Automatic Transmission PROBLEM - no downshift to 1st gear

[jdmasf*ck]

I own '89 Green Aerodeck CA5 with A20A3 engine and automatic transmission. Recently transmission have a problem with downshift to 1st gear when I'm slowing down the car. That cause I can't accelerate from low speed until I dead stop the car. Because when I add the throttle only RPM raise but nothing happened. Besides that problem, transmission is working properly on all gears and make downshift/upshift accurately. On cold engine/transmission is a little bit better.

First of all I changed transmission fluid to ATF Mobil 220 (Dextron II). Is it good choice.? In service manual is nothing about OEM Honda ATF Z1 (now DW-1) so I didn't buy it. Service manual claim that we should pour 3 l. of new ATF but on dipstick I have too much of it. I poured out aprox. 1 l. and now dipstick indicates the correct level. How much oil should it be?

Changing ATF doesn't help so I adjust the TV cable and throttle cable according to the service manual. It also doesn't help but I notice small leakage from throttle control lever in transmission.


What else can I check myself.? Should I rebuild transmission.?


English isn’t my first language, so please excuse any mistakes.
Greatings from Poland.

https://pl-pl.facebook.com/GreenAerodeckCA5/

[Dr_Snooz]

I'm amazed you can even find Dex II. It pretty well doesn't exist here anymore. It sounds like your valve body is getting hung up. This could be due to wear on the valves, or debris in the valve cavity. If it were mine, I would:

1.) Change fluid more often. If you're shifting problems are caused by dirt in the valve cavity, this will help to clear it out.
2.) Change to Dex III. Dex II went through several changes as problems appeared with the last formulation and a new formula was introduced to fix it. Eventually, Dex III replaced Dex II in almost every application. Try using Dex III to see if it helps.
3.) Also try using semi-synthetic or full-synthetic trans fluids too. The synthetics are generally more slippery than conventional oils, which will help with shifting.
4.) If nothing above helps, try a fluid flush.I've had good luck with flushes in the past, but they can make things worse too, so do this as a last resort and be prepared for a rebuild if things go wrong.
5.) Rebuild the trans.

Definitely focus your efforts on steps 1-3 because parts for these cars are getting scarce. You want to preserve what you have as long as possible.

Good luck and let us know how things go.

[jdmasf*ck]

First of all thank you for your reply Dr_Snooz.

Local automatic transmission service also told me that probably valve body is getting hung up. So I think it is the main reason. :(

Since I wrote the first post I make a small progress.:
1) I used Liqui Moly AUTOMATIC TRANSMISSION CLEANER (pn: 2512) https://products.liqui-moly.com/automatic-transmission-cleaner.html
2) Change fluid to new ATF Mobil 220 DEX II and drive a little bit
3) Change fluid once again, to be sure that all CLEANER is out of the transmission
4) Add Liqui Moly ADDITIVE (pn: 5135) https://products.liqui-moly.com/atf-additive-3.html

In result my transmission is working now a lot better. But it is still annoying.
To sum up, problem is still the same but occure much less frequently after using Liqui Moly ADDITIVE.

Do You think I should try full-synthetic Dextron III now.? I read that it can ruin the gaskets and depressurised old transmission because it is more agressive. Which brand do you recommend.?

It is hard to find someone who want to flush my old transmission. It is also expensive so I think it is better save that money for rebuild and be sure that help.

Maybe adding more Liqui Moly ADDITIVE is the "solution".? " The contents of 250 ml are sufficient for up to 8 l oil volume. " Ours transmission is 9 l volume..

[Dr_Snooz]

How many miles are on this trans? What's the general condition of the car otherwise?

1. You have an old transmission. It's already having problems which means the more you fiddle with it, the more likely you are to make things worse. Every shop is going to tell you to leave it alone, drive it till it stops and then have it rebuilt. That's good advice and you should ignore it with great caution. There are many stories out there about people who neglected regular transmission maintenance until they had a problem, then they changed the oil and it started slipping and they were forced to overhaul it. Don't let that be you.
2. Magic potions, super flushes, wonder additives and the like should ONLY be used as an absolute last resort. For instance, the trans is slipping and you have no money, but still need to get to work. In that case, a magic potion is warranted.
3. To restate, because it's really important: magic potions, super flushes, wonder additives and the like should ONLY be used as an absolute LAST RESORT!!!! Your valve body already has varnish, dirt and crud in it and you're putting in a high detergent flush that is mobilizing MORE varnish, dirt and crud. In big chunks that will float around the transmission and clog things up. Be grateful that you still have a working transmission and stop while you're ahead.
4. If you still have a problem, then the only thing you should do is to use a high quality oil and change it more often. The detergents in the fresh oil will help to dissolve dirt more quickly, but not so quickly that big chunks of it slough off and clog your valve body or clutch pack. Honda recommends you change the oil every 30,000 miles. You can adopt an aggressive oil change schedule by changing oil every 15,000 miles. You could even take it down to 5,000 miles. The brand name of oil isn't important. Just use a quality brand like Valvoline or Mobil 1 or something.

Good luck and let us know how things work out.