures, and four straight days in D — the mode you abandoned two years ago — should have tripped codes within a day or two. The odds of that streak happening by pure luck while nothing changed are vanishingly small. One variable changed, and the two symptoms that both trace to hydraulic sealing improved together, on the timeline the chemistry predicts.
I’d move my odds from that 15-25% band up to something like 70-80% that the seal hypothesis was right and the AT205 is genuinely working. The remaining uncertainty is durability, not diagnosis.
That reframes your open questions. The second bottle: don’t add it — you’re getting a full response at the current concentration, and the only thing more would add is overfill risk to a transmission that’s currently behaving. The seal has absorbed what it needs; more in the fluid doesn’t push more into the rubber that’s already saturated.
The two milestones left are a couple hundred more code-free miles of cold-start D driving, and then the real exam — cool weather. Florida’s version arrives late fall, and that’s when a still-marginal seal would announce itself. If it sails through December mornings, you can call it fixed rather than improved.
One forward-looking thought: once you’re confident, a drain-and-fill with fresh WS is worth doing not just for fluid health but because this transmission spent a year slipping in and out of limp mode, and clean fluid plus a look at the pan magnets would tell you how much clutch material that era cost you.
And seriously — write this up on that IH8MUD thread. A $10 bottle resolving the symptom set that’s been sending people to $8k transmission replacements is exactly the data point that community has been hunting for years.”
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Very interesting. I regularly fed all my results before pulling the trans into Chat GPT. I’m hoping it’s building a GX460 database that can help owners.Posting this here because you all might find it interesting although it’s a bit of a sidebar. I just updated my AI with how the AT205 treatment has been working now that I’ve put 300 miles on the truck, 7 days, 50+ reverse engagements, and driving only in D for 4 days… and it thought of you
“At this point the evidence has crossed from “encouraging” to “statistically hard to dismiss.” Think about what your baseline predicts: under the old regime, 50+ reverse attempts should have produced a pile of failures, and four straight days in D — the mode you abandoned two years ago — should have tripped codes within a day or two. The odds of that streak happening by pure luck while nothing changed are vanishingly small. One variable changed, and the two symptoms that both trace to hydraulic sealing improved together, on the timeline the chemistry predicts.
I’d move my odds from that 15-25% band up to something like 70-80% that the seal hypothesis was right and the AT205 is genuinely working. The remaining uncertainty is durability, not diagnosis.
That reframes your open questions. The second bottle: don’t add it — you’re getting a full response at the current concentration, and the only thing more would add is overfill risk to a transmission that’s currently behaving. The seal has absorbed what it needs; more in the fluid doesn’t push more into the rubber that’s already saturated.
The two milestones left are a couple hundred more code-free miles of cold-start D driving, and then the real exam — cool weather. Florida’s version arrives late fall, and that’s when a still-marginal seal would announce itself. If it sails through December mornings, you can call it fixed rather than improved.
One forward-looking thought: once you’re confident, a drain-and-fill with fresh WS is worth doing not just for fluid health but because this transmission spent a year slipping in and out of limp mode, and clean fluid plus a look at the pan magnets would tell you how much clutch material that era cost you.
And seriously — write this up on that IH8MUD thread. A $10 bottle resolving the symptom set that’s been sending people to $8k transmission replacements is exactly the data point that community has been hunting for years.”
Thank you for the write ups. As much as I like the truck, outside of transmission issues, I could see buying another one. I put my 16yo daughter in my LX450 as her first vehicle (heavy, slow, safe). I plan on my 9 yo have the GX as her first car. These are really functional safe vehicles. Their biggest failure needs something other than a rebuild to help keep them on the road, at least for short term reliability.
For those who have gone through a complete rebuild…including the one going on now, it would be great data to find out exactly what is screwed up when you do the rebuild. Like an autopsy.
That’s exactly my intention. I plan on pulling everything out and displaying it in order, then as I put it back together, remove the parts I’m replacing, put calipers an everything, photograph everything and post it here. I’ll put up close ups of the bonded seals and any damage I find on metal components. I’ve already done the VB and valves, so I’ll skip all that
Two pairs of locking 6-ton stands are very stable (24,000# rated capacity under a 5,000# rig), and will be more stable the rig on ramps as the rig will be level and will be solid frame-to-concrete (i.e., not moving around on the suspension, not trying to roll back off the ramps). Mine's been up on all 4 multiple times, including for pulling out the front and rear differential. The is no physical way the rig can come off of appropriately-positioned locking jackstands unless another vehicles were to crash into it, on top of that the locks physically prevent the jackstand from lowering. You can always put the removed tires under the framerails as a failsafe (I usually do that but they are not shown in this picture).
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I’m expecting to find hard/inflexible/separated piston seals along with shrunken/damaged O rings. My recent new symptom of rough reverse under throttle is likely due to partial engagement from fluid bypassing the piston seals.
I’ve had my ramps for 20+ years. I’ll always trust them before stands. Used them all the time with my Duramax (heavy front end). I have stands. I use them a lot. But I prefer ramps when I’m completely under trying to wrestle a 200+ lb trans out. It wasnt really a problem as the cheap jack I bought couldn’t handle the load with the transfer case. The jack lift worked just fine but the frame for the wheels bent (see pic). I really just needed it to raise and lower. The trans was slid out on its side with help from my floor jack. I’ll weld on larger gussets for reinstall. Bellhousing came out just behind the ramp. I may reinstall the bellhousing after I get it under when going back in.
The chocks are on the drivers side
Acrad
GOLD Star
I would totally put in a lift if my garage could accommodate it but I think I will finally pick up some Quick Jacks instead. Still not the same but IMO.. better than ramps and jack stands and greater lift height.
Personally.. I'd feel more safe under this than any jack stand setup. As-is I usually have jack stands, jack, ramps, and throw the tire under there as well just for safe measure
Personally.. I'd feel more safe under this than any jack stand setup. As-is I usually have jack stands, jack, ramps, and throw the tire under there as well just for safe measure
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