The shop said nothing as the guy who had the technical abilities to diagnose and test the transmission didn't show up. I'll try again in the weekdays.

 

Sounds like the viscosity related. When the ATF is not warmed up, the viscosity is higher/bigger and the line pressure is higher. As temperature goes up, the viscosity becomes lower/smaller and the dropped pressure causes the engagement slower/harsher. You definitely need to check the line pressure.

 

Will do as soon as I can set a time with the guy at the shop.

 

You'd better also ask the shop to clean the cooling line using the compressed air as is shown below. This is from the manual for a Gen 2 but may be the same with a Gen 1. Remember that the air pressure should not exceed 2.0kg/square cm. A clogged cooling line causes the insufficient cooling capability and this reduces the pressure because the ATF is hotter than normal and the viscosity becomes too low.

 

I'll get this done. I currently need to find the proper speed sensor in order for the speedometer to show the correct speed as the one right now is not from a LS400. I'll get the line pressure checked before and after cleaning out any restrictions and also get the fluid flushed out.

 

I went to the shop, turns out they don't have an oil pressure gauge and the guy just said replace the transmission. I tired to other shops in hope someone will have a pressure gauge but no luck. I did however flush out the oil today and the engagement is a bit smoother but it still has a 1-2 second delay. Is there any other way by which this can be diagnosed?

 

Check the condition of your negative grounds. Electronics are sensitive to voltage drop. If necessary, add one between transmission housing and body;

Reference;

https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/828619-negative-grounding-issues.html

 

I'll check the ground but I assume they are OK as my car doesn't have rust and I've been under the car a couple of time and did not spot rust on the ground wires. I'll still check and report back.

 

Saw something similar recently in a video. Totally different car, but delayed/hard shifting was caused by a damaged shift solenoid valve.

 

I'll check the shift solenoids

 

So what did the guy at the shop say about all this? Have they looked at it?

 

I talked to the guy over the phone to set a time during which he asked the symptoms and his answer to replace the gearbox. Now I know that the gearbox is perfectly fine and is just showing these symptoms due to the car been driven 3000km in three years, so I didnt even bother going as it was no use.

 

You probably have an internal pressure leak. Possibly around the accumulators under the valve body. The engagement should be nearly instant. The shift control rod actuated a manual control valve in the valve body instantly diverting fluid and pressure to engage the pistons on the clutch packs. If you're running under a low line pressure the transmission will operate what may be somewhat normal to you but actually the pistons have a hard time holding against the return springs. This is just like driving around a manual transmission car with the clutch partially depressed. The clutches slip and this is where you get burnt clutch packs that eventually turn into the car not engaging into a gear at all. The forward and direct clutches seem to go first in the A340E. Many times this is caused by a clogged strainer. Even though it may look clean while it's mounted, the areas near the 3 pickups may not be. I just remove the strainer and spray it out with a water hose or parts cleaner. They clean up pretty nicely. Unfortunately the transmission shouldn't shed enough material to ever clog the strainer, so this is usually a temporary fix ending eventually in a transmission overhaul.

 

The strainer and filter were cleaned during the first fluid flush. We did another flush 2 days ago, dropped the pan out and very small deposits were on the magnets.

If I could know the procedure by which I can clean out the transmission while it's on the car and possibly remove any blockade, I would do it, as I have no luck in finding a shop that has an oil pressure gauge. I may as well just clean it out and hope for the best.

 

So new update, started the car to pull back into the driveway in order to wash it and the engagement has gotten extremely harsh. Took it out for a drive and when up to operating temp, the engagement was like before, harsh but bearable.