A343f long/soft shift from 1st to 2nd ??

[JDUBinCO]

Looking for some help here on next steps...
Background: '97 LX450 with 288K miles, original transmission, which had Amsoil 100K mile ATF for more than 100K miles. I drained it because I was worried about towing and heat. Everything work fine, oil was still red, and the shifting was normal, if a bit firm. I topped refilled it with standard O'Reilly store ATF ( Dev IV or whatever - the right stuff) at 277K miles and did a drain and refill again at 287K miles. The second drain and refill didn't really change the shifting behavior...
The result of a single drain and fill (4 quarts) was that the shifting everywhere got softer. Reverse didn't seem to lock up so easily, but importantly, the shift between 1st and 2nd gear got longer - up to 1.5 seconds long, depending on the how hard I am on the gas. If I have it floored the shift will take about 1.5 seconds and it feels like things are slipping bad, but then I can feel the 2nd gear kick in and lock up. If I'm light on the gas it will shift nicely in about 0.5 seconds. It feels like the problem exists only between 1 and 2. All other gear shifts are good and firm.
Question 1: During this long time of shifting, what is slipping? Is it oil is it a band? Do I have a concern about burning something up?
Question 2: Since it still locks up nice in 2nd, what is the recommended course of action?

I've done a fair amount of research and it seems like the 1-2 solenoid could be leaking at the O-ring, or the oil circuit could be a bit plugged up, or the solenoid could be dying, causing a long engagement between the oil circuits, or the oil could be crap and I should do the whole purge and refill option. Above all, I'm trying to maximize lifespan and reliability from the transmission.

My following thoughts are,
A: Purge and refill with Valvoline high mileage ATF.
B. Drop the oil pan, put new seals on the the solenoids or replace them, depending on condition, and increase the line pressure. Clean everything up, and put it back together with new fluid.
C. Leave it, its fine.
D. Plan for a rebuild.

Please let me know if you experienced this and know how to resolve it.

 

[Batameez]

I had poor shifting when I thought it was a good idea to "flush" the A340F in my 4Runner with Supertech ATF. These store brand fluids might meet spec but I wouldn't use it for anything more than a power steering system. I switched to Castrol High Mileage ATF and it went back to normal. I'm suspicious of these multi-vehicle fluids that meet WS spec like Maxlife, I would imagine they are too thin for an old transmission.

 

[Kernal]

Some random thoughts:

@JDUBinCO

IME Valvoline MaxLife Multi-Vehicle Full Synthetic ATF is backwards compatible with transmissions that called for Dexron II/III fluid. IME it works well in the A343F ATM. The shifts IME are slightly less firm (smoother) compared to another FZJ80 A343F using Mobil 1 Synthetic ATF (but no slipping or prolonged shift times with either).

There was a TSB (Tech Service Bulletin) years ago for the A343F ATM about judder/shudder in Reverse, mostly fixed by the 97 model. IME those symptoms can happen even in Drive by using the wrong ATF (cheapo bulk ATF at the Quick Lube place).

You could collect a sample of used ATF and send it to Blackstone laboratories for an Oil Analysis. That will tell you if there are elevated wear metal levels
in the fluid. You could also ask for a Particle test to check particle size and amounts in the fluid. ie: if the clutch material is failing the particle count could be way up.

 

[JDUBinCO]

Follow up and a question...
I did the full flush with Amsoil ATF and all the fluid is now a nice cherry red. The 1-2 shift still feels long, so I measured it at full throttle and got 1.4 seconds. Anyone care to share how long theirs takes to shift from 1-2 under full throttle?

I'm thinking this must be normal for the LX450, but I've only driven my own. TIA!

 

[alia176]

Follow up and a question...
I did the full flush with Amsoil ATF and all the fluid is now a nice cherry red. The 1-2 shift still feels long, so I measured it at full throttle and got 1.4 seconds. Anyone care to share how long theirs takes to shift from 1-2 under full throttle?

I'm thinking this must be normal for the LX450, but I've only driven my own. TIA!

This hasn't been mentioned so I'll bring it up. Have you checked the "line pressure cable" (or something like that ) clearance per the FSM at the throttle body? We're talking mm here but that has helped some folks' shifting issue. This cable does stretch a little over its lifetime.

 

[JDUBinCO]

This hasn't been mentioned so I'll bring it up. Have you checked the "line pressure cable" (or something like that ) clearance per the FSM at the throttle body? We're talking mm here but that has helped some folks' shifting issue. This cable does stretch a little over its lifetime.

No, I didn't think about that or realize it could be a factor. Would that cable only affect the 1-2 shift? The other shifts feel fine.

 

[JDUBinCO]

I'll close this thread out with findings - I messed up when I put the throttle body back on (from doing the valve cover gasket) and the transmission cable was not installed. I re-installed the cable and a flushed transmission with AMSOIL so I should be good for another 100K miles. It shifts perfect now!

 

[Kernal]

Glad you figured it out.