Toyota 4Runner 1988 SR5 22RE W56B transmission, 33" tires, stock height in the front, rear 1" higher than the front after Zuk mod, 130000 miles on the clock.
It is our holiday vehicle, mild off road every summer, nothing hard, we don not tow any trailer with it.
Our Toyota runs 3000 miles per summer (mostly highway), stays in the garage the rest of the year.
I am the second owner, the first one did all the maintenance in a Toyota dealership, I have all records, it looks like he took care of the 4R, it is in excellent shape for its age, I do not know if the previous owner used to tow a trailer/loads with the truck.
I have been driving manual transmission cars/trucks for decades, I do not have experience with automatic transmissions, in case you wonder.
The manual transmission does not shift smoothly.
There is some resistance (it grinds if I am not careful) when I shift from 1st to 2nd, and sometimes happens from 4th to 5th.
The clutch feels spongy.
I started to notice the problem a few hundred miles after installing the Zuk mod.
What I did until now:
I tried shifting with the rpm under 800 from 1st to 2nd, sometimes works.
I tried double clutch, sometimes works.
First I replaced the manual transmission oil with AmsOil synthetic Manual Transmission SAE 75W-90 API GL-4. After a while, same problems.
After that I found a small leak/drop in the master clutch cylinder. I replaced it, and the slave cylinder also from MC. After replacing the fluid with another DOT 3 and bleeding the system, same problems.
Later, I found out the gear stick seat was disintegrated. I replaced with MC heavy duty seat, and I also installed the MC heavy duty nylon shift lever bushing (socket). Same problems.
Please, help me to solve this problem.